Wildfire smoke PM2.5 and cancer history prevalence in the contiguous United States.

BACKGROUND

Little is known about the role of wildfire smoke PM2.5 in cancer burden, despite ambient PM2.5 being classified as a human carcinogen.

METHODS

Daily wildfire smoke PM2.5 estimates were aggregated into cumulative (2006-2020) and recent (2018-2020) averages, and linked to 2022 tract-level cancer history prevalence estimates for all tracts in the contiguous US. Quasi-Poisson generalized additive models with random effects and spatial splines estimated prevalence ratios and 95% CIs for each exposure window, modeling smoke PM2.5 continuously (per IQR) and across tertiles. Models adjusted for tract-level sociodemographic factors, health behaviors, health status, population density, climate, and Census region. Effect modification was assessed using interaction terms and stratified analyses.

RESULTS

Smoke PM2.5 exposure was not associated with cancer history prevalence in fully adjusted models across either exposure window. However, we observed effect modification by Census region. Higher cumulative and 3-year smoke PM2.5 exposure was associated with higher cancer history prevalence in the Midwest (IQR-difference in 3-year exposure PR: 1.020; 95% CI: 1.013-1.026) and Northeast (PR: 1.040; 95% CI: 1.032-1.049).

CONCLUSION

Wildfire smoke PM2.5 was not associated with cancer history prevalence at the tract level in this cross-sectional ecological study, although there may be potential effect modification by region. Further investigation using individual-level data on smoke PM2.5 exposure and cancer outcomes is needed to confirm these findings and better understand the implications of wildfires for cancer burden.