Homeowners often apply herbicides to their lawns to control weeds, but sometimes pets can be unintentionally exposed to those pesticides scientists say. In a new study published in the July 1, 2013 issue of Science of The Total Environment, scientists found detectable levels of commonly used herbicides in the urine of dogs. At the very least, they recommend that homeowners follow label instructions and allow any pesticide residues to dry completely before allowing pets onto lawns that have been treated.
Scientists from Purdue University and the University of North Carolina tested the urine of 25 dogs that lived in households where the homeowners applied herbicides to their lawns. They looked for and detected three commonly used herbicides (2,4-D, MCPP and dithiopyr). The herbicide levels were about 1.5 to 12.5 times higher in the dogs 24 hours after applications. By 48 hours, herbicide levels in the dog urine had decreased somewhat to near pre-treatment levels.
In experimental grass plots that were sprayed with herbicides (2,4-D, MCPP and dicamba) the scientists were able to detect a substantial amount of pesticide residue up to 48 hours after treatment. At the very least, they recommend that homeowners follow label instructions and allow any pesticide residues to dry completely before allowing pets onto lawns that have been treated. They also suggest that homeowners wash their dog’s feet if they come into contact with a recently treated lawn and to consider alternating the treatment of a front and back lawn by one week so that pets have an untreated area available to them.
Surprisingly, the scientists also detected pesticides in the urine of dogs from homes where no pesticides were applied. They suspect that these dogs may have been exposed to herbicides on lawns in other areas away from the home or that the home lawns were contaminated by pesticide drift from nearby areas.
While the exposure levels found in this study were not high enough to cause concern for acute poisoning, some studies have found that low level pesticide exposures may increase the risk for developing cancer in certain types of susceptible dog breeds.
Deborah Knapp, lead author of the study, is a professor at the Purdue University College of Veterinary Medicine. Her and her colleagues conducted the study out of concern for both pet health and the health of people. She explained to Discovery News how both people and pets can be exposed to lawn care chemicals:
Dogs can pick up the chemicals on their paws and their fur. They can then track the chemicals inside the house, leaving chemicals on the floor or furniture. In addition, if the dog has chemicals on its fur, the pet owner could come in contact with the chemicals when they pet or hold the dog.
Co-authors of the study included Wendy Peer, Abass Conteh, Alfred Diggs, Bruce Cooper, Nita Glickman, Patty Bonney, Jane Stewart, Lawrence Glickman and Angus Murphy. Funding for the research was provided in part by Purdue University Center for Cancer Research and private donations in support of bladder cancer research.
Bottom line: In a new study published in the July 1, 2013 issue of Science of The Total Environment, scientists found detectable levels of three commonly used herbicides in the urine of dogs after lawn applications. At the very least, they recommend that homeowners follow label instructions and allow any pesticide residues to dry completely before allowing pets onto lawns that have been treated.
Deanna Conners is an Environmental Scientist who holds a Ph.D. in Toxicology and an M.S. in Environmental Studies. Her interest in toxicology stems from having grown up near the Love Canal Superfund Site in New York. Her current work is to provide high-quality scientific information to the public and decision-makers and to help build cross-disciplinary partnerships that help solve environmental problems. She writes about Earth science and nature conservation for EarthSky.