There are many forms of acid rain that are seen around the world. In parts of the world where there is wet weather, there is acid rain, acid snow, and acid fog. In parts of the world where there is dry weather, there is acid gas and acid dust. All of the lakes and streams in the world are normally slightly acidic. Heavy rainstorms or melting snow can cause the acidity in lakes and in streams to increase.
What effect does acid rain have on sea life?
Acid rain is very harmful to the environment. Acid rain damages everything over a period of time because it makes the living things in the environment die. Acid rain affects the life in the water as well as the life on land. It is almost worse in water than on land because the fish that are in the water need the water to breathe. When the water gets polluted, then the fish get sick and end up dying.
All rainwater contains some level of acidity. Acidity is measured by pH, which stands for potential of hydrogen. The pH scale measures the amount of acid in a substance. PH is measured on a scale from 0-14, with 7 being neutral. The lower the number is on the pH scale, the more acidic that substance is. Normal rainwater has a pH of 5.6. When the pH level of rainwater goes below 5.6, it is considered acid rain.
All of the sea life will die when the water that they swim in gets to be too acidic. For example, all fish will die when the water goes below a pH of 4.5. Most of the frogs and insects that live around the water will also die when the water reaches a pH of 4.5. With a pH of 5.5, all of the bottom-dwelling bacterial decomposers, animals that eat the remains of the food that other animals don’t want, will begin to die. When these decomposers die, they leave the un-decomposed food on the bottom of the water. This pollutes the water by making the water dirty for all of the fish to swim in. All fresh water shrimp die when there gets to be a pH of 6.0. Aquatic plants will grow the best when the water is a pH between 7.0 and 9.2. If acid rain gets to be more of a problem, then all of the sea life will eventually be gone.
Some of the lakes that were once acidic are recovering, but many more are not recovering. Of the 202 lakes that were chosen to be studied in the early 1980s; only 33% of them have become less acidic.
What effect does acid rain have on the forests of the world?
Trees are also harmed by acid rain. In Germany, the forests are believed to be dying because acid rain is harming them. Scientists say that acid rain damages the waxy outer coating that protects
the leaves. When this happens, it allows the acid to seep into the tree. Instead of water changing from a liquid to a gas inside the leaves, gas is taking the place of the water. This prevents the plant from taking in carbon dioxide to perform photosynthesis, and the plant will eventually die.
Acid rain, acid fog, and acid vapor also damage forests by

This is a picture of acid rain falling into a lake.
 damaging the surface of the leaves and needles. This makes it harder for the trees to withstand the cold and will cause the tree to die. Acid rain also harms the soil that the trees are growing in by taking most of the valuable nutrients away from the soil. Acid rain also leaves a lot of aluminum in the soil, which can be harmful to the trees that grow there.
The atmosphere deposits a lot of toxic metals into the forests because acid rain contains metal. Some of these metals are lead, zinc, copper, chromium, and aluminum. When there is acid rain, the rain releases these metals. This is believed to stunt the growth of many trees and plants. This also stunts the growth of mosses, algae, nitrogen-fixing bacteria, and fungi that are needed to help the forest grow. Forests need these because they eat the harmful things that will kill the trees, such as bad bacteria. Acid rain hurts trees because they cannot grow any more.
What effect does acid rain have on the air, us, and our health?
Acid rain affects us in many different ways. One major way is our health. Breathing and lung problems in children and adults who have asthma and in children have been linked to acid air pollution. Everything that we eat, drink, and breathe has at one time come in contact with acid deposits. This could threaten our health by making us become sick. The following health problems occur each year in the U.S. and Canada due to acid rain:
                550 premature deaths
                1,520 emergency room visits
                210,070 asthma symptom days
As you see, if acid rain became a little less of a problem, then there would be many health problems that could be avoided.
What can acid rain do to non-living things?
Acid rain can also damage non-living things, such as buildings and statues. It can decay building materials and paints. Worst of all, it can damage non-replaceable buildings, statues, and sculptures that are part of our nation’s memories that we want to last for a very long time.
What is acid rain caused by?
Acid rain is mainly caused by these substances that are being released into the air:
                Carbon dioxide: Carbon dioxide is released by burning coal, oil, and natural gas. If you inhale carbon dioxide, then since it is toxic, it can cause you to have to breathe more than usual, unconsciousness, and other serious health problems.
                Carbon monoxide: Carbon monoxide is released by burning gasoline, oil, and wood. When carbon monoxide enters your body, it goes into the bloodstream. When this happens, it will slow down the delivery of oxygen to the rest of the body, causing dizziness, headaches, and fatigue.
                Chlorofluorocarbons (CFCs): CFCs are the chemicals that are used in industry, refrigeration, air conditioning systems, and consumer products. Whenever CFCs are released into the air, they reduce the stratospheric ozone layer. The stratospheric ozone layer protects Earth’s surface from the harmful rays of the sun.
                Hazardous air pollutants (HAPS): HAPS are released into the air by sources such as chemical plants, dry cleaners, printing plants, and motor vehicles (cars, trucks, buses, and planes). HAPS can cause serious health problems like cancer, birth defects, nervous system problems, and deaths that are all due to people accidentally letting them go into the air.
                Lead: Lead is released by house and car paint as well as the manufacturing of lead batteries, fishing lures, certain parts of bullets, some ceramic ware, water pipes, and fixtures. In young children, lead can cause nervous system damage and learning problems.
                Nitrogen oxides: Nitrogen Oxides are released into the air by burning fuels such as gasoline and coal. When nitrogen oxides combine with VOCs, they can cause breathing difficulty in people who have asthma, coughs in children, and general illness in your respiratory system.
                Ozone: Ozone is released by motor vehicles, industries, burning coal, gasoline, and other fossil fuels, and in the chemicals that are in hairspray and paints. When ozone is close to the ground (ground level ozone) it can cause chest pain, irritated respiratory tract, or persistent cough, can make you unable to take deep breaths, and can make you more likely to get lung infections.
                Particulate matter (PM): PM, little particles of pollution, is released by cars, trucks, and buses that are burning diesel fuel, fertilizers, pesticides, road construction, steel making, mining, and turning on fire places and wood stoves. When PMs mix with air particles and get breathed in by something, they get stuck in the lung tissue. There they can cause increased respiratory disease and lung damage.
                Sulfur dioxides: Sulfur dioxides are released by burning coal, paper production, and melting metal. Sulfur dioxide can harm vegetation, harm metals, and cause lung problems, which include breathing problems and permanent lung damage.
                Volatile organic compounds (VOCs): VOCs are released into the air by burning gasoline, wood, coal, or natural gas, solvents, paints, glues, and other products that are used at work or at home.
There are a lot of similarities in all of these pollutants. Most of the pollutants are from automobiles. Automobiles release harmful smoke into the air, which causes acid rain. Coal, oil, and gasoline are also some of the most common causes of all of the pollutants. If people reduce the amount of these things that they release into the air, then there will be less pollutants. Some of the most common health problems are breathing problems, nervous system problems, and lung problems.

Air Pollutant       % that mobile sources contribute to acid rain      % that other sources contribute to acid rain
Volatile organic compound          37%        63%
Nitrogen oxide  49%        51%
Carbon monoxide            81%        19%
Particulate matter           27%        73%
The table above shows that the biggest air pollutant that mobile sources contribute to acid rain is carbon monoxide. Of all of the carbon monoxide releases that contribute to acid rain, 81% of them come from mobile sources. The biggest other source is particulate matter, little particles of pollution that are released into the air by cars, trucks, and buses that are burning diesel fuel, fertilizers, pesticides, road construction, steel making, mining, and turning on fire places and wood stoves. 73% of the non-mobile sources that contribute to acid rain are caused by the release of particulate matter. The table above shows how much mobile and other sources of pollution can make acid rain more of a problem. Seeing that carbon monoxide and particulate matter are the leading sources of pollution, by cutting down on these, acid rain will not be as much of a problem.
What can you do?
There are many ways that people can stop pollution. One major way is to reduce the amount of trips that you take in your car. Another way that a lot of our pollution is caused is by creating electrical energy. When electricity is created, fuels are usually burned, and this causes the pollution, which causes acid rain. The generation of electric power produces more pollution than any other industry in the United States. Burning coal and other fossil fuels causes most of our pollution. This is why in some places around the world, acid rain is monitored very closely. In 1998, data shows that by using electricity, the pollution that comes with it was responsible for 67% of the sulfur dioxide emissions that caused acid rain that year. Every time that you turn on the lights, that causes the pollution that causes acid rain. Even doing little things that you may think don’t cause pollution sometimes really do. Some things that you can do to make acid rain less of a problem are:
In Your Home
                Only run the dishwasher with a full load
                Only run the washing machine with a full load
                Turn off the lights in empty rooms or when you will be away from home
                Turn off the hot water tank when you will be gone for a long period of time
                Turn down the heat at night and when you will not be home for the night
                Don’t use your air conditioner as much
                Install fluorescent light bulbs instead of incandescent light bulbs
                Try to reduce, reuse, and recycle as often as you can
                Try not to burn a fire as often as you usually do
In the yard
                Keep the pool cover on the pool whenever you are not using it
                When you are going to work, you could walk, ride your bike, or take a bus
                Car-pool to a place with someone else
                For alternate fuels, try ethanol, propane, or natural gas
                Take the train or a bus for long trips
                Limit the amount of long trips you take in your car
                Make sure that your vehicle’s air conditioning system isn’t leaking
                Try not to overflow the gas tank
                Make sure that you are traveling at high speeds only when you need to


Main articles: Pollutant and Greenhouse gas

Before flue gas desulfurization was installed, the emissions from this power plant in New Mexico contained excessive amounts of sulfur dioxide.

Schematic drawing, causes and effects of air pollution: (1) greenhouse effect, (2) particulate contamination, (3) increased UV radiation, (4) acid rain, (5) increased ozone concentration, (6) increased levels of nitrogen oxides
An air pollutant is known as a substance in the air that can cause harm to humans and the environment. Pollutants can be in the form of solid particles, liquid droplets, or gases. In addition, they may be natural or man-made.[2]
Pollutants can be classified as either primary or secondary. Usually, primary pollutants are substances directly emitted from a process, such as ash from a volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories.
Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground level ozone — one of the many secondary pollutants that make up photochemical smog.
Note that some pollutants may be both primary and secondary: that is, they are both emitted directly and formed from other primary pollutants.
About 4 percent of deaths in the United States can be attributed to air pollution, according to the Environmental Science Engineering Program at the Harvard School of Public Health.
Major primary pollutants produced by human activity include:
             Sulfur oxides (SOx) - especially sulfur dioxide, a chemical compound with the formula SO2. SO2 is produced by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain.[2] This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.
             Nitrogen oxides (NOx) - especially nitrogen dioxide are emitted from high temperature combustion. Can be seen as the brown haze dome above or plume downwind of cities. Nitrogen dioxide is the chemical compound with the formula NO2. It is one of the several nitrogen oxides. This reddish-brown toxic gas has a characteristic sharp, biting odor. NO2 is one of the most prominent air pollutants.
             Carbon monoxide - is a colourless, odourless, non-irritating but very poisonous gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide.
             Carbon dioxide (CO2) - a greenhouse gas emitted from combustion but is also a gas vital to living organisms. It is a natural gas in the atmosphere.
             Volatile organic compounds - VOCs are an important outdoor air pollutant. In this field they are often divided into the separate categories of methane (CH4) and non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhanced global warming. Other hydrocarbon VOCs are also significant greenhouse gases via their role in creating ozone and in prolonging the life of methane in the atmosphere, although the effect varies depending on local air quality. Within the NMVOCs, the aromatic compounds benzene, toluene and xylene are suspected carcinogens and may lead to leukemia through prolonged exposure. 1,3-butadiene is another dangerous compound which is often associated with industrial uses.
             Particulate matter - Particulates, alternatively referred to as particulate matter (PM) or fine particles, are tiny particles of solid or liquid suspended in a gas. In contrast, aerosol refers to particles and the gas together. Sources of particulate matter can be man made or natural. Some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of aerosols. Averaged over the globe, anthropogenic aerosols—those made by human activities—currently account for about 10 percent of the total amount of aerosols in our atmosphere. Increased levels of fine particles in the air are linked to health hazards such as heart disease[3], altered lung function and lung cancer.
             Persistent free radicals connected to airborne fine particles could cause cardiopulmonary disease.[4][5]
             Toxic metals, such as lead, cadmium and copper.
             Chlorofluorocarbons (CFCs) - harmful to the ozone layer emitted from products currently banned from use.
             Ammonia (NH3) - emitted from agricultural processes. Ammonia is a compound with the formula NH3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceuticals. Although in wide use, ammonia is both caustic and hazardous.
             Odors — such as from garbage, sewage, and industrial processes
             Radioactive pollutants - produced by nuclear explosions, war explosives, and natural processes such as the radioactive decay of radon.
Secondary pollutants include:
             Particulate matter formed from gaseous primary pollutants and compounds in photochemical smog. Smog is a kind of air pollution; the word "smog" is a portmanteau of smoke and fog. Classic smog results from large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide. Modern smog does not usually come from coal but from vehicular and industrial emissions that are acted on in the atmosphere by sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog.
             Ground level ozone (O3) formed from NOx and VOCs. Ozone (O3) is a key constituent of the troposphere (it is also an important constituent of certain regions of the stratosphere commonly known as the Ozone layer). Photochemical and chemical reactions involving it drive many of the chemical processes that occur in the atmosphere by day and by night. At abnormally high concentrations brought about by human activities (largely the combustion of fossil fuel), it is a pollutant, and a constituent of smog.
             Peroxyacetyl nitrate (PAN) - similarly formed from NOx and VOCs.
Minor air pollutants include:
             A large number of minor hazardous air pollutants. Some of these are regulated in USA under the Clean Air Act and in Europe under the Air Framework Directive.
             A variety of persistent organic pollutants, which can attach to particulate matter.
Persistent organic pollutants (POPs) are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. Because of this, they have been observed to persist in the environment, to be capable of long-range transport, bioaccumulate in human and animal tissue, biomagnify in food chains, and to have potential significant impacts on human health and the environment.
Main article: AP 42 Compilation of Air Pollutant Emission Factors

Dust storm approaching Stratford, Texas

Controlled burning of a field outside of Statesboro,Georgia in preparation for spring planting
Sources of air pollution refer to the various locations, activities or factors which are responsible for the releasing of pollutants in the atmosphere. These sources can be classified into two major categories which are:
Anthropogenic sources (human activity) mostly related to burning different kinds offuel
             "Stationary Sources" include smoke stacks of power plants, manufacturing facilities (factories) and waste incinerators, as well as furnaces and other types of fuel-burning heating devices
             "Mobile Sources" include motor vehicles, marine vessels, aircraft and the effect of sound etc.
             Chemicals, dust and controlled burn practices in agriculture and forestry management. Controlled or prescribed burning is a technique sometimes used in forest management, farming, prairie restoration or greenhouse gas abatement. Fire is a natural part of both forest and grassland ecology and controlled fire can be a tool for foresters. Controlled burning stimulates the germination of some desirable forest trees, thus renewing the forest.
             Fumes from paint, hair spray, varnish, aerosol sprays and other solvents
             Waste deposition in landfills, which generate methane.Methane is not toxic; however, it is highly flammable and may form explosive mixtures with air. Methane is also an asphyxiant and may displace oxygen in an enclosed space. Asphyxia or suffocation may result if the oxygen concentration is reduced to below 19.5% by displacement
             Military, such as nuclear weapons, toxic gases, germ warfare and rocketry
Natural sources
             Dust from natural sources, usually large areas of land with little or no vegetation.
             Methane, emitted by the digestion of food by animals, for example cattle.
             Radon gas from radioactive decay within the Earth's crust. Radon is a colorless, odorless, naturally occurring, radioactive noble gas that is formed from the decay of radium. It is considered to be a health hazard. Radon gas from natural sources can accumulate in buildings, especially in confined areas such as the basement and it is the second most frequent cause of lung cancer, after cigarette smoking.
             Smoke and carbon monoxide from wildfires.
             Volcanic activity, which produce sulfur, chlorine, and ash particulates.
Emission factors
Main article: AP 42 Compilation of Air Pollutant Emission Factors
Air pollutant emission factors are representative values that attempt to relate the quantity of a pollutant released to the ambient air with an activity associated with the release of that pollutant. These factors are usually expressed as the weight of pollutant divided by a unit weight, volume, distance, or duration of the activity emitting the pollutant (e.g., kilograms of particulate emitted per megagram of coal burned). Such factors facilitate estimation of emissions from various sources of air pollution. In most cases, these factors are simply averages of all available data of acceptable quality, and are generally assumed to be representative of long-term averages.
The United States Environmental Protection Agency has published a compilation of air pollutant emission factors for a multitude of industrial sources.[6] The United Kingdom, Australia, Canada and many other countries have published similar compilations, as well as the European Environment Agency.[7][8][9][10][11]
Indoor air quality (IAQ)
Main article: Indoor air quality
A lack of ventilation indoors concentrates air pollution where people often spend the majority of their time. Radon (Rn) gas, a carcinogen, is exuded from the Earth in certain locations and trapped inside houses. Building materials including carpeting and plywood emit formaldehyde(H2CO) gas. Paint and solvents give off volatile organic compounds (VOCs) as they dry. Lead paint can degenerate into dust and be inhaled. Intentional air pollution is introduced with the use of air fresheners, incense, and other scented items. Controlled wood fires in stoves andfireplaces can add significant amounts of smoke particulates into the air, inside and out[12]. Indoor pollution fatalities may be caused by usingpesticides and other chemical sprays indoors without proper ventilation.
Carbon monoxide (CO) poisoning and fatalities are often caused by faulty vents and chimneys, or by the burning of charcoal indoors. Chroniccarbon monoxide poisoning can result even from poorly adjusted pilot lights. Traps are built into all domestic plumbing to keep sewer gas,hydrogen sulfide, out of interiors. Clothing emits tetrachloroethylene, or other dry cleaning fluids, for days after dry cleaning.
Though its use has now been banned in many countries, the extensive use of asbestos in industrial and domestic environments in the past has left a potentially very dangerous material in many localities. Asbestosis is a chronic inflammatory medical condition affecting the tissue of the lungs. It occurs after long-term, heavy exposure to asbestos from asbestos-containing materials in structures. Sufferers have severedyspnea (shortness of breath) and are at an increased risk regarding several different types of lung cancer. As clear explanations are not always stressed in non-technical literature, care should be taken to distinguish between several forms of relevant diseases. According to theWorld Health Organisation (WHO), these may defined as; asbestosis, lung cancer, and mesothelioma (generally a very rare form of cancer, when more widespread it is almost always associated with prolonged exposure to asbestos).
Biological sources of air pollution are also found indoors, as gases and airborne particulates. Pets produce dander, people produce dust from minute skin flakes and decomposed hair, dust mites in bedding, carpeting and furniture produce enzymes and micrometre-sized fecal droppings, inhabitants emit methane, mold forms in walls and generates mycotoxins and spores, air conditioning systems can incubateLegionnaires' disease and mold, and houseplants, soil and surrounding gardens can produce pollen, dust, and mold. Indoors, the lack of air circulation allows these airborne pollutants to accumulate more than they would otherwise occur in nature.
Health effects
The World Health Organization states that 2.4 million people die each year from causes directly attributable to air pollution, with 1.5 million of these deaths attributable to indoor air pollution.[13] "Epidemiological studies suggest that more than 500,000 Americans die each year fromcardiopulmonary disease linked to breathing fine particle air pollution. . ."[14] A study by the University of Birmingham has shown a strong correlation between pneumonia related deaths and air pollution from motor vehicles.[15] Worldwide more deaths per year are linked to air pollution than to automobile accidents.[citation needed] Published in 2005 suggests that 310,000 Europeans die from air pollution annually.[citation needed] Direct causes of air pollution related deaths include aggravated asthma, bronchitis, emphysema, lung and heart diseases, and respiratory allergies.[citation needed] The US EPA estimates that a proposed set of changes in diesel engine technology (Tier 2) could result in 12,000 fewer premature mortalities, 15,000 fewer heart attacks, 6,000 fewer emergency room visits by children with asthma, and 8,900 fewer respiratory-related hospital admissions each year in the United States.[citation needed]
The worst short term civilian pollution crisis in India was the 1984 Bhopal Disaster.[16] Leaked industrial vapors from the Union Carbide factory, belonging to Union Carbide, Inc., U.S.A., killed more than 2,000 people outright and injured anywhere from 150,000 to 600,000 others, some 6,000 of whom would later die from their injuries.[citation needed] The United Kingdom suffered its worst air pollution event when the December 4 Great Smog of 1952 formed over London. In six days more than 4,000 died, and 8,000 more died within the following months.[citation needed] An accidental leak of anthrax spores from a biological warfare laboratory in the former USSR in 1979 near Sverdlovskis believed to have been the cause of hundreds of civilian deaths.[citation needed] The worst single incident of air pollution to occur in the United States of America occurred in Donora, Pennsylvania in late October, 1948, when 20 people died and over 7,000 were injured.[17]
The health effects caused by air pollutants may range from subtle biochemical and physiological changes to difficulty in breathing, wheezing, coughing and aggravation of existing respiratory and cardiac conditions. These effects can result in increased medication use, increased doctor or emergency room visits, more hospital admissions and premature death. The human health effects of poor air quality are far reaching, but principally affect the body's respiratory system and the cardiovascular system. Individual reactions to air pollutants depend on the type of pollutant a person is exposed to, the degree of exposure, the individual's health status and genetics.[citation needed]
A new economic study of the health impacts and associated costs of air pollution in the Los Angeles Basin and San Joaquin Valley of Southern California shows that more than 3800 people die prematurely (approximately 14 years earlier than normal) each year because air pollution levels violate federal standards. The number of annual premature deaths is considerably higher than the fatalities related to auto collisions in the same area, which average fewer than 2,000 per year [18].
Diesel exhaust (DE) is a major contributor to combustion derived particulate matter air pollution. In several human experimental studies, using a well validated exposure chamber setup, DE has been linked to acute vascular dysfunction and increased thrombus formation.[19][20] This serves as a plausible mechanistic link between the previously described association between particulate matter air pollution and increased cardiovascular morbidity and mortality.
Effects on cystic fibrosis
Main article: Cystic fibrosis
A study from 1999 to 2000 by the University of Washington showed that patients near and around particulate matter air pollution had an increased risk of pulmonary exacerbations and decrease in lung function.[21] Patients were examined before the study for amounts of specific pollutants like Pseudomonas aeruginosa or Burkholderia cenocepacia as well as their socioeconomic standing. Participants involved in the study were located in the United States in close proximity to an Environmental Protection Agency.[clarification needed] During the time of the study 117 deaths were associated with air pollution. A trend was noticed that patients living closer or in large metropolitan areas to be close to medical help also had higher level of pollutants found in their system because of more emissions in larger cities. With cystic fibrosis patients already being born with decreased lung function everyday pollutants such as smoke e

Indoor & Outdoor
Air Pollution

When people think about air pollution, they usually think about smog, acid rain, CFC's, and other forms of outdoor air pollution. But did you know that air pollution also can exist inside homes and other buildings? It can, and every year, the health of many people is affected by chemical substances present in the air within buildings.
A great deal of research on pollution is being conducted at laboratories and universities. The goals of the research are to find solutions and to educate the public about the problem. Two


What is global warming?
Global warming is when the earth heats up (the temperature rises).  It happens when greenhouse gases (carbon dioxide, water vapor, nitrous oxide, and methane) trap heat and light from the sun in the earth’s atmosphere, which increases the temperature.  This hurts many people, animals, and plants.  Many cannot take the change, so they die.
What is the greenhouse effect?
The greenhouse effect is when the temperature rises because the sun’s heat and light is trapped in the earth’s atmosphere.  This is like when heat is trapped in a car. On a very hot day, the car gets hotter when it is out in the parking lot.  This is because the heat and light from the sun can get into the car, by going through the windows, but it can’t get back out.  This is what the greenhouse effect does to the earth.  The heat and light can get through the atmosphere, but it can’t get out.  As a result, the temperature rises.

The squiggle lines coming from the sun are visible light and the lines and arrows inside the car are infrared light.
The sun’s heat can get into the car through the windows but is then trapped.  This makes what ever the place might be, a greenhouse, a car, a building, or the earth’s atmosphere, hotter.  This diagram shows the heat coming into a car as visible light (light you can see) and infrared light (heat).  Once the light is inside the car, it is trapped and the heat builds up, just like it does in the earth’s atmosphere.
Sometimes the temperature can change in a way that helps us.  The greenhouse effect makes the earth appropriate for people to live on.  Without it, the earth would be freezing, or on the other hand it would be burning hot.  It would be freezing at night because the sun would be down.  We would not get the sun’s heat and light to make the night somewhat warm.  During the day, especially during the summer, it would be burning because the sun would be up with no atmosphere to filter it, so people, plants, and animals would be exposed to all the light and heat.
Although the greenhouse effect makes the earth able to have people living on it, if there gets to be too many gases, the earth can get unusually warmer, and many plants, animals, and people will die.  They would die because there would be less food (plants like corn, wheat, and other vegetables and fruits).  This would happen because the plants would not be able to take the heat.  This would cause us to have less food to eat, but it would also limit the food that animals have.  With less food, like grass, for the animals that we need to survive (like cows) we would even have less food.  Gradually, people, plants, and animals would all die of hunger. 
What are greenhouse gasses?
Greenhouse gasses are gasses are in the earth’s atmosphere that collect heat and light from the sun.  With too many greenhouse gasses in the air, the earth’s atmosphere will trap too much heat and the earth will get too hot.  As a result people, animals, and plants would die because the heat would be too strong.
What is global warming doing to the environment?
Global warming is affecting many parts of the world.  Global warming makes the sea rise, and when the sea rises, the water covers many low land islands.  This is a big problem for many of the plants, animals, and people on islands.  The water covers the plants and causes some of them to die.  When they die, the animals lose a source of food, along with their habitat.  Although animals have a better ability to adapt to what happens than plants do, they may die also.  When the plants and animals die, people lose two sources of food, plant food and animal food. They may also lose their homes.  As a result, they would also have to leave the area or die.  This would be called a break in the food chain, or a chain reaction, one thing happening that leads to another and so on. 
The oceans are affected by global warming in other ways, as well.  Many things that are happening to the ocean are linked to global warming.  One thing that is happening is warm water, caused from global warming, is harming and killing algae in the ocean.
Algae is a producer that you can see floating on the top of the water.  (A producer is something that makes food for other animals through photosynthesis, like grass.)  This floating green algae is food to many consumers in the ocean.  (A consumer is something that eats the producers.)  One kind of a consumer is small fish.  There are many others like crabs, some whales, and many other animals.  Fewer algae is a problem because there is less food for us and many animals in the sea.
Global warming is doing many things to people as well as animals and plants.  It is killing algae, but it is also destroying many huge forests.  The pollution that causes global warming is linked to acid rain.  Acid rain gradually destroys almost everything it touches.  Global warming is also causing many more fires that wipe out whole forests.  This happens because global warming can make the earth very hot.  In forests, some plants and trees leaves can be so dry that they catch on fire.
What causes global warming? 
Many things cause global warming.  One thing that causes global warming is electrical pollution.  Electricity causes pollution in many ways, some worse than others.  In most cases, fossil fuels are burned to create electricity.  Fossil fuels are made of dead plants and animals.  Some examples of fossil fuels are oil and petroleum.  Many pollutants (chemicals that pollute the air, water, and land) are sent into the air when fossil fuels are burned.  Some of these chemicals are called greenhouse gasses.
We use these sources of energy much more than the sources that give off less pollution.  Petroleum, one of the sources of energy, is used a lot.  It is used for transportation, making electricity, and making many other things.  Although this source of energy gives off a lot of pollution, it is used for 38% of the United States’ energy.
Some other examples of using energy and polluting the air are:
                Turning on a light
                Watching T.V.
                Listening to a stereo
                Washing or drying clothes
                Using a hair dryer
                Riding in a car
                Heating a meal in the microwave
                Using an air conditioner
                Playing a video game
                Using a dish washer
When you do these things, you are causing more greenhouse gasses to be sent into the air.  Greenhouse gasses are sent into the air because creating the electricity you use to do these things causes pollution.  If you think of how many times a day you do these things, it’s a lot.  You even have to add in how many other people do these things!  That turns out to be a lot of pollutants going into the air a day because of people like us using electricity. The least amount of electricity you use, the better.
When we throw our garbage away, the garbage goes to landfills.  Landfills are those big hills that you go by on an expressway that stink.  They are full of garbage.  The garbage is then sometimes burned.  This sends an enormous amount of greenhouse gasses into the air and makes global warming worse.
Another thing that makes global warming worse is when people cut down trees.  Trees and other plants collect carbon dioxide (CO2), which is a greenhouse gas.
Carbon dioxide is the air that our body lets out when we breathe. With fewer trees, it is harder for people to breathe because there is more CO2 in the air, and we don’t breathe CO2, we breathe oxygen.  Plants collect the CO2 that we breathe out, and they give back oxygen that we breathe in.  With less trees and other plants, such as algae, there is less air for us, and more greenhouse gases are sent into the air. This means that it is very important to protect our trees to stop the greenhouse effect, and also so we can breathe and live.
This gas, CO2, collects light and heat (radiant energy), produced by the sun, and this makes the earth warmer.  The heat and light from the sun is produced in the center of the sun.  (The sun has layers just like the earth.)

The dirty yellow color on outside is the surface.  The light and dark yellow colored area is the convection zone.  The orange colored area is the radiative zone, and the red colored area is the core.  The squiggle lines represent radiant energy.    

