National Ambient Air Quality Standards
Encyclopedia
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
under authority of the Clean Air Act
Clean Air Act
A Clean Air Act is one of a number of pieces of legislation relating to the reduction of airborne contaminants, smog and air pollution in general. The use by governments to enforce clean air standards has contributed to an improvement in human health and longer life spans...
(42 U.S.C. 7401 et seq.) that apply for outdoor air throughout the country. Primary standards are designed to protect human health, with an adequate margin of safety, including sensitive populations such as children, the elderly, and individuals suffering from respiratory diseases. Secondary standards are designed to protect public welfare from any known or anticipated adverse effects of a pollutant. A district meeting a given standard is known as an "attainment area" for that standard, and otherwise a "non-attainment area".
Standards
The standards are listed in Title 40 of the Code of Federal RegulationsTitle 40 of the Code of Federal Regulations
Title 40 is a part of the United States Code of Federal Regulations. Title 40 arranges mainly environmental regulations that were promulgated by the US Environmental Protection Agency , based on the provisions of United States laws...
Part 50.
| Pollutant | Type | Standard | Regulatory Citation | |
|---|---|---|---|---|
| SO2 | Primary | 0.14 ppm (365 μg Microgram In the metric system, a microgram is a unit of mass equal to one millionth of a gram , or 1/1000 of a milligram. It is one of the smallest units of mass commonly used... /m3 Cubic metre The cubic metre is the SI derived unit of volume. It is the volume of a cube with edges one metre in length. An alternative name, which allowed a different usage with metric prefixes, was the stère... ) |
24-hour | 40 CFR Code of Federal Regulations The Code of Federal Regulations is the codification of the general and permanent rules and regulations published in the Federal Register by the executive departments and agencies of the Federal Government of the United States.The CFR is published by the Office of the Federal Register, an agency... 50.4(b) |
| SO2 | Primary | 0.030 ppm (80 μg/m³) | annual | 40 CFR 50.4(a) |
| SO2 | Secondary | 0.5 ppm (1,300 μg/m³) | 3-hour | 40 CFR 50.5(a) |
| PM10 | Primary and Secondary | 150 μg/m³ | 24-hour | 40 CFR 50.6(a) |
| PM2.5 | Primary and Secondary | 35 μg/m³ | 24-hour | 40 CFR 50.7(a) |
| PM2.5 | Primary and Secondary | 15 μg/m³ | annual | 40 CFR 50.7(a) |
| CO | Primary | 35 ppm (40 mg/m³) | 1-hour | 40 CFR 50.8(a)(2) |
| CO | Primary | 9 ppm (10 mg/m³) | 8-hour | 40 CFR 50.8(a)(1) |
| O3 | Primary and Secondary | 0.12 ppm (235 μg/m³) | 1-hour | 40 CFR 50.9(a) |
| O3 | Primary and Secondary | 0.075 ppm (150 μg/m³) | 8-hour | 40 CFR 50.10(a) |
| NO2 | Primary and Secondary | 0.053 ppm (100 μg/m³) | annual | 40 CFR 50.11(a) and (b) |
| Pb | Primary and Secondary | 0.15 μg/m³ | Rolling 3 months | 40 CFR 50.12 |
Each standard has its own criteria for how many times it may be exceeded, in some cases using a three year average.As of June 15, 2005, the 1-hour ozone standard no longer applies to areas designated with respect to the 8-hour ozone standard (which includes most of the United States, except for portions of 10 states).
- Source: USEPA
Air quality control region
An air quality control region is an area, designated by the federal government, where communities share a common air pollution problem.See also
- Air pollutionAir pollutionAir pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment or built environment, into the atmosphere....
- Air Quality IndexAir Quality IndexAir quality is defined as a measure of the condition of air relative to the requirements of one or more biotic species or to any human need or purpose. Air quality indices are numbers used by government agencies to characterize the quality of the air at a given location...
- AsthmaAsthmaAsthma is the common chronic inflammatory disease of the airways characterized by variable and recurring symptoms, reversible airflow obstruction, and bronchospasm. Symptoms include wheezing, coughing, chest tightness, and shortness of breath...
- Atmospheric dispersion modelingAtmospheric dispersion modelingAtmospheric dispersion modeling is the mathematical simulation of how air pollutants disperse in the ambient atmosphere. It is performed with computer programs that solve the mathematical equations and algorithms which simulate the pollutant dispersion...
- Clean Air Act (1990)
- Portable Emissions Measurement SystemPortable Emissions Measurement Systema portable emissions measurement system is essentially a lightweight ‘laboratory’ that is used to test and/or assess mobile source emissions for the purposes of compliance, regulation, or decision-making...
- Toxic Substances Control Act of 1976Toxic Substances Control Act of 1976The Toxic Substances Control Act is a United States law, passed by the United States Congress in 1976, that regulates the introduction of new or already existing chemicals. It grandfathered most existing chemicals, in contrast to the Registration, Evaluation and Authorization of Chemicals ...
External links
- EPA summary of the National Ambient Air Quality Standards
- EPA summary for Air & Radiation
- EPA Green Book showing non-attainment, maintenance, and attainment areas
- Most Polluted Cities, 2005 - American Lung Association