Their first study analysed 100 dog and cat food products and detected multiple PFAS compounds, with fish-based products showing particularly high levels of some long-chain chemicals.
A second linked study examined PFAS in the blood serum of 23 privately owned dogs and 30 cats across Japan.
Researchers also compared blood samples with dry pet food eaten by the same animals in an Ehime-based cohort, providing a more direct assessment of the relationship between diet and PFAS exposure.
The results point to PFAS in pet food as a potential contributor to exposure, particularly in cats. Stronger relationships between food and serum concentrations were observed for several PFAS in cats, while dogs showed more varied exposure patterns, suggesting that diet is only one of several possible sources.
PFAS detected across commercial pet foods
PFAS are a large family of synthetic chemicals valued for their resistance to water, oil, heat and degradation. Their persistence means they can remain in the environment and move through food chains, with some compounds accumulating in wildlife and people.
For companion animals, the issue is particularly relevant because dogs and cats can consume the same commercial diet every day for years. They also share indoor environments with their owners, potentially encountering PFAS through household dust, water, treated materials and other products.
In the first study, the CMES team tested 100 commercial dog and cat foods available in Japan for 34 PFAS compounds. The researchers examined differences associated with food type, ingredients and product characteristics.
Fish-based foods stood out as a potential source of PFAS contamination. These products tended to contain higher concentrations of PFOS and long-chain perfluoroalkyl carboxylic acids, including PFUnDA and PFTrDA.
The researchers suggest that this may reflect the ability of some PFAS to accumulate through aquatic food webs, meaning contaminated fish ingredients could transfer these persistent chemicals into pet food.
An emerging PFAS known as 9Cl-PF3ONS was also identified in some products, highlighting the importance of looking beyond a small number of well-known PFAS when assessing contamination.
Cats showed higher levels of long-chain PFAS
The second study moved the research from the food itself to the animals consuming it. Serum samples were collected from privately owned dogs in Hokkaido, Osaka and Ehime, alongside samples from cats in the same regions.
Using liquid chromatography-tandem mass spectrometry, the researchers targeted 38 PFAS, including branched isomers and emerging compounds.
The results revealed a clear difference between species. Cats generally carried higher concentrations of several long-chain perfluoroalkyl carboxylic acids, including PFNA, PFDA, PFUnDA, PFDoDA and PFTrDA.
Dogs, meanwhile, displayed profiles more strongly associated with PFOS and PFHxS.
The most significant finding came from the paired samples collected in Ehime. Among cats, serum concentrations showed stronger relationships with the PFAS levels in the dry food they were actually eating. Associations were observed for PFOS, PFUnDA, PFTrDA and total PFAS.
This does not prove that pet food is the sole source of exposure, but it strengthens the evidence that diet can contribute to PFAS accumulation in cats.
Diet is only part of the exposure picture
The researchers caution against viewing pet food as the only route through which companion animals encounter PFAS.
Indoor dust, drinking water, household materials, grooming behaviour and outdoor activity could all contribute to exposure. The weaker relationship between food and serum PFAS in dogs also suggests that exposure pathways may differ considerably between species.
These differences could reflect variations in metabolism, behaviour, diet, body size and the way individual PFAS are absorbed and retained.
Pets could provide a One Health warning
The linked studies are significant because they connect environmental contamination with real-world exposure in household animals. Companion animals live alongside people and share many of the same indoor environments, making them potentially useful sentinels for chemical exposure.
The findings therefore extend beyond the question of PFAS in pet food. They highlight a broader One Health issue in which environmental pollutants, animal health and human exposure are closely connected.
Further research will be needed to establish how PFAS move through pet food supply chains and how different exposure routes contribute to the chemical burden found in dogs and cats.
Combining analysis of pet food with indoor dust, drinking water, grooming behaviour and other household exposures could provide a clearer picture.
Researchers also say species-specific toxicokinetic data and health-based guidance values for companion animals are needed to improve understanding of the potential risks.
