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Arsenic Adaptation

People living high in the Andes Mountains have a genetic variant that seems to enable them to quickly process arsenic, a team of Swedish researchers reports in Molecular Biology and Evolution.

The available drinking water in the area contains naturally high levels of arsenic — some 20 times higher than the maximum recommended by the World Health Organization, NPR notes. But people living in the northern Argentinian village San Antonio de los Cobres appear to have adapted to arsenic, which otherwise causes vomiting, convulsions, and coma at high doses and skin lesions, liver damage, and cancer at chronic exposure levels. Mummies from the area dating back some 7,000 years ago also exhibited high arsenic levels, indicating that people in the region have been exposed to the poison for many generations, NPR adds.

The Swedish team genotyped 124 women from the village at more than 4 million SNPs to find a strong association between an AS3MT gene variant and processed arsenic in the women's urine. AS3MT, the team adds, encodes an arsenic methyltransferase.

Senior author Karin Broberg from the Karolinska Institutet tells NPR that this variant is found in other human populations, but seems to be more prevalent among the villagers. Though studies have indicated that the faster people excrete arsenic, the lower their risk of cancer and related problems, Broberg notes that the effect of the poison on this population isn't clear.

"We haven't looked at the toxic effects in this population," she tells NPR. "We can't say that they are not harmed by arsenic. And besides, we should aim for very low arsenic in drinking water and food everywhere — that will protect everybody."