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Ambient air pollution and COVID-19 in California

Principal Investigator: 

University of California, Davis

This study will investigate the chronic and acute effects of air pollution exposure on COVID-19 incidence, mortality, and long-term complications, including onset of disease formation. Long- (2017−2018) and short- (2020) term exposures will be linked to a large medical records database in Southern California, with assessments at both the neighborhood and individual level.

Funded under

Poster abstract for HEI Annual Conference 2022

Chronic and Acute Ambient Air Pollution Exposure Fields for COVID-19 Studies in Southern California

Michael Kleeman1, Yusheng Zhao1, Jason Su2, Claudia Nau3, Deborah Young3, Rebecca Butler3, Michael Jerrett4, Christina Batteate4, Richard Burnett

1University of California at Davis, Davis, CA, USA; 2University of California at Berkeley, Berkeley, USA; 3Kaiser Permanente Southern California, Los Angeles, CA, USA, 4University of California at Los Angeles, Los Angeles, CA, USA

Background: A comprehensive study of 316,224 COVID-19 patients in Southern California found that chronic ambient air pollution exposures contribute to a higher risk of death within 90 days of COVID-19 infection. Additional studies are needed to test for the effects of acute air pollution exposure on COVID-19 outcomes to determine whether short-term interventions such as lock-downs that are designed to reduce direct transmission will also provide public health benefits through reduced air pollution. 

Methods: Standard emissions inventories for the year 2020 that do not account for altered behaviors during COVID-19 time periods were obtained from the California Air Resources Board (CARB) with a spatial resolution of 4 km. Emissions were downscaled to 1 km using spatial surrogates that are correlated with emissions activity. Mobile source emissions were adjusted for altered traffic patterns during COVID-19 using real-time traffic count data.  Freight transportation emissions were adjusted using reports on the number of twenty-foot-equivalent (TEU) containers passing through the Ports of LA, Long Beach, and Oakland. Changes to aircraft operations induced by COVID-19 were obtained from the U.S. Federal Aviation Administration (FAA) database.  Restaurant and retail store activity was estimated using employment statistics for each county in California. Simulations for the years 2017, 2018 and 2020 were carried out across California using the source-oriented UCD/CIT regional air quality model. A nested domain configuration was used with 24km resolution over the entire state of California, 4km resolution over the southern portion of the state, and 1km resolution over the study region.

Results: Criteria pollutant emissions were significantly reduced across California during the initial lockdown periods in April 2020. Mobile source emissions decreased by 30-40%, aircraft emissions decreased by 90%, freight transportation emissions reduced by 10-20%, and restaurant emissions decreased by 50%. The recovery time period for these emissions varied across sectors, with the fastest recovery for on-road vehicles and the slowest recovery for aircraft. Air pollution fields created for the year 2020 predict a decrease in acute exposures during the COVID-19 pandemic compared to the same months in the year 2016 as a result of the interventions such as lockdowns, but the magnitude of the reduction is mitigated by meteorological differences between the comparison years. Exposure reductions for primary food cooking particles and aircraft were larger and more sustained than reductions to gasoline and diesel vehicle primary particles.

Conclusions: The air pollution exposure fields created for Southern California in the year 2020 capture the major effects of altered behaviors during the pandemic. These exposure fields will support upcoming epidemiological studies investigating the effects of changes to acute air pollution exposures during the COVID-19 pandemic.