A highly publicized study by the National Cancer Institute erroneously linked a widely used agricultural and lawn chemical with cancer in dogs, according to Michigan State University researchers.
The chemical, 2,4-dichlorophenoxyacetic acid or "2,4-D," is a weed killer used by homeowners and Midwest farmers of corn, wheat and dairy animals. It is found in popular lawn-treatment fertilizers and in spray-on lawn treatment.
The U.S. Environmental Protection Agency requires that areas sprayed with 2,4-D be posted with signs warning pet owners to keep their animals away.
But the anxiety is unwarranted, the Michigan researchers said.
"We were unable to support the conclusions reached by the (Cancer Institute) concerning the relationship between 2,4-D exposure and canine malignant lymphoma," said researcher John Kaneene, director of the Population Medicine Center at the Michigan State University School of Veterinary Medicine.
Kaneene's study, which was financed with a grant from 2,4-D producers, is published in the current issue of the scientific journal Veterinary and Human Toxicology.
In 1991, the Cancer Institute published a study reporting that the rate of canine lymphoma, a cancer that strikes the immune system, doubled among dogs whose owners used 2,4-D on lawns four or more times per year. Cancer Institute researchers said at the time that the study was consistent with studies of farmers exposed to 2,4-D.
The study was widely reported in the media, causing concern among pet owners and fueling calls for a ban on 2,4-D. Banning 2,4-D would cost U.S. farmers and other users about $ 1.7 billion annually, a 1996 study by the U.S. Agriculture Department concluded.
According to Kaneene's analysis, the NCI erred in automatically classifying dogs as exposed to 2,4-D simply because their owners used a professional lawn service, or if the owners did not know whether a professional lawn service was used. "Misclassification . . . needed to be appropriately addressed," Kaneene said.
Dr. Stephen Sternberg of Memorial Sloan-Kettering Cancer Center in New York said he was not surprised by the Kaneene study, adding: "The (Cancer Institute) study was no good. . . . There was no physical examination of any of the dogs. The researchers assumed the dogs were exposed to 2,4-D from licking the bottoms of their feet, which they don't really do."
The Cancer Institute, which has studied 2,4-D since 1986, is taking a "wait-and-see" approach, according to Sheila Zahm, deputy director of the institute's Division of Cancer Epidemiology and Genetics. "We stand by the decision of the original investigators to classify dogs as exposed to 2,4-D if a professional lawn service was used. 2,4-D was the cheapest and most commonly used chemical at the time," Zahm said.
"The (National Cancer Institute) has been targeting 2,4-D since the 1980s," said Don Page, director of the 2,4-D Task Force II, a group of Midwest-based 2,4-D manufacturers. "Despite a scientific review committee from the Environmental Protection Agency concluding in 1997, the NCI studies provided insufficient evidence that 2,4-D caused cancer. And now with the Kaneene study, the NCI appears unwilling to admit it was wrong."
Concerned about potential bias at the institute against 2,4-D, the industry used the Freedom of Information Act to request the original data used in the 1991 dog study.
"We were rebuffed for 18 months," Page said. "It wasn't until the NCI was threatened with a lawsuit that the agency finally consented to provide us the data."
With a grant from the 2,4-D Task Force, Kaneene conducted her own analysis.
Kaneene's analysis was published amid controversy over a recent federal law that permits the public to obtain access through the Freedom of Information Act to scientific data developed by grantees of federal agencies and used to set government policy.
"That the original data from the dog study was able to be re-examined at all is a tribute to the Freedom of Information Act," said Michael Gough, a former government researcher. Gough spearheaded the effort to make available to the public data from a study of Air Force veterans' exposure to Agent Orange, the controversial defoliant used in Vietnam.
"But the public's ability to obtain such data in the future is in serious jeopardy," Gough said.
Since its enactment in October 1998, the law has been under fierce attack.
A bill was introduced last January by the late Rep. George Brown (D-Calif.) to repeal the law, and an effort to block implementation of the law was led by Representatives James Walsh (R-N.Y.) and David Price (D-N.C.) in the House Appropriations Committee in July.
Fearing the law may compromise intellectual property rights, the National Academy of Sciences, American Association for the Advancement of Science and pharmaceutical industry all have lobbied against the law. None of these efforts has met with success.
The fight over the public access to federally funded scientific data is likely to continue.
"The public should have the right to examine scientific data it paid for and (that) are used by government agencies to regulate the public," Gough said. "Apparently, some don't think government scientists should be accountable to the public for their use of tax dollars. They'll probably keep fighting against the data-access bill and for 'secret science.'
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