This layer is called the core.  Just like a core of an apple, it is in the middle.  Here there is a very high temperature, about 27,000,000F. This heat escapes out of this layer to the next layer, the radiative zone. This layer is cooler, about 4,500,000F.   Gradually, the heat and light will pass through the convection zone at a temperature of around 2,000,000F.  When it gets to the surface, the temperature is about 10,000F.  Finally, the heat and light is sent into space.  This is called radiant energy (heat and light).  The radiant energy reaches the earth’s atmosphere.  As a result of this process we get light and heat. When you pollute, you send chemicals into the air that destroy our atmosphere, so more heat and light cannot escape from the earth’s atmosphere.
What are people doing to stop global warming? 
People are doing many things to try to stop global warming.  One thing people are doing is carpooling.  Carpooling is driving with someone to a place that you are both going to.  This minimizes the amount of greenhouse gases put into the air by a car.
Another thing that people are doing is being more careful about leaving things turned on like the television, computer, and the lights.   A lot of people are taking time away from the television, and instead, they are spending more time outdoors.  This helps our planet out a lot.  Now, more people are even riding busses, walking to school, and riding their bikes to lower the amount of greenhouse gases in the air.  Planting trees and recycling also helps.  If you recycle, less trash goes to the dump, and less trash gets burned.  As a result, there are fewer greenhouse gasses in our atmosphere.
Watch what you buy.  Many things, such as hairspray and deodorant, now are made to have less of an impact on the atmosphere.  Less greenhouse gasses will rise into the air, and global warming will slow down.
What is the government doing to stop global warming?
The government is doing many things to help stop global warming. The government made a law called The Clean Air Act so there is less air pollution.  Global warming is making people get very bad illnesses that could make them disabled, very sick, and sometimes even die.  The Clean Air Act is making many companies change their products to decrease these problems.  Part of the law says that you may not put a certain amount of pollutants in the air.  Hairspray and some other products, like foam cups, had this problem. Making and using these products let out too much volatile organic compounds (VOC’s), ozone-destroying chemicals (chlorofluorocarbons (CFC’s), and related chemicals (such as CO2) into the air.  Now, almost all of these products have a label on them telling people what this product can do to the environment and many people.  By 2015 all products listed on the Clean Air Act will have this label on them:
WARNING: contains or manufactured with (the chemical would go here.  For example chlorofluorocarbons (CFC’s), a substance which harms public health and the environment by destroying ozone in the upper atmosphere. 
Almost all of the other chemicals that could be harmful will have this label on them hopefully by this time (2015) as well.
The Clean Air Act has also made car companies change some of the things inside of the cars.  Cars pollute a lot.  While cars make more than half of the world’s smog (visible pollution in the air), many things that cars need to move and heat up make even more pollution.  Some things that are inside of cars, buses, trucks, and motorcycles, like gasoline, pollute the air when the fuel is burned.  It comes out as a chemical and when mixed in the air, forms smog.  Smog is a kind of pollution that you see in the form of a cloud.  If you have ever been to California you can see a lot of smog in some places.  Sometimes the smog gets so bad that you cannot see at all!  Smog forms when car exhaust, pollution from homes, and pollution from factories mixes in the air and has a chemical reaction.  The sun’s heat and light add to the reaction.
Cars, buses, and trucks are also responsible for over 50% of dangerous chemicals let into the air.  Some of these chemicals can cause cancer, birth defects, trouble breathing, brain and nerve damage, lung injures, and burning eyes.  Some of the pollutants are so harmful that they can even cause death.
What are some of the other dangerous chemicals?
Some other chemicals that cause air pollution and are bad for the environment and people are:
                Ozone- Ozone is produced when other pollution chemicals combine.  It is the basic element of smog.  It causes many different kinds of health issues dealing with the lungs.  It can damage plants and limit sight.  It can also cause a lot of property damage.
                VOC’s (volatile organic compounds, smog formers)- VOC’s are let into the air when fuel is burned. This chemical can cause cancer.  It can also harm plants.
                NOx (nitrogen dioxide)- This chemical forms smog.  It is also formed by burning sources of energy, like gas, coal, and oil, and by cars.  This chemical causes problems in the respiratory system (including the lungs).  It causes acid rain, and it can damage trees.  This chemical can eat away buildings and statues.
                CO (carbon monoxide)- The source of this chemical is burning sources of energy.  It causes blood vessel problems and respiratory failures.
                PM-10 (particulate matter)- The source of this chemical is plowing and burning down fields.  It can cause death and lung damage.  It can make it hard for people to breathe.  The smoke, soot, ash, and dust formed by this chemical can make many cities dirty.
                Sulfur Dioxide- This chemical is produced by making paper and metals.  This chemical can cause permanent lung damage.  It can cause acid rain which kills trees and damages building and statues.
                Lead- This chemical is in paint, leaded gasoline, smelters, and in lead storage batteries.  It can cause many brain and nerve damages and digestive problems.

A hazardous waste is waste that poses substantial or potential threats to public health or the environment. There are four factors that determine whether or not a substance is hazardous:
             ignitability (i.e., flammable)
U.S. environmental laws (see Resource Conservation and Recovery Act) additionally describe a "hazardous waste" as a waste (usually a solid waste) that has the potential to:
             cause, or significantly contribute to an increase in mortality (death) or an increase in serious irreversible, or incapacitating reversible illness; or
             pose a substantial (present or potential) hazard to human health or the environment when improperly treated, stored, transported, or disposed of, or otherwise managed.
These wastes may be found in different physical states such as gaseous, liquids, or solids. Furthermore, a hazardous waste is a special type of waste because it cannot be disposed of by common means like other by-products of our everyday lives. Depending on the physical state of the waste, treatment and solidification processes might be available. In other cases, however, there is not much that can be done to prevent harm.
             1 Regulatory history
o             1.1 Resource Conservation and Recovery Act (RCRA)
o             1.2 Comprehensive Environmental Response, Compensation, and Liability Act
             2 Hazardous wastes in the United States
o             2.1 Characteristic wastes
             2.1.1 Ignitability
             2.1.2 Corrosive
             2.1.3 Reactivity
             2.1.4 Toxicity
o             2.2 Listed wastes
             2.2.1 The F-list (non-specific source wastes)
             2.2.2 The K-list (source-specific wastes)
             2.2.3 Discarded wastes (P-List and U-List)
o             2.3 Hazardous Waste Mapping Systems
             3 Universal wastes
             4 Other hazardous wastes
             5 Exempted hazardous wastes
             6 Household Hazardous Waste
             7 Final disposal of hazardous waste
o             7.1 Recycling
o             7.2 Portland cement
o             7.3 Neutralization
o             7.4 Incineration, destruction and waste-to-energy
o             7.5 Hazardous waste landfill (sequestering, isolation, etc.)
o             7.6 Pyrolysis
             8 See also
             9 References
             10 External links
[edit]Regulatory history
[edit]Resource Conservation and Recovery Act (RCRA)
Modern hazardous waste regulations in the U.S. began with the Resource Conservation and Recovery Act (RCRA) which was enacted in 1976. The primary contribution of RCRA was to create a "cradle to grave" system of record keeping for hazardous wastes. Hazardous wastes must be tracked from the time they are generated until their final disposition.
RCRA's record keeping system helps to track the life cycle of hazardous waste and reduces the amount of hazardous waste illegally disposed.
[edit]Comprehensive Environmental Response, Compensation, and Liability Act
The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), was enacted in 1980. The primary contribution of CERCLA was to create a "Superfund" and provided for the clean-up and remediation of closed and abandoned hazardous waste sites.Before this act was created, hazardous wastes were being disposed in regular landfills until scientists measured unfavorable amounts of hazardous materials seeping into the ground. These chemicals eventually made their way to the water systems, and contaminated the soil that animals and crops used, as well as the soil that people employed to build their communities. After these regulations were put into practice, many landfills require now countermeasures against groundwater contamination; for example installing a barrier along the foundation of the landfill to contain the hazardous substances that may remain in the disposed waste.[1]Currently, in order to enter a landfill, hazardous wastes must be stabilized and solidified, thus the new waste produced is less harmful than the original.
[edit]Hazardous wastes in INDIA
Many types of businesses generate hazardous waste. Some are small areas that may be located in a community. For example, dry cleaners, automobile repair shops, hospitals, exterminators, and photo processing centers all generate hazardous waste. Some hazardous waste generators are larger companies like chemical manufacturers, electroplating companies, and oil refineries.
A US facility that treats, stores or disposes of hazardous waste must obtain a permit for doing so under the Resource Conservation and Recovery Act. Generators of and transporters of hazardous waste must meet specific requirements for handling, managing, and tracking waste. Through the RCRA, Congress directed the United States Environmental Protection Agency (EPA) to create regulations to manage hazardous waste. Under this mandate, the EPA developed strict requirements for all aspects of hazardous waste management including the treatment, storage, and disposal of hazardous waste. In addition to these federal requirements, states may develop more stringent requirements or requirements that are broader in scope than the federal regulations.
In the United States, hazardous wastes generated by commercial or industrial activities may be classified as "listed" hazardous wastes or "characteristic" hazardous wastes by the EPA.
In regulatory terms, a Resource Conservation and Recovery Act (RCRA) hazardous waste is a waste that either a "characteristic waste" or a "listed waste":
Characteristic Waste - exhibits at least one of the four "characteristics" of hazardous waste (ignitability, corrosivity, reactivity, or toxicity)
Listed Waste - appears on one of the four hazardous wastes lists (F-list, K-list, P-list, or U-list), or
Individual states may regulate particular wastes more stringently than mandated by federal regulation. This is because the U.S. EPA is authorized to delegate primary rulemaking authorization to individual states. Most states take advantage of this authority, implementing their own hazardous waste programs that are at least as stringent as the federal program.
[edit]Characteristic wastes
Characteristic Hazardous Wastes are defined as wastes that exhibit the following characteristics: ignitability, corrosivity, reactivity, or toxicity.
Ignitable wastes can create fires under certain conditions, are spontaneously combustible, or have a flash point less than 60 °C (140 °F). Examples include waste oils and used solvents. For more details, see 40 CFR §261.21. Test methods that may be used to determine ignitability include the Pensky-Martens Closed-Cup Method for Determining Ignitability, the Setaflash Closed-Cup Method for Determining Ignitability, and the Ignitability of Solids.
Corrosive wastes are acids or bases (pH less than or equal to 2, or greater than or equal to 12.5) that are capable of corroding metal containers, such as storage tanks, drums, and barrels. Battery acid is an example. For more details, see 40 CFR §261.22. The test method that may be used to determine corrosivity is the Corrosivity Towards Steel (Method 1110A) (PDF).
Reactive wastes are unstable under "normal" conditions. They can cause explosions, toxic fumes, gases, or vapors when heated, compressed, or mixed with water. Examples include lithium-sulfur batteries and explosives. For more details, see 40 CFR §261.23. There are currently no test methods available.
Toxic wastes are those containing concentrations of certain substances in excess of regulatory thresholds which are expected to cause injury or illness to human health or the environment. For more details see [3]
[edit]Listed wastes
Listed hazardous wastes are generated by specific industries and processes and are automatically considered hazardous, based solely on the process that generates them and irrespective of whether a test of the waste shows any of the "characteristics" of hazardous waste. Examples of listed wastes include:
             many sludges leftover from electroplating processes.
             certain waste from iron and steel manufacturing
             wastes from certain cleaning and/or degreasing processes
Hazardous wastes are incorporated into lists published by the Environmental Protection Agency. These lists are organized into three categories:
[edit]The F-list (non-specific source wastes)
This list identifies wastes from common manufacturing and industrial processes, such as solvents, that have been used in cleaning or degreasing operations. Because the processes producing these wastes can occur in different sectors of industry, the F-listed wastes are known as wastes from non-specific sources.
[edit]The K-list (source-specific wastes)
This list includes certain wastes from specific industries, such as petroleum refining or pesticide manufacturing. Certain sludges and wastewaters from treatment and production processes in these industries are examples of source-specific wastes.
[edit]Discarded wastes (P-List and U-List)
P-List and U-List wastes are actually sublists of the same major list applying to discarded wastes. These wastes apply to commercial chemical products that are considered hazardous when discarded and are regulated under the following U.S. Federal Regulation: 40 C.F.R. 261.33(e) and 261.33(f). P-List wastes are wastes that are considered "acutely hazardous" when discarded and are subject to more stringent regulation. Nitric oxide is an example of a P-list waste and carries the number P076. U-Listed wastes are considered "hazardous" when discarded and are regulated in a somewhat less stringent manner than P-Listed wastes.
[edit]Hazardous Waste Mapping Systems
There are several tools for mapping hazardous wastes to particular locations. These tools also allow the user to view additional information.
             TOXMAP is a Geographic Information System (GIS) from the Division of Specialized Information Services [4] of the United States National Library of Medicine (NLM) that uses maps of the United States to help users visually explore data from the United States Environmental Protection Agency's (EPA) Toxics Release Inventory and Superfund Basic Research Programs. TOXMAP is a resource funded by the US Federal Government. TOXMAP's chemical and environmental health information is taken from NLM's Toxicology Data Network (TOXNET) [5] and PubMed, and from other authoritative sources.
             The US Environmental Protection Agency (EPA) "Where You Live" [6] allows users to select a region from a map to find information about Superfund sites in that region.
[edit]Universal wastes
Universal wastes are hazardous wastes that (in the U.S.):
             generally pose a lower threat relative to other hazardous wastes
             are ubiquitous and produced in very large quantities by a large number of generators.
Some of the most common "universal wastes" are: fluorescent light bulbs, some specialty batteries (e.g. lithium or lead containing batteries),cathode ray tubes, and mercury-containing devices.
Also, in worldwide, The United Nations Environmental Programme(UNEP) estimated that more than 400 million tons of hazardous wastes are produced universally each year, mostly by industrialized countries (schmit, 1999). About 1- percent of this total is shipped across international boundaries, with the majority of the transfers occurring between countries in the Organization for the Economic Cooperation and Development(OECD) (Krueger, 1999).[2] In a country like the United States, some undefined portion of the total is shipped legally or illegally to underdeveloped countries. some of the reasons for industrialized countries to ship the hazardous waste to industrializing countries for disposal are the rising cost of disposing hazardous waste in the home country.[3]
Universal wastes are subject to somewhat less sringent regulatory requirements and small quantity generators of universal wastes may be classified as "conditionally exempt small quantity generators" (CESQGs) which releases them from some of the regulatory requirements for the handling and storage hazardous wastes.
Universal wastes must still be disposed of properly. (For more information, see Fact Sheet: Conditionally Exempt Small Quantity Generator)
[edit]Other hazardous wastes
The U.S. Environmental Protection Agency has other ways of regulating hazardous waste. These "rules" include:
             The "Mixture Rule" - 400 CFR Section 261-23 (incorrect citation)
applies to a mixture of a listed hazardous waste and a solid waste and states that the result of a mixture of these two wastes is regulated as a hazardous waste. Exemptions may apply in some cases.
             The "Derived-from Rule" - 40 CFR Section 261.3(b) applies to a waste that is generated from the treatment, storage or disposal of a hazardous waste (for example, the ash from the incineration of hazardous waste). Wastes "derived" in this manner may be regulated as hazardous wastes.
             The "Contained-in Rule" - - 40 CFR Section 261.3(f) applies to soil, groundwater, surface water and debris that are contaminated with a listed hazardous waste.
[edit]Exempted hazardous wastes
USEPA regulations automatically exempt certain solid wastes from being regulated as "hazardous wastes". This does not necessarily mean the wastes are not hazardous nor that they are not regulated. An exempted hazardous waste simply means that the waste is not regulated by the primary hazardous waste regulations. Many of these wastes may by regulated by different statutes and/or regulations and/or by different regulatory agencies. For example, many hazardous mining wastes are regulated via mining statutes and regulations. "Exempted" hazardous wastes include:
             Household hazardous waste (HHW); (see below)
             Agricultural wastes which are returned to the ground as fertilizer;
             Mining overburden returned to the mine site;
             Utility wastes from [coal] combustion to produce electricity;
             Oil and natural gas exploration drilling waste;
             Wastes from the extraction of beneficiation, and processing of ores and minerals, including coal;
             Cement kiln wastes;
             Wood treated with arsenic preservatives.
             Certain chromium-containing wastes (See Code of Federal Regulations Section 261.4(b))
             Recycled hazardous wastes: Some hazardous wastes that are recycled may also be exempted from hazardous waste regulations.
[edit]Household Hazardous Waste
Household Hazardous Waste (HHW) (also referred to as domestic hazardous waste) is waste that is generated from residential households. HHW only applies to wastes that are the result of the use of materials that are labeled for and sold for "home use".
The following list includes categories often applied to HHW. It is important to note that many of these categories overlap and that many household wastes can fall into multiple categories:
             Paints and solvents
             Automotive wastes (used motor oil, antifreeze, etc.)
             Pesticides (insecticides, herbicides, fungicides, etc.)
             Mercury-containing wastes (thermometers, switches, fluorescent lighting, etc)
             Electronics (computers, televisions, cell phones)
             Aerosols / Propane cylinders
             Caustics / Cleaning agents
             Refrigerant-containing appliances
             Some specialty Batteries (e.g. lithium, nickel cadmium, or button cell batteries)
             Radioactive waste (some home smoke detectors are classified as radioactive waste because they contain very small amounts of a radioactive isotope of americium (see: Disposing of Smoke Detectors).
Disposal of HHW in the United States
Because of the expense associated with the disposal of HHW, it is still legal for most homeowners in the U.S. to dispose of most types of household hazardous wastes as municipal solid waste (MSW) and these wastes can be put in your trash. Laws vary by state and municipality and they are changing every day. Be sure to check with your local environmental regulatory agency, solid waste authority, or health department to find out how HHW is managed in your area.
Modern landfills are designed to handle normal amounts of HHW and minimize the environmental impacts. However, there are still going to be some impacts and there are many ways that homeowners can keep these wastes out of landfills.[4]
Laws regulating HHW in the U.S. are gradually becoming more strict. As of 2007, radioactive smoke detectors are the only HHW that are managed nationally. While it is still legal in the United States to dispose of smoke detectors in your trash in most places, manufacturers of smoke detectors must accept returned units for disposal as mandated by the Nuclear Regulatory law 10 CFR 32.27. If you send your detector back to a manufacturer then it will be disposed in a nuclear waste facility.
In the U.S., states are regulating various HHW waste disposal in MSW landfills on a state by state basis. Some commonly regulated wastes in some (but not all) states include restrictions on the disposal of:
             Recyclables (especially "source-separated" recyclables or recyclables that have already been separated from solid waste). In this case this would only apply to household hazardous wastes that have been separated for recycling.
             Lead-acid batteries
             Mercury-containing wastes
             Rechargeable batteries
             Cathode ray tubes (CRTs) from older computer monitors and televisions
             Cell phones and computers
             Refrigerant containing appliances such as a refrigerator, air conditioner or dehumidifier.
(Note: Yard waste or "green waste" (particularly "source-separated" yard waste such as from a city leaf collection program) is not hazardous but may be a regulated household waste)
Local solid waste authorities and health departments may also have specific bans on wastes that apply to their service area.
Solid Waste Haulers and HHW - One "catch-22" that residents often encounter is that while it may be legal to dispose of some HHW in their regular trash, the waste hauler that collects the trash can choose not to haul the waste. It is not uncommon for a waste hauler to refuse to pick up municipal solid waste that contains things like paint and fluorescent light bulbs. There is often little recourse for residents in this case. In these cases the resident may have to make their own arrangements to dispose of the waste by taking it directly to a landfill or solid waste transfer station.
From Wikipedia, the free encyclopedia
For other uses, see Smog (disambiguation).

