Inequity of Exposure to Wildfire Smoke PM2.5 in the United States

JING LI, Xinlei Liu, Qiao Yu, Yifang Zhu, University of California, Los Angeles

     Abstract Number: 233
     Working Group: Aerosol Exposure

Abstract
Understanding the inequity of exposure to wildfire smoke PM2.5 is limited, particularly lacking consideration of indoor infiltration. Here, we aimed to address this gap by quantifying smoke PM2.5 exposure in 2020, considering both indoor infiltration and time spent outdoors and indoors at the census tract level, and examining disparities using various vulnerability variables. Additionally, we incorporated data on the prevalence of residential air conditioning (AC) to investigate its impact on the inequity of smoke PM2.5 exposure across the U.S. Our results revealed that vulnerable populations were disproportionately exposed to higher levels of smoke PM2.5, with 25% of the most vulnerable population being exposed to 31% of smoke PM2.5. In addition, we found that smoke PM2.5 exposure varied more by race-ethnicity than by income. Annual population-weighted racial-ethnic exposure disparities across the U.S. and California exhibited differences. Nationally, Natives, Asians, Hispanics, and others (some other race or two or more races) were more exposed than average. In California, however, Asians and Hispanics flipped to be less exposed than average, while Whites were more exposed than average. These shifts can largely be attributed to the fact that within the United States, compared with other states, Asians and Hispanics are primarily concentrated in California, a state with the highest risk of wildfires in the U.S. Furthermore, we found that the prevalence of residential AC systems exacerbated smoke PM2.5 exposure inequity at the national level but mitigated it in California. This underscores the importance of investigating disparities in exposure to smoke PM2.5 from the bottom up to better address this inequity based on local conditions. In summary, our findings emphasize the imperative need to incorporate smoke PM2.5 into air quality assessments and control practices to enhance protection for vulnerable populations, as well as the importance of addressing this environmental inequity at the local scale.