|
April 2000
Nature and Sources
Health Effects
National Standards
For More Information
NATURE AND SOURCES
OF THE POLLUTANT
Particulate matter is the generic term used for a
type of air pollution that consists of complex and varying mixtures
of particles suspended in the air we breathe. Particles are present
everywhere, but high concentrations and/or specific types of
particles have been found to present a serious danger to human
health.
Particulate matter is a combination of fine solids
such as dirt, soil dust, pollens, molds, ashes, and soot; and
aerosols that are formed in the atmosphere from gaseous combustion
by-products such as volatile organic compounds, sulfur dioxide and
nitrogen oxides.
Particulate pollution comes from such diverse
sources as factory and utility smokestacks, vehicle exhaust, wood
burning, mining, construction activity, and agriculture.
HEALTH
EFFECTS
Particles of special concern to the protection of
lung health are those known as fine particles, less than 2.5 microns
in diameter. (For comparison, a human hair is about 75 microns in
diameter.) Fine particles are easily inhaled deeply into the lungs
where they can be absorbed into the bloodstream or remain embedded
for long periods of time. A recent study showed a 17% increase in
mortality risk in areas with higher concentrations of small
particles.
Particulate matter air pollution is especially
harmful to people with lung disease such as asthma and chronic
obstructive pulmonary disease (COPD), which includes chronic
bronchitis and emphysema. Exposure to particulate air pollution can
trigger asthma attacks and cause wheezing, coughing, and respiratory
irritation in individuals with sensitive airways.
Recent research has also linked exposure to
relatively low concentrations of particulate matter with premature
death. Those at greatest risk are the elderly and those with
pre-existing respiratory or heart disease.
NATIONAL AMBIENT
AIR QUALITY STANDARDS
The Clean Air Act requires the U.S. Environmental
Protection Agency (EPA) to set National Ambient Air Quality
Standards (NAAQS) for the six major air pollutants considered
harmful to public health and the environment. Localities where air
pollution levels exceed the NAAQS are required to develop plans to
reduce emissions.
The current federal standard for particulate matter
(PM10) is 150 micrograms per cubic meter (ug/m3) of air averaged
over 24 hours and 50 ug/m3 averaged over a one-year
period.
In July 1997, the EPA set a new stricter standard
that will regulate fine particulate matter (PM2.5) for the first
time: 65 ug/m3 measured over a 24-hour period and 15 ug/m3 averaged
over a year. This new standard will be phased in over the next
decade.
FOR MORE
INFORMATION
For more information about the EPA's air quality
standards, visit the EPA website at http://www.epa.gov/oar/oaqps/cleanair.html. | 
