| Sulfur Dioxide. Elevated levels of
ambient SO2 are usually associated with emissions from large coal or oil burning power
plants, industrial facilities incorporating sulfuric acid plants, and other industrial
facilities where sulfur is exposed to high temperatures such as pulp mills. The dominant
SO2 source locally was the ASARCO smelter located in Tacoma, which closed in 1985. A total
of four monitoring stations sited in the Everett, Seattle and Tacoma industrial areas
measure SO2.
Trends. The only SO2 exceedance in the past nine years was
attributed to emissions from an Everett pulp and paper mill in 1994. This single
exceedance did not constitute a violation of the state one-hour standard. Our four-county
area remains in attainment for SO2. |
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