Air quality implications of COVID-19 in California

Abstract

The COVID-19 pandemic has caused enormous adverse impacts on human health and the economy. To combat the virus spread, many regional and national governments have issued the stay-at-home orders in order to improve social distancing and minimize person-to-person contact. The implementation of such practices (including telecommuting), however, have led to notable improvements in air quality. Several studies have assessed the impacts of the stay-at-home orders on air quality in worldwide regions. Generally, they reported reductions in concentrations of nitrogen dioxide (NO2) and fine particulate matter (PM2.5), and in some cases an increase in ground-level ozone (O3). Hence, change in air quality due to the pandemic may potentially affect the health outcomes. To date, no similar detailed quantitative analysis has been conducted for the state of California. In California, the Greater Los Angeles Area (LA) and San Joaquin Valley (SJV) are classified as “Moderate” nonattainment areas for PM2.5, by the United States Environmental Protection Agency (U.S. EPA). Additionally, the LA, SJV, and San Francisco Bay Area (SF) are respectively classified as “Extreme”, “Extreme”, and “Marginal” nonattainment areas for O3. Thus, air quality issues are still a major concern in these areas. In this study, we investigate the change in air quality using measurements from surface monitoring stations operated by the U.S. EPA’s AirNow and Air Quality System (AQS) networks. This study aims to answer the following questions: (1) What are the magnitudes of changes in regional PM2.5 and O3 concentrations during the pandemic time period? (2) What are the magnitudes of PM2.5- and O3- attributable premature mortality? How could the health outcome vary across regions in California? (3) How could the transportation activity change due to the pandemic? What are the opportunities in attaining air quality improvement in the post-pandemic period?