Air pollution is associated with increased incidence-rate of head and neck cancers: A nationally representative ecological study

Introduction: Early studies show conflicting findings regarding particulate matter < 2.5 mu m in diameter (PM2.5) exposure and development of head and neck cancers (HNC). We analyzed the relationship between PM(2.5 )exposure and various types of HNC in a nationally representative ecological sample. Methods: We determined HNC incidence in 608 US counties from 2011 to 2019 using the Surveillance, Epidemiology and End Results (SEER) Program from the National Cancer Institute. We also collected information on sociodemographic factors from SEER and data on smoking and alcohol intake from CDC data frames (county level). PM2.5 exposure levels were estimated using satellite and meteorological data via previously validated general additive models. Flexible semi-nonparametric regression models were used to test the relationship between PM2.5 exposure levels and HNC incidence, adjusting for demographics, socioeconomic factors, and comorbidity. Results: Increased PM2.5 exposure levels were associated with higher incidence-rates of oral cavity and pharyngeal cancers controlling for confounders in our primary analyses (IRR = 1.04, 95 % CI 1.01, 1.07, p = 0.02 per 1 mu g/m(3 )increase in PM2.5). This relationship was maintained after adjusting for multiple testing (Holm s method, p = 0.04) and in ordinary least squares (OLS) regression (beta = 0.17, 95 % CI 0.01, 0.57, p = 0.01). Increased exposure was also associated with other HNC: esophagus (IRR = 1.06, 95 % CI 1.01, 1.11, p = 0.02), lip (IRR = 1.16, 95 % CI 1.03, 1.31, p = 0.01), tonsil (IRR = 1.10, 95 % CI 1.03, 1.16, p < 0.01). However, these relationships were not maintained in secondary analyses. Conclusions: This nationally representative ecological study shows that increased levels of air pollution are associated with increased incidence of overall oral cavity and pharyngeal cancers in the US.