Elevated intake of arsenic present in drinking water is associated with an increased risk of renal pelvis and ureter cancers, according to a case-control study conducted in northern Chile.

The study compared 122 kidney cancer cases and 640 population-based controls. The cases included 76 renal cell cancers, 24 renal pelvis and ureter transitional cell carcinomas (TCC), and 22 other kidney cancers.

Compared with subjects whose average arsenic intake from drinking water was less than 400 μg/day, those whose average intake was 400-1,000 μg/day and greater than 1,000 μg/day had a significant 5.7-fold and 11-fold increased risk of renal pelvis and ureter cancers, respectively, researchers led by Craig Steinmaus, MD, MPH, reported online in the American Journal of Epidemiology. Elevated arsenic intake was not associated with an increased risk of renal cell cancer.

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Dr. Steinmaus’ group pointed out that northern Chile is one of the best places in the world to investigate the carcinogenicity of arsenic in part because of high exposures to the heavy metal and the availability of good records on past arsenic water concentrations.

They noted that several factors support the biological plausibility of their findings. First, ingested arsenic is a well-established cause of bladder cancer, most of which also is TCC. Second, the kidney is the primary route of arsenic excretion, so almost all ingested arsenic reaches the kidneys.

“With these new findings,” the authors concluded, “including evidence of a dose-response, we believe there is now sufficient evidence in humans that drinking-water arsenic causes renal pelvis and ureter cancer.”