Nitrogen oxides, or NOx, is the generic term for a group of
highly reactive gases, all of which contain nitrogen and oxygen
in varying amounts. Many of the nitrogen oxides are colorless
and odorless. However, one common pollutant, nitrogen dioxide
(NO2) along with particles in the air can often be seen as a
reddish-brown layer over many urban areas.

Particulate matter, or PM, is the term for particles found in
the air, including dust, dirt, soot, smoke, and liquid
droplets. Particles can be suspended in the air for long
periods of time. Some particles are large or dark enough to be
seen as soot or smoke. Others are so small that individually
they can only be detected with an electron microscope.

A hazardous air pollutant is a substance that is defined as
hazardous by the 1990 amendments of the Clean Air Act. These
substances include certain volatile organic chemicals,
pesticides, herbicides, and radionuclides that present tangible
hazard, based on scientific studies of exposure to humans and
other mammals.

Fine particulate matter is a complex mixture of very small
liquid droplets or solid particles in the air. Major sources are
cars, trucks, construction equipment, coal-fired power plants,
wood burning, vegetation and livestock. These particles can be
directly released when coal, gasoline, diesel fuels and wood are
burned. Many fine particles are also formed in the atmosphere
from chemical reactions of nitrogen oxides, sulfur oxides,
organic compounds and ammonia. Fine particulates are associated

Waste perchlorates are regulated as hazardous waste because they
exhibit the characteristic of an oxidizer. (MN Rule. 7045.0131,
sub.3). Ammonium perchlorate if in solution and stored in an
aboveground storage tank would be regulated and if stored in an
underground storage tank would be regulated as a hazardous
substance. However, currently there are no risk-based soil,
ground water, or surface water criteria developed at least at the
state level. Some states, however (i.e. California has

In July 1987, EPA began using a new indicator, PM-10, which
includes only those particles with aerodynamic diameter smaller
than 10 um. Ten microns is approximately one seventh the diameter
of a human hair. This fraction of TSP is responsible for most of
the adverse human health effects of particulate matter because of
the particles' ability to reach the lower regions of the
respiratory tract.

DPLP (Delisted Permanent List of Priority) sites are those that
have been removed from the state Superfund Program priority list
because they have been cleaned up, pose no further risk to
public health or the environment, or have been transferred to a
more appropriate cleanup program.

DPLP (Delisted Permanent List of Priority) sites are those that
have been removed from the state Superfund Program priority list
because they have been cleaned up, pose no further risk to
public health or the environment, or have been transferred to a
more appropriate cleanup program. For more information, visit
the <a
href="http://www.pca.state.mn.us/programs/superf_p.html">MPCA
Superfund Program page.</a>

National Priority List (NPL) sites are those considered high
priority for cleanup under the federal Superfund program. These
are sites where known or suspected environmental contamination
threatens public health or the environment. The U.S.
Environmental Protection Agency updates the NPL once a year. For
more information, visit the <a
href="http://www.pca.state.mn.us/programs/superf_p.html">MPCA
Superfund Program page.</a>