In September 2003, EPA released a summary
of the status of the Nation's air quality and emissions. EPA's
findings on carbon monoxide, lead, nitrogen dioxide, ozone, particulate
matter, and sulfur dioxide are
- National air quality
levels measured at thousands of monitoring stations across the
country have shown improvements over the past 20 years for all
six principal pollutants.
- Of the six tracked
pollutants, progress has been slowest for ground-level ozone.
Over the pat 20 years, almost all geographic areas experienced
some progress in lowering ozone concentrations. The Northeast
and Pacific Southwest exhibited the greatest improvement. In
particular, substantial progress seen in Los Angeles has continued
through 2002. However, the national average ozone (8-hour) levels
have been fairly constant in other metropolitan areas. An analysis
to adjust 8-hour ozone levels in metropolitan areas to account
for the influence of meteorological conditions shows the 10-year
trend to be relatively unchanged. At the same time, for some
national parks, the 8-hour ozone levels have increased. Seven
monitoring sites in five of the national parks experienced statistically
significant upward trends in the 8-hour ozone levels. Monitoring
data for one park site showed statistically significant improvements
over the period 1983-2002. For the remaining 22 parks with ozone
trends data, the 8-hour ozone levels at 13 increased only slightly,
while 5 showed decreasing levels and 4 were unchanged.
- Between 1983 and
2002, NOx emissions in the United States decreased 15 percent
(with a 12 percent decrease in the past 10 years).
- Sulfates formed primarily from sulfur
dioxide (SO2) emissions from coal-fired power plants are a major
component of fine particles in the eastern United States. SO2
emissions decreased 33 percent from 1983 to 2002 and 31 percent
from 1993 to 2002.
A summary table of the percent change
in national air quality concentrations and emissions is available
at this web site. A table (in
pdf format) describing the peak air quality statistics for the
six principle pollutants by county is provided.
For additional information
about the EPA National Air Quality Status and Trends: 2002 report,
please visit EPA's web