National Ambient Air Quality Standards

NAAQS Non Attainment Counties 09302017

National Ambient Air Quality Standards (NAAQS) are regulations established by the United States Environmental Protection Agency (EPA) that apply to outdoor air throughout the country. These standards are designed to protect public health and the environment by setting limits on the concentration of certain pollutants in the air. The NAAQS are a central element in the United States' efforts to ensure clean air and are part of the Clean Air Act (CAA).

Overview

The Clean Air Act, which was first enacted in 1970 and has been amended several times since, requires the EPA to set National Ambient Air Quality Standards for pollutants considered harmful to public health and the environment. The EPA has identified six "criteria" pollutants for which it has established NAAQS: particulate matter (PM10 and PM2.5), sulfur dioxide (SO2), carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), and lead (Pb).

There are two types of NAAQS:

• Primary standards are set to protect human health, including the health of "sensitive" populations such as asthmatics, children, and the elderly.
• Secondary standards are set to protect public welfare, including protection against decreased visibility and damage to animals, crops, vegetation, and buildings.

Criteria Pollutants

Each of the six criteria pollutants has a specific NAAQS based on scientific evidence about the health and environmental effects of these pollutants. The standards are reviewed and potentially revised every five years to ensure they continue to provide adequate health and environmental protection.

Particulate Matter (PM)

Particulate matter is divided into two categories based on size: PM10 (particles with a diameter of 10 micrometers or smaller) and PM2.5 (particles with a diameter of 2.5 micrometers or smaller). PM can be made up of a variety of components including acids, organic chemicals, metals, and soil or dust particles.

Sulfur Dioxide (SO2)

SO2 is a gas produced by volcanic eruptions and industrial processes, particularly the burning of coal and oil at power plants and the refining of sulfur-containing ores.

Carbon Monoxide (CO)

CO is a colorless, odorless gas that is harmful to the cardiovascular system. It is produced by incomplete combustion of carbon-containing fuels, including natural gas, coal, and wood.

Nitrogen Dioxide (NO2)

NO2 is part of a group of gases called nitrogen oxides (NOx). NO2 and other NOx are produced from burning fuels, including gasoline, diesel, and coal.

Ozone (O3)

Ozone at ground level is created by a chemical reaction between NOx and volatile organic compounds (VOC) in the presence of sunlight. It is a major component of smog.

Lead (Pb)

Lead is a metal found naturally in the environment as well as in manufactured products. The major sources of lead in the air are ore and metals processing and the burning of fossil fuels.

Implementation and Enforcement

The EPA works with state, tribal, and local governments to implement the NAAQS. States are required to develop State Implementation Plans (SIPs) that outline how they will achieve and maintain the NAAQS. The EPA must approve these plans. If a region does not meet the standards, it may be designated as a nonattainment area, triggering specific planning and control requirements to bring the area into compliance.

Challenges and Controversies

The process of setting and revising NAAQS has been subject to political and economic debates. Industries that are major sources of air pollutants often argue that the standards are too stringent and costly to meet. Environmental and public health groups, on the other hand, argue that the standards are necessary to protect human health and the environment.

Conclusion

The National Ambient Air Quality Standards are a cornerstone of the United States' efforts to ensure a clean and healthy environment. By setting limits on the concentration of key pollutants in the air, the NAAQS protect public health and the environment from the harmful effects of air pollution.