LAS VEGAS (KLAS) — A study of private water wells in rural Nevada found that nearly a quarter of the wells had arsenic that exceeded safe levels.

The study released Wednesday by the Desert Research Institute reported that some of the wells had arsenic levels 80 times higher than the limit in some cases. Uranium was the second-most commonly detected metal, along with elevated levels of lead, cadmium and iron.

Private wells are the primary source of drinking water for about 182,000 Nevadans, according to the study. Consuming water contaminated by metals such as arsenic can cause adverse health effects. “Long-term exposure to inorganic arsenic, mainly through drinking-water and food, can lead to chronic arsenic poisoning. Skin lesions and skin cancer are the most characteristic effects,” according to the World Health Organization.

Most of the 174 wells studied were in Northern Nevada around Reno, Carson City and Fallon. A map provided with the study showed five to seven of the wells were in Southern Nevada, but precise locations were not provided.

The study was published in Science of The Total Environment. Scientists from DRI and the University of Hawaii Cancer Center recruited households with private wells through the Healthy Nevada Project. Households were sent free water testing kits, and participants were notified of their water quality results and recommended actions they could take.

“We know from previous research that Nevada’s arid climate and geologic landscape produce these heavy metals in our groundwater,” says Monica Arienzo, Ph.D., an associate research professor at DRI who led the study. “It was important for us to reach out to community members with private wells to see how this is impacting the safety of their drinking water.”

Fewer than half (41%) of the wells sampled used water treatment systems, and some treated water samples still contained arsenic levels over EPA guidelines. Although average levels of heavy metal contaminants were lower in treated water, many homes were unable to reduce contaminants to levels considered safe.

The state leaves private well owners responsible for monitoring their own water quality, and well water testing helps ensure water is safe to drink. This study shows that more frequent testing is needed to ensure Nevada’s rural communities have safe drinking water. This is particularly important as the effects of climate change and population growth alter the chemistry of groundwater, potentially increasing metal concentrations.