Long-term environmental background radiation is associated with urinary tract cancer incidence: A population-based...

The long-term carcinogenic effects of natural radioactive elements in the environmental background on urinary tract cancer (UTC) have not been fully investigated in the general population.

The entire Finnish population was linked to long-term municipality-level data on concentrations of uranium and radon in water and radon in indoor air by residential location annually between 1987 and 2016, and UTC incidence was tracked until 2021 based on multiple registries. The first principal component (PC1) of the three radiation exposures was used as a proxy for radiation exposure, and was assessed using the Cox proportional hazards model for its association with UTC risk. Age-standardized incidence rates (ASR) and population attributable fractions (PAF) of radiation exposure were estimated. Spatial association between regional radiation exposure and UTC risk was assessed.

Among a total of 2,816,495 residents with 30-year exposure data, 6718 primary UTC cases were diagnosed during 2017-2021. UTC risk increased significantly with each standard deviation (SD) increase in PC1 (hazard ratio [HR] = 1.05, 95 %CI 1.02-1.07). Dose-response relationship was observed when exposure was modelled via natural cubic splines. Increasing UTC incidence was observed across exposure quintiles (lowest quintile: ASR = 47, 95 % CI 45-50; highest quintile: ASR = 53, 95 %CI 50-55). About 5.1 % (PAF, 95 %CI 0.5 %-9.7 %) of UTC incidence was attributable to radiation exposure. Stronger association (HR=1.06, 95 %CI 1.03-1.09, per 1-SD increase) and attributable fraction (PAF = 9.0 %, 95 %CI 3.2 %-14.8 %) were observed among men than among women. Regional UTC risk was significantly associated with regional radiation exposure adjusted for the spatial lag effect in the total population (β = 0.08, p < 0.01), men (β = 0.07, p < 0.01) and women (β = 0.1, p = 0.02).

Association between long-term environmental radiation exposure and UTC risk was observed in the Finnish population. Dose-response patterns were observed, especially among men. UTC risks attributable to radiation exposure and geographical patterns warrant further investigations.