A team of North Carolina State University scientists have identified elevated levels of “forever chemicals” in the blood of every pet dog and horse they tested in a recent community study.
The research, published Wednesday in Environmental Science and Technology, establishes horses and confirms dogs as important sentinel species for gauging human exposure to cancer-linked per- and polyfluoroalkyl substances (PFAS) inside and outside the home.
Blood chemistry panels conducted on the animals also revealed changes in the biological indicators used to assess liver and kidney dysfunction — two systems that are the primary targets of PFAS toxicity in humans, according to the study.
The region of Central North Carolina where the dogs and horses reside is highly contaminated with PFAS, due to the local production of these long-lasting, synthetic compounds, the authors explained.
Known for their ability to linger in both the body and the environment, PFAS are found in industrial discharge, certain firefighting foams and a variety of household items. Many of these substances — of which there are thousands — are linked to kidney cancer, thyroid disease, testicular cancer and other illnesses.
“Bolstering their utility as sentinels for human health effects, domestic animals have substantial overlap in shared health risks,” the authors stated.
While this method has historically been used to study disease spread, the researchers described “growing interest in its application for chemical-induced health risks to inform regulatory and public health response to chemical hazards like PFAS.”
The NC State researchers evaluated PFAS blood levels for 31 dogs and 32 horses from Gray’s Creek, N.C., at the request of community members who had voiced concerns about the well-being of their pets.
All of the households included in the study were on well water, and all of these wells had been tested by state inspectors and deemed contaminated with PFAS, according to the study.
After receiving a general veterinary health check, the animals underwent a blood serum screening for 33 different types of PFAS — chosen based on compounds present in the adjacent Cape Fear River Basin, the authors explained.
Among those 33 compounds of interest, the scientists identified 20 different PFAS in the pets. While all animals participating in the study had at least one such substance in their blood, more than 50 percent of the subjects had at least 12 of the 20 types of PFAS.
One of the most notorious types of PFAS, an industrial and commercial product ingredient called PFOS, had the highest concentrations in dog serum, according to the study.
The researchers found PFHxS, a surfactant used in certain firefighting foams and consumer products, in the blood of dogs but not of horses.
Other specific types of PFAS — including the compound known colloquially as GenX — was identified only in the blood of dogs and horses that drank well water.
In dogs that drank well water, median levels of two types of PFAS — PFOS and PFHxS — were similar to those of children included in the university’s GenX Exposure Study, also conducted in the Cape Fear River Basin.
Such parallels suggest that pet dogs could serve as significant indicators of household PFAS, the authors explained.
Dogs that drank bottled water, on the other hand, had different types of PFAS in their blood, and were by no means free of these substances, according to the study. In fact, the scientists identified 16 out of the 20 PFAS in dogs that drank bottled water.
“The fact that some of the concentrations in dogs are similar to those in children reinforces the fact that dogs are important in-home sentinels for these contaminants,” corresponding author Scott Belcher, an associate professor of biology at NC State, said in a statement.
“And the fact that PFAS is still present in animals that don’t drink well water points to other sources of contamination within homes, such as household dust or food,” Belcher added.
In comparison to the dogs, the horses overall had lower concentrations of PFAS in their blood, the authors found. Nonetheless, these animals had higher levels of a substance called NBP2, a byproduct of fluorochemical manufacturing.
This heightened presence of a manufacturing byproduct suggests that contamination of the outdoor environment — potentially the discharge of PFAS onto forage — could be linked to their exposure, according to the study.
“Horses have not previously been used to monitor PFAS exposure,” first author Kylie Rock, a postdoctoral researcher at NC State, said in a statement.
“But they may provide critical information about routes of exposure from the outdoor environment when they reside in close proximity to known contamination sources,” Rock added.