My favorite people to buy holiday presents for are animal people. They are always so grateful! But sometimes maybe they shouldn’t be.

A new study out of Texas Tech finds that the chemicals in hard plastic bumper dog toys readily leach into dogs’ mouths.

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Dogs’ chewing action stresses the chemical bonds in the plastics that comprise their toys, allowing for the leaching of hormone-mimicking bisphenol A (BPA) and phthalates. From Environmental Health News:

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“A lot of plastic products are used for dogs, so to understand the potential for some of the chemicals to leach out from toys is a new and important area of research,” said veterinarian Safdar Khan, senior director of toxicology research at the American Society for the Prevention of Cruelty to Animals’ Poison Control Center in Illinois. Dr. Khan was not involved in the current study.

Philip Smith, a toxicologist at The Institute of Environmental and Human Health at Texas Tech, became interested in chemical exposures from bumpers after using them to train his own Labrador retrievers.

“Some of the dogs are exposed to plastic bumpers from the time they are born until the day they die.”

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Because the researchers conducted the study using synthetic dog saliva (gross? awesome? both?), they can’t say for sure what dogs’ exposure would be post-chew. A previous study found phthalate levels in dogs were as much as 4.5 times higher than the human average. BPA and phthalates have been linked to a variety of health issues in humans and rodents, from decreased fertility to cancers. Some phthalates have been banned from children’s toys, and BPA is not allowed in baby bottles.

For now, best options for dog parents may be good old-fashioned ropes and bones.