Air Toxics: Overview The air we breathe can become contaminated
with pollutants from a variety of natural and man-made sources.
Since federal legislation involving ambient air quality was
enacted in 1970, air pollution control has focused on criteria
air pollutants, including sulfur dioxide (SO2), carbon monoxide
(CO), nitrogen oxides (NOx), ozone (O3) and particulate matter,
which are primarily by-products of fossil fuel combustion.
However, due to increasing scientific evidence of their effects
on human health, the focus of ambient air quality has begun to
shift to include not only "criteria" air pollutants, but also
"toxic" air pollutants. Toxic air pollutants are also referred
to as air toxics or hazardous air pollutants (HAPs) and are
defined as those pollutants that are suspected of causing cancer
or other serious health effects in humans, or of having serious
adverse effects on the environment. In order to help protect the
health of Maine residents and preserve our environment, the
State of Maine Depar