Environment/Climate Change
Wildfire smoke PM2.5 and cancer prevalence in the US: a national cross-sectional analysis Hiwot Zewdie* Hiwot Zewdie Seigi Karasaki Malia Cortez Jiayu Lin Amanda Phipps Trang VoPham
Introduction: Climate change has contributed to increasing incidence of wildfires. The composition of fine particulate matter (PM2.5) from wildfire smoke may be more harmful to human health than other sources of PM2.5, due to its higher carbon content and oxidative potential. Little is known about the role of wildfire smoke PM2.5 in cancer burden.
Methods: Census tract-level wildfire smoke PM2.5 exposure, estimated for the contiguous US using ground monitors and satellite-based smoke plumes, was aggregated to a cumulative annual average (2006-2020). Smoke PM2.5 data was linked with tract-level cancer prevalence (% of adults in 2022 ≥18 years diagnosed with cancer excluding non-melanoma skin cancer) using national data. Robust Quasi-Poisson models estimated prevalence ratios (PRs) and 95% confidence intervals (CIs) for associations between tract-level smoke PM2.5 and cancer prevalence. Models were adjusted for tract-level sociodemographics and population density as confounders, and health conditions and behaviors as precision variables. We examined effect modification using stratified models.
Results: Average estimated tract-level cancer prevalence was 7.4% (SD 2.7; n= 81,838 tracts). Smoke PM2.5 exposure was not associated with cancer prevalence (PR per IQR [0.13-0.32 µg/m3]: 1.00; 95% CI 0.99-1.00) in fully adjusted models. There was statistically significant effect modification by age, racial composition, and region (p < 0.01). However, the magnitude of the interactions was modest (region: PR per IQR in Northeast: 1.04, 95% CI 1.02-1.06; West: 0.99, 95% CI 0.99-0.99; South: 1.02, 95% CI 1.01-1.03; Midwest: 0.99, 95% CI 0.97-1.00).
Conclusion: Wildfire smoke PM2.5 was not associated with cancer prevalence at the tract-level, although there may be potential effect modification by region. Further investigation using individual-level data on wildfire smoke PM2.5 exposure and cancer incidence are needed to better understand the potential health implications of wildfires.