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NEW YORK, Mar 15 (Reuters Health) - As US regulators work toward lowering arsenic levels in drinking water, a new study from Taiwan shows that levels currently considered "acceptable" can increase cancer risk.
Earlier this year, the US Environmental Protection Agency (EPA) issued a ruling that called for maximum allowable arsenic levels to be lowered from 50 parts per billion (ppb) to 10 ppb in an effort to cut the health risks associated with the contaminant. That ruling, due to take effect in 2002, is being reviewed by the new EPA administrator, Christie Whitman, who "has the option to delay the effective date or make changes to the final ruling," said Robin Woods, an EPA spokesperson.
Now, in the American Journal of Epidemiology for March 1st, researchers from the National Taiwan University in Taipei report that arsenic levels between 10 ppb and 50 ppb in drinking water increase a person's risk for developing bladder cancer.
Dr. Chien-Jen Chen and colleagues looked at the occurrence of cancers affecting the bladder, kidney and urinary tract among 8,102 residents of northeastern Taiwan, as well as their level of exposure to arsenic in drinking water.
The risk of urinary cancer increased as exposure to arsenic increased, the investigators found. Exposure to arsenic levels between 10.1 ppb to 50 ppb in drinking water nearly doubled cancer risk compared to the risk in the general population. Risk was roughly eight times higher when levels were between 50 ppb and 100 ppb and 15 times higher for people exposed to arsenic levels exceeding 100 ppb.
The new findings "make an important contribution to improving the precision of the estimated risk of cancer of the urinary tract associated with ingested arsenic from drinking water," Dr. Kenneth P. Cantor of the National Cancer Institute in Bethesda, Maryland, said in a commentary on the study.
"The great strength of this study is that it is based on information from people whose levels of exposure to arsenic and disease outcome were known on an individual basis," Cantor told Reuters Health.
Arsenic is found naturally in rocks, soil, water and air. Industrial, agricultural or mining operations can also cause arsenic contamination in the surrounding environment. Scientists say that most water sources in the United States contain less than 5 ppb of arsenic, but "there may be hot spots with...higher than the predicted occurrence," the EPA cautions.
"More water systems in the western states that depend on underground sources of drinking water have naturally occurring levels of arsenic at levels greater than 10 ppb than in other parts of the US. Parts of the Midwest and New England have systems whose current arsenic levels range from 2 to 10 ppb," according to the EPA.
SOURCE: American Journal of Epidemiology 2001;153:411-418.
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