'Acceptable' arsenic levels increase cancer risk
2001-03-16 11:48
New York - 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 of March 1,
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 said.
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.