Well water radioactivity and risk of cancers of the urinary organs.

Water from bedrock frequently contains higher concentrations of natural radionuclides than water from other sources. Bladder and kidneys receive a radiation dose when radioactive isotopes are excreted into urine. The subjects for this case-cohort study were selected from all drilled wells users in Finland. The study comprised 61 bladder cancer and 51 kidney cancer cases diagnosed between 1981 and 1995, as well as a random sample of 274 reference persons, stratified by age and sex. The median activity concentrations of radon in drilled wells used by bladder and kidney cancer cases and the reference cohort were 170, 140, and 130 Bq/L, respectively. The radium concentration was 0.01 Bq/L for all groups and the uranium concentrations were 0.08, 0.07, and 0.06 Bq/L, respectively. The bladder cancer risks associated with radon, radium, and uranium activity concentrations in drinking water were 1.02 (0.68-1.54) per log(100 Bq of radon/L), 0.73 (0.21-2.50) per log(0.1 Bq of radium/L), and 0.77 (0.32-1.89) per log(1 Bq of uranium/L). The corresponding figures for kidney cancer were 0.81 (0.47-1.37), 0.12 (0.01-1.10), and 0.92 (0.36-2.35), respectively. In conclusion, even though ingested radionuclides from drilled wells are a source of radiation exposure, they are not associated with a substantially increased risk of bladder or kidney cancers in concentrations occurring in drilled wells.