Beyond Health Co-Benefits: Air Quality-Related Equity Implications of US Decarbonization Policy

Abstract

Emissions of greenhouse gases (GHG) that contribute to climate change are often associated with emissions of air pollutants that react to form fine particulate matter (PM2.5), which is a significant cause of premature mortality and disproportionally harms people of color and low-income populations in the U.S. Ambitious climate policy to decarbonize the economy may be an appealing pathway to concurrently reduce air pollution and improve health, and a growing body of literature has established the significant health benefits from policies aimed to reduce GHG emissions. However, uncertainty remains about how different U.S. decarbonization strategies might affect air pollution-related health disparities.

This thesis explores the extent to which near-term federal carbon pricing can reduce racial/ethnic disparities in air pollution exposure, as well as pathways to reduce these disparities more generally. The main policy instrument evaluated here is an economy-wide cap-and-trade program that reduces carbon dioxide (CO2) emissions by 50% in 2030. The analysis leverages modeled energy-economic scenarios to estimate emissions reductions under the policy and applies an air quality model to evaluate PM2.5-related equity outcomes. In 2030, we estimate that the policy drives national emission reductions of sulfur dioxide (49%) and nitrogen oxides (16%), with smaller changes in other PM2.5-related pollutants, relative to a baseline with no federal carbon policy. The policy reduces average PM2.5 exposure for all racial/ethnic groups that we evaluate, with the greatest benefit for Black and non-Hispanic white populations primarily due to changes in the electricity sector. However, despite reductions in average PM2.5 exposures, disparities remain under the policy, and the relative gap in exposure between non-Hispanic white people and people of color slightly widens on average. Sensitivity analysis evaluating alternative distributions of emissions that are consistent with total CO2 reductions under the policy have limited impact on the results. We conclude that near-term federal carbon pricing can reduce air pollution exposure overall but has minimal impact on disparities, emphasizing the need for complementary policy to fulfill goals of mitigating environmental injustices.