Fish-based food can expose cats and dogs to chemicals forever

Many pet foods – especially those based on fish – contain amounts of so-called forever chemicals that exceed the European Health Agency’s thresholds for humans.

The findings point to an urgent need for increased monitoring of contaminants in pet products and a better understanding of the risks to pets, he says. Kei Nomiyama at Ehime University in Japan.

“Our findings do not indicate an immediate health emergency, but they do point to a gap in knowledge,” he says. “Pet owners who wish to reduce potential exposure may consider paying attention to ingredient composition and diversifying protein sources.”

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are man-made chemicals used in a wide variety of products that can persist in the environment for hundreds or thousands of years. People who are regularly exposed to PFAS have an increased risk of liver damage, some cancers and other health problems. While research on their effects on pets remains limited, studies in cats have linked certain PFASs with diseases of the liver, thyroid gland, kidneys and respiratory system.

Nomiyama and his colleagues had already found persistent organic pollutants in pet food. Because PFASs are so widely present worldwide—especially in rivers and oceans—they suspected they would also find traces of these contaminants.

To find out, they measured the concentrations of 34 types of PFAS in popular wet and dry pet food varieties—48 for dogs and 52 for cats—sold in Japan between 2018 and 2020. Then, using approximate meal sizes and body weights for dogs and cats, the team calculated how much PFAS a pet would consume per day for each product.

Several products had moderate to high levels of PFAS – often exceeding the daily intake limits (per kilogram of body weight) set for humans by the European Food Safety Agency (EFSA).

Among dog foods, some of the highest levels appeared in Japanese grain products — likely due to agricultural waste or fish byproducts as protein sources, Nomiyama says. In contrast, meat products were generally low in PFAS, with one Japanese and two Australian brands containing none.

For cat foods, fish-based products from Asia, the US, and Europe had the highest PFAS values, especially wet fish-based food produced in Thailand.

“The ocean often acts as a final sink for many synthetic chemicals,” says Nomiyama. “Simply put, PFAS can move and concentrate in aquatic food webs.”

Regional differences may reflect historical and current patterns of PFAS production and use, as well as differences in raw material sourcing, he says. Even so, PFAS contamination is a global problem. “More globally harmonized monitoring would be valuable,” he says.

EFSA declined to comment on the study’s findings, but said the proposed intake limits for humans should not be applied as such to risk assessments in other animals.

Nomiyama agrees — but stresses that the findings still reflect abnormally high levels of PFAS, and that the risk assessment for pets deserves further development.

“Companion animals share our environment and in many ways act as gatekeepers for chemical exposure,” he says. “Understanding contaminant levels in pet food is not only a matter of animal health, but also contributes to our broader understanding of environmental pollution pathways. Long-term exposure and species-specific toxicity assessments in pets deserve further attention.”

Håkon Austad Langberg at Akvaplan-niva, a Norwegian non-profit research institute, says the findings are no surprise. “These substances are globally distributed, and several PFASs are known to persist and, in some cases, accumulate and/or scale up through food webs,” he says.

“The bigger issue is that PFASs are everywhere, and humans and animals are exposed from multiple sources,” says Langberg. “These compounds are found in environmental media and in many products, leading to cumulative exposure for both humans and animals. The study contributes valuable data to this broader challenge.”

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