Wildfire Air Pollution Exposure and Head and Neck Cancer Incidence.

OBJECTIVES

To determine the association between wildfire-specific particulate matter 2.5 (wPM2.5) exposure and the overall and site-specific incidences of head and neck and aerodigestive cancer (HNC).

STUDY

DESIGN

Epidemiological retrospective cohort analysis.

METHODS

HNC incidence data were derived from the Surveillance, Epidemiology, and End Results Program (2016-2022). The relationship between county-level wPM2.5 exposure metrics and HNC incidence rates were examined using a distributed lag non-linear model, adjusting for health behaviors (tobacco/alcohol use, diet, exercise, and sexual activity), demographics (age, sex, race/ethnicity), population size, and year, with county as a random effect. Lag effects were analyzed over 10 years. HNC subsites included nasal/sinus/ear, nasopharynx, oral cavity, oropharynx (stratified by p16 status), hypopharynx, and larynx.

RESULTS

Higher wildfire-specific PM2.5 exposure was associated with increased cumulative HNC incidence over 0-10-year lags, with a cumulative relative risk (cRR) of 1.06 (95% CI: 1.04-1.09) per additional smoke exceedance day, 1.41 (1.24-1.60) for any annual exposure, and 1.23 (1.13-1.33) per percentage-point increase in days above 5 μg/m3. Among subsites, oral cavity cancer showed consistent increases (cRR 1.03, 95% CI: 1.00-1.06), oropharyngeal cancer risk increased to 1.09 (1.06-1.13), and laryngeal cancer exhibited the largest effect, with a cRR of 1.13 (1.07-1.19) per additional exceedance day over a 10-year lag period. When stratified by p16 status, significant associations were noted for p16-positive, p16-negative, and p16-unknown tumors.

CONCLUSIONS

Higher frequency, intensity, or persistence of wildfire-smoke exposure is associated with increased HNC risk, with the strongest associations driven by long-term exposures.