Cancer is one of the most important health issues affecting household pets. Causes of cancer are many and varied, including genetic predispositions, certain viruses, and exposure to environmental toxins. Many studies in both humans and animals have focused on the increased risk of cancer from chronic use of chemicals such as pesticides and herbicides around the household. Since dogs and cats have significant exposure to grassy areas of properties, lawn chemicals in particular have been studied for the potential of causing health problems.
Several studies have now shown an association between the frequently used chemicals on household lawns and cancer in dogs.(1-4) Dogs chronically exposed to the herbicides and pesticides in lawn sprays and granules are more likely to get cancers such as lymphoma and transitional cell carcinoma of the urinary bladder. An initial study published in the Journal of the National Cancer Institute in 1991 found that homeowners that frequently used the herbicide 2,4- dichlorophenoxyacetic acid on their lawn had a statistically significant higher rate of lymphosarcoma in their dogs.(1) Lymphosarcoma, also called malignant lymphoma, is a common cancer affecting lymph nodes and other organs and lymphatic tissues. This study was heavily criticized by other investigators who questioned the validity of the results. However, a more recent study published in 2012 analyzed 263 dogs with lymphosarcoma and found a 70% increase in risk of the cancer in households with professionally applied pesticides on the lawns.(2)
Two studies at Purdue University College of Veterinary Medicine have also found disturbing results of dogs exposed to herbicides, particularly the phenoxy herbicides such as the previously mentioned 2,4- dichlorophenoxyacetic acid, also called 2,4-D.(3,4)
Herbicides were found in the urine of 76% of dogs from households that used them on their lawn.(4) The herbicides were also found in the urine of some dogs from households where the herbicide was not used, indicating they were exposed to them in areas other than their own property.
The additional study from Purdue found that Scottish Terriers living in households that used herbicides alone or herbicides and pesticides on their lawns were markedly more prone to transitional cell carcinoma of the urinary bladder.(3) This study, along with the former one looking at the chemicals being present in the urine, are convincing evidence that the herbicide exposure is directly related to bladder cancer in this breed. Other breeds could be examined in the future to further define the risks of exposure.
More research is needed to elaborate the dangers of lawn chemicals to our pets, but these well designed and executed studies make it clear that the commonly used pesticides and herbicides being indiscriminately sprayed and broadcast on our lawns are causing cancer in dogs. Many provinces in Canada have completely banned what they call “cosmetic” use of herbicides and pesticides because of the potential health problems. Cosmetic is a good term because the cancer causing chemicals are being used merely to improve the appearance of our lawns. Maybe we should be more tolerant of less than perfect grass if it decreases the adverse health effects on our pets.
Although additional studies will help to better define the problem, we now have sufficient evidence to raise serious concerns about the dangers of herbicides and pesticides used on lawns. Homeowners should be educated about these issues so that they can take appropriate action to protect their pets from harm. Professional lawn care companies also need to carefully consider their protocols and make necessary changes to stop contaminating the environment with chemicals that are now proven to be carcinogenic to pets.
References
1. Hayes HM1, Tarone RE, Cantor KP, Jessen CR, McCurnin DM, Richardson RC. Case-control study of canine malignant lymphoma: positive association with dog owner's use of 2,4- dichlorophenoxyacetic acid herbicides. J Natl Cancer Inst. 1991 Sep 4;83(17):1226-31.
2. Biki B. Takashima-Uebelhoer, Lisa G. Barber, Sofija E. Zagarins, Elizabeth Procter-
Gray, Audra L. Gollenberg, Antony S. Moore, and Elizabeth R. Bertone-Johnson. Household Chemical Exposures and the Risk of Canine Malignant Lymphoma, a Model for Human Non-Hodgkin’s Lymphoma. Environ Res. 2012 January ; 112: 171–176.
3. Glickman LT1, Raghavan M, Knapp DW, Bonney PL, Dawson MHJ. Herbicide exposure and the risk of transitional cell carcinoma of the urinary bladder in Scottish Terriers. J Am Vet Med Assoc. 2004 Apr 15;224(8):1290-7.
4. Knapp DW1, Peer WA, Conteh A, Diggs AR, Cooper BR, Glickman NW, Bonney PL, Stewart JC, Glickman LT, Murphy AS. Detection of herbicides in the urine of pet dogs following home lawn chemical application. Sci Total Environ. 2013 Jul 1;456-457:34-41.
