Dogs Spreading Lawn Chemicals

Study finds that pets can track potentially harmful herbicides inside the house.
By JoAnna Lou, June 2015

When I treat my lawn with herbicides, I usually keep my dogs off of the grass for a couple of days. But a new study has me rethinking my use of chemicals in the yard all together.

A study at Purdue University has found that dogs can pick up garden and lawn chemicals, contaminate themselves, and transfer the herbicides to people. Some of these chemicals have been associated with an increase in cancer , particularly bladder cancer, in dogs and humans. Researchers suggested that Scottish Terriers, West Highland White Terriers, Shetland Sheepdogs, Beagles, and Wire Hair Fox Terriers are at particular risk because those breeds have a high genetic propensity for bladder cancer.

In the study scientists sprayed herbicides on plots that were green, dry brown, wet, or recently mowed, then measured how much of the chemicals remained up to 72 hours post treatment. They found the highest levels on dead or dying plant material. Dry brown grass doesn't absorb the chemicals as readily, leaving the herbicides lingering on the surface longer. Applying excessive amounts of the chemical was another way surface levels remained high, since the plants already absorbed as much as they could.

In the second part of the study, researchers analyzed urine samples of dogs from households that used herbicides and those who didn't. The majority of pets from homes that used chemicals were found to have the same herbicides in their urine. But some of the dogs from untreated homes also had the chemicals in their urine. Wind can cause herbicides to travel up to 50 feet away from the application site, so the researchers theorized that the chemicals pose a risk even to those who don't use them on their own yards. There are industry guidelines for restricting lawn chemical application based on wind speed, but the average homeowner is probably not aware of those best practices.

For now the researchers recommend only using herbicides if absolutely necessary. And when you do, always follow manufacturer guidelines, allow gardens and lawns to dry before allowing pets out, and wash your dogs' feet each time they come inside the house. They also said ideally you should treat the front and back yard separately, a week apart, which would give your dogs a safe area to use while the other part gets sprayed.

Do you use herbicides on your lawn? What precautions do you take to protect your pups?

JoAnna Lou is a New York City-based researcher, writer and agility enthusiast.