Dogs whose owners use a herbicide containing 2,4-D are up to twice as likely to develop lymphatic cancer, a finding that suggests the common plant-killing chemical may pose a hazard to humans. In a study published in the Journal of the National Cancer Institute, researchers at the National Cancer Institute reported that dogs were two times more likely to develop lymphoma if their owners sprayed or sprinkled the 2,4-D herbicide on the lawn four or more times a year.
The risk of lymphoma among the dogs dropped if the chemical was used less frequently, but even with just one application a season, the cancer risk was one-third higher than among dogs whose owners did not use the chemical.
An elevated risk of lymphoma has previously been found among farmers who use the herbicide and come in contact with it frequently. Some experts have suggested that the widespread use of the herbicide on lawns, parklands and golf courses could pose a risk to the non-farming population, but no formal studies on such casual exposure have been conducted.
The new study of lymphoma among pet dogs that were permitted to romp on herbicide-treated lawns intensifies the concern, the study said.