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. The authors of the studies state how their findings can be used to further research on human cancers. 

A six-year study from Tufts University School of Veterinary Medicine linked lawn pesticides to canine malignant lymphoma (CML). Based on questionnaire results from dog owners, the study found “specifically, the use of professionally applied pesticides was associated with a significant 70% higher risk of CML. Risk was also higher in those reporting use of self-applied insect growth regulators.”

A different study with similar methods discovered that herbicides also contribute to canine malignant lymphoma. The study found that herbicides containing 2,4-D doubled the risk of CML when dog owners used 2,4-D four or more times per year.