July 1, 2005

Arsenic toxicity may vary, depending on genes

By Alison McCook

NEW YORK (Reuters Health) - Some children with particular
genetic patterns appear to process arsenic differently,
suggesting that they may be more -- or less -- vulnerable to
its effects, according to new study findings.

Researchers found that children who carry a certain
variation of the CYT19 gene tend to break down arsenic
differently than children with different variations of the same

"If people metabolize arsenic differently," Dr. Walter T.
Klimecki told Reuters Health, "it's reasonable to suspect they
may have a different risk of toxicity." If that's the case,
"then the regulators need to consider regulating with that in
mind" -- perhaps by capping acceptable levels at what's safe
for the more vulnerable group, not the population at large, he

Klimecki, of the University of Arizona at Tucson, explained
that arsenic has always posed somewhat of a "conundrum" for
researchers. A significant body of "unequivocal" evidence shows
it can cause cancer and other health problems, but researchers
remain unclear about how arsenic does its damage, the
researcher noted.

To understand more how people respond to arsenic, Klimecki
and his colleagues collected urine samples from 139 people
whose drinking water contained a range of arsenic
concentrations, from very little to amounts that approached the
current upper U.S. limit for arsenic in drinking water.

Reporting in the journal Environmental Health Perspectives,
the investigators found that children who carried one
particular variant in the CYT19 gene -- which investigators
have linked to arsenic metabolism -- showed different amounts
of arsenic breakdown products in their urine, suggesting that
they metabolized the chemical differently.

Whether that means those children are more or less
susceptible to arsenic is unclear, Klimecki noted.

Interestingly, variants in the CYT19 gene appeared to have
no relationship to how adults metabolized arsenic, suggesting
that the CYT19 gene may be more active in childhood, then gets
turned off in adulthood, Klimecki noted.

SOURCE: Environmental Health Perspectives, June 2005.