Studies Link Canine Cancers To Lawn Chemicals

“Lawn chemicals, particularly, ones containing 2,4-D, have been linked to at least two types of canine cancers. Studies found that lawn chemicals travel to neighboring yards and inside homes, and chemicals have been found in the urine of dogs whose owners did not spray their lawns.”¹

Evidence that lawn chemicals are linked to cancers in dogs has been accumulating steadily over the past 20 years. Even if you don’t own a pet this should raise alarms for anyone who cares about children or just your own health.

As Prof. John Reiff of Colorado State University reminds us, “Animals may be sensitive indicators of environmental hazards and provide an early warning system for public health intervention, as exemplified by the iconic canary in the coal mine.”² He shared the results of work at Purdue University’s School of Veterinary Medicine that found exposure to lawns or gardens treated with herbicides was associated with an increased risk of bladder cancer in dog breeds studied.

While there is current controversy in public health circles and the news about the use of Monsanto/Bayer’s Roundup (glyphosate), another herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), has a controversial history as well. It was banned in Sweden for use in the lumber industry because of concerns about cancer among lumberjacks in 1988 and banned for general use in 1990.³

2,4-D made up about half of the ingredients of Agent Orange used in Vietnam, though most Agent Orange problems are said to have been associated with dioxin according to the Pesticide Information Project of Cooperative Extension Offices of Cornell University, Michigan State University, Oregon State University, and the University of California at Davis.”⁴

In 1991 a U.S. hospital-based case-control study of companion dogs funded with public money was published by a team from the National Cancer Institute’s (NCI) Epidemiology and Biostatistics Program. They found that dogs whose owners used the herbicide 2,4-D on their lawns 4 times/year or more were twice as likely to develop Canine Malignant Lymphoma as dogs whose owners did not use 2,4-D, saying their findings were “consistent with occupational studies in humans, which have reported modest associations between agricultural exposure to 2,4-D and increased risk of non-Hodgkin’s lymphoma.”⁵

Another study published in 1994 by researchers at Colorado State University provided further evidence for concern by examining whether dogs absorb 2,4-D and excrete it in urine after their owners used the lawn herbicide. The study found a correlation between recent application of the lawn herbicide and measurable 2,4-D in the dog urine. More worrisome was that some dogs had small amounts of 2,4-D in their urine even though their owners had not recently applied 2,4-D on their lawns. This raised the possibility that the dogs had been exposed to 2,4-D on neighboring lawns and at parks.⁶

However, an industry-funded reassessment of the NCI study by Michigan State University published in 1999 found “no association between 2,4-D and cancer in dogs.”^{7, 8}  This work is featured prominently on a website maintained by An Industry Task Force on 2,4-D maintains a website defending the safety of the herbicide that includes a page entitled “The Myth of Cancer in Dogs.” The task force’s mission is to provide funding for “research studies required to respond to the US EPA registration review and Canada’s Pesticide Management Regulatory Agency pesticide re-evaluation programs.”

The task force is comprised of companies holding technical registrations for 2,4-D including Dow AgroSciences, Nufarm Ltd, Agro-Gor Corp.⁹ Research shared by the Task Force showing 2,4-D is safe centers on feeding 2,4-D to laboratory animals. According to the Pesticide Information Project, 2,4-D is “readily absorbed through the skin and lungs.”⁴ This raises questions whether the industry task force is using an apples comparison (ingestion of the herbicide) to assess an oranges issue (exposure of animals and people through physical contact with skin/feet and lung inhalation).

Published reports linking 2,4-D to cancers in dogs continues to accumulate. A study conducted between 2000-2006 of dogs treated for Canine malignant lymphoma at a Tufts University tertiary-care veterinary hospital found that the use of professionally applied pesticides on lawns was associated with a 70% higher risk of the cancer.¹⁰

A study published in 1999 studied 2,4-D in floor dust throughout homes following homeowner and commercial lawn applications. They found measurable 2,4-D in floor dust in rooms from entryways, through living rooms, dining rooms, kitchens, and bedrooms, both before after herbicide application. This work by scientists from the Battelle Memorial Institute and the EPA’s National Exposure Research Laboratory raises real concerns about chemical exposure via contact with skin and lungs.¹¹

Scottish Terriers are a dog breed known to suffer from a higher incidence of bladder cancer than other breeds. A case-control study of Scottish Terriers conducted at Purdue University School of Veterinary Medicine found that the risk of transitional cell carcinoma of the bladder “was significantly increased among dogs exposed to lawns or gardens treated with both herbicides and insecticides or with herbicides alone, but not among dogs exposed to lawns or gardens treated with insecticides alone, compared with dogs exposed to untreated lawns.” They advise that owners of Scottish Terriers should minimize their dogs’ access to lawns or gardens treated with phenoxy herbicides (such as 2,4-D).¹²

A Purdue University study published in 2013 found that lawn herbicide “chemicals were detected in the urine of dogs in 14 of 25 households before lawn treatment, in 19 of 25 households after lawn treatment, and in 4 of 8 untreated households. Chemicals were commonly detected in grass residues from treated lawns, and from untreated lawns suggesting chemical drift from nearby treated areas.” They concluded, “dogs could be exposed to chemicals through contact with their own lawn (treated or contaminated through drift) or through contact with other grassy areas if they travel.”¹³

The issue remains controversial as more money is needed to fund independent studies at the same time big money flows from industry. People are taking their concerns to local government as seen in Bucks County Pennsylvania in 2018 where residents who took their dogs for walks in a local park believe the herbicide used at the park was killing their pets.¹⁴

