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Air Quality and Public Health

Note: EPA no longer updates this information, but it may be useful as a reference or resource.

The health consequences of air pollution are considerable. On a global basis, the World Health Organization (WHO) estimates that 800,000 people per year die from the effects of air pollution. Moreover, air pollution contributes significantly to respiratory disease in children. The World Health Report 2002 - Reducing Risks, Promoting Healthy Life Exit EPA disclaimerhas more information about the global effects of air pollution.

Information on health effects, EPA standards, and pollutant trends for six air pollutants can be found on EPA's Common Air Pollutants page. Exposures to these air pollutants, which are often called "criteria air pollutants," are associated with health effects in humans. EPA sets National Ambient Air Quality Standards, based on health effects, for these six pollutants. Each year EPA tracks the levels of these pollutants in the air and how much of each pollutant (or the pollutants that form them) is emitted from various pollution sources.

EPA has developed a health benefits estimation tool to help quantify the health benefits of reducing air pollution called BenMAP.

Toxic air pollutants -- including mercury, benzene, dioxin, and asbestos, among others -- also pose health risks. More information on these substances is available on the Toxic Air Pollutants page.

Additional resources include a World Health Organization (WHO) fact sheet devoted to Air Quality and Health. Exit EPA disclaimerWHO also publishes Air Quality Guidelines Exit EPA disclaimer as an international reference on the adverse health effects of exposure to different air pollutants. is dedicated to providing relevant science on the health effects of pollutants.


Ground-level ozone is an air pollutant that causes human health problems and damages crops and other vegetation. It is a key ingredient of urban smog. Ozone and the chemicals that react to form it can be carried hundreds of miles from their origins, causing air pollution over wide regions.

Particulate Matter

Particulate matter, or PM, is the term for particles found in the air, including dust, dirt, soot, smoke, and liquid droplets. Particles can be suspended in the air for long periods of time. Particles can be carried over long distances by wind and then settle on ground or water.

Carbon Monoxide

Carbon monoxide, or CO, is a colorless, odorless gas that is formed when carbon in fuel is not burned completely. It is a component of motor vehicle exhaust, which contributes to about 56 percent of all CO emissions nationwide.

Nitrogen Dioxide

Nitrogen oxides, or NOx, is the generic term for a group of highly reactive gases, all of which contain nitrogen and oxygen in varying amounts. Many of the nitrogen oxides are colorless and odorless. However, one common pollutant, nitrogen dioxide (NO2) along with particles in the air can often be seen as a reddish-brown layer over many urban areas.

Sulfur Dioxide

Sulfur dioxide, or SO2, belongs to the family of sulfur oxide gases (SOx). These gases dissolve easily in water. Sulfur is prevalent in all raw materials, including crude oil, coal, and ore that contains common metals like aluminum, copper, zinc, lead, and iron. SOx gases are formed when fuel containing sulfur, such as coal and oil, is burned, and when gasoline is extracted from oil, or metals are extracted from ore. SO2 dissolves in water vapor to form acid, and interacts with other gases and particles in the air to form sulfates and other products that can be harmful to people and their environment.


Lead is a metal found naturally in the environment as well as in manufactured products. The major sources of lead emissions have historically been motor vehicles (such as cars and trucks) and industrial sources. Other stationary sources are waste incinerators, utilities, and lead-acid battery manufacturers.

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