(CN) - Environmental regulators should have been more critical in two rules concerning fine particulate matter, the D.C. Circuit ruled, siding with environmental and health groups.
In 2007 and 2008, the EPA set new regulations for states regarding fine particle emissions pursuant to Subpart One of Part D, Title I of the Clean Air Act.
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.
"Epidemiological studies have shown statistically significant correlations between elevated PM2.5 levels and premature mortality," the EPA said. "Other important effects associated with PM2.5 exposure include aggravation of respiratory and cardiovascular disease (as indicated by increased hospital admissions, emergency room visits, absences from school or work, and restricted activity days), changes in lung function and increased respiratory symptoms, as well as new evidence for more subtle indicators of cardiovascular health. Individuals particularly sensitive to PM2.5 exposure include older adults, people with heart and lung disease, and children."
The Sierra Club, the National Resources Defense Council, the American Lung Association and Medical Advocates for Healthy Air challenged the new rules in federal court, arguing that they should be implemented in accord with Subpart Four of the Clean Air Act, which has more demanding standards than Subpart One.
The D.C. Circuit found the challenge timely last week, and ordered the EPA to rewrite the regulations.
"The EPA contends PM2.5 must be implemented pursuant to the general (and less stringent) implementation procedure in Subpart 1," Judge Karen Henderson wrote for a three-judge panel (parentheses in original).
Subpart Four requires an area with bad air quality to be classified as "moderate," then reclassified as "serious" if it does not make improvements. Under Subpart One, an area "may" be reclassified.
Subpart Four also requires implementation of "reasonable available control measures" within four years of a "serious" designation, whereas Subpart One requires implementation of these measures "as expeditiously as practicable."
"Before the Congress enacted Subpart 4, EPA had promulgated a single particulate matter standard - the PM10 standard - which encompassed all particulate matter with a diameter of 10 micrometers or less - including both coarse and fine particulate matter, that is, particulate matter now governed by both the PM10 and PM2.5 standards - and the 1990 CAA [Clean Air Act] amendments adopted this broad meaning in defining 'PM10,'" Henderson wrote. "Thus, by its express terms, Subpart 4, when enacted, governed all PM10 particles, including those now denominated PM2.5. The scope of the statutory definition - and consequently of Subpart 4's application - did not change when EPA subdivided PM10 by regulation."