Smog in New York City as viewed from the World Trade Center in 1988

German road sign, Verkehrsverbot bei Smog (No traffic allowed in smog conditions)
Smog is a type of air pollution; the word "smog" is a blend of smoke and fog. Modern smog is a type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes that react in the atmosphere with sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog. Smog is also caused by large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide.
             1 Origin of term
             2 Photochemical smog
             3 Health effects
             4 Areas affected
o             4.1 London
o             4.2 Mexico City
o             4.3 Tehran
o             4.4 United States
             4.4.1 Los Angeles and the San Joaquin Valley
             4.4.2 Major incidents in the US
             5 Southeast Asia
             6 Natural causes
             7 Pollution index
             8 Cultural references
             9 See also
             10 References
             11 External links
[edit]Origin of term
Coinage of the term "smog" is generally attributed to Dr. Henry Antoine Des Voeux in his 1905 paper, "Fog and Smoke" for a meeting of thePublic Health Congress. The July 26, 1905 edition of the London newspaper Daily Graphic quoted Des Voeux, "He said it required no science to see that there was something produced in great cities which was not found in the country, and that was smoky fog, or what was known as 'smog.'"[1] The following day the newspaper stated that "Dr. Des Voeux did a public service in coining a new word for the London fog." "Smog" also appears in a January 19, 1893, Los Angeles Times article and is attributed to "a witty English writer."
[edit]Photochemical smog

Smog in the Syrian city of Aleppo, summer 2006
In the 1950s a new type of smog, known as photochemical smog, was first described.
This forms when sunlight hits various pollutants in the air and forms a mix of inimical chemicals that can be very dangerous. A photochemical smog is the chemical reaction of sunlight, nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the atmosphere, which leaves airborne particles (called particulate matter) and ground-level ozone.[2]
Nitrogen oxides are released by nitrogen and oxygen in the air reacting together under high temperature such as in the exhaust of fossil fuel-burning engines in cars, trucks, coal power plants, and industrial manufacturing factories. VOCs are released from man-made sources such as gasoline (petrol), paints, solvents, pesticides, and biogenic sources, such as pine and citrus tree emissions.
This noxious mixture of air pollutants can include the following:
             Aldehydes (RCHO)
             Nitrogen oxides, such as nitrogen dioxide
             Peroxyacyl nitrates (PAN)
             Tropospheric ozone
             Volatile organic compounds (VOCs)
All of these chemicals are usually highly reactive and oxidizing. Photochemical smog is therefore considered to be a problem of modern industrialization. It is present in all modern cities, but it is more common in cities with sunny, warm, dry climates and a large number of motor vehicles.[3] Because it travels with the wind, it can affect sparsely populated areas as well.

Characteristic coloration for smog in California in the beige cloud bank behind Golden Gate Bridge. The brown coloration is due to the NOx in the photochemical smog.
[edit]Health effects

Highland Park Optimist Club wearing smog-gas masks at banquet, Los Angeles, circa 1954
Smog is a serious problem in many cities and continues to harm human health.[4] Ground-level ozone, sulfur dioxide, nitrogen dioxide and carbon monoxide are especially harmful for senior citizens, children, and people with heart and lung conditions such as emphysema, bronchitis, andasthma.[5] It can inflame breathing passages, decrease the lungs' working capacity, cause shortness of breath, pain when inhaling deeply, wheezing, and coughing. It can cause eye and nose irritation and it dries out the protective membranes of the nose and throat and interferes with the body's ability to fight infection, increasing susceptibility to illness. Hospital admissions and respiratory deaths often increase during periods when ozone levels are high.[6]
The U.S. EPA has developed an Air Quality Index to help explain air pollution levels to the general public. 8 hour average ozone concentrations of 85 to 104 ppbv are described as "Unhealthy for Sensitive Groups", 105 ppbv to 124 ppbv as "unhealthy" and 125 ppb to 404 ppb as "very unhealthy".[7] The "very unhealthy" range for some other pollutants are: 355 μg m−3 - 424 μg m−3for PM10; 15.5 ppm - 30.4ppm for CO and 0.65 ppm - 1.24 ppm for NO2.[8]
The Ontario Medical Association announced that smog is responsible for an estimated 9,500 premature deaths in the province each year.[9]
A 20-year American Cancer Society study found that cumulative exposure also increases the likelihood of premature death from a respiratory disease, implying the 8-hour standard may be insufficient.[10]
[edit]Areas affected

Beijing air on a day after rain (left) and a smoggy day (right)
Smog can form in almost any climate where industries or cities release large amounts of air pollution, such as smoke or gases. However, it is worse during periods of warmer, sunnier weather when the upper air is warm enough to inhibit vertical circulation. It is especially prevalent in geologic basins encircled by hills or mountains. It often stays for an extended period of time over densely populated cities or urban areas, such as London, Atlanta, Houston, Phoenix, Las Vegas,New Delhi, New York, Cairo, Los Angeles, Sacramento, São Paulo, Mexico City, Santiago of Chile, Toronto, Athens, Beijing, Shanghai, Manila, Hong Kong, Seoul, the Randstad or Ruhr Areaand can build up to dangerous levels.

Victorian London was notorious for its thick smogs, or "pea-soupers", a fact that is often recreated to add an air of mystery to a period costume drama
In 1306, concerns over air pollution were sufficient for Edward I to (briefly) ban coal fires in London.[11] In 1661, John Evelyn's Fumifugium suggested burning fragrant wood instead of mineral coal, which he believed would reduce coughing. The Ballad of Gresham College the same year describes how the smoke "does our lungs and spirits choke, Our hanging spoil, and rust our iron."
Severe episodes of smog continued in the 19th and 20th centuries and were nicknamed "pea-soupers". The Great Smog of 1952 darkened the streets of London and killed approximately 4,000 people in the short time of 4 days (a further 8,000[12] died from its effects in the following weeks and months). Initially a flu epidemic was blamed for the loss of life. In 1956 the Clean Air Actintroduced smokeless zones in the capital. Consequently, reduced sulfur dioxide levels made the intense and persistent London smog a thing of the past. It was after this the great clean-up of London began and buildings recovered their original stone façades which, during two centuries, had gradually blackened. Smog caused by traffic pollution, however, does occur in modern London.
[edit]Mexico City
Due to its location in a highland "bowl", cold air sinks down onto the urban area of Mexico City, trapping industrial and vehicle pollution underneath, and turning it into the most infamously smog-plagued city of Latin America. Within one generation, the city has changed from being known for some of the cleanest air of the world into one with some of the worst pollution, with pollutants likenitrogen dioxide being double or even triple international standards.[13]
In December 2005, schools and public offices had to close in Tehran, Iran and 1600 people were taken to hospital, in a severe smog blamed largely on unfiltered car exhaust.[14]
[edit]United States

A NASA astronaut photograph of a smog layer over central New York.

Counties in the United States where one or more National Ambient Air Quality Standards are not met, as of June 2007.
The United States Environmental Protection Agency has designated over 300 U.S. counties to be non-attainment areas for one or more pollutants tracked as part of the National Ambient Air Quality Standards.[15] These areas are largely clustered around large metropolitan areas, with the largest contiguous non-attainment zones in California and the Northeast. Various U.S. and Canadian government agencies collaborate to produce real-time air quality maps and forecasts.[16]
[edit]Los Angeles and the San Joaquin Valley
Being in low basins surrounded by mountains, Los Angeles and the San Joaquin Valley are notorious for their smog. The millions of vehicles in these basins plus the added effects of the San Francisco Bay and Los Angeles/Long Beach port complexes contribute to further air pollution. While strict regulations by the multiple California government agencies overseeing this problem have reduced the number of Stage 1 smog alerts from several hundred annually to just a few, these geologically predisposed entrapment zones collect pollution levels from cars, trucks and fixed sources which still exceeds health standards and is a pressing issue for the more than 25 million people who live there.
[edit]Major incidents in the US
             1948, October 30–31, Donora, PA: 20 died, 600 hospitalized, thousands more stricken. Lawsuits were not settled until 1951.[17]
             1953, November, New York: Smog kills between 170 and 260 people.[17]
             1954, October, Los Angeles: heavy smog shuts down schools and industry for most of the month.[17]
             1963, New York: blamed for 200 deaths [18]
             1966, New York: blamed for 169 deaths [18]
[edit]Southeast Asia
See also: Asian brown cloud

Singapore's Downtown Core on 7 October 2006, when it was affected byforest fires in Sumatra, Indonesia
Smog is a regular problem in Southeast Asia caused by land and forest fires in Indonesia, especially Sumatra and Kalimantan, although the less political term haze is preferred in describing the problem. Farmers and plantation owners are usually responsible for the fires, which they use to clear tracts of land for further plantings. Those fires mainly affect Brunei, Indonesia, Philippines,Malaysia, Singapore and Thailand, and occasionally Guam and Saipan.[19][20] The economic losses of the fires in 1997 have been estimated at more than US$9 billion.[21] This includes damages in agriculture production, destruction of forest lands, health, transportation, tourism, and other economic endeavours. Not included are social, environmental, and psychological problems and long-term health effects. The latest bout of haze to occur in Malaysia, Singapore and theMalacca Straits is in October 2006, and was caused by smoke from fires in Indonesia being blown across the Straits of Malacca by south-westerly winds.
The Association of Southeast Asian Nations (ASEAN) reacted and signed Agreement on Transboundary Haze Pollution, formed a Regional Haze Action Plan (RHAP) and established a co-ordination and support unit (CSU).[22] RHAP, with the help of Canada, established a monitoring and warning system for forest/vegetation fires and implemented a Fire Danger Rating System (FDRS). The Malaysian Meteorological Service (MMS)[23] has issued a daily rating since September 2003. The Indonesians have been ineffective at enforcing legal policies on errant farmers.
[edit]Natural causes
An erupting volcano can also emit high levels of sulphur dioxide, creating volcanic smog, or vog.
[edit]Pollution index

Smog in São Paulo
The severity of smog is often measured using automated optical instruments such asNephelometers, as haze is associated with visibility and traffic control in ports. Haze however can also be an indication of poor air quality though this is often better reflected using accurate purpose built air indexes such as the American Air Quality Index, the Malaysian API (Air Pollution Index) and the Singaporean Pollutant Standards Index.
In hazy conditions, it is likely that the index will report the suspended particulate level. The disclosure of the responsible pollutant is mandated in some jurisdictions.
The American AQI is divided into six color coded categories. Technically AQI runs only from 0 to 500. The 301 to 500 range is categorised as hazardous and colored maroon.[24]
The Malaysian API does not have a capped value; hence its most hazardous readings can go above 500. Above 500, a state of emergency is declared in the affected area. Usually, this means that non-essential government services are suspended, and all ports in the affected area are closed. There may also be prohibitions on private sector commercial and industrial activities in the affected area excluding the food sector. So far, state of emergency rulings due to hazardous API levels were applied to the Malaysian towns of Port Klang, Kuala Selangor and the state of Sarawak during the 2005 Malaysian haze and the 1997 Southeast Asian haze.
[edit]Cultural references

Claude Monet made several trips to London between 1899 and 1901, during which he painted views of the Thames andHouses of Parliament which show the sun struggling to shine through London's smog-laden atmosphere.
             The London "pea-soupers" earned the capital the nickname of "The Smoke". Similarly,Edinburgh was known as "Auld Reekie". The smogs feature in many London novels as a motif indicating hidden danger or a mystery, perhaps most overtly in Margery Allingham's The Tiger in the Smoke (1952), but also in Dickens' Bleak House (1852):
[A]s he handed me into a fly after superintending the removal of my boxes, I asked him whether there was a great fire anywhere? For the streets were so full of dense brown smoke that scarcely anything was to be seen.
"Oh, dear no, miss," he said. "This is a London particular."
I had never heard of such a thing.
"A fog, miss," said the young gentleman.
—Charles Dickens, Bleak House
             The 1970 made-for-TV movie A Clear and Present Danger, which featured Hal Holbrook, E.G. Marshall, Joseph Campanella, Jack Albertson and Pat Hingle, was one of the first American television network entertainment programs to warn about the problem of smog and air pollution.[25] (This film is not to be confused with the 1994 film with a similar name.)
             'Smog' or 'Smoggy' has also come into use to describe a resident of Teesside (in North East England) or a supporter of Middlesbrough Football Club, due to the high concentration of chemical and heavy industry in the Teesside area. Although it has now been proven that the Teesside air is cleaner than London, Newcastle, Sunderland and many other British cities, the main source of pollution in the air is now vehicle exhaust fumes, like most urban areas.[citation needed]
             Ulrich Beck, Classic Quote by Ulrich ‘Poverty is hierarchic, smog is democratic’.[26]
             Hedorah, a monster from the Godzilla movie, Godzilla vs. Hedorah, feeds on pollution and is referred to as "The Smog Monster".
             South Park, The town of South park is beset by smug, in the episode Smug Alert!, a satirical reference to both smog and celebrities who wish to prevent environmental degradation.
             The history of smog in LA is detailed in Smogtown by Chip Jacobs and William J. Kelly (Overlook Press).[27]


Causes of rainforest destruction
                                                                                Q & A on Rainforest Animals
                                                                                                                Immediate Causes

The immediate causes of rainforest destruction are clear. The main causes of total clearance are agriculture and in drier areas, fuelwood collection. The main cause of forest degradation is logging. Mining, industrial development and large dams also have a serious impact. Tourism is becoming a larger threat to the forests.

