Does your cat food contain metal?

Popular U.S. cat foods contain detectable levels of heavy metals and other contaminants, according to a report released Friday, as industry representatives are challenging the methodology as they reassure consumers that their pet food is safe.

“Most cats eat the same foods—or a small rotation of foods—every day for their entire lives. Without any dietary variety, any contaminants present in the foods a cat eats can become a consistent and ongoing source of exposure, potentially accumulating in their bodies over the course of their lives,” the report by the Clean Label Project states.

The Colorado-based nonprofit tested 100 cat food products from 62 brands, finding lead in 99 percent of tested samples, cadmium in 96 percent and arsenic in 94 percent. Mercury, glyphosate and plastic-related chemicals were also detected, according to the report.

The organization said dry cat food contained roughly three times as much lead as wet or air-dried products, while fish- and seafood-based formulas carried significantly higher mercury and cadmium levels than foods made with other proteins.

Clean Label Project named only three brands that meet its certification: BIXBI, Freshpet and Smalls.

The findings have drawn scrutiny from industry groups and nutrition experts who say the report compares contaminant levels across products rather than determining whether any food poses a health risk to felines. The study also relied on a single batch of each product tested, a limitation acknowledged by the authors.

Hana Bieliaskas, a spokesperson for the Pet Food Institute, told Newsweek that the study compared products against the Clean Label Project's proprietary "purity standard" rather than recognized scientific and regulatory benchmarks developed by organizations such as the Association of American Feed Control Officials and the National Research Council.

Bieliauskas also noted that the report did not demonstrate that any detected contaminants were present at levels capable of causing health problems in cats. She questioned whether the study had undergone independent peer review, whether underlying product-level data and statistical analyses would be released publicly and whether testing a single batch of each product was sufficient to draw broad conclusions about brands.

The Pet Food Institute said consumers would benefit from more transparency about the commercial relationship between Clean Label Project and brands that receive certifications or awards through its programs.

The trade group's criticism echoes a key limitation acknowledged in the report itself. According to the Clean Label Project, each product was tested from a single batch, meaning the data could not account for variation between production runs. The organization also noted that the analysis "does not determine whether a specific product will cause harm to a cat."

"Cat owners increasingly choose premium meats, organic vegetables and cleaner labels, assuming higher prices and quality ingredients mean healthier food," Molly Hamilton, executive director of the Clean Label Project, told CNN. "That's not necessarily the case."

The Pet Food Institute maintains that pet owners should remain confident in commercially available products. In a statement to CNN, CEO Elise Fenning said manufacturers use ingredient specifications, supplier verification, testing protocols and preventive controls designed to ensure products are safe and nutritious.

“Cat owners should feel confident that the food they feed their pets is safe and produced according to rigorous regulatory and quality standards," she said.

Newsweek has contacted the Clean Label Project for responses to the Pet Food Institute's criticisms, including questions regarding regulatory benchmarks, peer review, underlying data and certification programs.

Jennifer Larsen, a professor of clinical nutrition at the University of California-Davis School of Veterinary Medicine, told Newsweek that she questioned whether the study’s findings provided enough context to determine the actual risk to cats.

“This is fearmongering without any contextual background on safe or unsafe exposure levels,” Larsen said. “There is no need to be alarmed at this theoretical concern, and we do not see heavy metal contamination in pet food as a common issue.”

The detection of a substance does not, by itself, establish that an animal has been exposed to a dangerous amount. She also questioned the report’s measurement of total mercury rather than methylmercury, which she described as the more toxic and relevant form, Larsen said.

She urged the Clean Label Project to submit its data for peer review and publicly provide author names, affiliations and disclosures. She also called for more transparency and oversight of pet-food manufacturing, while cautioning against drawing conclusions from data that she said had not undergone a process with sufficient scientific rigor.

“A dismissive attitude is not appropriate, but we have to be cautious about this sort of reported data that has not undergone any process with any scientific rigor prior to making conclusions,” Larsen said. “It’s just not a credible or responsible approach.”

She added that research could instead help establish the risks associated with chronic, low-level exposures, noting that scientists still have limited data on their long-term effects and that some environmental exposure is unavoidable.

Generally speaking, Europe regulates cat food more tightly and centrally than the United States, particularly on ingredients, additives, labeling, and precautionary safety rules, while the U.S. system is decentralized and allows somewhat greater flexibility for manufacturers.

The FDA primarily regulates U.S.-made cat food, while the Association of American Feed Control Officials (AAFCO) develops nutritional standards and model labeling rules, which states largely enforce. European cat food, by contrast, is regulated as animal feed under EU law, and the European Pet Food Industry Federation develops nutritional guidelines.

Both the U.S. and Europe allow animal by-products, but the EU has extensive rules governing sourcing, processing, and traceability of them.

While you may see major U.S.-made cat food brands in Europe, the formulas may be different. One example is the use of ethoxyquin, a preservative that the EU suspended in 2017 for use in pet food. It's used to prevent fats and fish meal from going rancid, which can still be found in U.S. pet food.

Newsweek’s reporters and editors used Martyn, our AI assistant, to produce this story. Learn more about Martyn here.

Contact Newsweek editors on this story: Jennifer Radcliffe and Gray R. Thomas