The Seasonal Cancer Danger to Steer Your Dog Clear Of

Pet Herbicide Exposure

Story at-a-glance

  • A new study to be published in July points to a link between garden and lawn chemicals and canine bladder cancer. The chemicals are common herbicides containing 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2- methylphenoxypropionic acid (MCPP) and/or dicamba.
  • Dogs are exposed to these chemicals through ingestion, inhalation, and through the skin. Breeds with a genetic predisposition to bladder cancer are at particularly high risk. These include Beagles, Scottish Terriers, Shetland Sheepdogs, West Highland White Terriers, and Wire Hair Fox Terriers.
  • In the study, urine samples were obtained from dogs in homes where herbicides were used, and from dogs in untreated homes. Chemicals were detected in the urine of dogs in 14 of 25 households before lawn treatment, in 19 of 25 households after lawn treatment, and in 4 of 8 untreated households.
  • Researchers discovered the presence of herbicide in untreated lawns, leading them to conclude the chemicals can “drift” from treated to untreated properties. This means dogs can potentially be exposed in their own yard even if the yard is untreated, and from other properties if they travel from yard to yard.
  • Dr. Becker recommends avoiding the use of herbicides in your own yard; being aware that chemicals from other properties have the potential to contaminate your yard; keeping your pet off treated lawns; and using detoxifying supplements, baths and/or foot soaks to decontaminate your dog if you suspect he’s been exposed to lawn and garden chemicals.

By Dr. Becker

Last year around this time, I reported on a six-year study conducted at Tufts University's Cummings School of Veterinary Medicine linking lawn pesticides to canine malignant lymphoma (CML). That study found an increased risk for CML of as much as 70 percent in certain dogs exposed to professionally applied pesticides and herbicides, or lawn care products containing insect growth regulators.

This year I have an additional warning for dog owners. According to a study to be published in the July issue of Science of the Total Environment1, dogs are being exposed to garden and lawn chemicals linked to bladder cancer.

New Study Links Herbicide Exposure to Bladder Cancer in Dogs

The chemicals in question are common herbicides containing 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxypropionic acid (MCPP) and/or dicamba.

According to lead study author Deborah Knapp of Purdue University's Department of Veterinary Clinical Services, in an interview with Discovery News:

"The routes of exposure that have been documented in experimental settings include ingestion, inhalation and transdermal exposures. In the case of dogs, they could directly ingest the chemicals from the plant, or they could lick their paws or fur and ingest chemicals that have been picked up on their feet, legs or body."

Breeds with a genetic predisposition for bladder cancer, including Beagles, Scottish Terriers, Shetland Sheepdogs, West Highland White Terriers, and Wire Hair Fox Terriers are at particularly high risk.

You can learn more about canine bladder cancer here.

Your Neighbor's Herbicides Can Contaminate Your Property

Knapp and her colleagues sprayed the herbicides on a variety of grass plots, including some that were green, dry brown, wet, and recently mowed. Then they measured how much chemical remained on the plants up to 72 hours after spraying.

Dying and dead plants don't absorb herbicides well, so the chemicals remain longer on the surface. Also, if too much herbicide is applied, the plant can't absorb it all.

The researchers then analyzed urine samples of dogs whose owners used herbicides, as well as dogs whose owners did not. The study showed that most of the dogs from homes using the chemicals had herbicides in their urine. Since some dogs from homes that did not use the products also had herbicides in their urine, researchers concluded the wind could carry the chemicals up to 50 feet from the site where they were applied.

From the study:

"Chemicals were detected in the urine of dogs in 14 of 25 households before lawn treatment, in 19 of 25 households after lawn treatment, and in 4 of 8 untreated households. Chemicals were commonly detected in grass residues from treated lawns, and from untreated lawns suggesting chemical drift from nearby treated areas. Thus dogs could be exposed to chemicals through contact with their own lawn (treated or contaminated through drift) or through contact with other grassy areas if they travel. The length of time to restrict a dog's access to treated lawns following treatment remains to be defined."

This means that even if you don't use these products, if a neighbor does, your dog could still be at risk. According to Knapp, there are restrictions on lawn chemical application based on wind speed, but many homeowners aren't aware of theses guidelines.

Once a dog is exposed, other people and pets can also become contaminated. Dogs get the chemicals on their coats and paws and spread them throughout the house on floors and furniture. Owners can also be exposed by petting or holding their dog.

My Recommendations

The study authors recommend that if you must use herbicides, you should follow manufacturer guidelines, allow sprayed areas to dry before letting pets out, and treat areas of the yard at different times so pets always have an area to roam in with less potential chemical exposure.

My additional recommendations:

  • Don't apply chemical herbicides to your yard, and be aware that a neighbor's herbicide can potentially contaminate your property and pose a risk to your pet.
  • Don't allow your dog access to any lawn unless you can confirm no herbicides have been used.
  • If you think your pet has rolled around on chemically treated grass, bathe him as soon as possible.
  • If you've walked your dog in a grassy area that might be contaminated, giving him a foot soak as soon as you get home should flush away any chemical residue that may be clinging to his feet and lower legs.
  • If you live in a townhouse or community that applies chemicals to common areas, I recommend "detoxing" a patch of grass in your backyard by watering the chemicals down into the soil to reduce skin contact after application. Keep your pet on a leash (and on the sidewalk) until you've walked to your pesticide-free destination, and consider a periodic detoxification protocol for your pet.


As many of you know, I'm a big fan of periodic detoxification. The level of environmental exposure to chemicals will dictate the frequency and type of detox appropriate for your pet. If your dog has constant exposure to toxic chemicals all summer, supplying a daily detox protocol is a wise idea.

If your pet's only source of chemical exposure is heartworm pills, or if you are applying flea and tick chemicals directly on your pet, then offering a detox program the week after each pill or topical treatment makes sense.

There are many detoxifying herbs and supplements to choose from. A detox protocol should not cause any side effects or visible changes in your pet.



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