User:Milton Beychok/Sandbox
The U.S. Clean Air Act,[1] enacted by the U.S. Congress and last amended in 1990,[2] required the U.S. Environmental Protection Agency (U.S. EPA) to set National Ambient Air Quality Standard (NAAQS)[3][4] for outdoor ambient air pollutants considered harmful to public health and the environment.
The Clean Air Act established two types of national air quality standards. Primary standards that define air pollutant concentration limits intended to protect the public health, including the health of sensitive populations such as asthmatics, children and the elderly. Secondary standards that define limits intended to protect the public welfare and environment, including damage to animals, crops, vegetation and buildings as well as providing protection against decreased visibility.[3]
Summary of the NAAQS
The NAAQS set air pollutant concentration limits for six pollutants, called the criteria pollutants, namely sulfur dioxide (SO2), nitrogen dioxide (NO2), ozone (O3), lead (Pb), Particulate Matter (PM10)[5] and Particulate Matter (PM2.5).[5] The NAAQS for those six pollutants are listed in the table below:[3]
| Primary Standard | Secondary Standard | |||
|---|---|---|---|---|
| Pollutant | Limit | Averaging Time | Limit | Averaging Time |
| Carbon monoxide | 9 ppmv | 8-hour | ||
| 35 ppmv | 1-hour | |||
The units of measure used for the concentrations in the above table are parts per million by volume (ppmv), milligrams per cubic meter of air (mg/m3), and micrograms per cubic meter of air (µg/m3).
References
- ↑ Clean Air Act (The entire text as of February 24, 2004)
- ↑ Clean Air Act (From the U.S. EPA website: "Legislation passed since 1990 has made several minor changes.")
- ↑ 3.0 3.1 3.2 National Air Quality Standards As summarized on the website of the U.S. EPA
- ↑ Full text of 40 CFR 50 Title 40 Part 50 of the United States Code of Federal Regulations (CFR) containing the National Ambient Air Quality Standards
- ↑ 5.0 5.1 PM10 is particulate matter having an aerodynamic diameter of 10 μm (micrometer) or less. PM2.5 is particulate matter having an aerodynamic diameter of 2.5 μm (micrometer) or less.