| Regional Differences on Sources for Ozone and Particle Pollution
Region 8: Colorado, Montana, North Dakota, South Dakota, Utah and Wyoming
Local Sources of VOCs
The largest human-generated source of VOCs in Region 8 is solvent use, at 31 percent, higher than the nation as a whole. Highway vehicles contribute just over one-fourth at 27 percent, lower than the 29 percent produced nationally. Off-highway vehicle use, the third largest source, is 18 percent, the same as the national rate. In 1999, Region 8 produced 778,485 tons of VOCs, the second lowest of all the regions.
Local Sources of NOx
The largest sources of NOx emissions in Region 8 were electric utilities and off-highway vehicles, which each generated one-fourth of the total of 1.5 million tons in 1999. Nearly another fourth came from highway vehicles (23%). While the electric utility and off-highway contributions are higher than the nation as a whole, the highway vehicle contribution is lower by ten percent (23% v 33%). Industrial fuel combustion in the region makes up a much larger proportion at 20 percent than it does nationwide (12%). Other industrial sources are less of a factor than in the nation as a whole (2% v 4%).
Local sources of Particle Pollution (PM 2.5)
Seventy-six percent of particle pollution in Region 8 can be attributed to agriculture and forestry and other combustion; Region 8 exceeds the nationwide average for miscellaneous sources of particle pollution by 29 percent. Other fuel combustion from residential woodstoves and fireplaces contributed the second highest source of particle pollution emissions at 5 percent. Other emissions sources include: off-highway vehicles (4%), waste disposal and recycling (3%), other industrial processes (3%), chemical and allied product manufacturing (2%), fuel combustion from electric utilities (2%), industrial fuel combustion (2%). Metals processing, storage and transport, petroleum and related industries, solvent use, and highway vehicles contributed a combined total of 3 percent for particle pollution emissions in Region 8. Region 8 reported 507,054 short tons of particle pollution in 1999.
Trends
Monitored ozone levels dropped by 10 percent between 1983 and 2002, a trend slower than the nation as a whole, which dropped 14 percent during the same period. Furthermore, the long-term decline could have been greater had not the region’s ozone levels risen by 3 percent between 1991 and 2000. Comparable trend data are not available for PM2.5 levels.
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