Long-term Residential Exposure to Air Pollution and Risk of Testicular Cancer in Denmark: A Population-Based Case-Control Study

Background: The incidence rate risk of testicular cancer has increased over the last four decades, and the most significant increase has been among Caucasian men in Nordic countries. Second-generation immigrant studies indicate a significant role of environmental exposure in testicular cancer. Methods: We conducted a nationwide register-based case- control study including 6,390 testicular cancer cases registered in the Danish Cancer Registry between 1989 and 2014. Up to four agematched controls for each case (n 18,997) were randomly selected fromthe Civil Registration System.Ambient air pollution levels were estimated at addresses of cases and controls with a state-of-the-art air pollution modeling system. Results: We mostly found ORs close to 1.00 and with 95% confidence intervals (CI) spanning 1.00. Exposure during the year preceding birth was associated with ORs for nitrogen dioxide (NO2) of 0.87 (95% CI, 0.77-0.97) per 10 mg/m3 and for organic carbon of 0.84 (95% CI, 0.72-0.98) per 1 mg/m3. Exposure during the first 10 years of life was associated with ORs for organic carbon of 0.79 (95% CI, 0.67-0.93) per 1 mg/m3, for ozone (O3) of 1.20 (95% CI, 1.07-1.34) per 10 mg/m3, and for secondary inorganic aerosols of 1.07 (95% CI, 1.00-1.15) per 1 mg/m3. Conclusions: Early-life exposure to NO2 and organic carbon (OC) was associated with lower risk for testicular cancer whereas early-life exposure to O3 and secondary inorganic aerosols (SIA) was associated with higher risk.