We assessed the levels of arsenic in drilled wells in Finland and studied the association of arsenic exposure with the risk of bladder and kidney cancers. The study persons were selected from a register-based cohort of all Finns who had lived at an address outside the municipal drinking-water system during 1967-1980 (n = 144,627). The final study population consisted of 61 bladder cancer cases and 49 kidney cancer cases diagnosed between 1981 and 1995, as well as an age- and sex-balanced random sample of 275 subjects (reference cohort). Water samples were obtained from the wells used by the study population at least during 1967-1980. The total arsenic concentrations in the wells of the reference cohort were low (median = 0.1 microg/L; maximum = 64 microg/L), and 1% exceeded 10 microg/L. Arsenic exposure was estimated as arsenic concentration in the well, daily dose, and cumulative dose of arsenic. None of the exposure indicators was statistically significantly associated with the risk of kidney cancer. Bladder cancer tended to be associated with arsenic concentration and daily dose during the third to ninth years prior to the cancer diagnosis; the risk ratios for arsenic concentration categories 0.1-0.5 and [Greater/equal to] 0.5 microg/L relative to the category with < 0.1 microg/L were 1.53 [95% confidence interval (CI), 0.75-3.09] and 2.44 (CI, 1.11-5.37), respectively. In spite of very low exposure levels, we found some evidence of an association between arsenic and bladder cancer risk. More studies are needed to confirm the possible association between arsenic and bladder cancer risk at such low exposure levels.
The water from some drilled wells in southwest Finland contains high arsenic concentrations (min-max: 17-980 microg/L). We analyzed inorganic arsenic (As-i) and organic arsenic (monomethylarsonate [MMA] and dimethylarsinate [DMA]) species in urine and conducted a clinical examination of current users (n = 35) and ex-users (n = 12) of such wells. Ex-users had ceased to use the water from the wells 2-4 months previously. Urinary arsenic species were also analyzed from persons whose drinking water contained less than 1 microg/L of arsenic (controls, n = 9). The geometric means of the concentrations of total arsenic in urine were 58 microg/L for current users, 17 microg/L for ex-users, and 5 microg/L for controls. The excreted arsenic was associated with the calculated arsenic doses, and on average 63% of the ingested arsenic dose was excreted in urine. The ratios of MMA/DMA and As-i/As-tot (As-tot = As-i + MMA + DMA) in urine tended to be lower among the current users and in the higher exposure levels than in controls, suggesting that As-i was better methylated in current users. However, the differences were mainly explained by age; older persons were better methylators of inorganic arsenic than younger individuals. The arsenic content of hair correlated well with the past and chronic arsenic exposure; an increase of 10 microg/L in the arsenic concentration of the drinking water or an increase of 10-20 microg/day of the arsenic exposure corresponded to a 0.1 mg/kg increase in hair arsenic. The individuals were interviewed and complained of muscle cramps, mainly in the legs, and this was associated with elevated arsenic exposure. The present study demonstrates that arsenic methylation has no threshold at these exposure levels.
We assessed the levels of arsenic in drilled wells in Finland and studied the association of arsenic exposure with the risk of bladder and kidney cancers. The study persons were selected fom a register-based cohort of all Finns who had lived at an address outside the municipal d -water system during 1967-1980 (n = 144,627
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