Research overview
Researchers at the Center for Marine Environmental Studies (CMES), Ehime University, have published two linked studies on PFAS exposure in companion animals. The first study examined PFAS contamination in commercial pet foods sold in Japan. The second study followed up by analyzing PFAS in the blood serum of pet dogs and cats, including paired analysis of serum and the dry pet foods actually consumed by the same animals. Together, the studies suggest that pet food may be one contributor to long-chain PFAS exposure, particularly in cats.

Background
PFAS, or per- and polyfluoroalkyl substances, are a large group of synthetic chemicals used for their water- and oil-repellent properties. Because many PFAS are highly persistent and can be detected in water, food, wildlife, and humans, they are a growing concern for environmental and public health. Dogs and cats live in close contact with humans, share household environments, and often consume commercial diets every day. This makes companion animals important for understanding chemical exposure in domestic settings.

Methods
In the first study, the research team analyzed 100 commercial dog and cat food products sold in Japan and quantified 34 PFAS compounds. The study examined how PFAS patterns differed according to food type, ingredients, and country-related product characteristics.

In the follow-up study, the team analyzed serum samples from privately owned dogs (n = 23) and cats (n = 30) collected from Hokkaido, Osaka, and Ehime, Japan. In the Ehime cohort, dry pet food samples actually consumed by the same animals were also collected, allowing paired serum-food analysis. Thirty-eight PFAS, including branched isomers and emerging compounds, were targeted by LC-MS/MS.

Main findings
PFAS were widely detected in commercial pet foods. Fish-based products tended to contain higher levels of PFOS and long-chain perfluoroalkyl carboxylic acids such as PFUnDA and PFTrDA. These compounds are known to accumulate in aquatic food webs, suggesting that fish-derived ingredients can be an important factor in PFAS contamination of pet foods. An emerging PFAS, 9Cl-PF3ONS, was also detected in some products.

The follow-up serum study revealed clear differences between dogs and cats. Cats showed higher burdens of long-chain perfluoroalkyl carboxylic acids, including PFNA, PFDA, PFUnDA, PFDoDA, and PFTrDA, whereas dogs showed profiles more influenced by PFOS and PFHxS. In the paired Ehime cohort, stronger serum-food relationships were observed in cats for PFOS, PFUnDA, PFTrDA, and total PFAS. These results suggest that the pet food actually consumed by the animals may contribute to feline long-chain PFAS exposure under real-world household conditions.

The study does not indicate that diet is the only source of PFAS exposure in pets. Indoor dust, drinking water, grooming behavior, outdoor activity, household products, and species-specific biological differences may also contribute. In dogs, the weaker serum-food relationships suggest that more diverse exposure pathways may be involved.

Significance
The key advance of these linked studies is that the team moved from detecting PFAS in pet food to asking whether those chemicals are reflected in the animals that consume the food. By pairing serum samples with the foods actually eaten by the same animals, the research provides new evidence for dietary contribution to PFAS exposure in household pets, especially cats.

Because companion animals share domestic environments with humans, these findings are relevant not only to animal health but also to broader household chemical exposure. The work highlights the value of companion animals as potential One Health sentinels connecting environmental contamination, animal health, and human living environments.

Future perspectives
Further studies should integrate pet food, indoor dust, drinking water, grooming behavior, and ingredient supply chains to better understand PFAS exposure in companion animals. Species-specific toxicokinetics and health-based guidance values for dogs and cats are also needed to improve risk assessment for pets.