Opinion ID: 187302
Heading Depth: 2
Heading Rank: 3

Heading: Choice of the PM10 Indicator

Text: The industry petitioners also level a direct challenge to the EPA's choice of the PM10 indicatora challenge that significantly overlaps with that addressed in Part IV.B above. The EPA initially proposed using a PM10-2.5 indicator instead of a PM10 indicator. See 2006 Proposed Rule, 71 Fed.Reg. at 2665-68. The PM10-2.5 indicator would have measured only the coarse fraction (PM10-2.5) of PM smaller than 10 ¢g, see id., and would have disposed of concerns about the PM10 indicator that this court raised in ATA I. See 175 F.3d at 1054-55. In response to comments expressing concern with the PM10-2.5 indicator, see 2006 Final Rule, 71 Fed.Reg. at 61,188-94, the EPA's final rule reverted to the PM10 indicator that the agency had adopted in the 1997 NAAQS review. Id. at 61,194-99. The petitioners challenge the PM10 indicator on three grounds. First, they argue that ATA I holds that the PM10 indicator is inherently confounded, and that no explanation by the EPA for the indicator's utility could make it acceptable. Industry Reply Br. 13-14. For support, the petitioners rely on the court's statement that it is the very presence of a separate PM2.5 standard that makes retention of the PM10 indicator arbitrary and capricious. ATA I, 175 F.3d at 1054. But ATA I did not definitively preclude the use of a PM10 indicator. It held only that the EPA had not offered an adequate explanation to aid us in understanding its decision to select PM10 as the indicator for coarse PM. Id. Without that explanation, we were constrained to conclude the PM10 and PM2.5 indicators could lead to arbitrary `double regulation' of the PM2.5 component of PM10 and potential underregulation of the PM10-2.5 component. Id. As recounted in Part IV.B, the EPA has now cured that failure of explanation and provided a reasonable rationale for its choice of PM10. See 2006 Final Rule, 71 Fed.Reg. at 61,193-97; EPA Br. 107. Second, the industry petitioners argue that the EPA's choice of a PM10 indicator also runs afoul of ATA I because it was based solely on reasons of administrative convenience, which ATA I found impermissible. ATA I, 175 F.3d at 1055 (The administrative convenience of using PM10 cannot justify choosing an indicator poorly matched to the relevant pollution agent). This time, however, the EPA expressly disavowed reliance upon administrative convenience, 2006 Final Rule, 71 Fed.Reg. at 61,195, and chose the PM10 indicator only after considering and rejecting alternatives on the basis of flaws discerned during the comment period. Id. at 61,193-97. For example, the final rule explains that an unqualified PM10-2.5 indicator would not have been requisite because it would have been too stringent in nonurban areas and insufficiently stringent in urban areas. As discussed above, the agency rejected a qualified indicatorone with different levels for urban and nonurban areasbecause determining appropriate levels for different kinds of ambient mixes is not feasible at this time. Id. at 61,195; see also id. at 61,193. Finally, as also discussed above, the EPA explained its choice of PM10 on scientific rather than administrative grounds: PM10 allows for targeting regulation of PM10-2.5 concentrations in those areas that experience high concentrations of PM2.5, which can contaminate and thus render more dangerouscoarse PM. Id. at 61,196-97. Third, the petitioners argue that the PM10 standard will overregulateor rather, double-regulatefine particles because such particles are also subject to the PM2.5 standard. The discussion in Part IV.B, however, rebuts this argument as well. As we concluded there, the EPA has reasonably explained that the variance allowed by the PM10 indicator will target protection by allowing less coarse PM in areas that experience high concentrations of potentially contaminating fine PM. Id. at 61,196. This will not double-regulate PM2.5. Fine PM will primarily be regulated via the newly tightened daily PM2.5 standard. Id. at 61,196 n. 72. Any residual regulation of PM2.5 by the PM10 standard will serve a different, non-duplicative purpose[] in providing requisite protection from thoracic coarse particles that can be contaminated by PM2.5. Id. at 61,196. Moreover, the petitioners' over-regulation argument wrongly assumes that an area in violation of the PM10 coarse standard must decrease the fine fraction of PM to achieve compliance with the standard. Such an area could, however, simply choose to decrease the amount of coarse PM (PM10-2.5), a choice that would yield no additional regulation of fine PM. For the foregoing reasons, we reject these and all of the industry petitioners' other objections to the EPA's revised NAAQS for coarse PM and deny their petitions for review.