Opinion ID: 213650
Heading Depth: 2
Heading Rank: 2

Heading: Regulation of Particulate Matter

Text: Particulate matter is the generic term for a broad class of chemically and physically diverse substances that exist as discrete particles (liquid droplets or solids) over a wide range of sizes. National Ambient Air Quality Standards for Particulate Matter, 62 Fed.Reg. 38,652-01, 38,653 (July 18, 1997) (1997 NAAQS Rule). The EPA regulates particulate matter as an air pollutant for purposes of the Clean Air Act. Id. The EPA originally regulated all particulate matter as a single class. Id. at 38,653-54. In 1987, the EPA created a subclass of particulate matter: all particles with a diameter equal to or less than 10 micrometers, referred to as PM-10. Id. In 1997, spurred by extensive scientific research into the deleterious effects of very small particles, the EPA added to the list of regulated air pollutants a new subset of particulate matter: those particles with a diameter equal to or less than 2.5 micrometers, referred to as PM-2.5. Id. at 38,654. In 2006, the EPA imposed more stringent air quality requirements by decreasing the acceptable level of PM-2.5. 71 Fed.Reg. 61,144-01, 61,224 (Oct. 17, 2006) (2006 NAAQS Rule). The EPA has promulgated regulations describing the requirements for SIPs concerning PM-2.5. 40 C.F.R. §§ 51.1007-51.1009. The EPA designated 2002 as the default baseline emission inventory year to be used for attainment planning purposes. Id. § 51.1008(b). The EPA also specified requirements concerning a nonattainment area's plan for reasonable further progress. Id. § 51.1009. For certain SIPs, including the one at issue here, the SIP must demonstrat[e] that reasonable further progress will be achieved for the 2009 and 2012 emissions years, known as milestone years. Id. § 51.1009(c)(2). The RFP plan must demonstrate that in each applicable milestone year, emissions will be at a level consistent with generally linear progress in reducing emissions between the base year and the attainment year. Id. § 51.1009(d). The rule details the specific calculations that correspond to a straight-line decrease in emissions from the emissions level in the base year to the target emissions level in the attainment year. Id. § 51.1009(f).