INDUSTRY TASK FORCE II ON
2,4-D RESEARCH DATA
Information Line: 1-800-345-5109 Web Page: www.24d.org
Fax: 252-393-6327 E-mail: This email address is being protected from spam bots, you need Javascript enabled to view it

Issue Backgrounder

CANCER IN DOGS

Issue:
It is sometimes reported in the news media that lawn and turf herbicides
containing 2,4-D are a cause of cancer in dogs. This is not supported by the simple
fact that all regulatory agencies in the world that have examined the scientific data
have arrived at the same conclusion: 2,4-D is not an animal carcinogen.

Background:

In 1991, the Journal of the National Cancer Institute published a study which
purportedly showed a positive association between canine malignant lymphoma
(CML), a form of cancer in dogs, and dog owners use of the herbicide 2,4-D,
(Hayes 1991)1. The authors claimed to have demonstrated that dogs whose owners
used the herbicide 2,4-D on their lawns four or more times per year were twice as
likely to develop canine malignant lymphoma compared to dogs whose owners
did not use 2,4-D (please note that the maximum labeled use of 2,4-D on turf is
two applications per year).

The study was immediately controversial in scientific circles since it was in direct
conflict with the extensive 2,4-D toxicology database including rodent and dog
feeding studies. There are also lifetime feeding bioassays in rodents (Charles, et
al., 1996a)2 and a chronic feeding study in the dog (Charles, et al., 1996b)3 that did
not indicate oncogenic effects. These animal feeding studies were done under
controlled conditions by EPA/GLP qualified laboratories. The current EPA
toxicology profile shows 2,4-D to be "non-carcinogenic" in animals.4

The Hayes study received widespread coverage by the news media, with the story
being carried by almost 200 newspapers across the United States and Canada.
Today, the study is often cited by anti-pesticide groups as evidence supporting the
suggested relationship of 2,4-D and non-Hodgkin’s lymphoma (NHL), a human
disease somewhat similar to canine malignant lymphoma. Some veterinarians
advise dog owners not to use 2,4-D on their lawns.

The 2,4-D Task Force was curious how the dose-response of frequency of 2,4-D
use was calculated. Since the Hayes dog study was publicly funded, the data file
was given to Dr. John B. Kaneene, Director, Population Medicine Center, School
of Veterinary Medicine, Michigan State University (MSU), for independent
analysis. Neither the Task Force nor MSU were able to obtain additional
information from the NCI investigators regarding exposure criteria or the dose
response algorithm. Dr. Kaneene, using NCI’s own data, found that the data would
not support the CML conclusions reached by the author, and that there was no
association between 2,4-D and cancer in dogs. Dr. Hayes was offered an
opportunity to defend his study, which he declined. The MSU reanalysis was then
published in the peer-reviewed journal (Kaneene, et al., 1999)5. Subsequently, a
second more recent epidemiological case-control study (Gavazza et al., 2001)6
failed to show any association between dogs whose owners used lawn care
herbicides and canine malignant lymphoma. This study concluded, “Variables
describing animal care and pesticide use were either not associated with the
disease [CML] or were uninformative.”

Regulatory decisions around the world confirm that 2,4-D is not an animal
carcinogen (WHO 19967, EU 20018, PMRA 20059, EPA 20054).

Reprints for “Re-Analysis of 2,4-D Use and the Occurrence of Canine Malignant
Lymphoma” (Kaneene 1999)5, are available through this Task Force. For
information on other NCI epidemiologic case-control studies involving 2,4-D, see
the Epidemiology page on this web site.

About the Task Force

The Industry Task Force II on 2,4-D Research Data is organized to provide
funding for some 300 Good Laboratory Practice (GLP) research studies required
to respond to the EPA reregistration and PMRA pesticide re-evaluation programs.
The 2,4-D Task Force is comprised of those companies owning the technical
registrations on the active ingredient in 2,4-D herbicides. They are Dow
AgroSciences (U.S.), Nufarm, Ltd. (Australia) and Agro-Gor Corp., a U.S.
corporation jointly owned by Atanor, S.A. (Argentina) and PBI Gordon Corp.
(U.S.).

1 Hayes et al. 1991. Case-control study of canine malignant lymphoma: Positive association with dog

owner’s use of 2,4-dichlorophenoxyacetic acid herbicides. J. Natl Cancer Inst 83(17):1226-1231.
2 Charles, JM, Bond, DM, Jeffries, TK, Yano, BL, Stott, WT, Johnson, KA, Cunny, HC, Wilson, RD and
Bus, JS. 1996a. Chronic Dietary Toxicity/Oncogenicity Studies on 2,4-Dichlorophenoxyacetic Acid in
Rodents. Fund. Appl. Toxicol. 33: 166-172.

3 Charles, JM, Dalgard, DM, Cunny, HC, Wilson, RD and Bus JS. 1996b. Comparative Subchronic and
Chronic Dietary Toxicity Studies on 2,4-Dichlorophenoxyacetic Acid, Amine, and Ester in the Dog. Fund.
Appl. Toxicol. 29: 78-85.

4 U.S. EPA. 2005. Reregistration Eligibility Decision for 2,4-D. Docket # OPP-2004-0167

<http://docket.epa.gov/edkpub/index.jsp>
5 Kaneene, JB and R. Miller. 1999. Re-analysis of 2,4-D Use and the Occurrence of Canine Malignant
Lymphoma. Veterinary and Human Toxicology, Vol. 41, No. 2:164-170.

6 Gavazza, A, S Presciuttini, R Barale, G Lubas, and B Gugliucci. 2001. Association between Canine
Malignant Lymphoma, Living in Industrial Area, and Use of Chemicals by Dog Owners. J. Vet Intern.
Med. 15: 190-195.

7 World Health Organization & Food and Agriculture Organization of the United Nations, Pesticide

residues in food, Toxicological evaluations, 1996.
8 European Commission Health & Consumer Protection Directorate-General. 2001. Commission Working
document. