Geographic patterns in wildfire exposures and county-level lung cancer mortality in the United States

Authors

• A Talukder
• D Yeung
• Y Li
• N Anandanadarajah
• DM Umbach
• Z Fan
• L Li

Abstract

Emissions from wildland fire plumes are composed of modified biomass combustion by-products, including carcinogens. However, studies of the association between wildland fire exposures and lung cancer are scant. We evaluated geographic patterns in these exposures and lung cancer mortality to explore possible associations.

We extracted historical fire (wildfires and prescribed burns) information and satellite imagery for the conterminous U.S. from the Monitoring Trends in Burn Severity program (1984-2001). Age-adjusted, sex-specific lung cancer mortality rates at the county level for two 5-year periods (2011-2015 and 2016-2020) were obtained from the National Center for Health Statistics. Lee’s L statistic for bivariate spatial association was used to identify geographic patterns with significant associations between fire exposures and lung cancer mortality rates.

There were over 6,100 wildland fires (67% were wildfires) and 7,650,000 km2 burned area during the exposure period. Among females, we observed clusters of counties where area burned ratios and lung cancer mortality rates (2011-2015) were both high across eastern Kentucky (n=17 counties, p-values: 0.009-0.03), southwestern West Virginia (n=9, p-values: 0.009-0.01), and Florida (n=17, p-values: 0.009-0.03). Among western counties, greater fire exposure was associated with lower lung cancer mortality (n=47, p-values: 0.009-0.03). These patterns were consistent among men and by time period. Our findings differed from recently published lung cancer mortality clusters associated with smoking prevalence.

Our novel analysis identified U.S. counties where wildfires might contribute to lung cancer mortality; the inverse association in some Western counties requires additional investigation. Studies with individual-level exposure-response assessments are needed to evaluate this relationship further.

Scientific Focus Area: Epidemiology

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