(CN) - Sources of fine particulate emissions near national parks cannot get exemptions from air-quality monitoring regulations, the D.C. Circuit ruled.
Fine particulate pollution, or PM2.5, describes particulate matter no larger than 2.5 micrometers in diameter, making it one-30th the diameter of a human hair.
The Environmental Protection Agency has said that epidemiological studies found statistically significant correlations between elevated PM2.5 levels and premature mortality.
It requires sources that release emissions near a national park to get a Prevention of Significant Deterioration (PSD) permit. Permits issuance turns a source's adherence to EPA-designated Significant Impact Levels and Significant Monitoring Concentration (SMC) regulations for PM2.5.
Under the permit program, sources must show that emissions from construction or operation of a facility will not cause any increase over the maximum allowable increases over baseline concentrations.
The new rules exempt sources that "can show through modeling of its emissions alone that its impacts are less than the corresponding SMC."
After the Sierra Club balked, the EPA conceded the need to revise portions of the regulations. Still the nonprofit pressed forward with litigation, claiming that the agency lacked the authority to issue exemptions to air-monitoring under any circumstances.
Though the D.C. Circuit found that the agency had overstepped its authority in giving some sources an exemption, it declined last week to check the EPA's issuing authority. It instead gave the EPA leave to retract and rewrite its rules.
"We read § 165(e)(2) of the act as an 'extraordinarily rigid' mandate that a PSD permit applicant undertake preconstruction monitoring," Judge David Sentelle wrote for a three-member panel.
"Congress's use of the word 'shall' in each sentence of the act evidences a clear legislative mandate that the preconstruction monitoring requirement applies to PSD permit applicants," he added.
The decision also faults the EPA for not explaining how the statute is ambiguous, asserting instead "that there is a 'virtual presumption' of inherent agency authority."
"This argument is circular," Sentelle wrote. "Even if a 'virtual presumption' exists, that presumption can be rebutted by an 'extraordinarily rigid' statutory mandate. ...
"Congress's express statement that the public shall have air quality data to allow for informed participation in PSD application hearings bolsters our conclusion that the EPA has no authority to exempt the monitoring requirement."
This is the second opinion from the D.C. Circuit this year to complicate the EPA's implementation of the PM2.5 regulations. Earlier this month, the D.C. Circuit overturned the agency's PM2.5 implementation rules.
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