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Regional Differences on Sources for Ozone and Particle Pollution
Region 10: Alaska, Idaho, Oregon, and Washington
Local Sources of VOCs
In this section of the country, off-highway vehicles dominate the VOC sources from all human activity, contributing nearly two-fifths (39%) of the total. By contrast, the nation’s off-highway section is less than half that at 18 percent. Highway vehicles represent only 16 percent, about half the national rate of 29 percent. Solvent use also contributes less than half the rate seen nationally, at 13 percent versus 27 percent. Other VOC sources are more similar to the national rates, though storage and transport sources are about half (4% v 7%) of the nationwide rate. Region 10 produced 1.3 million tons of VOCs in 1999.
Local Sources of NOx
Highway vehicles contribute the largest amount of NOx in the region — 41 percent of the 892,073 tons generated in 1999. This is the second lowest NOx total of all regions in the nation. The percentage of highway vehicle NOx emissions in Region 10 is higher than it is in the nation as a whole, where it makes up 33 percent of emissions. Off-highway vehicles contribute 31 percent of NOx, higher than the national rate of 22 percent. Electric utilities emit only 5 percent of total NOx in this region, compared with 23 percent nationwide. Miscellaneous sources are an unusually high percentage at 11 percent. Industrial fuel combustion is only 7 percent compared with 12 percent nationally. Industrial emissions that are not fuel combustion account for 3 percent, slightly less than the national rate of 5 percent.
Local sources of Particle Pollution (PM2.5 )
Eighty percent of particle pollution emissions in Region 10 can be attributed to agriculture and forestry and other combustion; this figure exceeds the national average for miscellaneous particle pollution emissions by 33 percent. Waste disposal and recycling was the second largest source of particle pollution at 5 percent; other sources of particle pollution in the region include other fuel combustion (4%), other industrial processes (3%), industrial fuel combustion (2%), and off-highway vehicles (3%). Highway vehicles, metals processing, chemical and allied product manufacturing, fuel combustion from electric utilities, storage and transport, petroleum and related industries, and solvent use contribute a combined total of 3% of the particle pollution emission sources for Region 10. Region 10 produced 536,476 short tons of particle pollution according to its 1999 inventory.
Trends
Ozone monitors show a surprising 2 percent increase in ozone readings in Region 10, the lone up-tick among the 10 regions in the nation during the period 1983-2002. During the same period the nation declined by 14 percent. However, between 1991 and 2000, the northwest and Alaska reported a decline of 8 percent. Comparable trend data are not available for PM2.5 levels.
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