Study finds heavy metals, glyphosate, and plastic-related chemicals in nearly all cat foods tested, but health risks remain unclear

Most cats eat the same food, or a small rotation of foods, every day for years. That means even relatively low levels of contaminants in their diets could result in repeated exposure long-term. Now, a new analysis suggests that such exposure may be widespread, finding evidence of plastic-related chemicals, heavy metals, and the herbicide glyphosate in nearly all of the 100 cat food products tested from 62 brands in the US. The analysis, however, does not establish whether those contaminants pose a health risk to cats.

For the analysis, the Clean Label Project, a nonprofit that tests consumer products and certifies brands it considers cleaner, purchased the products at retail. The sample included 31 dry, 40 wet and 29 air-dried or freeze-dried foods, with one batch of each product tested. An independent laboratory accredited for the testing methods screened each product for more than 122 contaminants, including heavy metals, pesticides, plastic-related chemicals, and compounds that can form during high-heat cooking.¹

Heavy metals were among the most frequently detected contaminants. Lead was detected in 99% of the products, cadmium—which is classified as a human carcinogen—was detected in 96%, and arsenic was detected in 94%. The products with the highest lead levels contained about 3.5 times as much lead as the “typical” product, according to the report. The report does not specify how it defined a typical product.¹

The findings are potentially relevant to a large population of cats. An estimated 53 million US households, or 39% of all households, have a cat, according to a 2025 national pet owners survey from the American Pet Products Association.²

The report also highlights potential concern about long-term exposure to metals in cats, particularly in the context of kidney health. Chronic kidney disease is the most common metabolic disease in domestic cats and primarily affects cats older than 12,³ while researchers at the Royal Veterinary College in London have identified it as the most frequent cause of death among cats older than 5.⁴

“As obligate carnivores, [cats] eat a high-protein diet drawn heavily from animal tissue, including fish that can contain mercury. Their kidneys carry the long-term burden of metal accumulation,” wrote Clean Label Project.¹

The analysis did not examine whether the contaminants detected in the tested foods were associated with kidney disease in cats.

The report did not compare the detected contaminant levels with regulatory safety thresholds, stating that there are no applicable standards for the contaminants it measured in cat food.

Clean Label Project also argued that existing contaminant limits sometimes referenced by brands may be based on human health standards, general dietary assumptions or older studies and may not account for differences between cats and humans, such as how cats absorb and process heavy metals and their tendency to eat the same foods over long periods. Instead, the organization compared contaminant levels among the products tested, rather than determining whether individual products exceeded a health-based safety threshold.

“The absence of safety standards does not mean a contaminant is safe,” the organization wrote.¹

Contaminants were measured per calorie, not by weight

The researchers measured contaminants per 1000 calories rather than per kilogram of food. Calorie density ranged from 547 to 5290 calories per kilogram, largely because wet food is mostly water, and a weight-based measure would have made it look several times cleaner than it is. Because cats eat to meet a calorie target, the authors argue, per-calorie exposure better reflects what reaches the animal.

Fish-based foods carried about 18 times the mercury of other foods

Foods with fish or seafood in their names contained about 18 times as much mercury as other products, even after accounting for whether a food was wet or dry. Among wet foods alone, fish-based products contained about 28 times as much mercury as wet foods made with other proteins. Nearly half of the fish-based products ranked among the highest for mercury, and none of the poultry-based products did. Fish-based foods also carried about 2.5 times as much cadmium,¹ a metal that shellfish and other marine invertebrates are known to accumulate.⁵

Clean Label Project also evaluated each product against its own purity standard. According to the report, the organization uses "benchmarked data to compare individual product test results to the test results of the best-selling products in the same product category," but it does not publish the numeric cutoffs a product must meet. About 85% of poultry-based foods met the standard, compared with about 26% of fish and seafood products. Dry and wet foods met it at rates within 1 percentage point of each other.

Herring meal, tuna, and fish broth were most closely tied to contamination

Foods that did not mention fish in their names but listed a marine ingredient still tended to carry more mercury than those with none. When the researchers pooled the new results with earlier cat food testing, for 541 samples across 87 brands, herring meal, tuna, and fish broth were the ingredients most strongly associated with contamination. Products containing herring meal landed in the most contaminated 10% of products about 60% of the time, roughly 17 times more often than would be expected by chance alone. That risk was driven by mercury, arsenic, and cadmium. Turmeric ranked fourth, which the report links to the spice's documented history of lead adulteration.