1 Logging
Commercial logging companies cut down mature trees that have been selected for their timber. The timber trade defends itself by saying that this method of 'selective' logging ensures that the forest regrows naturally and in time, is once again ready for their 'safe' logging practices (WWF).
In most cases, this is untrue due to the nature of rainforests and of logging practices.
Large areas of rainforest are destroyed in order to remove only a few logs. The heavy machinery used to penetrate the forests and build roads causes extensive damage. Trees are felled and soil is compacted by heavy machinery, decreasing the forest's chance for regeneration.
The felling of one 'selected' tree, tears down with it climbers, vines, epiphytes and lianas. A large hole is left in the canopy and complete regeneration takes hundreds of years.
Removing a felled tree from the forest causes even further destruction, especially when it is carried out carelessly. It is believed that in many South East Asian countries 'between 45-74% of trees remaining after logging have been substantially damaged or destroyed' (WWF).
The tracks made by heavy machinery and the clearings left behind by loggers are sites of extreme soil disturbance which begin to erode in heavy rain. This causes siltation of the forests, rivers and streams. The lives and life support systems of indigenous people are disrupted as is the habitat of hundreds of birds and animals.
Little if any industrial logging of tropical forests is sustainable. The International Tropical Timber Organisation (ITTO), the body established to regulate the international trade in tropical timber, found in 1988 that the amount of sustainable logging was "on a world scale, negligible".
"Logging roads are used by landless farmers to gain access to rainforest areas. For this reason, commercial logging is considered by many to be the biggest single agent of tropical deforestation"
Apart from its direct impact, logging plays a major role in deforestation through the building of roads which are subsequently used by landless farmers to gain access to rainforest areas. These displaced people then clear the forest by slashing and burning to grow enough food to keep them and their families alive, a practice which is called subsistence farming. This problem is so widespread that Robert Repetto of the World Resources Institute ranks commercial logging as the biggest agent of tropical deforestation. This view was supported by the World Wide Fund for Nature's 1996 study, Bad Harvest?, which surveyed logging in the world's tropical forests.
Most of the rainforest timber on the international market is exported to rich countries. There, it is sold for hundreds of times the price that is paid to the indigenous people whose forests have been plundered. The timber is used in the construction of doors, window frames, crates, coffins, furniture, plywood sheets, chopsticks, household utensils and other items.

2 Agriculture - Shifted Cultivators
'Shifted cultivators' is the term used for people who have moved into rainforest areas and established small-scale farming operations. These are the landless peasants who have followed roads into already damaged rainforest areas. The additional damage they are causing is extensive. Shifted cultivators are currently being blamed for 60% of tropical forest loss (Colchester & Lohmann).
The reason these people are referred to as 'shifted' cultivators is that most of them people have been forced off their own land. For example, in Guatemala, rainforest land was cleared for coffee and sugar plantations. The indigenous people had their land stolen by government and corporations. They became 'shifted cultivators', moving into rainforest areas of which they had no previous knowledge in order to sustain themselves and their families (Colchester & Lohmann).
Large-scale agriculture, logging, hydroelectric dams, mining, and industrial development are all responsible for the dispossession of poor farmers.
"One of the primary forces pushing landless migrants into the forests is the inequitable distribution of agricultural land" (WRI 1992, Colchester & Lohmann). In Brazil, approximately 42% of cultivated land is owned by a mere 1% of the population. Landless peasants make up half of Brazil's population (WRM).
Once displaced, the 'shifted cultivators' move into forest areas, often with the encouragement of their government. In Brazil, a slogan was developed to help persuade the people to move into the forests. It read "Land without men for men without land" (WRM).
After a time, these farmers encounter the same problems as the cash crop growers. The soil does not remain fertile for long. They are forced to move on, to shift again, going further into the rainforest and destroying more and more of it.
It is evident that the shifted cultivators "have become the agents for destruction but not the cause" (Westoby 1987: Colchester). Shifted cultivators do not move into pristine areas of undisturbed rainforests. They follow roads made principally for logging operations. "Shifted cultivators are often used by the timber industry as scapegoats" (Orams and McQuire). Yet logging roads lead to an estimated 90% of the destruction caused by the slash-and-burn farmers (Martin 1991: Colchester).
Solutions: Land reform is essential if this problem is to be addressed. However, according to Colchester and Lohmann, "an enduring shift of power in favour of the peasants" is also needed for such reforms to endure (Colchester &Lohmann).

3 Agriculture - Cash Crops and Cattle Ranching
Undisturbed and logged rainforest areas are being totally cleared to provide land for food crops, tree plantations or for grazing cattle (Colchester & Lohmann). Much of this produce is exported to rich industrialised countries and in many cases, crops are grown for export while the local populace goes hungry.
Due to the delicate nature of rainforest soil and the destructive nature of present day agricultural practices, the productivity of cash crops grown on rainforest soils declines rapidly after a few years.
Monoculture plantations - those that produce only one species of tree or one type of food - on rainforest soil are examples of non-sustainable agriculture.
They are referred to as cash crops because the main reason for their planting is to make money quickly, with little concern about the environmental damage that they are causing.
Modern machinery, fertilisers and pesticides are used to maximise profits. The land is farmed intensively. In many cases, cattle damage the land to such an extent that it is of no use to cattle ranchers any more, and they move on, destroying more and more rainforest. Not only have the forests been destroyed but the land is exploited, stripped of nutrients and left barren, sustaining no-one.
Solutions:"Reducing the demand for Southern-produced agribusiness crops and alleviating the pressure from externally-financed development projects and assistance is the essential first step" (Colchester and Lohmann).

4 Fuelwood
The United Nation's Food and Agriculture Organisation estimates that '1.5 billion of the 2 billion people worldwide who rely on fuelwood for cooking and heating are overcutting forests'. This problem is worst in drier regions of the tropics. Solutions will probably involve a return to local peoples' control of the forests they depend on.

5 Large Dams
In India and South America, hundreds of thousands of hectares of forests have been destroyed by the building of hydro-electric dams. It was the dominant view that new dams had to be built or otherwise these countries would suffer an energy crisis. However, a recent study by the World Bank in Brazil has shown that 'sufficient generating capacity already exists to satisfy the expected rise in demand for power over the medium term, provided that the energy is used more efficiently' (WRM).
The construction of dams not only destroys the forest but often uproots tens of thousands of people, destroying both their land and their culture. The rates of waterborne diseases increase rapidly. Downstream ecosystems are damaged by dams which trap silt, holding back valuable nutrients. Reduced silt leads to coastal erosion. The sheer weight of water in dams has in Chile, Zimbabwe, and Greece led to earthquakes. The irrigation and industrial projects powered by dams lead to further environmental damage. Irrigation leads to salination of soils and industry leads to pollution.
Solutions: Aid organisations like the World Bank have traditionally favoured spectacular large-scale irrigation and hydro-electric projects. In all cases when such projects are proposed, there has been massive opposition from local people. Reform of the World Bank and other such organisations, and support for campaigns against large-scale dams is needed.

6 Mining and Industry
Mining and industrial development lead to direct forest loss due to the clearing of land to establish projects. Indigenous people are displaced. Roads are constructed through previously inaccessible land, opening up the rainforest. Severe water, air and land pollution occurs from mining and industry.
Solutions: Local campaigns against mining and industrial development, and the campaigns to reform the large aid agencies which fund such schemes, should be supported.

7 Colonisation Schemes
Governments and international aid agencies for a time believed that by encouraging colonisation and trans-migration schemes into rainforest areas, they could alleviate some of the poverty felt by the people of the financially poorer countries. It has since become increasingly obvious that such schemes have failed, hurting the indigenous people and the environment (Colchester & Lohmann).
These schemes involve the relocation of millions of people into sparsely populated and forested areas. In Indonesia, the Transmigrasi Program, begun in 1974, is believed to be 'the greatest cause of forest loss in Indonesia', directly causing an average annual loss of 200,000 hectares (Colchester & Lohmann).
The resettled people suffered the same problems as 'shifted cultivators'. The soil is not fertile enough to be able to sustain them for very long.
Even after such projects have officially ended, the flow of 'shifted cultivators' continues as the area remains opened up. "The World Bank estimates that for every colonist resettled under the official transmigration project, two or more unofficially move into the forest due to the drawing effect of the program" (Colchester & Lohmann).

8 Tourism
The creation of national parks has undoubtedly helped to protect rainforests. Yet, as national parks are open to the public, tourism is damaging some of these areas.
Often, national parks are advertised to tourists before adequate management plans have been developed and implemented. Inadequate funding is allocated for preservation of forests by government departments. Governments see tourism as an easy way to make money, and therefore tourism is encouraged whilst strict management strategies are given far less government support.
Ecotourism, or environmentally friendly tourism, should educate the tourists to be environmentally aware. It should also be of low impact to its environment. Unfortunately, many companies and resorts who advertise themselves as eco-tourist establishments are in fact exploiting the environment for profit.
In Cape Tribulation, Australia, for example, the rainforest is being threatened by excessive tourism. Clearing for roads and pollution of waterways are two of the major problems in this area. The Wet Tropics Management Authority which oversees the surrounding World Heritage Area is promoting tourism to the area before any management plans have been formulated, before any effective waste management strategy has been devised and before any ecofriendly power alternatives have been fully explored.  
From Wikipedia, the free encyclopedia
For other uses, see Rainforest (disambiguation).

The Daintree Rainforest in Queensland,Australia.

The Daintree Rainforest near Cairns, inQueensland, Australia.

Part of the Illawarra Brush, in New South Wales, Australia.
Rainforests are forests characterized by high rainfall, with definitions setting minimum normal annual rainfall between 1750–2000 mm (68-78 inches). The monsoon trough, alternately known as the intertropical convergence zone, plays a significant role in creating Earth's tropical rain forests.
A total of 40 to 75% of all species on the world's habitats are indigenous to the rainforests.[1] It has been estimated that many millions of species of plants, insects, and microorganisms are still undiscovered. Tropical rainforests have been called the "jewels of the Earth", and the "world's largest pharmacy", because over one quarter of natural medicines have been discovered there.[2]Rainforests are also responsible for 28% of the world's oxygen turn over, often misunderstood as oxygen production,[3] processing it through photosynthesis from carbon dioxide and storing it ascarbon through biosequestration.
The undergrowth in a rainforest is restricted in many areas by the lack of sunlight at ground level. This makes it possible to walk through the forest. If the leaf canopy is destroyed or thinned, the ground beneath is soon colonized by a dense, tangled growth of vines, shrubs, and small treescalled a jungle. There are two types of rainforest, tropical rainforest and temperate rainforest.

General distribution of tropical rainforest
Main article: Tropical rainforest
Many of the world's rainforests are associated with the location of the monsoon trough, also known as the intertropical convergence zone.[4] Tropical rainforests are rainforests in the tropics, found near the Equator (between the Tropic of Cancer and Tropic of Capricorn) and present in Southeast Asia (Myanmar to Philippines, Indonesia, Papua New Guinea, and northeastern Australia), Sri Lanka, Sub-Saharan Africa from Cameroon to the Congo (Congo Rainforest), South America (e.g. the Amazon Rainforest), Central America (e.g. Bosawás, southern Yucatán Peninsula-El Peten-Belize-Calakmul), and on many of the Pacific Islands (such as Hawaiʻi). Tropical rainforests have been called the "Earth's lungs," although it is now known that rainforests contribute little netoxygen additions to the atmosphere through photosynthesis.[5][6]


General distribution of temperate rainforest.
Main article: Temperate rainforest
Temperate rainforests are rainforests in temperate regions. They can be found in North America(in the Pacific Northwest, the British Columbia Coast, and in the inland rainforest of the Rocky Mountain Trench east of Prince George), in Europe (parts of the British Isles such as the coastal areas of Ireland, Scotland, southern Norway, parts of the western Balkans along the Adriaticcoast, as well as in the North West of Spain and coastal areas of the eastern Black Sea, includingGeorgia and coastal Turkey), in East Asia (in southern China, Taiwan, much of Japan and Korea, and on Sakhalin Island and the adjacent Russian Far East coast), in South America (southernChile) and also Australia and New Zealand.

A tropical rainforest is typically divided into four main layers, each with different plants and animals adapted for life in that particular area: the emergent, canopy, understory, and forest floor layers.
Emergent layer
The emergent layer contains a small number of very large trees called emergents, which grow above the general canopy, reaching heights of 45–55 m, although on occasion a few species will grow to 70–80 m tall.[7][8] They need to be able to withstand the hot temperatures and strong winds in some areas. Eagles, butterflies, bats, and certain monkeys inhabit this layer.

The canopy at the Forest Research Institute Malaysia
Canopy layer
Main article: Canopy (ecology)
The canopy layer contains the majority of the largest trees, typically 30–45 m tall. The densest areas of biodiversity are found in the forest canopy, a more or less continuous cover of foliage formed by adjacent treetops. The canopy, by some estimates, is home to 50 percent of all plant species, suggesting that perhaps half of all life on Earth could be found there. Epiphytic plantsattach to trunks and branches, and obtain water and minerals from rain and debris that collects on the supporting plants. The fauna is similar to that found in the emergent layer, but more diverse. A quarter of all insect species are believed to exist in the rainforest canopy. Scientists have long suspected the richness of the canopy as a habitat, but have only recently developed practical methods of exploring it. As long ago as 1917, naturalist William Beebe declared that "another continent of life remains to be discovered, not upon the Earth, but one to two hundred feet above it, extending over thousands of square miles." True exploration of this habitat only began in the 1980s, when scientists developed methods to reach the canopy, such as firing ropes into the trees using crossbows. Exploration of the canopy is still in its infancy, but other methods include the use of balloons and airships to float above the highest branches and the building of cranes and walkways planted on the forest floor. The science of accessing tropical forest canopy using airships, or similar aerial platforms, is called dendronautics.[9]
Understory layer
Main article: Understory
The understory layer lies between the canopy and the forest floor. The understory (or understorey) is home to a number of birds, snakes, and lizards, as well as predators such as jaguars, boa constrictors, and leopards. The leaves are much larger at this level. Insect life is also abundant. Many seedlings that will grow to the canopy level are present in the understory. Only about 5% of the sunlight shining on the rainforest reaches the understory. This layer can also be called a shrub layer, although the shrub layer may also be considered a separate layer.
Forest floor

Rainforest in the Blue Mountains, Australia
The forest floor, the bottom-most layer, receives only 2% of sunlight. Only plantsadapted to low light can grow in this region. Away from riverbanks, swamps, and clearings where dense undergrowth is found, the forest floor is relatively clear of vegetation because of the low sunlight penetration. It also contains decaying plant and animal matter, which disappears quickly due to the warm, humid conditions promoting rapid decay. Many forms of fungi grow here which help decay the animal and plant waste.
Flora and fauna

