For the last 30 years, the federal government's Environmental Protection Agency (EPA)—as well as the nation's engine manufacturers—have focused on controlling criteria pollutants. Emphasis has been on limiting the nitrogen oxides, carbon monoxide, volatile hydrocarbons, and particulates that engine exhaust put into the air. That changed early this decade, when the EPA amended the Clean Air Act to include a specific list of hazardous air pollutants, or HAPs, totaling 188 compounds that can have potentially dangerous effects on people. The revised and expanded law stated that by Nov. 15, 2000, the EPA must have rules in place to deal with HAPs.
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