Last week, I discussed the Administration’s guidance concerning the exercise of its enforcement discretion during the COVID-19 pandemic. Now comes evidence that the guidance may actually be self-defeating. While the administration is – understandably – trying to cut regulated industries some slack while they are trying to deal with COVID-19, it turns out that exposure to PM_2.5 has a significant impact on the COVID-19 death rate.

A study released earlier this week by researchers at the Harvard T.H. Chan School of Public Health concludes that an increase in the ambient PM_2.5 concentration of just 1 ug/m³ causes an increase of 15% in the death rate from COVID-19. And lest you think that the results stem from other factors unique to New York City and other places particularly hard-hit by the virus, the authors took into account all of the obvious confounding factors, including:

population density, percent of the population ≥65, percent living in poverty, median household income, percent black, percent Hispanic, percent of the adult population with less than a high school education, median house value, percent of owner-occupied housing, population mean BMI (an indicator of obesity), percent ever-smokers, [and] number of hospital beds.

A 15% increase in the COVID-19 death rate for a 1 ug/m3 increase in PM_2.5 is an extraordinary result. At some level, we knew it already, but let me summarize very simply. PM_2.5 is really, really, bad for you.

And so we come back to this administration. I’ll pass over the enforcement discretion memorandum and focus instead on EPA’s apparent decision not to change the current national ambient air quality standard for PM_2.5. Of course, the current chair of the SAB doesn’t believe in basing NAAQS on epidemiological studies, but for those of us who still believe in science, this study certainly only strengthens the case for reduction in the PM_2.5 NAAQS.