Inorganic
arsenic exposure through
drinking water causes
cancer in adults; however, the carcinogenic potential in children remains unknown. A recent
leukemia cluster in Churchill County, Nevada, where
arsenic levels in water supplies are relatively high, has prompted concern. The authors investigated the incidence of childhood
cancer between 1979 and 1999 in all 17 Nevada counties, grouped by low (i.
e., < 10 microg/l), medium (10-25 microg/l), and high (35-90 microg/l) population-weighted
arsenic levels in public
drinking water supplies. The standardized incidence ratios (SIRs) for
all childhood cancers combined were 1.00 (95% confidence interval [CI] = 0.94, 1.06), 0.72 (95% CI = 0.43, 1.12), and 1.25 (95% CI = 0.91, 1.69) for low-, medium-, and high-exposure counties, respectively. There was no relationship between
arsenic levels in water and childhood
leukemia (SIRs = 1.02, 0.61, and 0.86, respectively [95% CIIs = 0.90, 1.15; 0.12, 1.79; and 0.37, 1.70, respectively]). For
all childhood cancers, excluding
leukemias, the SIRs were 0.99 (95% CI = 0.92, 1.07), 0.82 (95% CI = 0.42, 1.22), and 1.37 (0.92, 1.83), respectively. The excess in 5- to 9-yr-old children and 10- to 14-yr-old children was in bone
cancers, and the excess in 15- to 19-yr-old young adults was primarily in
lymphomas. The findings in this study are reassuring in that
leukemia risks were not increased at the concentrations of
arsenic in water found in this study. Nonetheless, the results raise the possibility that there are increased risks for nonleukemic childhood
cancers that require confirmation in other studies, particularly those in which higher exposures are addressed.