Commercial dog food contains ‘alarming’ levels of lead, mercury and other contaminants

By Sandee LaMotte, CNN

(CNN) — Samples of popular commercial dog foods contained “dangerous levels” of heavy metals, plastic contaminants, and acrylamide, a cancer-causing compound created when food is subjected to high heat, according to a new investigation.

“The levels of heavy metals and other contaminants we found were alarming,” said Molly Hamilton, the executive director of Clean Label Project, which conducted the investigation. The Colorado-based nonprofit tests consumer products for purity and offers manufacturers a certified label if their commodities meet strict standards.

“Pet owners care for their dogs as deeply as parents care for their children,” Hamilton said. “They should be able to buy dog food without worrying it might harm their pet.”

Dog foods contained three to 13 times more heavy metals than human food tested over the past decade by Clean Label Project, according to the report. The levels are similar to those found in prior research done by veterinarian Dr. Joseph Wakshlag, a professor and nutritional specialist at Cornell University College of Veterinary Medicine in Ithaca, New York.

“We wrote a paper in 2018 comparing the intake of heavy metals between people and dogs based on a calorie,” said Wakshlag, referring to a report he coauthored with three Cornell colleagues. Wakshlag was not involved in the new investigation.

“Compared to a person, we found dogs consumed three to seven times the amounts of heavy metals each day,” he said.

Dry dog food, also called kibble, contained the highest levels of heavy metals and other contaminants, followed by air- and freeze-dried dog food. Fresh and frozen dog foods contained the lowest levels of heavy metals, according to the laboratory tests.

The report did not release specific test results by brand or product name.

“Over 85% of dog owners feed dry foods to their pets, and most dogs are eating one type of dog food each and every day, often for their entire life,” Hamilton said. “If dry dog food is all they consume, it’s possible the accumulation of heavy metals could be contributing to the higher cancer rate in dogs.”

Studies show heavy metals can accumulate in the kidney and liver in a dog, potentially contributing to chronic disease. Exposure to lead and cadmium has been linked to canine cancer, a leading cause of death in dogs. About 1 in 4 dogs will develop cancer during their lifetime, according to the American Veterinary Medical Association.

The Pet Food Institute, or PFI, which represents manufacturers of dog food, told CNN in an email it will review the Clean Label Report.

“PFI and U.S. pet food makers are continuously monitoring to best support the health and safety of dogs and cats,” a spokesperson said.

Fewer contaminants in fresh and frozen dog foods

Clean Label Project purchased 79 samples of best-selling fresh and frozen dog foods, kibble and air- and freeze-dried products. A federally certified laboratory then conducted 11,376 individual tests for plastics, pesticides, lead, arsenic, mercury, cadmium and acrylamide.

Fresh and frozen dog foods, which only entered the mainstream pet food market in 2006, were least contaminated. Lead and mercury levels in dry food were about 21 times higher than fresh and frozen dog foods. Kibble also contained over 13 times more arsenic and six times more cadmium than fresh and frozen products.

One potential reason: “Fresh and frozen dog foods are at least 70% water, and water contains far fewer heavy metals than a highly condensed piece of kibble,” Wakshlag said. In addition to doing academic research, Wakshlag consults for a dog food company.

“You also can’t take those numbers at face value, because a dog has to eat about 3 cups of fresh or frozen dog food to get the same calories and nutrients as 1 cup of dry food,” he said. “Therefore, the dog’s exposure to heavy metals in fresh or frozen foods goes up because it has to eat two to three times as much.”

An October 2021 study also detected high levels of two heavy metals in dog foods. Nearly 81% of the commercial dog foods analyzed in the study exceeded the maximum tolerated level of mercury set by regulatory agencies while 100% of the dog food products exceeded the maximum tolerated level of lead.

There is no safe level of lead for humans, according to the US Environmental Protection Agency. The EPA does not list levels for dogs.

Safety thresholds for all animal feed are set by the Association of American Feed Control Officials, or AAFCO, and the National Research Council, or NRC. Maximum levels for heavy metals are based on the species that would be the most susceptible to the toxins, Wakshlag said.

“The difficulty of using NRC or AAFCO expectations is that they don’t have guidelines that are specific to dogs. Pet food is lumped into the same category as agricultural animals,” Hamilton said. “The prevailing industry theory is that dogs have a higher tolerance for heavy metals than humans, though what this theory is based on is up for debate.”

That’s not known, because there are so few studies on toxic exposure in dogs, Wakshlag said.

“How would chronic consumption of these contaminants at really high levels affect a dog? We don’t know,” he said. “We have very few studies that have followed dogs for years on different diets to find those answers.”

A solution would be for pet food companies to regularly test their products for toxins and report the results to consumers, Wakshlag added.

“But extensive analyses take time and money,” he said. “So if you want this kind of information, then expect your bag of dog food to go up $3 or $4 a bag, because that’s what it’s going to cost to do these tests.”

Acrylamide and chemicals used in plastics

Acrylamide levels in dry dog food were about 24 times higher than fresh and frozen, with one food testing at 780 parts per billion, according to the Clean Label Project report.

“I’ve never seen acrylamide at a 780 level in a food,” Wakshlag said. “That company must be cooking the hell out of their food or using ingredients that are leading to more acrylamide formation. That’s like a person eating five servings of french fries every day in terms of acrylamide exposure.”

Acrylamide appears in foods rich in carbohydrates when they are fried, grilled or baked at temperatures above 248 degrees Fahrenheit (120 degrees Celsius). The browning of toast, french fries, coffee and baked goods can create acrylamide, which is considered “likely to be carcinogenic to humans” by the EPA. The chemical is also present in tobacco smoke and is used to make paper, dyes and plastics.

“Acrylamide reduces the ability of male animals to produce offspring,” the US Agency for Toxic Substances and Disease Registry states on its website. “Acrylamide has caused several types of cancer in animals. Adequate human data are not available.”

The investigation also tested levels of two bisphenols — Bisphenol A (BPA) and Bisphenol S (BPS) — and one phthalate called Di(2-ethylhexyl)phthalate, or DEHP. In line with the other findings, dry dog food contained the highest levels; fresh and frozen food contained the lowest.

While no studies have been done in dogs, the phthalate DEHP may have contributed to more than 10% of all adult global mortality from heart disease among men and women ages 55 through 64, according to a study published in April 2025.

Bisphenol A, or BPA, has been linked to fetal abnormalities, low birth weight, and brain and behavior disorders in infants and children. In adults, the chemical compound is associated with the development of type 2 diabetes, heart disease, erectile dysfunction, cancer and a 49% higher risk of early death within 10 years.

Bisphenol S, or BPS, is a common replacement for BPA. Studies show that BPS may have a similar negative impact on the reproductive system and may disrupt cellular function.

So with all these toxins, what can a pet parent do?

First, don’t panic, Hamilton advised. If your veterinarian agrees and it fits your budget, consider fresh and frozen foods. Many pets, however, are picky and won’t allow owners to switch from kibble to fresh or frozen.

“If you’re going to keep using dry food, rotate it with other brands to diversify your dog’s diet,” she said. “You wouldn’t want to eat the same thing every day for every meal, and many dogs are thrilled to eat new foods. Rotating the diet is probably the best thing you can do.”

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