Purdue researchers explore link between lawn herbicides and bladder cancer

W. Lafeyette, Ind.-A study conducted by Purdue University researchers revealed the risk for Scottish Terriers of developing bladder cancer (transitional cell carcinoma, TCC), to be between four to seven times greater if exposed to lawn chemicals. The risk for Scottish Terriers developing TCC is about 18 times greater than that of mixed breed dogs.

Environmental exposure histories were compared between 83 Scottish Terriers who had developed TTC and 83 Scotties of approximately the same age with other health-related conditions as controls. The study was published in the Journal of the American Veterinary Medical Association.

Dr. Larry T. Glickman

Dr. Larry T. Glickman, professor of epidemiology and environmental medicine in Purdue's School of Veterinary Medicine, says he and other researchers hope to determine which of the chemicals in lawn treatments are responsible for the heightened levels of bladder cancer found in the dogs. If a similarity between human and dog genomes is found, the genetic predisposition toward this form of cancer found in certain people may also be determined since humans and animals often share genes that can predispose them to cancer.

"Finding the dog gene could save years of research for it in humans and could also help us determine which kids need to stay away from lawn chemicals," Glickman says.

While the research hit national media at presstime, Glickman adds that pressure from the lawncare industry following publication of the results wasn't as great as the questions that followed from concerned pet owners.

"The criticism has not been focused on the study, just the results," Glickman says. "We can't do the science and run away from it. We have to be responsible."

Glickman's team plans to survey children and dogs in households that have treated lawns and compare the chemicals in their urine samples to households with untreated lawns.

Lawn care companies have said as long as the chemicals are dry before pets or humans walk on them, it should be safe. Glickman doesn't know if people comply, but he would like to find out. Activity questionnaires have been given to homeowners to chronicle their children/pets habits outside.

Half of the study was funded by the American Kennel Club and Scottish Terrier clubs.

There are other breeds that carry certain genes that predispose them to these types of problems. The researchers plan to find the gene, and then look for a connection.

If signs of bladder cancer are picked up early or the pets are kept off of treated lawns, there is some hope for the breed. More frequent exams on high-risk animals would help to determine how the chemicals are affecting the animal's health.

Glickman says the role of herbicides in the etiology of cancer is controversial, but there is "pretty clear cut evidence of bladder cancer in terriers from herbicides in the lawn."

Glickman advises veterinarians to educate owners about the signs of bladder cancer in order to pick up the diagnose earlier, and educate owners about risks.

In dogs, highest risk factors include one or more of the following: female, neutered, overweight and having a history of flea/tick dips. While humans TCC risk is associated with cigarette smoke, occupational exposures to chemicals in the dye industry and ionizing radiation. A wide variety of other chemical exposures have been suspected to play a role in the etiology of bladder cancer, according to Glickman.

The case control study for the research began in June 2001. Control dogs were at least 6 years of age and free of urinary tract infections for at least two years prior to entry in the study. About 63 percent of the case dogs were deceased at the time of entry into the study versus 12 percent of control dogs. Gender was equally distributed in both case control groups.

Data presented on the research revealed that approximately 71 percent of the TCC cases were confirmed by tissue biopsy, while the remaining cases were diagnosed through cytology. Research found dogs that had more exposure to treated lawns were at higher risk than those with no or little access.

About 50 percent of the cases and 18 percent of the controls were reported to have been exposed to herbicides. Nearly 40 percent of the cases and 24 percent of the controls were exposed to insecticides.

The risk of herbicide-treated lawns or gardens is substantially higher according to results from research. The research also revealed the risk of TCC increasing with the number of applications of herbicide applied per year.

Dogs exposed to both phenoxy and non-phenoxy herbicides were at a significantly increased risk of TCC.

Many pesticides have inert ingredients that are not listed on the container. This does not mean the ingredients are chemically or physically inert. Many inert ingredients are known to be hazardous to health, he explains.

Until the "inert" ingredients are listed it may be impossible to determine to hypothesize the mechanism in which they cause cancer in genetically susceptible subpopulations such as Scottish Terriers, Glickman says.

In conclusion of the research, Glickman says he could advise owners to keep Scottish Terriers from having access to chemical-treated lawns his until additional risk studies can be conducted.