Air
Pollution
National Ambient Air Quality Standards
Since 1970, the
Clean Air Act has provided the primary framework for protecting
people and the environment from the harmful effects of air pollution by
reducing the emission of "hazardous air pollutants (HAPs)." Stationary
sources emit about one-half of the anthropogenic HAPs.
Health Effects
People who are
exposed to HAPs at sufficient concentrations for sufficient durations
may develop and increased risk of contracting forms of cancer or
experiencing other serious health effects. Depending on which air
pollutants an individual is exposed to, these health effects can include
damage to the immune system, as well as neurological, reproductive,
developmental, and respiratory problems.
The
Clean Air Act, which was last amended in 1990, requires EPA to set
National Ambient Air Quality Standards (NAAQS) for pollutants
considered harmful to public health and the environment. The Clean Air
Act established two types of national air quality standards.
Primary standards set limits to protect public health. These
standards are “harm-based” standards, meaning economic implications are
not considered. Secondary standards set limits to protect
public welfare.
The
EPA Office of Air Quality Planning and Standards (OAQPS) has set
National Ambient Air Quality Standards for six principal pollutants,
which are called "criteria" pollutants considered harmful to public
health and the environment. They are listed below. Units of measure for
the standards are parts per million (ppm) by volume, milligrams per
cubic meter of air (mg/m3), and micrograms per cubic meter of
air (µg/m3).
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