The COVID-19-wildfire smoke paradox: Reduced risk of all-cause mortality due to wildfire smoke in Colorado during the first year of the COVID-19 pandemic

Sheena E Martenies; Ander Wilson; Lauren Hoskovec; Kirk A Bol; Tori L Burket; Laura Jean Podewils; Sheryl Magzamen

doi:10.1016/j.envres.2023.115591

The COVID-19-wildfire smoke paradox: Reduced risk of all-cause mortality due to wildfire smoke in Colorado during the first year of the COVID-19 pandemic

Environ Res. 2023 May 15:225:115591. doi: 10.1016/j.envres.2023.115591. Epub 2023 Mar 5.

Authors

Sheena E Martenies¹, Ander Wilson², Lauren Hoskovec², Kirk A Bol³, Tori L Burket⁴, Laura Jean Podewils⁵, Sheryl Magzamen⁶

Affiliations

¹ Department of Kinesiology and Community Health, University of Illinois at Urbana-Champaign, Urbana, IL, USA. Electronic address: smarte4@illinois.edu.
² Department of Statistics, Colorado State University, Fort Collins, CO, USA.
³ Center for Health and Environmental Data, Colorado Department of Public Health and Environment, Denver, CO, USA.
⁴ Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, USA; Denver Department of Public Health and Environment, Denver, CO, USA.
⁵ Center for Health Systems Research, Denver Health Office of Research, Denver, CO, USA.
⁶ Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO, USA; Department of Epidemiology, Colorado School of Public Health, University of Colorado Anschutz Medical Campus, Aurora, CO, USA.

Abstract

Background: In 2020, the American West faced two competing challenges: the COVID-19 pandemic and the worst wildfire season on record. Several studies have investigated the impact of wildfire smoke (WFS) on COVID-19 morbidity and mortality, but little is known about how these two public health challenges impact mortality risk for other causes.

Objectives: Using a time-series design, we evaluated how daily risk of mortality due to WFS exposure differed for periods before and during the COVID-19 pandemic.

Methods: Our study included daily data for 11 counties in the Front Range region of Colorado (2010-2020). We assessed WFS exposure using data from the National Oceanic and Atmospheric Administration and used mortality counts from the Colorado Department of Public Health and Environment. We estimated the interaction between WFS and the pandemic (an indicator variable) on mortality risk using generalized additive models adjusted for year, day of week, fine particulate matter, ozone, temperature, and a smoothed term for day of year.

Results: WFS impacted the study area on 10% of county-days. We observed a positive association between the presence of WFS and all-cause mortality risk (incidence rate ratio (IRR) = 1.03, 95%CI: 1.01-1.04 for same-day exposures) during the period before the pandemic; however, WFS exposure during the pandemic resulted in decreased risk of all-cause mortality (IRR = 0.90, 95%CI: 0.87-0.93 for same-day exposures).

Discussion: We hypothesize that mitigation efforts during the first year of the pandemic, e.g., mask mandates, along with high ambient WFS levels encouraged health behaviors that reduced exposure to WFS and reduced risk of all-cause mortality. Our results suggest a need to examine how associations between WFS and mortality are impacted by pandemic-related factors and that there may be lessons from the pandemic that could be translated into health-protective policies during future wildfire events.

Keywords: COVID-19; Mortality; Wildfire smoke.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Air Pollutants* / analysis
COVID-19* / epidemiology
Colorado / epidemiology
Environmental Exposure
Humans
Nicotiana
Pandemics
Particulate Matter / analysis
Smoke / adverse effects
Wildfires*

Substances

Smoke
Particulate Matter
Air Pollutants