Air is 99.9% nitrogen, oxygen, water vapour and inert gases. Human activities can release substances into the air, some of these can cause problems for humans, plants, and animals.

There are several main types of air pollution and well-known effects of this pollution. These include smog, acid rain, the greenhouse effect, and ‘holes’ in the ozone layer. Each of these problems has serious implications for our health and well-being, as well as for the whole environment.

One type of air pollution is the release of particles into the air from burning fuel for energy. This type of pollution is sometimes referred to as "black carbon" pollution. The exhaust from burning fuels in automobiles, homes, and industries is a major source of pollution in the air.

Another type of air pollution is the release of noxious gases, such as sulphur dioxide, carbon dioxide and nitrogen oxides. These can take part in further chemical reactions once they are in the atmosphere, forming smog and acid rain.

Pollution also needs to be considered inside our homes, offices, and schools. Some of these pollutants can be created by indoor activities such as smoking and cooking. It is therefore important to consider both indoor and outdoor air pollution.

Air pollution can affect our health in many ways with both short-term and long-term effects. Different groups of individuals are affected by air pollution in different ways. Some individuals are much more sensitive to pollutants than others. Young children and elderly people often suffer more from the effects of air pollution. People with health problems such as asthma, heart and lung disease may also suffer more when the air is polluted. The extent to which an individual is harmed by air pollution usually depends on the total exposure to the damaging chemicals, i.e., the duration of exposure and the concentration of the chemicals must be taken into account.

Examples of short-term effects include irritation to the eyes, nose and throat, and upper respiratory infections such as bronchitis and pneumonia. Other symptoms can include headaches, nausea, and allergic reactions. Short-term air pollution can aggravate the medical conditions of individuals with asthma and emphysema.

Long-term health effects can include chronic respiratory disease, lung cancer, heart disease, and even damage to the brain, nerves, liver, or kidneys. Continual exposure to air pollution affects the lungs of growing children and may aggravate or complicate medical conditions in the elderly.

The first step to solving air pollution is assessment. Researchers have investigated outdoor air pollution and have developed standards for measuring the type and amount of some serious air pollutants.

Scientists must then determine how much exposure to pollutants is harmful. Once exposure levels have been set, steps can be undertaken to reduce exposure to air pollution. These can be accomplished by regulation of man-made pollution through legislation. Many countries have set controls on pollution emissions for transportation vehicles and industry. This is usually done to through a variety of coordinating agencies which monitor the air and the environment. At the United Nations, the Atmosphere Management Program carries out world wide environmental projects.

Adequate ventilation is a key to controlling exposure to indoor air pollution. Home and work environments should be monitored for adequate air flow and proper exhaust systems should be installed.

One of the most dangerous air pollutants is cigarette smoke. Restricting smoking is an important key to a healthier environment. Legislation to control smoking is in effect in some locations, but individual exposure should be monitored and limited wherever possible.

Only through the efforts of scientists, business leaders, legislators, and individuals can we reduce the amount of air pollution on the planet. This challenge must be met by all of us in order to assure that a healthy environment will exist for ourselves and our children.

Many people spend large portion of time indoors; as much as 80-90% of their lives. We work, study, eat, drink and sleep in enclosed environments where air circulation may be restricted. For these reasons, some experts feel that more people suffer from the effects of indoor air pollution than outdoor pollution.

There are many sources of indoor air pollution. Tobacco smoke, cooking and heating appliances, and vapours from building materials, paints, furniture, etc. cause pollution inside buildings.

Pollution exposure at home and work is often greater than outdoors. The California Air Resources Board estimates that indoor air pollutant levels are 25-62% greater than outside levels and can pose serious health problems.

Smog is a type of large-scale outdoor air pollution. It is caused by chemical reactions between pollutants derived from different sources, primarily automobile exhaust and industrial emissions. Cities are often centres of these types of activities, and many suffer from the effects of smog, especially during the warm months of the year.

For each city, the exact causes of pollution may be different. Depending on the geographical location, temperature, wind and weather factors, pollution is dispersed differently.

A consequence of outdoor air pollution is acid rain. When a pollutant, such as sulphuric acid, combines with droplets of water in the air, the water can become acidified. The effects of acid rain on the environment can be very serious. It damages plants by destroying their leaves, it poisons the soil, and it changes the chemistry of lakes and streams. Damage due to acid rain kills trees and harms animals, fish, and other wildlife.

The greenhouse effect, also referred to as global warming, is generally believed to come from the build up of carbon dioxide gas in the atmosphere. Carbon dioxide is produced when fuels are burned. Plants convert carbon dioxide back to oxygen, but the release of carbon dioxide from human activities is higher than the world's plants can process. The situation is getting worse since many of the earth's forests are being removed, and plant life is being damaged by acid rain. Thus, the amount of carbon dioxide in the air is continuing to increase. 

Ozone depletion is another result of pollution. Chemicals released by our activities affect the stratosphere, one of the atmospheric layers surrounding earth. The ozone layer in the stratosphere protects the earth from harmful ultraviolet radiation from the sun. Release of chlorofluorocarbons (CFC's) from aerosol cans, cooling systems and refrigerator equipment removes some of the ozone, causing ‘holes’. Ultraviolet radiation is known to cause skin cancer and has damaging effects on plants and wildlife. 

Carbon monoxide (CO)
Carbon dioxide (CO2)
Chloroflorocarbons (CFC)
Lead (Pb)
Ozone (O3)
Nitrogen oxide (Nox)
Suspended particulate matter (SPM)
Sulphur dioxide (SO2)

Airnow 
Air Quality 
Lawrence Berkeley Lab
Edugreen - Air Pollution 
National Safety Council
National Resource Defence Council - Air pollution