On January 14th, the Environmental Protection Agency published a final rule in the Federal Register updating the National Ambient Air Quality Standards (NAAQS) for particulate matter (PM). The rule reduces allowable annual concentrations of fine particles (PM2.5) by 20 percent, from 15.0 μg/m3
(last set in 2006) to 12.0 μg/m3.
According to EPA, meeting the standard “will provide health benefits worth an estimated $4
billion to $9.1 billion per year in 2020 – a return of $12 to $171 for every dollar invested in
pollution reduction.” This is such an impressive return on investment that it begs the question of why EPA chose a standard of 12.0 μg/m3, when a tighter standard would have yielded even greater returns.