Reduced - Form Modeling of Public Health Impacts of 1 Inorganic PM 2 . 5 and Precursor Emissions

Highlights 21 • Method brings results from detailed chemical transport models to policy analysis. 22 • Method estimates marginal social cost and intake fraction accurately and quickly. 23 • Reduced-form models produce errors comparable to state-of-the-art models' 24 errors. Abstract 26 It is challenging to estimate the public health costs of fine particulate matter (PM 2.5) and 27 its precursor emissions accurately and quickly for policy research because of their 28 complex physical and chemical processes occurring over a large downwind area. We 29 developed a method for building statistical regressions that estimate public health cost of 30 emissions accurately like a state-of-the-art chemical transport model (CTM) but without 31 its high computational cost. This method achieves high spatial resolution according to the 32 location of the emission source, accounting for differences in the exposed population 33 downwind. Using tagged CTM simulations, our method builds a large dataset of air 34 quality public health costs from marginal emissions throughout the United States. Two 35 methods were developed to describe exposed population, one that assumes a generic 36 downwind plume concentration profile derived from CTM outputs and a simpler method 37 that uses the size of population within certain distances as variables. Using the former 38 method, we parameterized marginal public health cost [$/t] and intake fraction [ppm] as a 39 function of exposed population and key atmospheric variables. We derived models for 40 elemental carbon, sulfur dioxide, nitrogen oxides, and ammonia. Compared to estimates 41 calculated directly using CTM outputs, our models generally show mean fractional errors 42 of only 10%–30% and up to 50% for NO x in some seasons, which are generally similar to 43 or less than CTM's performance. Our results show that the public health costs of 44 emissions can be efficiently parameterized for policy analyses based on state-of-the-art 45 CTMs with negligible increase in error. 46 47