If you’ve ever eaten a juicy ear of corn or admired a perfectly manicured garden, you can probably thank a chemical engineer. But the pesticides and herbicides that make mass food production and smooth grass easier may negatively impact not just the ecosystem, but the health of our pets.
All cancers arise from some combination of genes, behavioral factors and environmental influences, but some are more strongly linked to environmental factors. For example, there are clear links between herbicide exposure and non-Hodgkin lymphoma and bladder cancer in humans, says Dr. Lauren Trepanier, professor of internal medicine at the University of Wisconsin-Madison School of Veterinary Medicine. Both cancers are also common in dogs, and some breeds are diagnosed with environmental cancers at far higher rates than others, such as lymphoma in boxers and bladder cancer in beagles.
“Cancer is increasingly common in dogs and disturbingly, canine cancers are occurring at younger ages,” much like the increase in childhood cancers, explains Dr. Barbara Hodges, program director of advocacy and outreach for the Humane Society Veterinary Medical Association. “A dog who is not a member of a breed linked to a particular cancer is not immune to that cancer—or any other cancer, for that matter.”
A 1991 study found that dogs whose owners used herbicide 2,4-D were up to 200% more likely to develop lymphoma, and despite a follow-up study with ties to the chemical industry refuting the claim, a 2012 study confirmed an increased risk. According to a 2013 study, Scottish terriers exposed to herbicide-treated lawns had a greater risk of cancer—up to seven times higher. Trepanier is currently comparing chemical exposures in dogs with and without cancer in three ongoing studies. (Boxers are especially needed—email Lauren Trepanier to learn more.)
People enrolled in the studies complete questionnaires on their dogs’ household environments; provide household dust, air and water samples; and submit their dogs’ urine and other samples. Using this information, Trepanier compares home proximity to chemical manufacturing plants, nuclear power plants and crematoriums; exposure to household paints and solvents, air fresheners, cooking fumes and secondhand smoke; and exposure to weed killers glyphosate, 2,4-D and atrazine.
“We’re finding evidence of weed killer in a lot of dogs, whether they’re cases [with cancer] or controls [without cancer]. Some of [the levels] were so high that they had to be rerun,” she says. The studies haven’t concluded yet, but already Trepanier wishes she’d counseled clients to avoid lawn chemicals when she was a practicing veterinarian.
Herbicide and pesticide companies do offer safe application guidelines, which are the source of those turf flags in your neighborhood warning people and pets to stay off freshly treated lawns for a few hours. But a 2014 study found that herbicides persisted on lawns for at least 48 hours after application, and a 2001 study found that herbicide 2,4-D drifted into the air and onto the surfaces of homes after application.
What about artificial turf?
Artificial turf comes with its own problems for the health of animals and people. Consider installing a drought-tolerant native grass instead.
It’s worth noting that the Environmental Protection Agency says glyphosate, the world’s most used herbicide and pesticide, is “not likely to be carcinogenic.” However, the World Health Organization International Agency for Research on Cancer calls glyphosate (and pesticides malathion and diazinon) “probably carcinogenic,” and over 130,000 people who developed cancer after long-term glyphosate use have filed lawsuits against pharmaceutical company Bayer. Some of the controversy is likely because it’s tough to measure and prove the cumulative effects of herbicide exposure long-term, says Hodges.
“We’re not all going out and rolling on our lawns after we put herbicides on it,” says Trepanier, yet the link persists; a 2019 review concluded that exposure to glyphosate might increase the risk of non-Hodgkin lymphoma in humans by 41%. And while we might not be rolling on our lawns, our dogs are rolling on it, chewing it, sniffing it, digging in it and sleeping on it, while our cats are ingesting their environments through grooming. Our pets’ smaller statures make them more vulnerable to ground-level toxins, explains Hodges.
Better safe than sorry
As a practicing veterinarian, “one of my guiding principles is, ‘First, do no harm.’ Another is the ‘precautionary principle’ that if a substance or an activity has a suspected risk of causing harm, protective action against exposure to it or engagement in it should be taken or supported before there is conclusive scientific proof of that risk,” says Hodges.
“Although there are still a limited number of studies on the link between lawn chemicals and cancer in dogs, these studies have raised my threshold of concern sufficiently that I advise my clients about the risks of cancer from these products and recommend that they not use lawn chemicals—for the sake of their pets and the human animals in their families, and also for the sake of wildlife species and the overall environment.”
If lawn chemicals worry you, here are Trepanier’s suggestions for reducing your and your dog’s exposure to herbicides and pesticides.
Use pesticides and herbicides sparingly or not at all, and ask your homeowners association to do the same. Learn More
Avoid walking your dog in pristine parks and yards (such as those that are a vibrant green even during hot, dry weather); they are likely the result of pesticide and herbicide use.
If you supplement dog food with fruits and vegetables, wash and peel the produce first. Use a home water filtration system that specifically filters out pesticides and herbicides.
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