In April, I noted that researchers at the T.H. Chan Harvard School of Public Health had identified a relationship between PM-2.5 exposure and mortality from COVID-19. 
That study received some criticism, and it certainly did not move the Clean Air Science Advisory Committee to alter its recommendation to keep the PM2.5 NAAQS unchanged at 12 ug/m3.
Earlier this month, the same researchers updated the study,… More
There have been numerous studies that support a decrease in the current PM2.5 annual standard of 12 ug/m3. EPA has nonetheless proposed to retain the current standard on the basis that there is too much uncertainty regarding whether those studies provide a basis for concluding that PM2.5 concentrations below the standard cause increased mortality. As I have previously noted, the statutory provision requires that NAAQS be set with an “adequate margin of safety.” That would seem to require EPA to resolve such uncertainty in favor of a more stringent standard.… More
Last week, the New England Journal of Medicine 
published The Need for a Tighter Particulate-Matter Air-Quality Standard, written by the Independent Particulate Matter Review Panel. For those who don’t remember, the Review Panel used to be a sub-committee of EPA’s Clean Air Science Advisory Committee, until EPA Administrator Wheeler decided that CASAC did not need the specific advice that the Review Panel had to offer.… More
After more than three years of ignoring science whenever it does not support this Administration’s preferred outcomes, the issue of the future of science in environmental regulation has now been well and truly joined. Yesterday, Administrator Wheeler, disagreeing with the recommendation of EPA’s own staff, announced that EPA is proposing to retain the current National Ambient Air Quality Standard for PM2.5 of 12 ug/m3, notwithstanding substantial evidence that PM2.5 poses significant risks even below 10 ug/m3. … More
EPA’s Office of Air Quality Planning and Standards has issued its final “Policy Assessment for the Review of the National Ambient Air Quality Standards for Particulate Matter.” 
The Policy Assessment comes with the standard disclaimer that its “findings and conclusions are those of the authors and do not necessarily reflect the views of EPA.” Sadly, truer words were never spoken.
Those following this issue know that,… More
According to Bloomberg Environment (subscription required), EPA’s Clean Air Science Advisory Committee cannot reach agreement whether to recommend that the NAAQS for PM2.5 be lowered. Even after two years, I guess I had not realized the extent to which the scientists relied on by this administration are willing to ignore what used to be generally known as the “scientific consensus.”
Last month, I noted that EPA’s Office of Air Quality Planning and Standards had released a draft reassessment of the particulate matter NAAQS. In a bold moment of speculation, I indicated that it would be difficult for EPA to avoid lowering the PM2.5 NAAQS to between 8.0 and 10.0 micrograms/cubic meter. Following issuance of the draft, and in order to ensure that EPA does not ignore the emerging scientific consensus,… More
EPA’s Office of Air Quality Planning and Standards has released a draft of its reassessment of the adequacy of the current national ambient air quality standard for particulate matter. Here’s the primary takeaway concerning PM2.5:
The risk assessment estimates that the current primary PM2.5 standards could allow a substantial number of PM2.5-associated deaths in the U.S.
When taken together, we reach the preliminary conclusion that the available scientific evidence,… More
Last week, EPA posted its draft Integrated Science Assessment for Particulate Matter. 
It’s the foundational document for EPA’s periodic review of its National Ambient Air Quality Standard for PM. The current standard for PM2.5, promulgated in 2012, is 12 ug/m3.
Section 109 of the Clean Air Act requires the Administrator to set the NAAQS “requisite to protect the public health” with “an adequate margin of safety.”
The new ISA states that:
Evidence from U.S.… More
As regular readers know, the tension between guidance and regulation is one of my favorite topics. My view is that, in general, guidance is too often used simply to avoid notice and comment rulemaking and that, once issued, it is treated by those implementing it in the agency street-level bureaucracy as though it were a rule. Nonetheless, guidance is sometimes appropriate. The recent decision in Sierra Club v.… More
On Friday, the Court of Appeals for the District of Columbia Circuit rejected EPA’s approach to implementation of the PM2.5 NAAQS. The fine particulate NAAQS was first published in 1997, and EPA issued implementation rules in 2007 and 2008. Those rules specified that EPA Subpart 1 of Part D of title I of the CAA – the general implementation provisions – rather than Subpart 4, which applies specifically to PM10. … More
On Friday, EPA announced promulgation of its revised fine particulate, or PM2.5, NAAQS. Why am I yawning? Let me count the ways:
1. Because, in 2009, the District of Columbia Court of Appeals rejected EPA’s prior effort to keep the PM2.5 standard at 15 ug/m3.
2. Because, as I have previously noted, the Court of Appeals pretty much told EPA that it could not ignore the advice of its Clean Air Science Advisory Committee in setting the NAAQS.… More
The batting average of the Bush administration EPA in appeals of its regulatory proposals may now have dropped below the proverbial Mendoza line. This week, the Court of Appeals for the District of Columbia remanded a substantial part of EPA’s particulate rule. That the Bush administration could achieve results where the Mendoza line is even a close metaphor is a testament to just how low its stock has fallen in the courts.… More