URINARY-EXCRETION OF ARSENIC SPECIES AFTER EXPOSURE TO ARSENIC PRESENT IN DRINKING-WATER

The water from some drilled wells in southwest Finland contains high a rsenic concentrations (min-max: 17-980 mu g/L). We analyzed inorganic arsenic (As-i) and organic arsenic (monomethylarsonate [MMA] and dimet hylarsinate [DMA]) species in urine and conducted a clinical examinati on of current users (n = 35) and ex-users (n = 12) of such wells. Ex-u sers had ceased to use the water from the wells 2-4 months previously. Urinary arsenic species were also analyzed from persons whose drinkin g water contained less than 1 mu g/L of arsenic (controls, n = 9). The geometric means of the concentrations of total arsenic in urine were 58 mu g/L for current users, 17 mu g/L for ex-users, acid 5 mu g/L for controls. The excreted arsenic was associated with the calculated ars enic doses, and on average 63% of the ingested arsenic dose was excret ed in urine. The ratios of MMA/DMA and As-i/As-tot (As-tot = As-i + MM A + DMA) in urine tended to be lower among the current users and in th e higher exposure levels than in controls, suggesting that As-i was be tter 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 correlat ed well with the past and chronic arsenic exposure; an increase of 10 mu g/L in the arsenic concentration of the drinking water or an increa se of 10-20 mu g/day of the arsenic exposure corresponded to a 0.1 mg/ kg increase in hair arsenic. The individuals were interviewed and comp lained of muscle cramps, mainly in the legs, and this was associated w ith elevated arsenic exposure. The present study demonstrates that ars enic methylation has no threshold at these exposure levels.