Ambient particulate matter air pollution is associated with increased risk of papillary thyroid cancer.

Abstract Background The association between exposure to air pollution and papillary thyroid carcinoma is unknown. We sought to estimate the relationship between long-term exposure to the fine (diameter ≤ 2.5 μm) particulate matter component of air pollution and the risk of papillary thyroid cancer. Methods Adult (age ≥18) patients with newly diagnosed papillary thyroid carcinoma between January 1, 2013 and December 31, 2016 across a single health system were identified using electronic medical records. Data from 1,990 patients with papillary thyroid carcinoma were compared with 3,980 age- and sex-matched control subjects without any evidence of thyroid disease. Cumulative fine (diameter Results Increased odds of developing papillary thyroid carcinoma was associated with a 5 μg/m3 increase of fine (diameter ≤2.5 μm) particulate matter concentrations over 2 years (adjusted odds ratio = 1.18, 95% confidence interval: 1.00–1.40) and 3 years (adjusted odds ratio = 1.23, 95% confidence interval: 1.05–1.44) of exposure. This risk differed by smoking status (pinteraction = 0.04). Among current smokers (n = 623), the risk of developing papillary thyroid carcinoma was highest (adjusted odds ratio = 1.35, 95% confidence interval: 1.12–1.63). Conclusion Increasing concentration of fine (diameter ≤2.5 μm) particulate matter in air pollution is significantly associated with the incidence of papillary thyroid carcinoma with 2 and 3 years of exposure. Our novel findings provide additional insight into the potential associations between risk factors and papillary thyroid carcinoma and warrant further investigation, specifically in areas with high levels of air pollution both nationally and internationally.