Bladder Cancer Among Dogs Exposed To Herbicides

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Study finds higher rates of bladder cancer among dogs exposed to herbicides
Suzanne Hively

Raw carrots are a far healthier snack for dogs than biscuits.

"Eat your veggies!" applies to dogs too.

A study at Purdue University in West Lafayette, Ind., revealed Scottish terriers that ate vegetables three times a week reduced their risk of cancer of the urinary bladder by 50 percent, or about the same as humans who ate vegetables.

Green leafy vegetables provided about a 90 percent reduction in risk of cancer; yellow vegetables, 70 percent; and cruciferous vegetables, about 80 percent, said Lawrence Glickman, veterinarian and researcher at Purdue.

The findings are part of a study that examined Scottish terriers and incidences of cancer of the urinary bladder (transitional cell carcinoma) caused by exposure to chemically treated lawns.

Scottish terriers were used for the test because they have an incidence of bladder cancer 20 times greater than any other breed of dogs, said Glickman.

Owners of 83 Scottish terriers with bladder cancer and 83 with other health-related conditions completed a written questionnaire pertaining to exposure to lawn or garden chemicals during the year before diagnosis of the cancer for case dogs and a comparable period for control dogs.

The risk of bladder cancer was significantly increased among Scotties exposed to lawns or gardens treated with both herbicides and insecticides or with herbicides only.

Scotties exposed to lawns or gardens treated with insecticides alone had a small but not significantly increased risk of bladder cancer compared with dogs exposed to untreated lawns.

The prevalence of bladder cancer in dogs examined at veterinary teaching hospitals in North America increased by more than 600 percent between 1975 and 1995, according to the Journal of the American Veterinary Medical Association.

Scottish terriers, Shetland sheepdogs, wirehaired fox terriers and West Highland white terriers had a significantly increased risk of bladder cancer, compared with mixed-breed dogs. This suggests a genetic predisposition to bladder cancers in terriers and primarily in Scottish terriers.

Glickman and colleagues found the risk of bladder cancer was higher among dogs exposed to phenoxy acid herbicides, the most commonly used chemical in agriculture, or nonphenoxy acid herbicides, compared with dogs exposed to lawns or gardens that did not receive an herbicide application.

Phenoxy acid is an active ingredient in 2,4-D, a commonly used herbicide. The Environmental Protection Agency says 2,4-D is safe.

Glickman said what goes on in the laboratory and the lawn are two different things. The EPA doesn't require inert ingredients in lawn products to be listed on the label, he said.

"Those inert ingredients are cancer-causing chemicals," Glickman said. "We know they contain heavy metals, petroleum-based solvents and cadmium.

"We can't do a study because the labels don't tell us what is in the product."

A follow-up study at Purdue will examine exposure to lawn chemicals in dogs and children.

When chemicals are applied to a lawn, it is generally recommended that people and pets stay off the lawn for 24 hours, Glickman said.

"We are studying 25 homes with lawns treated with herbicides and collecting grass clippings before application, 24 hours after and three days after, he said.

"We are looking at the chemicals found, if they change over a period of time and if they are still present beyond 24 hours."

Urine samples are being collected from children and dogs in these households. All breeds of dogs are included in the study.

The study will determine if children and dogs exposed to the lawn get these chemicals in their systems, how high the concentrations are and the nature of exposure beyond three days.

A control group in which lawns have not been chemically treated is included in the study.

"We are going to look at chemicals to see if there are known cancer-causing agents," Glickman said. "If we find chemicals for which there is little information, we will conduct tests to see if they are possibly cancer-causing agents."