Dry food carried about 3 times the lead of wet or air-dried food

Dry kibble contained about 3 times as much lead as wet or air-dried food after accounting for calories, and that difference held after the researchers considered protein source. Unlike mercury, lead was not linked to any type of protein, and the report suggests the format of the food may play a role.

Each added plant ingredient raised glyphosate levels by about 40%

Glyphosate, the widely used herbicide, was detected in 37% of products and its breakdown product, α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA), in 12%. Each additional plant ingredient that appeared in the first 10 ingredients on a label was associated with about 40% more glyphosate. Still, the number of plant ingredients mattered more than where they appeared on the list, Clean Label Project noted.

A plasticizer was the most common contaminant after heavy metals

Di(2-ethylhexyl) phthalate (DEHP), a phthalate linked to hormone disruption, appeared in 48 products. Detection rates were similar across formats, but canned and pouched foods that contained it carried about 5 times as much as bagged products, which the authors say may reflect contact with packaging. Acrylamide was measurable in 4 products and was present at trace levels in 24 more foods. Bisphenols, once common in can linings, were nearly absent. Bisphenol A (BPA) appeared in 2 products and bisphenol S (BPS) in one.

In 35 foods, the first ingredient did not reflect most of the recipe

In 35 of the 100 products, the first-listed ingredient was usually a meat or fish, but most of the first 10 ingredients came from a different category, most often plants. In some cases, the same plant ingredient appeared in several forms, such as pea protein and pea flour. The practice, known in the industry as ingredient splitting, is legal. Foods in which plant ingredients outnumbered the first-listed meat or fish tended to carry more lead.

The study does not show what levels of these contaminants pose a health risk to cats

The analysis found differences in contaminant levels among the cat foods tested, but it did not assess whether those levels could harm cats. Clean Label Project states that its results show how products compare with one another, rather than whether a specific product contains enough of a contaminant to cause illness.

The organization also questions whether existing maximum tolerable levels for contaminants in animal feed are appropriate for cats. The organization points to maximum tolerable levels published by the National Research Council and the Association of American Feed Control Officials, which it says were “derived to prevent acute poisoning in livestock, not to protect a housecat eating the same food every day for fifteen years.”¹

The report notes that chronic exposure to lead, cadmium, mercury, glyphosate, and DEHP has been linked to health effects in mammals, including cancer, brain damage and reproductive harm.

However, the analysis did not examine those health effects in cats or determine whether the contaminant levels it measured were associated with them.

The findings also have limitations when it comes to individual products. Each product was represented by a single batch, so the analysis does not show how contaminant levels might vary between batches of the same food. Most brands contributed one product, and the report limits its brand-level comparisons to brands with at least 3 products tested.

Clean Label Project also operates a certification program. According to the report, its Purity Award recognizes brands whose products contain lower levels of contaminants, including heavy metals, pesticide residues, and plasticizers, than best-selling products in the same category. Three brands included in the analysis, Bixbi, Freshpet, and Smalls, hold the award.

The report advises rotating proteins and asking brands about testing

The report advises caregivers of cats that eat mostly fish-based food to rotate in other proteins. It also recommends reading past the first ingredient and asking manufacturers whether they test finished products for heavy metals, not just the ingredients that go into them.

“Rotating proteins may help reduce exposure from a single source. This does not mean you need to eliminate fish—some fish-based cat foods met our quality standards,” Clean Label Project wrote.¹

Still, the organization said feeding cats a complete diet they will actually eat remains the priority.

References

1. Clean Label Project. CLP Insights: cat food category report. 2026. Accessed October 6, 2026. https://cleanlabelproject.org/wp-content/uploads/clean-label-project-cat-food-study-2026.pdf
2. American Pet Products Association. Gen Z and cat dads are leading cat ownership's cultural boom: new APPA report reveals what's driving growth in America's feline household. ACCESS Newswire. 2026. Accessed October 6, 2026. https://www.accessnewswire.com/newsroom/en/business-and-professional-services/gen-z-and-cat-dads-are-leading-cat-ownerships-cultural-boom-new-1220581
3. Brown CA, Elliott J, Schmiedt CW, Brown SA. Chronic kidney disease in aged cats: clinical features, morphology, and proposed pathogeneses. Vet Pathol. 2016;53(2):309-326. doi:10.1177/0300985815622975
4. Royal Veterinary College. Chronic kidney disease in cats explored. May 16, 2019. Accessed October 6, 2026. https://rvc.ac.uk/vetcompass/news/chronic-kidney-disease-in-cats-explored
5. Frazier JM. Bioaccumulation of cadmium in marine organisms. Environ Health Perspect. 1979;28:75-79. doi:10.1289/ehp.792875