WASHINGTONAbundant evidence links arsenic in drinking water to an
increased risk of bladder and lung cancer and it is stronger than ever,
according to a new report from the National Research Council (NRC), the
research arm of the National Academy of Sciences.
Even very low concentrations "appear to be associated with a higher
incidence of cancer," said Robert Goyer, MD, professor emeritus of
pathology, University of Western Ontario.
Dr. Goyer chaired the committee that wrote the report, which was funded by
the U.S. Environmental Protection Agency (EPA). The findings support a 1999 NRC
report that found high cancer risks at the maximum allowable level of 50 parts
per billion (ppb) of arsenic. The Clinton Administration lowered that rate to
10 ppb in January, but in March, the Bush White House put a hold on the lower
limit and asked for another NRC assessment.
The new report estimated that men and women who ingest 3 ppb of arsenic
daily in their drinking water have an increased risk of bladder and lung cancer
of 1 in 1,000, or 0.001%. At 5 ppb, the increased risk rises to 0.0015%, and at
10 ppb, the risk is greater than 0.003%. Consumption of 20 ppb daily pushes the
increased risk to nearly 0.007%.
The new estimates are higher than those used by EPA in setting its limit of
10 ppb because the NRC panel used several estimation methods and assumptions
that differ from those applied by EPA.
The committee also noted that detecting any increased cancer that resulted
from drinking arsenic-contaminated water would be statistically difficult
because the excess risk is only a small percent of a person’s overall risk of
bladder and lung cancer from all causes. As an example, it said an increased
risk of 0.0045% for bladder cancer would represent only 13% of the total risk
for male bladder cancer in the United States from all causes.