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 t