Spatiotemporally Detailed Quantification of Air Quality Benefits of Emissions Reductions–Part I: Benefit-per-Ton Estimates for Canada and the U.S.

Abstract

The U.S. EPA’s Community Multiscale Air Quality (CMAQ)-adjoint model is used to map monetized health benefits (defined here as benefits of reduced mortality from chronic PM_2.5 exposure) in the form of benefits per ton (of emissions reduced) for the U.S. and Canada for NOx, SO₂, ammonia, and primary PM_2.5 emissions. The adjoint model provides benefits per ton (BPTs) that are location-specific and applicable to various sectors. BPTs show significant variability across locations, such that only 20% of primary PM_2.5 emissions in each country makes up more than half of its burden. The greatest benefits in terms of BPTs are for primary PM_2.5 reductions, followed by ammonia. Seasonal differences in benefits vary by pollutant: while PM_2.5 benefits remain high across seasons, BPTs for reducing ammonia are much higher in the winter due to the increased ammonium nitrate formation efficiency. Based on our location-specific BPTs, we estimate a total of 91,000 U.S. premature mortalities attributable to natural and anthropogenic emissions.

Due to the spatiotemporal variabilities in benefit per ton of emission reductions, reducing 20% of the primary emissions would result in over half the societal health benefits in both the U.S. and Canada.