How Lawn Chemicals and Herbicides Affect Dogs

Do you take as much pride in your lawn as in your adorable pooch? A recent study found that dogs exposed to lawn care chemicals can have a higher bladder cancer risk. Once contaminated with those chemicals, dogs also can pass these chemicals to their owners, children and other pets in the house.

The study, published in Science of the Total Environment, found that the incidence of lawn chemicals in the urine of pet dogs was widespread — even among dogs in households where chemicals were not applied.

Researchers at Purdue University and the University of North Carolina applied herbicides to grass plots under different conditions (e.g., green, dry brown, wet, and recently mowed grass) and tested for their presence up to 72 hours after the lawn treatment.

Some common herbicides — specifically 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxypropionic acid (MCPP), and dicamba — remained detectable on grass for at least 48 hours after application, and the chemicals persisted even longer on grass under certain environmental conditions.

In a separate study, researchers measured the concentration of these chemicals in the urine of dogs belonging to owners who applied and those who did not apply chemicals to their lawns. They found that the chemicals were detected in the urine of 14 of 25 households before lawn treatment, in 19 of 25 households after lawn treatment, and in four of eight untreated households. Finding the chemicals in the urine of dogs in households that were untreated should be a concern for dog owners. It indicates that the untreated lawns were contaminated through drift, or the dogs were exposed to the chemicals during walks.

How are the dogs being exposed to these toxic chemicals?

They can directly ingest these chemicals from sprayed lawns and weeds or they can lick their paws and fur where the chemicals were picked up. There are guidelines for the application of herbicides, but can you be sure that your neighbor has read and followed the directions on the packaging?

In 2004, researchers from Purdue University (several of whom also worked on the current study) found that Scottish terriers xposed to lawn and garden herbicides (specifically the aforementioned 2,4-D) had an occurrence of bladder cancer between four and seven times higher than Scottish terriers not exposed to herbicides. Previously, researchers had found that Scotties were already about 20 times more likely to develop bladder cancer as other breeds.

This makes Scotties "sentinel animals" to researchers because they require less exposure to carcinogens before contracting the disease. Other dog breeds with a genetic predisposition for bladder cancer include beagles, wire hair fox terriers, West Highland white terriers, and Shetland sheepdogs.

The implications of this study for human health are also frightening. These chemicals can be tracked inside the house and contaminate flooring and furniture. Dog owners may come in contact with the chemicals simply by petting or holding their pets.

How to avoid or lessen dog exposure to herbicides

Dr. Tina Wismer, medical director at the ASPCA Animal Poison Control Center, suggests homeowners always store, mix and dilute products in areas without pet access.

"Gastrointestinal upset is the most common sign seen when ingestion of fertilizer and herbicide occurs," she says. "However, if large amounts or concentrated products are ingested, veterinary intervention may be necessary. In addition, very young, very old, and debilitated animals may be more sensitive to exposures."

If your lawn is maintained by a company, Wismer suggests that you inform them that you have a pet with access to the lawn, and ask for the company's recommendation for how long pets should stay off treated lawns. In addition, Wismer recommends that homeowners obtain a list of the product names and EPA registration numbers to have on hand in case of an incident.

What can you do if you think your dog has ingested herbicides?

"If a pet parent witnesses a pet consuming material that might be toxic, the pet parent should seek emergency assistance, even if the pet seems fine," says Wismer. "Sometimes, even if poisoned, an animal may appear normal for several hours or for days after the incident."

With proper applications of herbicides, the health risks to our dogs is minimal, but you can't guarantee that your neighbors or the lawn crew you hire will read and follow label directions. In your own home, consider alternating when the front and back lawn are treated, or better yet ditch your lawn altogether and plant a garden for yourself and your dog.

Photo of Scotties by Joy Brown/Shutterstock