Pets & Pesticides
Here is an article, as promised in my weekly update to SafeLawns members, about a research project related to dogs and pesticides:
Leading Animal Researcher
Warns of Lawn Chemical Risks
As professor of epidemiology and environmental medicine at Purdue University’s internationally renowned School of Veterinary Medicine, Dr. Lawrence Glickman is one of the world’s leading experts on dogs and their diseases. His research has led to many breakthroughs, including: that certain dog breeds are more susceptible to the lethal parvovirus infection; that high-fat, high-protein, low-carbohydrate diets are associated with significantly improved survival rates in dogs with breast cancer; that exposure to asbestos increases dogs’ risk of lung cancer; and that exposure to certain weed killers increases the risk of bladder cancers in certain breeds of dogs. He has received the Pfizer Research Award for Research Excellence and the Ralston Purina Small Animal Research Award, and he has authored more than 200 scientific articles, book chapters and monographs on canine health.
To learn more about the specific research on the risks of lawn chemicals and dogs, SafeLawns spokesperson Paul Tukey recently contacted Dr. Glickman for a question-and-answer session.
SafeLawns: What factors led you to your research? Did you have an inkling that lawn pesticides were potentially harmful to dogs?
Dr. Glickman: We see so much bladder cancer in pet dogs that I suspected it could be due to chemicals in the environment, especially on grass where they spend so much time. Also, dogs do not smoke, which is known to increase the risk of bladder cancer in people. Then, when I found out that many pesticide formulations applied to lawns contain chemicals called “inert ingredients”that are known to be carcinogenic, I decided to do this study on Scottish Terrier dogs. We chose this breed to study because we previously proved that Terriers had a much higher risk of bladder cancer than did other dog breeds.
SL: Can you summarize your findings in lay terms?
Dr. Glickman: A case-control study in Scottish Terriers, a breed previously found to be at
a high risk of transitional cell carcinoma (TCC) of the urinary bladder, was conducted to determine if exposure to lawn chemicals further increases the risk of TCC. Environmental exposure histories were compared between 83 Scottish Terrier dogs with TCC and 83 Scottish Terrier dogs of approximately the same age with other health-related conditions.
A significantly increased risk of TCC — four to seven times greater — was found for dogs exposed to lawns or gardens treated with herbicides and insecticides or herbicides alone — but not with insecticides alone, compared with dogs exposed to untreated lawns or gardens. These findings suggest that Scottish Terrier dogs, as well as other dogs of high-risk breeds for TCC, be restricted from lawns treated with herbicides (at least until additional risk studies are conducted). Also, veterinarians should perform a routine urine cytological examination twice a year to detect TCC in Scottish Terrier dogs greater than six years of age. Dog owners should learn the early warning signs of TCC.
SL: Terriers are far more likely to be diagnosed with bladder cancer than some other breeds. Why did you choose Terriers for the study?
Glickman: Previous findings showed that Scottish Terriers had the highest risk of bladder cancer than did any other breed. Therefore we reasoned that they should be much more sensitive to the effects of chemical carcinogens in the environment and would be a good sentinel of cancer in humans.
SL: OK. The big question: Since the study involved only Terriers, is it reasonable to assume that lawn chemicals are potentially dangerous to all dogs?
Glickman: Yes, it is reasonable to assume that lawn chemicals are potentially dangerous to all dog breeds, but the risk would be lower than in Scottish Terriers. In our hospital, we see virtually all breeds of dogs with bladder cancer, but especially Scottish Terriers, Beagles, and Sheltie Collies.
SL: In lay terms, what types of lawn chemicals appear to be most dangerous?
Glickman: According to our study, 2,4-D herbicides (weed killers) were associated with the highest risk of bladder cancer. However, the 2,4-D itself is not necessarily the issue. When lawns are treated with herbicides, only about 0.5 percent of what is applied by volume is the active herbicide or pesticide. The other 99.5 percent of what is applied contains so-called “inert” ingredients, many of which are known to cause cancer such as benzene, toluene, xylene, petroleum distillates, and heavy metals such as cadmium. These inert ingredients are not required by the EPA to be listed on the label by the company. Also, while the active ingredient in the herbicides must be tested in laboratory studies prior to licensing, these so-called inert chemicals are not tested for safety in combination with the herbicides prior to their use in lawn treatment products.
SL: What other types of research need to be done to further the awareness?
Glickman: Other studies like ours need to be done to confirm the findings. However, funding for such studies is very difficult to obtain since the National Institutes of Health normally funds human studies and there is no agency that currently funds studies in pet animals.
We are currently performing a study to identify the specific genes in Scottish Terriers that predisposes them to bladder cancer. Once we find these genes, we hope to look for similar genes in humans. We have also conducted a study in which we collected urine from children and dogs living in homes that have been treated with lawn chemicals to determine how much is absorbed and excreted in urine. We are doing similar collections from children and dogs living in homes where the lawns were not treated (the findings are not yet available).
SL: Is it true that canine cancers/leukemias are on the rise in general?
Glickman: There is no federal agency that collects statistics on the frequency of diseases in dogs, so there is no good information available to answer this question. However, with the increase in the number of veterinary oncologists in private practice, many more dogs are being treated for cancer today than in the past. Lymphoma (leukemia) is one of the most common cancers in dogs.
SL: Have you developed any personal opinions about lawn chemicals in general? Do you recommend that people do not use them?
Glickman: All chemicals and drugs are potentially toxic. Therefore one should avoid using them if there are other ways to prevent the problem. If one must use them, take the lowest dose that is effective. I believe that if organic lawn treatments are effective, they should be preferred to chemical herbicides. Education is needed so homeowners are made aware of the risks of using lawn chemicals and if they must use them, what precautions to take. Clearly, children and pets should not be exposed to potentially hazardous substances.