An ecological study of Superfund contaminants and thyroid cancer incidence in the United States

Environmental contaminants potentially associated with thyroid cancer are found in Superfund sites, areas the United States Environmental Protection Agency (EPA) has listed for cleanup. This study investigated the association between thyroid cancer incidence rates and Superfund density for sites containing certain contaminants that have been found to be potentially associated with thyroid cancer. Public data on thyroid cancer incidence rates (2015–2019; U.S. Centers for Disease Control and Prevention) and Superfund sites (1980–2014; EPA) were used. Multiple linear regressions were conducted to account for potential confounders, including income, race, and ethnicity. The results showed significant, positive correlations between thyroid cancer incidence rates and log Superfund density in counties with at least one Superfund site for total incidence (B = 0.897, SE = 0.169, p < 0.001), female incidence (B = 1.363, SE = 0.169, p < 0.001), and male incidence (B = 0.438, SE = 0.169, p = 0.010). On sensitivity tests of all counties, including those with zero sites, only female thyroid cancer incidence rate was positively, significantly associated with log Superfund density (B = 0.264, SE = 0.053, p < 0.001). Future studies may assess thyroid cancer incidence, Superfund sites, and covariates at the individual and community levels.