1、 https:/crsreports.congress.gov Updated January 7, 2021The Diesel Emissions Reduction Act (DERA) ProgramEmissions from diesel enginesespecially particulate matter (PM), nitrogen oxides (NOx), sulfur oxides, and air toxicshave been shown to contribute to air pollution that adversely impacts public he
2、alth and welfare in the United States. Since 1970, the Clean Air Act (42 U.S.C. 7401 et seq.) has required the federal government to limit these emissions, among others, from new stationary (industrial) sources and new mobile sources. In the decades since, the U.S. Environmental Protection Agency (E
3、PA) has promulgated emission standards for a variety of source categories, including new heavy duty highway and nonroad diesel engines. EPAs most recent set of emission standards for newly manufactured heavy duty highway and nonroad diesel engines took effect in 2007 and 2008, respectively. At the t
4、ime, the standards required a 90% and 95% reduction in emission levels for PM and NOx, respectively, over the previous standards. However, because of the long operational lives of diesel engines, millions of pre-2007 engines remain in use. According to EPAs estimates in 2016, 10 million pre-2007 die
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