By THE ASSOCIATED PRESS
New York Times Archives from 1991
[This article is from 1991. Apparently, the herbicide containing 2,4-D (a substance used in Agent Orange) is still being used in some areas and applications, despite findings that conclude the herbicide is a carcinogen. Make sure you know what is on your lawn.]
Dogs whose owners use a herbicide containing 2,4-D are up to twice as likely to develop lymphatic cancer, a finding that suggests that the plant-killing chemical may be a health risk to humans.
In a study published today in The Journal of the National Cancer Institute, researchers report 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 been found among farmers who use the herbicide and come frequently in contact with it. Some experts have suggested that the widespread use of the herbicide on lawns and golf courses could pose a risk to the non-farming population, but no formal studies on such casual exposures have been conducted. An Intensified Concern
The new study of lymphoma among dogs that were permitted to romp on herbicide-treated lawns intensifies the concern, the study said.
“This study supports the idea that exposure to 2,4-D, as used for lawn care, plays a role in causing lymphomas in dogs,” Howard M. Hayes, the primary author of the study, said in a statement made public today. “The study also suggests that the potential health hazards of human exposure to 2,4-D at home warrant further study.”
Mr. Hayes and his co-authors suggested that new research was needed to determine if humans and dogs will react in a similar way to the home use of the herbicide.
Malignant lymphoma in dogs is similar to non-Hodgkin’s lymphoma in humans. It is a cancer that strikes the lymphatic, or immune, system and can involve lymph nodes, the spleen and some blood cells. The incidence of lymphoma among Americans has increased by about 50 percent since 1973, one of the largest increases of any cancer. The cancer institute estimates that 37,000 new cases will be detected in the United States this year. A Serious Risk Factor
Although malignant lymphoma is common in dogs, striking about one in seven, the study said exposure to 2,4-D was a much more serious risk factor for the disease than other chemicals commonly encountered by pet dogs.
The conclusion was based on a study of the chemical exposures of 491 dogs with lymphoma, compared with 466 dogs of similar age and background that did not have lymphoma. For a further comparison, the researchers also studied 479 dogs that had cancers other than lymphoma.
Details of the chemical exposures encountered by the dogs were based on survey forms and interviews with the dog owners.
Dogs with lymphoma were found to be 1.3 to 2 times more likely to have been exposed to 2,4-D in their yards than the other groups of dogs. Dogs that were not permitted outside were excluded from the study.
How Herbicides Are Ingested
The risk of lymphoma was highest for dogs whose owners applied the chemical more than four times a year. The cancer risk dropped slightly if the chemical was applied only by professional lawn companies.
Herbicides can be ingested by dogs when they lick their fur after walking or rolling on a treated lawn, or when they eat the treated grass. Breathing fumes from the chemical is not considered a cause of the lymphoma, the study said.
The chemical 2,4-D is often used by homeowners to kill weeds. Labels listing the contents of herbicides identify the chemical as 2,4-D, 2,4-D acid or 2,4-dichlorophenoxyacetic acid.
Professional lawn companies commonly use the herbicide. Homeowners can buy it in either granulated or liquid form; the study found that the chemical form made no difference in the cancer risk. The chemical is absorbed by plants and broken down by sunlight, but most manufacturers recommend that treated areas be avoided by pets and humans for several days.
For more on 2,D-4, check out this fact sheet.
