The population of an Argentine village in the Andes drinks water with arsenic levels 20 times higher than recommended, but has no health problems.
The inhabitants of San Antonio de los Cobres, a remote town on the Puna de Atacama plateau in the Andes, appear to have developed a rare genetic adaptation which allows them to safely process water contaminated with arsenic.
The discovery is the result of genetic research published in Molecular Biology and Evolution that analyzed the population’s DNA. For thousands of years, the inhabitants of this region depended on groundwater with arsenic levels well above globally recommended safety limits.
According to the World Health Organization, the safe limit for arsenic in drinking water is 10 micrograms per liter. However, before the installation of a filtration system in 2012, the water in San Antonio de los Cobres had concentrations of around 200 micrograms per liter.
Despite the risks associated with arsenic exposure, including cancer, birth defects and organ damage, the region is continuously inhabited for 11,000 years. This long exposure appears to have driven a process of natural selection, favoring individuals with genetic characteristics that resist arsenic toxicity, writes .
The researchers identified important variations close to the AS3MT genewhich plays a central role in how the human body metabolizes arsenic. These variants were found at significantly higher frequencies in the local population compared to other South American groups, including those from Peru and Colombia.
Genetic differences affect how arsenic is processed in the body. Typically, arsenic is converted into several chemical forms, including a highly toxic intermediate known as monomethylated arsenic (MMA). In the Andean population, however, the organism appears to be more efficient in conversion of arsenic into a less harmful form, dimethylated arsenic (DMA), which can be excreted more easily in the urine.
This biological advantage had already been suggested in previous studies, which showed that local inhabitants produced lower levels of the toxic intermediate compound. New genetic evidence helps explain the mechanism behind this observation.
The findings support the theory that humans can adapt not only to physical extremes, such as altitude or temperature, but also to prolonged exposure to toxic substances.