West Usambara Two-Horned Chameleon (Bradypodion fischeri) in the Usambara Mountains,Tanzania.
More than half of the world's species of plants and animals are found in the rainforest.[10] Rainforests support a very broad array of fauna including mammals, reptiles, birds, and invertebrates. Mammals may include primates, felids, and other families. Reptiles include snakes, turtles, chameleons, and other families while birds include such families as vangidae and Cuculidae. Dozens of families of invertebrates are found in rainforests. Fungi are also very common in rainforest areas as they can feed on the decomposing remains of plant and animal life. These species are rapidly disappearing due to deforestation, habitat loss, and biochemical releases into the atmosphere.[11]
                This section requires expansion.
Despite the growth of vegetation in a tropical rainforest, soil quality is often quite poor. Rapid bacterialdecay prevents the accumulation of humus. The concentration of iron and aluminium oxides by the laterization process gives the oxisols a bright red color and sometimes produces minable deposits such as bauxite. Most trees have roots near the surface as there are not many nutrients below the ground; most of the trees minerals come from the top layer of decomposing leaves (mainly) and animals. On younger substrates, especially of volcanic origin, tropical soils may be quite fertile. If the trees are cleared, the rain can get at the exposed soil, washing it away. Eventually streams will form, then rivers. Flooding becomes possible.
Effect on global climate
A natural rainforest emits and absorbs vast quantities of carbon dioxide. On a global scale, long-term fluxes are approximately in balance, so that an undisturbed rainforest would have a small net impact on atmospheric carbon dioxide levels,[12] though they may have other climatic effects (on cloud formation, for example, by recycling water vapor). No rainforest today can be considered to be undisturbed.[13] Human induced deforestation plays a significant role in causing rainforests to release carbon dioxide,[14] as do natural processes such as droughtthat result in tree death.[15] Some climate models run with interactive vegetation and predict a large loss of Amazonian rainforest around 2050 due to drought, leading to forest dieback and the subsequent feedback of releasing more carbon dioxide.[16] Five million years from now, the Amazon rainforest will have long since dried and transformed itself into a savannah; killing itself in the progress (even if all human deforestation activity ceases overnight).[17] The descendants of our known animals will adapt to the dry savannah of the former Amazonian rainforest and thrive in the new, warmer temperatures.[17]
Human uses

Amazon River rain forest in Peru
Main article: Tropical rainforest#Human uses
Tropical rainforests provide timber as well as animal products such as meat and hides. Rainforests also have value as tourism destinations and for the ecosystem services provided. Many foods originally came from tropical forests, and are still mostly grown on plantations in regions that were formerly primary forest.[18] Also, plant derived medicines are commonly used for fever, fungal infections, burns, gastrointestinal problems, pain, respiratory problems, and wound treatment.[19]
Native peoples
                This section requires expansion.
On January 18, 2007, FUNAI reported that it had confirmed the presence of 67 differentuncontacted tribes in Brazil, up from 40 in 2005. With this addition, Brazil has now overtaken the island of New Guinea as the country having the largest number of uncontacted tribes.[20] The province of Irian Jaya or West Papua in the island of New Guinea is home to an estimated 44 uncontacted tribal groups.[21]
Central African rainforest is home of the Mbuti pygmies, one of the hunter-gatherer peoples living in equatorial rainforests characterised by their short height (below one and a half metres, or 59 inches, on average). They were the subject of a study by Colin Turnbull, The Forest People, in 1962.[22] Pygmies who live in Southeast Asia are, amongst others, referred to as “Negritos.”
Main article: Deforestation

Jungle burned for agriculture in southernMexico.
Tropical and temperate rainforests have been subjected to heavy logging and agricultural clearance throughout the 20th century and the area covered by rainforests around the world is shrinking.[23]Biologists have estimated that large numbers of species are being driven to extinction (possibly more than 50,000 a year; at that rate, says E. O. Wilson of Harvard University, a quarter or more of all species on Earth could be exterminated within 50 years)[24] due to the removal of habitat with destruction of the rainforests.
Another factor causing the loss of rainforest is expanding urban areas. Littoral rainforest growing along coastal areas of eastern Australia is now rare due to ribbon development to accommodate the demand for seachange lifestyles.[25]
The forests are being destroyed at a rapid pace.[26][27][28] Almost 90% of West Africa's rainforest has been destroyed.[29] Since the arrival of humans 2000 years ago, Madagascar has lost two thirds of its original rainforest.[30] At present rates, tropical rainforests in Indonesia would be logged out in 10 years and Papua New Guinea in 13 to 16 years.[31]
Several countries,[32] notably Brazil, have declared their deforestation a national emergency.[33] Amazon deforestation jumped by 69% in 2008 compared to 2007's twelve months, according to official government data.[34] Deforestation could wipe out or severely damage nearly 60% of the Amazon Rainforest by 2030, says a new report from WWF.[35]

At Calakmul, Campeche, Mexico.
However, a January 30, 2009 New York Times article stated, "By one estimate, for every acre of rain forest cut down each year, more than 50 acres of new forest are growing in the tropics..." The new forest includes secondary forest on former farmland and so-called degraded forest.[36]
From a new recent report in September 2009, new opportunities are beginning to discover they could save the rainforest. In Brazil, Environment Minister Carlos Minc announced proudly that the rate of deforestation of the Amazon fell by 46 percent last year. That means the lowest logging level since the country began to keep annual statistics 21 years ago. But not only Brazil has reduced deforestation as a whole also slowed the loss of forest down. The annual decline is now over two thousand. Deforestation decreases in a country as it becomes richer and more industrialized. Therefore, there are exceptions in a group of countries where deforestation has become so profitable that it is an important part in the growth of prosperity. New goal is to stop felling the forest, but also in managing the forest long-term, which occurs on a larger scale. More police officers guarding the rainforest, and stifle the illegal logging.[37]

From Wikipedia, the free encyclopedia
This article is about overpopulation in humans. For other uses, see Overpopulation in wild animals and Overpopulation in companion animals.
                This article may require cleanup to meet Wikipedia's quality standards. Please improve this article if you can. (March 2010)

Map of countries by population density, per square kilometer. (SeeList of countries by population density.)

Areas of high population densities, calculated in 1994.

Map of countries and territories by fertility rate (See List of countries and territories by fertility rate.)

Human population growth rate in percent, with the variables ofbirths, deaths, immigration, and emigration - 2006
Overpopulation is a condition where an organism's numbers exceed thecarrying capacity of its habitat. In common parlance, the term often refers to the relationship between the human population and its environment, theEarth.[1]
Overpopulation does not depend only on the size or density of the population, but on the ratio of population to available sustainable resources. It also depends on the way resources are used and distributed throughout the population. Overpopulation can result from an increase in births, a decline in mortality rates due to medical advances, from an increase inimmigration, or from an unsustainable biome and depletion of resources. It is possible for very sparsely populated areas to be overpopulated, as the area in question may have a meager or non-existent capability to sustain human life (e.g. a desert).
The resources to be considered when evaluating whether an ecologicalniche is overpopulated include clean water, clean air, food, shelter, warmth, and other resources necessary to sustain life. If the quality of human life is addressed, there may be additional resources considered, such as medical care, education, proper sewage treatment and waste disposal. Overpopulation places competitive stress on the basic life sustaining resources,[2] leading to a diminished quality of life.[3]
The recent rapid increase in human population over the past two centuries has raised concerns that humans are beginning to overpopulate the Earth, and that the planet may not be able to sustain present or larger numbers of inhabitants. The population has been growing continuously since the end of the Black Death, around the year 1400;[4] at the beginning of the nineteenth century, it had reached roughly 1,000,000,000 (1 billion). Increases in life expectancy and resource availability during the industrial and green revolutions led to rapid population growth on a worldwide level. By 1960, the world population had reached 3 billion; it doubled to 6 billion over the next four decades. As of 2009, the estimated annual growth rate was 1.10%, down from a peak of 2.2% in 1963, and the world population stood at roughly 6.7 billion. Current projections show a steady decline in the population growth rate, with the population expected to reach between 8 and 10.5 billion between the year 2040[5][6] and 2050.[7]
The scientific consensus is that the current population expansion and accompanying increase in usage of resources is linked to threats to theecosystem. The InterAcademy Panel Statement on Population Growth, which was ratified by 58 member national academies in 1994, called the growth in human numbers "unprecedented", and stated that many environmental problems, such as rising levels of atmospheric carbon dioxide, global warming, and pollution, were aggravated by the population expansion.[8] At the time, the world population stood at 5.5 billion, and optimistic scenarios predicted a peak of 7.8 billion by 2050, a number that current estimates show will be reached around 2030.[9]
[edit]Population growth

[edit]History of overpopulation concern
Concern about booming population increase is of comparatively recent origin. In the 18th century intellectuals like Thomas Malthus, began raising the subject. For most of world history, mankind was more concerned with increasing its numbers. Populations grew slowly despite high birth rates, because of war, plagues and high infant mortality.
During the 750 years before the Industrial Revolution, the world's population hardly increased. George Moffett, author of "Critical Masses: The Global Population Challenge" (1994), states that the world's population remained under 250 million throughout most of history, "capped by birth rates and death rates locked in a seemingly permanent equilibrium."
Early 21st century, more than 250 million people are added to the world's population every three years, and the billion people of Malthus's day have swelled to 5.6 billion.
In economic theory. the physiocrats predicted that mankind would outgrow its resources: given the finite amount of land, it would not be able to support an endlessly increasing population. The mercantillists argued that a large population was a form of wealth, making it possible to create bigger markets and armies.
[edit]History of the world population
The human population has gone through a number of periods of different growth rates since the dawn of civilization in the Holocene period, roughly 10,000 years ago.
             The beginning of civilization coincides with the final receding of ice following the end of the most recent glacial period[citation needed].
             This in turn coincides with the start of the Neolithic Revolution, when there was a shift in human activity away from hunter-gathering and towards very primitive farming[citation needed].
             Around 8000 BC, at the dawn of agriculture, the population of the world was approximately 5 million.[10]
             For around 7,000 years, there was minimal change in the world population[citation needed].
             Beginning around 1000 BC, there was steady growth in the population, which plateaued (or alternatively, peaked[11]) at around 1 BC, at about 200 to 300 million people.
             From around 800 AD onwards, the population once again grew steadily, though with major disruption from frequent plagues, most notably the Black Death during the 14th century.[12]
             After the effects of the plagues had subsided during the 17th century, shortly before the Industrial Revolution, the world population began to grow once again. In parts of Asia, like China, the population doubled from 60 to 150 million under the Ming dynasty[citation needed].
             After the start of the Industrial Revolution, during the 18th century, the rate of population growth began to increase. By the end of the century, the world's population was estimated at just under 1 billion.[13]
             At the turn of the 20th century, the world's population was roughly 1.6 billion.[13] By 1940, this figure had increased to 2.3 billion[citation needed].
             Dramatic growth beginning in 1950 (above 1.8% per year) coincided with greatly increased food production as a result of the industrialisation of agriculture brought about by the Green Revolution.[14] The rate of growth peaked in 1964, at about 2.2% per year.
             The world population is currently estimated to be 6,860,900,000, with unreported variability.[15]
             Africa - 133 million
             Asia - 946 million
             Europe - 408 million
             Latin America & Caribbean - 74 million
             North America - 82 million[16]
[edit]Projections to 2050
According to projections, the world population will continue to grow until at least 2050, with the population reaching 9 billion in 2040,[17][18]and some predictions putting the population in 2050 as high as 11 billion.[19]
According to the United Nation's World Population Prospects report:[20]
             The world population is currently growing by approximately 74 million people per year. Current United Nations predictions estimate that the world population will reach 9.2 billion around 2050, assuming a decrease in average fertility rate from 2.5 down to 2.0.[21][22]
             Almost all growth will take place in the less developed regions, where today’s 5.3 billion population of underdeveloped countries is expected to increase to 7.8 billion in 2050. By contrast, the population of the more developed regions will remain mostly unchanged, at 1.2 billion. An exception is the United States population, which is expected to increase 44% from 305 million in 2008 to 439 million in 2050.[23]
             In 2000-2005, the average world fertility was 2.65 children per woman, about half the level in 1950-1955 (5 children per woman). In the medium variant, global fertility is projected to decline further to 2.05 children per woman.
             During 2005-2050, nine countries are expected to account for half of the world’s projected population increase: India, Pakistan, Nigeria,Democratic Republic of the Congo, Bangladesh, Uganda, United States, Ethiopia, and China, listed according to the size of their contribution to population growth. China would be higher still in this list were it not for its One Child Policy.
             Global life expectancy at birth, which is estimated to have risen from 46 years in 1950-1955 to 65 years in 2000-2005, is expected to keep rising to reach 75 years in 2045-2050. In the more developed regions, the projected increase is from 75 years today to 82 years by mid-century. Among the least developed countries, where life expectancy today is just under 50 years, it is expected to be 66 years in 2045-2050.
             The population of 51 countries or areas, including Germany, Italy, Japan and most of the successor States of the former Soviet Union, is expected to be lower in 2050 than in 2005.
             During 2005-2050, the net number of international migrants to more developed regions is projected to be 98 million. Because deaths are projected to exceed births in the more developed regions by 73 million during 2005-2050, population growth in those regions will largely be due to international migration.
             In 2000-2005, net migration in 28 countries either prevented population decline or doubled at least the contribution of natural increase (births minus deaths) to population growth. These countries include Austria, Canada, Croatia, Denmark, Germany, Italy, Portugal, Qatar, Singapore, Spain, Sweden, United Arab Emirates and United Kingdom.[24]
             Birth rates are now falling in a small percentage of developing countries, while the actual populations in many developed countries would fall without immigration.[22]
             By 2050 (Medium variant), India will have 1.6 billion people, China 1.4 billion, United States 439 million, Pakistan 309 million, Indonesia280 million, Nigeria 259 million, Bangladesh 258 million, Brazil 245 million, Democratic Republic of the Congo 189 million, Ethiopia 185 million, Philippines 141 million, Mexico 132 million, Egypt 125 million, Vietnam 120 million, Russia 109 million, Japan 103 million, Iran 100 million, Turkey 99 million, Uganda 93 million, Tanzania 85 million, Kenya 85 million and United Kingdom 80 million.
             Africa - 1.9 billion
             Asia - 5.2 billion
             Europe - 674 million
             Latin America & Caribbean - 765 million
             North America - 448 million [16]
[edit]Demographic transition

United Nation's population projections by location.
Main articles: Demographic transition and Sub-replacement fertility
The theory of demographic transition held that, after the standard of living and life expectancy increase, family sizes and birth rates decline. However, as new data has become available, it has been observed that after a certain level of development the fertility increases again [25]. This means that both the worry the theory generated about aging populations and the complacency it bred regarding the future environmental impact of population growth are misguided.
Factors cited in the old theory included such social factors as later ages ofmarriage, the growing desire of many women in such settings to seek careersoutside child rearing and domestic work, and the decreased need of children inindustrialized settings. The latter factor stems from the fact that children perform a great deal of work in small-scale agricultural societies, and work less in industrial ones; it has been cited to explain the decline in birth rates in industrializing regions.
Another version of demographic transition is proposed by anthropologist Virginia Abernethy in her book Population Politics, where she claims that the demographic transition occurs primarily in nations where women enjoy a special status (seeFertility-opportunity theory). In strongly patriarchal nations, where she claims women enjoy few special rights, a high standard of living tends to result in population growth[citation needed].
Many countries have high population growth rates but lower total fertility rates because high population growth in the past skewed the age demographic toward a young age, so the population still rises as the more numerous younger generation approaches maturity.[original research?][citation needed]
"Demographic entrapment" is a concept developed by Maurice King, Honorary Research Fellow at the University of Leeds, who posits that this phenomenon occurs when a country has a population larger than its carrying capacity, no possibility of migration, and exports too little to be able to import food. This will cause starvation. He claims that for example many sub-Saharan nations are or will become stuck in demographic entrapment, instead of having a demographic transition.[26]
For the world as a whole, the number of children born per woman decreased from 5.02 to 2.65 between 1950 and 2005. A breakdown by continent is as follows:
             Europe 2.66 to 1.41
             North America 3.47 to 1.99
             Oceania 3.87 to 2.30
             Central America 6.38 to 2.66
             South America 5.75 to 2.49
             Asia (excluding Middle East) 5.85 to 2.43
             Middle East & North Africa 6.99 to 3.37
             Sub-Saharan Africa 6.7 to 5.53
Excluding the observed reversal in fertility decrease for high development, the projected world number of children born per woman for 2050 would be around 2.05. Only the Middle East & North Africa (2.09) and Sub-Saharan Africa (2.61) would then have numbers greater than 2.05.[27]
[edit]Carrying capacity
Main article: Carrying capacity

