Regional Differences in Ozone
Region 3: Pennsylvania, Delaware, Maryland, Washington, D.C., West Virginia, and Virginia
Local Souces of VOCs
According to EPA’s emissions inventory, human activity in Region 3 in 1999 put 1.51 million tons of VOCs into the air. Once again, the transportation sector accounted for the single largest contribution to the inventory – 45 percent of the Region’s emissions, 29 percent from highway vehicles, and 16 percent from off-road vehicles. Transportation generates a similar percentage nationally (47%), but Region 3’s off-road vehicle sector is slightly smaller than the national highway vehicle sector (16% v 18%). The other significant source was the use of solvents, comprising 31 percent, nearly a third, of Region 3’s emissions of VOCs, higher than the national percentage of solvent use (27%).
Local Sources of NOx
According to EPA’s emissions inventory, human activity in Region 3 in 1999 put 2.43 million tons of NOx into the air. Fully half (50%) came from highway vehicles and off-highway vehicles. The other significant contributor was fuel combustion, comprising over 44 percent of Region 3’s NOx emissions. Contributions from electricity generation by utilities accounted for nearly two thirds of this sector and over one-quarter of the whole (28%). Compared with the nation as a whole, Region 3 has a higher percentage from electric utilities (28% v 23% nationally) and a lower percentage from off-highway vehicles (17% v 22% nationally).9
Trends
Monitored ozone levels dropped by 4 percent between 1982 and 2001, a trend much lower than the nation as a whole, which dropped 11 percent during the same period. Furthermore, the long-term decline could have been greater had not the region’s ozone levels risen by 9 percent in the 1990s.10
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