Last month, I posted that EPA’s decision to retain the current PM2.5 NAAQS of 12 ug/m3 was the single worst decision by Trump’s EPA. Since then, I have not received any comments suggesting that my ranking was incorrect. In case anyone was still in doubt, Environmental Research recently released an on-line Pre-proof of A National Difference in Differences Analysis of the Effect of PM2.5 on Annual Death Rates. The “difference in differences” approach is intended to address critics’ arguments that prior studies may have demonstrated an association between PM2.5 concentrations and mortality, but could not be used to demonstrate causality.
The study looked at excess mortality in the US Medicare population. The results aren’t pretty. For each 1 ug/m3 increase in PM2.5 concentrations, there are roughly an additional 14,000 deaths per year in the United States. With my typical gift for understatement, I’ll note that it’s difficult to review this work and conclude that the current standard of 12 ug/m3 protects the public with “with an adequate margin of safety.”
On the plus side, I can only suggest that everyone undertake a visualization exercise, and try to imagine what the world will look like when it is powered almost entirely by non-polluting electricity. How much cleaner the air will be. How many fewer asthma cases there will be. How much lower mortality will be. How much greater the quality of life will be.
It won’t be easy to get there, but we’ve got to start somewhere.
While I agree that tightening the standard is a good idea, I would caution readers that despite using a technique called “causality modeling “, this study ( like the original analysis by Levy et al, also from the Harvard School of Public Health) is still a correlation analysis rather than a defensible demonstration of cause and effect. See for example the (.not discussed) almost four- fold difference between men and women, and the assumption that their present zip code represents what these Medicare recipients have been exposed to over many years. I believe in a tightened ambient standard, but also that more attention should be paid to tightening the several nationally mandated emissions standards that will have more impact on exposures.
Charlie: Thanks for the note. I think that the range is evidence is starting to be overwhelming and I’m confident that the causal evidence is only going to get stronger. What are the emissions standards you want to tighten — and isn’t the basis for tightening that it’s necessary to meet a more stringent NAAQS?
Seth, I think this is an example of a disconnect between the original imperative fifty years ago to nationalize a regulatory framework to address what was then generally available data on a few individual “usual suspect “ pollutants, and today’s more sophisticated scientific understanding of combined pollutant impacts. We started with Total Suspended Particulates in 1970 and incrementally learned about the impacts of species like particulate sulfates, metals, and finer ( 2.5) particles of many different chemical combinations. I think the bottom line is that the broadest possible application of control trains like scrubbers in conjunction with fabric filters would get us the closest to really protecting people and the environment, because it would “get” the fine particles AND the problematic gases (Greenhouse and toxic). How about a two- step regulatory approach: 1. A national mandate ( EPA reg) to put these technologies in place as the preferred implementation mechanism for all the Criteria Pollutants, NESHAPs, etc. and 2. A Federal funding commitment (Congress, I fear) to ensure that it happens in the National ( International) best interest? Two years to step up!