2008 Summer Olympics torch relay inShenzhen.
There is wide variability both in the definition and in the proposed size of the Earth's carrying capacity, with estimates ranging from less than 1 to 1000 billion (1 trillion).[28] Around two-thirds of the estimates fall in the range of 4 billion to 16 billion (with unspecified standard errors), with a median of about 10 billion.[29] However, these estimates are likely biased by present reality, and there are beliefs that the Earth has an unlimited carrying capacity.[28]
In a study titled Food, Land, Population and the U.S. Economy, David Pimentel, professor of ecology and agriculture at Cornell University, and Mario Giampietro, senior researcher at the USNational Research Institute on Food and Nutrition (INRAN), estimate the maximum U.S. population for a sustainable economy at 200 million. According to this theory, in order to achieve a sustainable economy and avert disaster, the United States would have to reduce its population by at least one-third, and world population would have to be reduced by two-thirds.[30]
Steve Jones, head of the biology department at University College London, has said, "Humans are 10,000 times more common than we should be, according to the rules of the animal kingdom, and we have agriculture to thank for that. Without farming, the world population would probably have reached half a million by now." [31]

Ozone depletion
From Wikipedia, the free encyclopedia

Image of the largest Antarctic ozone hole ever recorded (September 2006).
Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4 percent per decade in the total volume of ozone in Earth's stratosphere (the ozone layer) since the late 1970s, and a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions during the same period. The latter phenomenon is commonly referred to as the ozone hole. In addition to this well-known stratospheric ozone depletion, there are also tropospheric ozone depletion events, which occur near the surface in polar regions during spring.
The detailed mechanism by which the polar ozone holes form is different from that for the mid-latitude thinning, but the most important process in both trends is catalytic destruction of ozone by atomic chlorine and bromine.[1] The main source of these halogen atoms in the stratosphere isphotodissociation of chlorofluorocarbon (CFC) compounds, commonly called freons, and ofbromofluorocarbon compounds known as halons. These compounds are transported into the stratosphere after being emitted at the surface.[2] Both ozone depletion mechanisms strengthened as emissions of CFCs and halons increased.
CFCs and other contributory substances are commonly referred to as ozone-depleting substances(ODS). Since the ozone layer prevents most harmful UVB wavelengths (270–315 nm) of ultraviolet light (UV light) from passing through theEarth's atmosphere, observed and projected decreases in ozone have generated worldwide concern leading to adoption of the Montreal Protocol that bans the production of CFCs and halons as well as related ozone depleting chemicals such as carbon tetrachloride andtrichloroethane. It is suspected that a variety of biological consequences such as increases in skin cancer, cataracts,[3] damage to plants, and reduction of plankton populations in the ocean's photic zone may result from the increased UV exposure due to ozone depletion.
             1 Ozone cycle overview
o             1.1 Quantitative understanding of the chemical ozone loss process
             2 Observations on ozone layer depletion
o             2.1 Chemicals in the atmosphere
             2.1.1 CFCs in the atmosphere
o             2.2 Verification of observations
             3 The ozone hole and its causes
o             3.1 Interest in ozone layer depletion
             4 Consequences of ozone layer depletion
o             4.1 Increased UV
o             4.2 Biological effects
             4.2.1 Effects on humans
             4.2.2 Effects on crops
             5 Public policy
             6 Prospects of ozone depletion
             7 History of the research
o             7.1 The Rowland-Molina hypothesis
o             7.2 The ozone hole
             8 Ozone depletion and global warming
             9 Misconceptions about ozone depletion
             10 ODS requirements in the Marine industry
             11 World Ozone Day
             12 See also
             13 References
o             13.1 Nontechnical books
o             13.2 Books on public policy issues
o             13.3 Research articles
             14 External links
[edit]Ozone cycle overview

The ozone cycle
Three forms (or allotropes) of oxygen are involved in the ozone-oxygen cycle: oxygen atoms (O or atomic oxygen), oxygen gas (O2 or diatomic oxygen), and ozone gas (O3 or triatomic oxygen).Ozone is formed in the stratosphere when oxygen molecules photodissociate after absorbing anultraviolet photon whose wavelength is shorter than 240 nm. This produces two oxygen atoms. The atomic oxygen then combines with O2 to create O3. Ozone molecules absorb UV light between 310 and 200 nm, following which ozone splits into a molecule of O2 and an oxygen atom. The oxygen atom then joins up with an oxygen molecule to regenerate ozone. This is a continuing process which terminates when an oxygen atom "recombines" with an ozone molecule to make two O2 molecules: O + O3 → 2 O2

Global monthly average total ozone amount.

Layers of the atmosphere (not to scale)
The overall amount of ozone in the stratosphere is determined by a balance between photochemical production and recombination.
Ozone can be destroyed by a number of free radical catalysts, the most important of which are the hydroxyl radical (OH•), the nitric oxide radical (NO•), atomic chlorine (Cl•) and bromine (Br•). All of these have both natural and manmade sources; at the present time, most of the OH• and NO• in the stratosphere is of natural origin, but human activity has dramatically increased the levels of chlorine and bromine. These elements are found in certain stable organic compounds, especially chlorofluorocarbons (CFCs), which may find their way to the stratosphere without being destroyed in the troposphere due to their low reactivity. Once in the stratosphere, the Cl and Br atoms are liberated from the parent compounds by the action of ultraviolet light, e.g. ('h' is Planck's constant, 'ν' is frequency ofelectromagnetic radiation)
CFCl3 + hν → CFCl2 + Cl
The Cl and Br atoms can then destroy ozone molecules through a variety of catalytic cycles. In the simplest example of such a cycle,[4] a chlorine atom reacts with an ozone molecule, taking an oxygen atom with it (forming ClO) and leaving a normal oxygen molecule. The chlorine monoxide (i.e., the ClO) can react with a second molecule of ozone (i.e., O3) to yield another chlorine atom and two molecules of oxygen. The chemical shorthand for these gas-phase reactions is:
Cl + O3 → ClO + O2
ClO + O3 → Cl + 2 O2
The overall effect is a decrease in the amount of ozone. More complicated mechanisms have been discovered that lead to ozone destruction in the lower stratosphere as well.
A single chlorine atom would keep on destroying ozone (thus a catalyst) for up to two years (the time scale for transport back down to the troposphere) were it not for reactions that remove them from this cycle by forming reservoir species such as hydrogen chloride (HCl) and chlorine nitrate (ClONO2). On a per atom basis, bromine is even more efficient than chlorine at destroying ozone, but there is much less bromine in the atmosphere at present. As a result, both chlorine and bromine contribute significantly to the overall ozone depletion. Laboratory studies have shown that fluorine and iodine atoms participate in analogous catalytic cycles. However, in the Earth's stratosphere, fluorine atoms react rapidly with water and methane to form strongly bound HF, while organic molecules which contain iodine react so rapidly in the lower atmosphere that they do not reach the stratosphere in significant quantities. Furthermore, a single chlorine atom is able to react with 100,000 ozone molecules. This fact plus the amount of chlorine released into the atmosphere by chlorofluorocarbons (CFCs) yearly demonstrates how dangerous CFCs are to the environment.[5]
[edit]Quantitative understanding of the chemical ozone loss process
In 2007 research on the breakdown of a key molecule in these ozone-depleting chemicals, dichlorine peroxide (Cl2O2), also known as the ClO dimer, called into question the completeness of present atmospheric models of polar ozone depletion. The ClO dimer serves as a reservoir for chlorine in the atmosphere. As long as the chlorine is tied up in the dimer it is not available for catalytic destruction of the ozone. Photolysis of the dimer produces two ClO molecules which can participate in catalytic destruction of ozone. Chlorine Nitrate (ClONO2) is another important reservoir molecule.
Chemists at NASA's Jet Propulsion Laboratory in Pasadena, California, remeasured the absorption cross-section for the ClO dimer which they reported to be an order of magnitude lower than previously thought in the region between 300 and 350 nm.[6][7][8] This lower absorption coefficient would imply that much less chlorine is available for catalytic destruction of ozone in the stratosphere, as more of it would remain tied up in the ClO dimer.
That result motivated further measurements by different methods, resulting in cross-sections that agree with the older, higher ones resolving the discrepancy. The first report, by Chen, et al., used a new method, determining the absorption cross section by observing the loss of the dimer in a mass spectrometer as a molecular beam is exposed to a UV laser.[9]. This method has the weakness that it can only be used at wavelengths where there are strong laser sources.
There has been another, even more recent study which show that major revisions in the ozone depletion model are not necessary. In addition to making new measurements, Papanastasiou, et al., from the NOAA Earth Systems Laboratory [10] hold that the JPL group did not properly account for the uncertainty in their modeling of the cross-sections, and that when this is done correctly, the JPL error estimates would encompass the other results although the central estimate remains much smaller. Other studies are underway and should be published shortly. Preliminary results from the Anderson group at Harvard, presented at the 2009 AGU Conference support the higher absorption cross-sections. These new experiments, motivated by the JPL result have significantly improved our knowledge of the ClO dimer absorption cross-section and increased our confidence in the ozone destruction photochemical models.
[edit]Observations on ozone layer depletion
The most pronounced decrease in ozone has been in the lower stratosphere. However, the ozone hole is most usually measured not in terms of ozone concentrations at these levels (which are typically of a few parts per million) but by reduction in the total column ozone, above a point on the Earth's surface, which is normally expressed in Dobson units, abbreviated as "DU". Marked decreases in column ozone in the Antarctic spring and early summer compared to the early 1970s and before have been observed using instruments such as the Total Ozone Mapping Spectrometer (TOMS).[11]

Lowest value of ozone measured by TOMSeach year in the ozone hole.
Reductions of up to 70% in the ozone column observed in the austral (southern hemispheric) spring over Antarctica and first reported in 1985 (Farman et al. 1985) are continuing.[12]Through the 1990s, total column ozone in September and October have continued to be 40–50% lower than pre-ozone-hole values. In the Arctic the amount lost is more variable year-to-year than in the Antarctic. The greatest declines, up to 30%, are in the winter and spring, when the stratosphere is colder.
Reactions that take place on polar stratospheric clouds (PSCs) play an important role in enhancing ozone depletion.[13] PSCs form more readily in the extreme cold of Antarctic stratosphere. This is why ozone holes first formed, and are deeper, over Antarctica. Early models failed to take PSCs into account and predicted a gradual global depletion, which is why the sudden Antarctic ozone hole was such a surprise to many scientists.[citation needed]
In middle latitudes it is preferable to speak of ozone depletion rather than holes. Declines are about 3% below pre-1980 values for 35–60°N and about 6% for 35–60°S. In the tropics, there are no significant trends.[14]
Ozone depletion also explains much of the observed reduction in stratospheric and upper tropospheric temperatures.[15][16] The source of the warmth of the stratosphere is the absorption of UV radiation by ozone, hence reduced ozone leads to cooling. Some stratospheric cooling is also predicted from increases in greenhouse gases such as CO2; however the ozone-induced cooling appears to be dominant.[citation needed]
Predictions of ozone levels remain difficult. The World Meteorological Organization Global Ozone Research and Monitoring Project—Report No. 44 comes out strongly in favor for the Montreal Protocol, but notes that a UNEP 1994 Assessment overestimated ozone loss for the 1994–1997 period.
[edit]Chemicals in the atmosphere
[edit]CFCs in the atmosphere
Chlorofluorocarbons (CFCs) were invented by Thomas Midgley in the 1920s. They were used in air conditioning/cooling units, as aerosol spray propellants prior to the 1980s, and in the cleaning processes of delicate electronic equipment. They also occur as by-products of some chemical processes. No significant natural sources have ever been identified for these compounds — their presence in the atmosphere is due almost entirely to human manufacture. As mentioned in the ozone cycle overview above, when such ozone-depleting chemicals reach the stratosphere, they are dissociated by ultraviolet light to release chlorine atoms. The chlorine atoms act as a catalyst, and each can break down tens of thousands of ozone molecules before being removed from the stratosphere. Given the longevity of CFC molecules, recovery times are measured in decades. It is calculated that a CFC molecule takes an average of 15 years to go from the ground level up to the upper atmosphere, and it can stay there for about a century, destroying up to one hundred thousand ozone molecules during that time.[17]
[edit]Verification of observations
Scientists have been increasingly able to attribute the observed ozone depletion to the increase of man-made (anthropogenic) halogencompounds from CFCs by the use of complex chemistry transport models and their validation against observational data (e.g. SLIMCAT,CLaMS). These models work by combining satellite measurements of chemical concentrations and meteorological fields with chemical reaction rate constants obtained in lab experiments. They are able to identify not only the key chemical reactions but also the transport processes which bring CFC photolysis products into contact with ozone.
[edit]The ozone hole and its causes

Ozone hole in North America during 1984 (abnormally warm reducing ozone depletion) and 1997 (abnormally cold resulting in increased seasonal depletion). Source: NASA[18]
The Antarctic ozone hole is an area of the Antarctic stratosphere in which the recent ozone levels have dropped to as low as 33% of their pre-1975 values. The ozone hole occurs during the Antarctic spring, from September to early December, as strong westerly winds start to circulate around the continent and create an atmospheric container. Within this polar vortex, over 50% of the lower stratospheric ozone is destroyed during the Antarctic spring.[19]
As explained above, the primary cause of ozone depletion is the presence of chlorine-containing source gases (primarily CFCs and related halocarbons). In the presence of UV light, these gases dissociate, releasing chlorine atoms, which then go on to catalyze ozone destruction. The Cl-catalyzed ozone depletion can take place in the gas phase, but it is dramatically enhanced in the presence of polar stratospheric clouds(PSCs).[20]
These polar stratospheric clouds(PSC) form during winter, in the extreme cold. Polar winters are dark, consisting of 3 months without solar radiation (sunlight). The lack of sunlight contributes to a decrease in temperature and the polar vortex traps and chills air. Temperatures hover around or below -80 °C. These low temperatures form cloud particles. There are three types of PSC clouds; nitric acid trihydrate clouds, slowly cooling water-ice clouds, and rapid cooling water-ice(nacerous) clouds; that provide surfaces for chemical reactions that lead to ozone destruction.[21]
The photochemical processes involved are complex but well understood. The key observation is that, ordinarily, most of the chlorine in the stratosphere resides in stable "reservoir" compounds, primarily hydrochloric acid (HCl) and chlorine nitrate (ClONO2). During the Antarctic winter and spring, however, reactions on the surface of the polar stratospheric cloud particles convert these "reservoir" compounds into reactive free radicals (Cl and ClO). The clouds can also remove NO2 from the atmosphere by converting it to nitric acid, which prevents the newly formed ClO from being converted back into ClONO2.

