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“Forever Chemicals” Detected in Blood of Dogs and Horses in PFAS Hotspot

A dog and a horse next to each other in a field.
Credit: Lucie Hošová/Unsplash
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Per- and polyfluoroalkyl substances (PFAS), or “forever chemicals”, have been found in the blood of horses and dogs – even those that exclusively drink bottled water – in a PFAS hotspot in North Carolina, USA. The study, published in Environmental Science and Technology, also establishes horses as an important sentinel species (a species used to detect possible risks to humans) and investigates possible links between PFAS exposure and the animals’ liver and kidney function.

The cost of PFAS contamination

PFAS are a group of chemicals widely used in non-stick cooking appliances, food packaging, firefighting foams and water-repellent clothing. Their durable nature makes them good materials for products that resist grease, water and oil – but this comes with serious environmental and health costs.

PFAS are incredibly difficult to break down and persist in the environment, contaminating soil, water, air and even our bloodstream. PFAS have been linked to negative health effects such as increased risk of cancer, decreased fertility, low birth weight and high cholesterol levels.

PFAS are found globally, but one town particularly blighted by their contamination is Gray’s Creek, near Fayetteville, North Carolina. PFAS contamination in the area’s drinking water wells comes from a chemical manufacturing facility – one of the world’s largest PFAS producers – that has discharged high levels of PFAS into the Cape Fear River. The manufacturer has since been tasked with sampling private wells in the area for PFAS and providing alternate drinking water to residents whose wells were found to have levels above the health advisory level.

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Nonetheless, relatively little is known about the long-term health implications for humans and animals living in these exposed communities. In the current study, researchers from North Carolina State University assessed PFAS exposures and the health of pet dogs and horses, aiming to help inform regulatory and public health responses to these chemicals.

At least one PFAS detected in all tested animals

The researchers studied 31 dogs and 32 horses from the Gray’s Creek area at the request of concerned owners in areas supplied by well water deemed as PFAS-contaminated by state inspectors.

Animals underwent veterinary health checks, and their blood was screened for 33 different PFAS chemicals that were known to be present in the nearby river basin.

The PFAS of interest include chemicals such as PFOS, which is used in many industrial and commercial products; PFHxS, a surfactant found in firefighting foams and HFPO-DA, also known as GenX.

All animals had at least one PFAS chemical detected in their blood. Overall, the researchers detected 20 different PFAS chemicals, and over half of the animals had at least 12 of these in their bloodstream.

Dogs had higher overall levels of PFAS compared to horses, and PFOS had the highest concentrations in dogs while PFHxS was found only in the dogs tested and not the horses. Additionally, GenX was found only in animals that drank well water, while dogs that only drank bottled water (approximately half of the dogs in the study) had a different variety of PFAS compounds, with researchers still detecting 16 of the 20 PFAS in their bloodstream.

Horses, however, did show higher concentrations of PFAS manufacturing byproducts, suggesting that contamination of the outdoor environment contributed to their exposure during foraging.

“Horses have not previously been used to monitor PFAS exposure,” said Dr. Kylie Rock, lead author of the study and postdoctoral researcher at North Carolina State University. “But they may provide critical information about routes of exposure from the outdoor environment when they reside in close proximity to known contamination sources.”

Finally, blood panels from veterinary health checks showed changes in diagnostic biomarkers used to assess liver and kidney dysfunction, two organs that are primary targets of PFAS toxicity in humans.

“While the exposures that we found were generally low, we did see differences in concentration and composition for animals that live indoors versus outside,” said Dr. Scott Belcher, senior author of the study and associate professor of biology at North Carolina State University.

“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,” Belcher continued. “And the fact that PFAS [are] still present in animals that don’t drink well water points to other sources of contamination within homes, such as household dust or food.”

Reference: Rock KD, Polera ME, Guillette TC, et al. Domestic dogs and horses as sentinels of per- and polyfluoroalkyl substance exposure and associated health biomarkers in Gray’s Creek North Carolina. Environ Sci Technol. 2023. doi: 10.1021/acs.est.3c01146

This article is a rework of a press release issued by North Carolina State University. Material has been edited for length and content.