Wells in Western Great Basin May Have Dangerous Levels of Arsenic

A new study reveals that more than 49 thousand private groundwater well users across the western Great Basin region may be at risk of exposure to harmful levels of arsenic in drinking water.

Using data from groundwater wells across the western Great Basin, researchers from the Desert Research Institute (DRI) and the University of Hawai'i Cancer Center built a model predicting the probability of elevated arsenic in groundwater and the location and number of private well users that may be exposed.

The study, published in the journal Environmental Science and Technology, found that populations living in the Carson Desert basin (including the town of Fallon, Nevada), Carson Valley (Minden and Gardnerville, Nevada), and the Truckee Meadows (Reno) are at the highest risk.

Researchers say arsenic naturally occurs in the region's groundwater, while geothermal and tectonic processes in the Great Basin contribute to its higher concentrations. Another source of arsenic is the region's mountains, where erosion of arsenic-rich volcanic and meta-sedimentary rocks results in sediment being transported to the valleys below and, eventually, into the groundwater.

"Community members can use our arsenic hazard map to see what the risk is at their location, which might motivate them to test their well water," says Monica Arienzo, Ph.D., associate research professor at DRI and study co-author. "Then, if they have high levels of arsenic or other contaminants, they can take steps to reduce their exposure, such as installing a water treatment system."

Predicted probability of arsenic ≥5 μg/L in alluvial aquifers of the western Great Basin

Long-term exposure to elevated levels of arsenic in drinking water is associated with various conditions, such as skin disorders, increased diabetes risks, and high blood pressure. Arsenic is also classified as a human carcinogen because it is linked to several cancers, including the bladder, lungs, skin, kidney, nasal passages, liver, and prostate.

The U.S. Environmental Protection Agency's (EPA) standard for arsenic in drinking water is 10 parts per billion. However, previous research has indicated various health impacts from long-term exposure to levels above 5 µg/L.

Using his concentration as the benchmark, the model predicted most of the region's groundwater to have more than a 50% probability of elevated arsenic levels.

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