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The Environmental Protection Agency (EPA) is authorized by the Clean Air Act (Act), 42 U.S.C.S. §§ 7401-7642, to regulate emissions of harmful pollutants from motor vehicles. The Act itself specifies the quantity of acceptable emissions from light-duty vehicles for three classes of pollutants: carbon monoxide, hydrocarbons, and oxides of nitrogen. Section 202(b)(1) of the Act, 42 U.S.C.S. § 7521. Section 202(a)(1) of the Act, 42 U.S.C.S. § 7521, confers on the EPA administrator the general power to prescribe by regulation standards applicable to the emission of any air pollutant from any class or classes of new motor vehicles or new motor vehicle engines, which in his judgment cause, or contribute to, air pollution that may reasonably be anticipated to endanger public health or welfare. These provisions are supplemented and qualified by various specific provisions relating to particular classes of vehicles or pollutants. Sections 202(a)(3)(A)(i), 202(a)(3)(F), 202(b)(6)(A) of the Act, 42 U.S.C.S. § 7521.
In setting the 1985 emissions control standards, the EPA predicted that an experimental device, known as a trap-oxidizer, would be perfected early enough to allow its installation in 1985 diesel vehicles. The environmental group contended that the EPA's promulgation of certain particulate emissions standards for light-duty diesel vehicles and trucks, and the EPA's waiver of the standards for NOx for light-duty vehicles, did not adequately protect the public health.
Was EPA's adoption of a single particulate standard for light-duty diesel vehicles within the EPA's regulatory discretion?
The court affirmed the EPA's standards and held that the EPA had the authority to regulate diesel particulate emissions pursuant to § 202(a)(1) of the Act. The court held that (1) the EPA's adoption of a single particulate standard for light-duty diesel vehicles was within the EPA's regulatory discretion, based on the EPA's prediction that even the worst performing diesel could have met the standard; (2) the EPA met the requirement of reasoned decision-making in concluding that the necessary steps in improving trap-oxidizer technology could be completed by 1985; and (3) the EPA's granting of certain NOx waivers was consistent with a reasonable interpretation of the Act. Thus, the court upheld the EPA's regulations.