In Case You Were Wondering, EPA's PM2.5 Decision Really Was Horrible

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