Concerns about dogs being the canaries in the coal mine for cancer are starting to be understood with devastating consequences for our children. In 2016 a team of Spanish researchers from nine different highly respected institutions including the Consortium for Biomedical Research in Epidemiology and Public Health and the Centre for Research in Environmental Epidemiology conducted a population-based case control study of childhood cancer covering 3,350 cases and 20,365 controls in two Spanish regions and concluded “our result points to the same conclusion as many previous studies and suggests that living in the proximity of cultivated land could be associated with many types of cancer in children.”¹⁵

That same year, a group of Italian and U.S. researchers published results of their population-based case-control study in a Northern Italy community to assess the possible relation between passive exposure to agricultural pesticides and risk of acute childhood leukemia. They found “increased leukemia risk among children residing close to arable crops” that were “characterized by the use of 2.4-D, MCPA, glyphosate, dicamba, triazine, and cypermethrin.”¹⁶

Finally, a massive 289 million dollar judgment against Monsanto suggests that Monsanto (now Bayer) intentionally kept information about glyphosate’s potential harms from the public. Though this is likely the first of many, many lawsuits against the company, we should all consider that we still have no idea just how poisonous and cancer-causing these herbicides and pesticides really may be so, unfortunately, we must decide for ourselves how to best protect our pets and children (and ourselves) from cancer and the effects of the life-long burden of toxins upon our bodies.

While we wait for more research to confirm or disprove a link between 2,4-D and cancer in people and pets, we must each decide whether to take steps to protect our family members from potentially dangerous herbicides.

Here is a link to a YouTube of a local CBS report, “Residents Believe Herbicide Used At Park Is Killing Pets, “CBS Philly April 9, 2018. :

As a follow-up to the above news report, the Springfield town supervisors voted 4-0 in favor of ending the lease with the farmer who had used herbicides in growing hay he harvested from the park land. One supervisor who was also a farmer abstained from the vote.¹⁷ 

Article originally published August 1, 2019, updated May 29, 2020.

Sources & References

¹ThinkAboutNow. Studies Link Canine Cancers to Lawn Chemicals. ThinkAboutNow. Website. 010117

²Reiff JS. Animal sentinels for environmental and public health. Public Health Reports. 2011;126(Suppl 1): 50-57.

³Thörn Å, Gustavsson P, Sadigh J, et al. Mortality and cancer incidence among Swedish lumberjacks exposed to phenoxy herbicides. Occupational and Environmental Health. 2000; 57:718-20.

⁴Pesticide Information Project. Extension Toxicology Network. 2,4-D. Website. 9/93.

⁵Hayes HM, Tarone RE, Cantor KP, et al. Case-Control Study of Canine Malignant Lymphoma: Positive Association With Dog Owner’s Use of 2, 4-Dichlorophenoxyacetic Acid Herbicides. JNCI: Journal of the National Cancer Institute 1991;83, pp 1226–31.

⁶Reynolds PM, Reif JS, Ramsdell HS, Tessar JD. April-May 1994. Canine Exposure to Herbicide-Treated Lawns and Urinary Excretion of 2,4-D Acid. Cancer Epidemiology Biomarkers & Prevention. 3(3):233-237.

⁷Kaneene JB, Miller R. 1999. Reanalysis of 2,4-D Use and the Occurrence of Canine Malignant Lymphoma. Veterinary and Human Toxicology, Vol. 41, No. 2:164170.

⁸Cottam J. Dogs and Exposure to Herbicide 2,4-D. Just Ottawa. Website.

⁹Industry Task Force II on 2,4-D Research Data. The Myth of Cancer in Dogs. 2,4D.com. Website.

¹⁰Takashima-Uebelhoer BB, Barber LG, Zagarins SE, et al. Household Chemical Exposures and the Risk of Canine Malignant Lymphoma, a Model for Human Non-Hodgkin’s Lymphoma. Environmental Research. 2012;112:171-176.

¹¹Nishioka MG, Burkholder HM, Brinkman MC, Lewis RG. Distribution of 2,4-Dichlorophenoxyacetic Acid in Floor Dust throughout Homes Following Homeowner and Commercial Lawn Applications: Quantitative Effects of Children, Pets, and Shoes. Environmental Science & Technology. 1999 33 (9), 1359-65.

¹²Glickman LT, Raghavan M, Knapp DW, Bonney PL, Dawson MH. Herbicide exposure and the risk of transitional cell carcinoma of the urinary bladder in Scottish Terriers. Journal of the American Veterinary Medical Association. 2004;224:1290–7.

¹³Knapp DW, Peer WA, Conteh A, et al.  Detection of herbicides in the urine of pet dogs following home lawn chemical application. The Science of the Total Environment. 2013 Jul 1;456-457:34-41.

¹⁴Ullery, Chris. Springfield residents seek to curb herbicide use after dog deaths. The Intelligencer. April 8, 2018.

¹⁵Gómez-Barroso D, García-Pérez J, Lopez-Abente G, et al. Agricultural crop exposure and risk of childhood cancer: new findings from a case-control study in Spain. International Journal of Health Geographics. 2016; 15:18.

¹⁶Malagoli C, Costanzini S, Heck JE, et al. Passive exposure to agricultural pesticides and risk of childhood leukemia in an Italian community. International Journal of Hygiene and Public Health. 2016; 219:742-748.

¹⁷ Ullery, Chris. Springfield ends lease with farmer to stop herbicide use of land. The Intelligencer. April 10, 2018.