Opinion ID: 187302
Heading Depth: 2
Heading Rank: 2

Heading: Level of the Daily Coarse PM NAAQS

Text: The industry petitioners next challenge the level of the daily coarse PM standard. The EPA used PM10 as the indicator for coarse PM and set the 24-hour coarse PM standard at 150 ¢g/m3, the same level it retained in the 1997 NAAQS revision. See 1997 Final Rule, 62 Fed.Reg. at 38,679. It did not differentiate between urban and nonurban coarse particles. The industry petitioners first contend that the agency should have set different limits for urban and nonurban PM coarse. Industry Br. 27. In response, the EPA maintains that it is not possible, given the current state of science, to set different standards for urban and nonurban areas because there is no reliable way to determine which ambient mixes are urban and which are nonurban. 2006 Final Rule, 71 Fed.Reg. at 61,195. The agency explains that, given the variety of sources contributing to PM10-2.5 concentrations in different locations, a wide variety of `ambient mixes' are likely to exist, greatly complicating the determination of the appropriate standard level for each location. Id. The agency further notes that there is insufficient evidence regarding coarse particle composition in different areas to allow for the proper assignment of different standard levels in different locations, and the technical capabilities necessary to make such determinations are currently lacking. Id. This is a reasonable explanation for declining to set different levels for urban and nonurban coarse. Because we affirm the EPA's decision not to set different urban and nonurban coarse PM standards, we do not reach the argument of the amicus National Association of Home Builders that the EPA does not have the authority to set different NAAQS for urban areas or for different emissions sources. See NAHB Amicus Br. 2-6. The industry petitioners also contend that the EPA's single standard of 150 ¢g/m3 is not requisite to protect the public health. Again, the EPA has a reasonable response. The EPA explains that the Staff Paper undertook an examination of epidemiologic studies, and that the studies showed mortality and morbidity effects in areas that exceed the 150 ¢g/m3 standard. 2006 Final Rule, 71 Fed.Reg. at 61,200 ([T]he Staff Paper found little basis for concluding that the degree of protection afforded by the current PM10 standards in urban areas is greater than warranted, since potential mortality effects have been associated with air quality levels not allowed by the current 24-hour standard, but have not been associated with air quality levels that would generally meet that standard, and morbidity effects have been associated with air quality levels that exceeded the current 24-hour standard only a few times); see also STAFF PAPER § 5.4.4.1, at 5-67. The Administrator agreed with the Staff Paper's findings, and on that basis concluded that the 150 ¢g/m3 standard did not provide more protection than necessary. 2006 Final Rule, 71 Fed. Reg. at 61,202. The Administrator further concluded that the very high degree of uncertainty in the relevant population exposures implied by the morbidity studies suggests there is little basis for concluding at this time that a greater degree of protection is warranted. Id. The industry petitioners next argue that the 150 ¢g/m3 standard for PM10 will result in arbitrarily varying levels of coarse PM, and that the agency should instead have used a PM10-2.5 indicator. The EPA does not dispute that using the PM10 indicator will result in coarse PM levels that vary within the limit of 150 ¢g/m3. As the EPA explains: Because the PM10 indicator includes both coarse PM (PM10-2.5) and fine PM (PM2.5), the concentration of PM10-2.5 allowed by a PM10 standard set at a single level declines as the concentration of PM2.5 increases. Thus, the level of coarse particles allowed varies depending on the level of fine particles present. Id. at 61,195. Although the EPA acknowledges that a PM10 indicator will result in varying coarse PM levels, it does not agree that the variance will be arbitrary. The EPA agrees with the industry petitioners that protection from coarse particles should be targeted at urban areas, where coarse particles have been shown to pose the greatest danger. Id. at 61,194. But the agency argues that targeting of urban areas is effectively accomplished by using an indicator that permits the varying levels that the industry petitioners challenge. As the EPA explains: PM2.5 levels tend to be lower in rural areas and higher in urban areas. Thus, to the extent that higher PM2.5 levels lead to a lower allowable level of coarse particles in some areas compared to others, this will occur in precisely those locations i.e. urban or industrial areaswhere the science has shown the strongest evidence of adverse health effects associated with exposure to coarse particles. Id. at 61,195-96 (citations omitted). In other words: The varying levels of coarse particles allowed by a PM10 indicator will therefore target protection in urban and industrial areas where the evidence of adverse health effects associated with exposure to coarse particles is strongest. Id. The EPA also offers a further rationale for tying the stringency of coarse PM regulation to increases in the level of PM2.5. The EPA explains that the contamination of coarse particles discussed above, which makes such particles more dangerous to health, is linked to the presence of fine PM. Specifically, [m]any of these contaminants in PM10-2.5 come originally from fine particles, which may become attached in the atmosphere or be deposited and mixed into coarse materials on the ground. Id. Because contamination increases the health risks posed by coarse particles, the EPA argues that it is logical to allow lower levels of coarse particles when fine particle concentrations are high.... [I]nclusion of PM2.5 in the PM10 indicator for purposes of coarse particle protection would appropriately reflect the contribution that contaminants emitted in fine particle form can make to the overall health risk posed by coarse particles. Id. Thus, inclusion of the PM2.5 fraction in the PM10 indicator ... ensures that this risk of contamination of coarse particles by PM2.5 is addressed in the suite of fine and coarse PM standards. Id. It is true that the EPA relies on a qualitative analysis to describe the protection the coarse PM NAAQS will provide. But the fact that the EPA's analysis is qualitative rather than quantitative does not undermine its validity as an acceptable rationale for the EPA's decision. As this court held in ATA III, [t]he [Clean Air] Act requires EPA to promulgate protective primary NAAQS even where, as here, the pollutant's risks cannot be quantified or `precisely identified as to nature or degree.' 283 F.3d at 369 (quoting 1997 Final Rule, 62 Fed.Reg. at 38,653). The EPA's qualitative explanation for the targeting capacity of the 150 ¢g/m3 PM10 standard is reasonable and warrants rejection of the petitioners' challenge on this point. In sum, we find that the EPA has provided a reasonable explanation for its decisions not to set separate urban and nonurban coarse PM standards, to set the single coarse PM standard at 150 ¢g/m3, and to utilize a standard that allows targeted variance in coarse PM levels in an inverse relationship to the amount of fine PM in the air. Consequently, we reject the industry petitioners' challenge to the level of the coarse PM standard.