Transportation noise and risk for colorectal cancer: a nationwide study covering Denmark.

PURPOSE Few studies have suggested that traffic noise is a risk factor for cancer, but evidence is inconclusive. We aimed to investigate whether road traffic and railway noise are associated with risk of colorectal cancer. METHODS We obtained address history for all 3.5 million people above 40 years of age and living in Denmark for the period 1990-2017 and estimated road traffic and railway noise (Lden) at the most and least exposed facades of all addresses as well as air pollution (PM2.5). During follow-up (2000-2017), 35,881 persons developed colon cancer and 19,755 developed rectal cancer. Information on individual and area-level demographic and socioeconomic variables was collected from Danish registries. We analyzed data using Cox proportional hazards models, including traffic noise as time-varying 10-year average exposure. RESULTS Exposure to road traffic noise at the most exposed facade was associated with an incidence rate ratio and 95% confidence interval for proximal colon cancer of 1.018 (0.999-1.038) per 10 dB higher noise. We observed no associations for road traffic noise at the least exposed facade or for railway noise in relation to proximal colon cancer. Also, we found no association between road traffic or railway noise and risk for distal colon cancer or rectal cancer. CONCLUSION Traffic noise did not seem associated with higher risk for colorectal cancer, although the suggestion of a slightly higher risk of proximal colon cancer following exposure to road traffic noise warrants further research.