Clean Label Project study finds heavy metals and plastic in popular cat foods

A new investigation into 100 top-selling cat foods has found widespread contamination, with nearly all products containing heavy metals, plastic chemicals or pesticide residues.

The study, published by the Colorado-based non-profit Clean Label Project, analysed products across 62 brands. It found lead in 99% of samples, cadmium in 96%, and arsenic in 94%.

Molly Hamilton, the group’s executive director, said these toxins present a cumulative risk because cats usually eat the same food day after day. "The contaminants are an ongoing exposure that may accumulate in cats’ bodies over their lifetimes," Hamilton said. She noted that chronic kidney disease is a leading cause of death in older cats, whose kidneys must filter out these heavy metals.

How protein choice alters the toxins

The study revealed that the type of meat in the food dramatically changes what contaminants are inside.

Fish and seafood products had the strongest link to mercury and cadmium. Mercury levels were about 18 times higher, and cadmium levels 2.5 times higher, in seafood-based foods compared to other proteins. The worst offenders were wet seafood products, which contained nearly 28 times more mercury than other wet foods, particularly poultry.

Microorganisms in water turn mercury into methylmercury, which binds to fish tissue and builds up in aquatic food chains.

By contrast, poultry-based foods performed much better on mercury and cadmium, but showed higher concentrations of lead and herbicides. Overall, nearly 85% of poultry-based products met the Clean Label Project's purity standards, compared to just 25.7% of fish and seafood options.

"It’s a whack-a-mole situation — which contaminant do you want to whack?" Hamilton said, though she added that some fish-based foods did pass their standards, showing that quality control varies among manufacturers.

Dry food, plants and plastic chemicals

The form of the food also mattered. Dry cat food contained roughly three times more lead than wet or air-dried products.

The study also looked for glyphosate, the world's most widely used herbicide. The chemical was found in 37% of the tested products. Foods that included more plant-based ingredients in their top 10 listed items had significantly more glyphosate. On average, having five plant ingredients in the top 10 led to nearly four times more glyphosate than having just one.

Additionally, a plastic-softening chemical called DEHP was found in roughly half of the products. This contaminant, which is linked to cancer and birth defects, was most prevalent in canned foods and pouches. Ryan Babadi, science director for the advocacy group Toxic Free Future, said this pollution likely happens during manufacturing, perhaps when food touches PVC pipes or other processing gear.

What should cat owners do?

Because there are few safety standards for contaminants in pet food, experts suggest varying a cat's diet to avoid a buildup of any single toxin. If a cat eats seafood, rotating in chicken or beef can help lower their mercury intake.

Hamilton warned that the first ingredient on the label does not tell the whole story, as manufacturers do not have to specify which parts of the animal they are using. Organs, skin and heads of fish store far more toxins than the fillets, but are often ground into the final product.

The Pet Food Institute, which represents pet food manufacturers, defended the industry. Its CEO, Elise Fennig, said in a statement that manufacturers use comprehensive safety programmes, including ingredient specifications, supplier verification, and testing protocols to ensure products are safe and consistent.