Two-thirds of dogs tested in a recent survey consume higher-than-recommended levels of heavy metals in their drinking water, according to a study published August 6, 2025 in the open-access journal PLOS Water by Audrey Ruple from Virginia Tech, U.S., and colleagues. The survey, which focused on well water households in 10 states, uncovered 13 instances where arsenic, lead and copper tested above EPA-recommended levels.
Roughly 15 million U.S. households use private well water and are not protected by the EPA's Safe Drinking Water Act , which regulates safety testing in drinking water. These households — and the canine companions inside — are at an increased risk for consuming heavy metals that leach into groundwater.
In this study, the researchers analyzed drinking water samples from 178 dogs in homes not served by municipal water sources. All dogs are part of the Dog Aging Project, a long-term study of canine health and aging. Samples ranged across 10 states and tested for 28 heavy metals, about half of which are regulated by the EPA. Owners mailed drinking water samples to the researchers and completed detailed surveys about their dogs' health and the home's drinking water supply.
Across all 178 samples obtained, the researchers found detectable levels of all 28 metals tested. Two-thirds of the samples tested included at least one heavy metal over the EPA's maximum contaminant level (MCL) or health guidance levels. In 13 instances, arsenic, lead and copper tested above the EPA's MCL guidance levels.
Correlations identified within the experiment include: nearby fracking sites are associated with more sodium and sulfur in the drinking water; railroad tracks are associated with increased levels of manganese; and dogs drinking from water treated with reverse osmosis or a sediment filter were less likely to have a non-chronic health condition.
The researchers emphasize that big-picture conclusions require further study, and expressed a desire to continue testing dogs' drinking water composition juxtaposed to their long-term health. Ultimately, this information can help guide veterinary care decisions and improve the health of the dogs' human companions.
The authors add: "Many households served by private wells are flying under the regulatory radar. Dogs living in these homes may be our first warning signs of environmental exposures in underserved rural areas."
