Study finds higher-than-recommended levels of heavy metals in dogs’ drinking water

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A recent survey has revealed that two-thirds of dogs are consuming heavy metals in their drinking water above levels set by the United States Environmental Protection Agency (EPA). The study, published August 6, 2025, in the journal PLOS Water, analyzed well water samples from households across 10 US states not connected to municipal water systems.

For the study, 178 owners of dogs participating in the Dog Aging Project—a long-term study of canine health and aging—mailed samples of their dogs’ drinking water for testing and provided information about their dogs’ health and their home’s drinking water supply.

Researchers then tested for the presence of 28 different metals in these water samples and identified 126 instances when arsenic, lead, copper, sodium, strontium, nickel, or vanadium were above EPA’s maximum contaminant levels or health guidance levels. Of the 28 metals tested, approximately half have established maximum contaminant levels or health guidance levels.

According to the study, 13 of the 126 instances tested above EPA-recommended levels for arsenic, lead, and copper. Detectable levels of all 28 metals tested were found in all 178 samples.

“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,” wrote the study’s authors.^1,2

According to reports, approximately 15 million households in the country use private well water that is not regulated by the EPA’s Safe Drinking Water Act.¹ This puts residents of these homes at an increased risk of ingesting heavy metals leaching into groundwater, which can cause health issues in the long run.

The metals with maximum contaminant levels from the 28 that were tested are known for causing chronic health issues in humans following long-term consumption.² Additionally, the researchers found a potential link between the presence of titanium and chromium in drinking water and the development of health conditions in dogs.²

The study also found a link between environmental factors and the presence of metals in these canines' drinking water. For example, water from homes near fracking sites contained higher levels of sodium and sulfur, while proximity to railroad tracks was associated with higher manganese levels. Moreover, dogs drinking water treated with reverse osmosis were less likely to experience non-chronic health conditions.¹

According to the researchers, a more in-depth study with a larger, stratified sample analyzing the composition of dogs’ drinking water may be needed to explore long-term health and wellness outcomes in dogs living in diverse geographies.²

“These results may impact veterinary care decisions and husbandry, and underscore the validity and importance of utilizing dogs as sentinels of human health outcomes in the context of drinking water contamination,” wrote the authors of the study.²

The study was carried out by researchers from the Virginia Polytechnic Institute and State University, University of Washington, and the Dog Aging Project Consortium, and was funded by the National Institute on Aging.

References

1. What’s in your pup’s bowl? Heavy metals, reveals 10-state survey. News release. August 6, 2025. PLOS Water.
2. Sexton CL, O’Brien J, Lytle J, et al. Testing for heavy metals in drinking water collected from Dog Aging Project participants. PLOS Water. 2025;4(7):e0000296. doi:10.1371/journal.pwat.0000296