Estimating future industrial emissions of hazardous air pollutants in the United States using the National Energy Modeling System (NEMS)

Abstract Retrospective studies such as the National Air Toxics Assessment have focused on modeling hazardous air pollutant (HAP) concentrations and exposures in the near past; however, future projections of HAPs emissions are relatively unexplored compared to those for greenhouse gases or criteria pollutants, and HAPs are typically not included in energy systems optimization or integrated assessment modeling. In this study, we demonstrate a method that harnesses sector-based emissions data from the US environmentally extended input-output (USEEIO) model and scenario results from the National Energy Modeling System (NEMS) to project HAPs emissions from industrial sectors in United States, disaggregated to 9 regions. The results show that most HAPs have higher projected emissions in 2050 compared to the baseline year when assuming constant emissions intensities per unit of economic output, but lower emissions when trend values for pollution control and technology improvements are incorporated. Regional and temporal patterns are diverse among the 237 HAPs considered. Using formaldehyde as a prominent example, the oil and gas sector is the largest national contributor (49%-77%) to future formaldehyde emissions across scenarios. Overall, this method enables projections of industrial HAPs emissions, aligned with official NEMS scenarios, that can be used in assessments of future air quality and potential health impacts from HAPs.