The role of sunlight in ozone depletion is the reason why the Antarctic ozone depletion is greatest during spring. During winter, even though PSCs are at their most abundant, there is no light over the pole to drive the chemical reactions. During the spring, however, the sun comes out, providing energy to drive photochemical reactions, and melt the polar stratospheric clouds, releasing the trapped compounds. Warming temperatures near the end of spring break up the vortex around mid-December. As warm, ozone-rich air flows in from lower latitudes, the PSCs are destroyed, the ozone depletion process shuts down, and the ozone hole closes.[22]
Most of the ozone that is destroyed is in the lower stratosphere, in contrast to the much smaller ozone depletion through homogeneous gas phase reactions, which occurs primarily in the upper stratosphere.[23]
[edit]Interest in ozone layer depletion
While the effect of the Antarctic ozone hole in decreasing the global ozone is relatively small, estimated at about 4% per decade, the hole has generated a great deal of interest because:
             The decrease in the ozone layer was predicted in the early 1980s to be roughly 7% over a 60 year period.[citation needed]
             The sudden recognition in 1985 that there was a substantial "hole" was widely reported in the press. The especially rapid ozone depletion in Antarctica had previously been dismissed as a measurement error.[24]
             Many[citation needed] were worried that ozone holes might start to appear over other areas of the globe but to date the only other large-scale depletion is a smaller ozone "dimple" observed during the Arctic spring over the North Pole. Ozone at middle latitudes has declined, but by a much smaller extent (about 4–5% decrease).
             If the conditions became more severe (cooler stratospheric temperatures, more stratospheric clouds, more active chlorine), then global ozone may decrease at a much greater pace. Standard global warming theory predicts that the stratosphere will cool.[25]
             When the Antarctic ozone hole breaks up, the ozone-depleted air drifts out into nearby areas. Decreases in the ozone level of up to 10% have been reported in New Zealand in the month following the break-up of the Antarctic ozone hole.[26]
[edit]Consequences of ozone layer depletion
Since the ozone layer absorbs UVB ultraviolet light from the Sun, ozone layer depletion is expected to increase surface UVB levels, which could lead to damage, including increases in skin cancer. This was the reason for the Montreal Protocol. Although decreases in stratospheric ozone are well-tied to CFCs and there are good theoretical reasons to believe that decreases in ozone will lead to increases in surface UVB, there is no direct observational evidence linking ozone depletion to higher incidence of skin cancer in human beings. This is partly due to the fact that UVA, which has also been implicated in some forms of skin cancer, is not absorbed by ozone, and it is nearly impossible to control statistics for lifestyle changes in the populace.
[edit]Increased UV
Ozone, while a minority constituent in the Earth's atmosphere, is responsible for most of the absorption of UVB radiation. The amount of UVB radiation that penetrates through the ozone layer decreases exponentially with the slant-path thickness/density of the layer. Correspondingly, a decrease in atmospheric ozone is expected to give rise to significantly increased levels of UVB near the surface.
Increases in surface UVB due to the ozone hole can be partially inferred by radiative transfer model calculations, but cannot be calculated from direct measurements because of the lack of reliable historical (pre-ozone-hole) surface UV data, although more recent surface UV observation measurement programmes exist (e.g. at Lauder, New Zealand).[27]
Because it is this same UV radiation that creates ozone in the ozone layer from O2 (regular oxygen) in the first place, a reduction in stratospheric ozone would actually tend to increase photochemical production of ozone at lower levels (in the troposphere), although the overall observed trends in total column ozone still show a decrease, largely because ozone produced lower down has a naturally shorter photochemical lifetime, so it is destroyed before the concentrations could reach a level which would compensate for the ozone reduction higher up.[citation needed]
[edit]Biological effects
The main public concern regarding the ozone hole has been the effects of increased surface UV and microwave radiation on human health. So far, ozone depletion in most locations has been typically a few percent and, as noted above, no direct evidence of health damage is available in most latitudes. Were the high levels of depletion seen in the ozone hole ever to be common across the globe, the effects could be substantially more dramatic. As the ozone hole over Antarctica has in some instances grown so large as to reach southern parts of Australia,New Zealand, Chile, Argentina, and South Africa, environmentalists have been concerned that the increase in surface UV could be significant.[28]
[edit]Effects on humans
UVB (the higher energy UV radiation absorbed by ozone) is generally accepted to be a contributory factor to skin cancer. In addition, increased surface UV leads to increased tropospheric ozone, which is a health risk to humans.[29]
1. Basal and Squamous Cell Carcinomas — The most common forms of skin cancer in humans, basal and squamous cell carcinomas, have been strongly linked to UVB exposure. The mechanism by which UVB induces these cancers is well understood—absorption of UVB radiation causes the pyrimidine bases in the DNA molecule to form dimers, resulting in transcription errors when the DNA replicates. These cancers are relatively mild and rarely fatal, although the treatment of squamous cell carcinoma sometimes requires extensive reconstructive surgery. By combining epidemiological data with results of animal studies, scientists have estimated that a one percent decrease in stratospheric ozone would increase the incidence of these cancers by 2%.[30]
2. Malignant Melanoma — Another form of skin cancer, malignant melanoma, is much less common but far more dangerous, being lethal in about 15–20% of the cases diagnosed. The relationship between malignant melanoma and ultraviolet exposure is not yet well understood, but it appears that both UVB and UVA are involved. Experiments on fish suggest that 90 to 95% of malignant melanomas may be due to UVA and visible radiation[31] whereas experiments on opossums suggest a larger role for UVB.[30] Because of this uncertainty, it is difficult to estimate the impact of ozone depletion on melanoma incidence. One study showed that a 10% increase in UVB radiation was associated with a 19% increase in melanomas for men and 16% for women.[32] A study of people in Punta Arenas, at the southern tip of Chile, showed a 56% increase in melanoma and a 46% increase in nonmelanoma skin cancer over a period of seven years, along with decreased ozone and increased UVB levels.[33]
3. Cortical Cataracts — Studies are suggestive of an association between ocular cortical cataracts and UV-B exposure, using crude approximations of exposure and various cataract assessment techniques. A detailed assessment of ocular exposure to UV-B was carried out in a study on Chesapeake Bay Watermen, where increases in average annual ocular exposure were associated with increasing risk of cortical opacity.[34] In this highly exposed group of predominantly white males, the evidence linking cortical opacities to sunlight exposure was the strongest to date. However, subsequent data from a population-based study in Beaver Dam, WI suggested the risk may be confined to men. In the Beaver Dam study, the exposures among women were lower than exposures among men, and no association was seen.[35]Moreover, there were no data linking sunlight exposure to risk of cataract in African Americans, although other eye diseases have different prevalences among the different racial groups, and cortical opacity appears to be higher in African Americans compared with whites.[36][37]
4. Increased Tropospheric Ozone — Increased surface UV leads to increased tropospheric ozone. Ground-level ozone is generally recognized to be a health risk, as ozone is toxic due to its strong oxidant properties. At this time, ozone at ground level is produced mainly by the action of UV radiation on combustion gases from vehicle exhausts.[citation needed]
[edit]Effects on crops
An increase of UV radiation would be expected to affect crops. A number of economically important species of plants, such as rice, depend on cyanobacteria residing on their roots for the retention of nitrogen. Cyanobacteria are sensitive to UV light and they would be affected by its increase.[38]
[edit]Public policy

NASA projections of stratospheric ozone concentrations if chlorofluorocarbons had not been banned.
The full extent of the damage that CFCs have caused to the ozone layer is not known and will not be known for decades; however, marked decreases in column ozone have already been observed (as explained before).
After a 1976 report by the U.S. National Academy of Sciences concluded that credible scientific evidence supported the ozone depletion hypothesis[39] a few countries, including the United States, Canada, Sweden, Denmark, and Norway, moved to eliminate the use of CFCs in aerosol spray cans.[40] At the time this was widely regarded as a first step towards a more comprehensive regulation policy, but progress in this direction slowed in subsequent years, due to a combination of political factors (continued resistance from the halocarbon industry and a general change in attitude towards environmental regulation during the first two years of the Reagan administration) and scientific developments (subsequent National Academy assessments which indicated that the first estimates of the magnitude of ozone depletion had been overly large). The United States banned the use of CFCs in aerosol cans in 1978.[40] The European Community rejected proposals to ban CFCs in aerosol sprays, and in the U.S., CFCs continued to be used as refrigerants and for cleaning circuit boards. Worldwide CFC production fell sharply after the U.S. aerosol ban, but by 1986 had returned nearly to its 1976 level.[40] In 1993, DuPont shut down its CFC facility.[41]
The U.S. Government's attitude began to change again in 1983, when William Ruckelshaus replaced Anne M. Burford as Administrator of theUnited States Environmental Protection Agency. Under Ruckelshaus and his successor, Lee Thomas, the EPA pushed for an international approach to halocarbon regulations. In 1985 20 nations, including most of the major CFC producers, signed the Vienna Convention for the Protection of the Ozone Layer which established a framework for negotiating international regulations on ozone-depleting substances. That same year, the discovery of the Antarctic ozone hole was announced, causing a revival in public attention to the issue. In 1987, representatives from 43 nations signed the Montreal Protocol. Meanwhile, the halocarbon industry shifted its position and started supporting a protocol to limit CFC production. The reasons for this were in part explained by "Dr. Mostafa Tolba, former head of the UN Environment Programme, who was quoted in the 30 June 1990 edition of The New Scientist, '...the chemical industry supported the Montreal Protocol in 1987 because it set up a worldwide schedule for phasing out CFCs, which [were] no longer protected by patents. This provided companies with an equal opportunity to market new, more profitable compounds.'"[42]
At Montreal, the participants agreed to freeze production of CFCs at 1986 levels and to reduce production by 50% by 1999.[40] After a series of scientific expeditions to the Antarctic produced convincing evidence that the ozone hole was indeed caused by chlorine and bromine from manmade organohalogens, the Montreal Protocol was strengthened at a 1990 meeting in London. The participants agreed to phase out CFCs and halons entirely (aside from a very small amount marked for certain "essential" uses, such as asthma inhalers) by 2000.[43] At a 1992 meeting in Copenhagen, the phase out date was moved up to 1996.[43]
To some extent, CFCs have been replaced by the less damaging hydro-chloro-fluoro-carbons (HCFCs), although concerns remain regarding HCFCs also. In some applications, hydro-fluoro-carbons (HFCs) have been used to replace CFCs. HFCs, which contain no chlorine or bromine, do not contribute at all to ozone depletion although they are potent greenhouse gases. The best known of these compounds is probably HFC-134a (R-134a), which in the United States has largely replaced CFC-12 (R-12) in automobile air conditioners. In laboratory analytics (a former "essential" use) the ozone depleting substances can be replaced with various other solvents.[44]
Ozone Diplomacy, by Richard Benedick (Harvard University Press, 1991) gives a detailed account of the negotiation process that led to the Montreal Protocol. Pielke and Betsill provide an extensive review of early U.S. government responses to the emerging science of ozone depletion by CFCs.
[edit]Prospects of ozone depletion

Ozone-depleting gas trends.
Since the adoption and strengthening of the Montreal Protocol has led to reductions in the emissions of CFCs, atmospheric concentrations of the most significant compounds have been declining. These substances are being gradually removed from the atmosphere—since peaking in 1994, the Effective Equivalent Chlorine (EECl) level in the atmosphere had dropped about 10% by 2008. It is estimated that by 2015, the Antarctic ozone hole will have reduced by 1 million km² out of 25 (Newman et al., 2004); complete recovery of the Antarctic ozone layer is not expected to occur until the year 2050 or later. Work has suggested that a detectable (and statistically significant) recovery will not occur until around 2024, with ozone levels recovering to 1980 levels by around 2068.[45] The decrease in ozone-depleting chemicals has also been significantly affected by a decrease in bromine-containing chemicals. The data suggest that substantial natural sources exist for atmospheric methyl bromide (CH3Br).[46]. The phase-out of CFCs means that nitrous oxide (N2O), which is not covered by the Montreal Protocol, has become the most highly emitted ozone depleting substance and is expected to remain so throughout the 21st century.[47]
When the 2004 ozone hole ended in November 2004, daily minimum stratospheric temperatures in the Antarctic lower stratosphere increased to levels that are too warm for the formation of polar stratospheric clouds (PSCs) about 2 to 3 weeks earlier than in most recent years.[48]
The Arctic winter of 2005 was extremely cold in the stratosphere; PSCs were abundant over many high-latitude areas until dissipated by a big warming event, which started in the upper stratosphere during February and spread throughout the Arctic stratosphere in March. The size of the Arctic area of anomalously low total ozone in 2004-2005 was larger than in any year since 1997. The predominance of anomalously low total ozone values in the Arctic region in the winter of 2004-2005 is attributed to the very low stratospheric temperatures and meteorological conditions favorable for ozone destruction along with the continued presence of ozone destroying chemicals in the stratosphere.[49]
A 2005 IPCC summary of ozone issues concluded that observations and model calculations suggest that the global average amount of ozone depletion has now approximately stabilized. Although considerable variability in ozone is expected from year to year, including in polar regions where depletion is largest, the ozone layer is expected to begin to recover in coming decades due to declining ozone-depleting substance concentrations, assuming full compliance with the Montreal Protocol.[50]
Temperatures during the Arctic winter of 2006 stayed fairly close to the long-term average until late January, with minimum readings frequently cold enough to produce PSCs. During the last week of January, however, a major warming event sent temperatures well above normal — much too warm to support PSCs. By the time temperatures dropped back to near normal in March, the seasonal norm was well above the PSC threshold.[51] Preliminary satellite instrument-generated ozone maps show seasonal ozone buildup slightly below the long-term means for the Northern Hemisphere as a whole, although some high ozone events have occurred.[52] During March 2006, the Arctic stratosphere poleward of 60° North Latitude was free of anomalously low ozone areas except during the three-day period from 17 March to 19 when the total ozone cover fell below 300 DU over part of the North Atlantic region from Greenland to Scandinavia.[53]
The area where total column ozone is less than 220 DU (the accepted definition of the boundary of the ozone hole) was relatively small until around 20 August 2006. Since then the ozone hole area increased rapidly, peaking at 29 million km² 24 September. In October 2006, NASAreported that the year's ozone hole set a new area record with a daily average of 26 million km² between 7 September and 13 October 2006; total ozone thicknesses fell as low as 85 DU on 8 October. The two factors combined, 2006 sees the worst level of depletion in recorded ozone history. The depletion is attributed to the temperatures above the Antarctic reaching the lowest recording since comprehensive records began in 1979.[54][55]
On October 2008 the Ecuadorian Space Agency published a report called HIPERION, a study of the last 28 years data from 10 satellites and dozens of ground instruments around the world among them their own, and found that the UV radiation reaching equatorial latitudes was far greater than expected, climbing in some very populated cities up to 24 UVI, the WHO UV Index standard considers 11 as an extreme index and a great risk to health. The report concluded that the ozone depletion around mid latitudes on the planet is already endangering large populations in this areas. Later, the CONIDA, the Peruvian Space Agency, made its own study, which found almost the same facts as the Ecuadorian study.
The Antarctic ozone hole is expected to continue for decades. Ozone concentrations in the lower stratosphere over Antarctica will increase by 5%–10% by 2020 and return to pre-1980 levels by about 2060–2075, 10–25 years later than predicted in earlier assessments. This is because of revised estimates of atmospheric concentrations of Ozone Depleting Substances — and a larger predicted future usage in developing countries. Another factor which may aggravate ozone depletion is the draw-down of nitrogen oxides from above the stratosphere due to changing wind patterns.[56]















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