Analysis of the scientific and engineering response to the CAA. The Clean Air Act Amendments of 1990 require fuel producers to reformulate the chemistry of gasoline in an effort to reduce emissions; The U.S. EPA implemented a two-phase program of ever-more restrictive emission requirements. Phase 1 was enacted in 1995 in a two-part process, the second part of which began in January 1998. Phase II will go into effect in 2000 and will require even lower levels of emissions. .
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