Letter addressed to The Canadian Veterinary Medical Association
April 30, 2001 Donald L. Page
Dr. Darcy Shaw, DWM
President
The Canadian Veterinary Medical Association
339 Booth Street
Ottawa. Ontario,
KIR7Kl
Dear Dr. Shaw,
I am writing to you with regard to the use of lawn care herbicides and the alleged effects on domestic animals such as dogs.
There are many contradictory statements in the public domain about the potential effects of pesticides on human and animal health. In particular, it is often reported in the news media and alleged by certain anti-pesticide groups that 2,4-D causes cancer in family pets.
Those groups that make this allegation usually refer to the “Hayes study” (JNCI, vol. 83. 1226-1231, 1991). This research purportedly demonstrated that dogs whose owners used the herbicide 2,4-D on their lawns four times a year or more were twice as likely to develop canine malignant lymphoma compared to dogs whose owners did not use 2,4.D. The study, which was based on mailed questionnaires and telephone interviews, received extensive media coverage, being reported in more than 250 papers in Canada and the U.S.
The study was immediately controversial in scientific circles, since it was in direct conflict with the extensive 2,4-D toxicology data base (animal feeding studies, including dog feeding studies, done in EP A qualified laboratories under controlled conditions). For example, in a study done by the U.S. Food and Drug Administration (Hansen et al, 1971), dogs were fed massive doses of 2,4-D (far in excess of what humans or animals could be exposed to in the environment) daily for two years and these dogs did not develop cancer or any other serious disease.
Since the Hayes dog study was government funded, the School of Veterinary Medicine at Michigan State University (MSU) was able to obtain copies of the raw data on which the study was based. They found that the data would not support the conclusions reached by the author, and that there was no association between 2,4-D and cancer in dogs. The author of the study was offered and opportunity to defend his study, which he declined. The MSU reanalysis was then published in the peer-reviewed journal, Human and Animal Toxicology (Kancene vol. 41 (3), 1999), a copy of which is attached or may be obtained online at http://www.24d.org/dogs.html.
You will also be pleased to know that the current United States Environmental Protection Agency (EPA) 2,4-D toxicology profile shows it to be non-carcinogenic, non-mutagenic and non-teratogenic. Furthermore, the World Health Organization’s current 2,4-D monograms states, “There was no evidence of carcinogenicity”.
I am hopeful that you may be able to disseminate this information to your members in order to clarify any misunderstandings that may exist about this important manner.
Sincerely,
Executive Director
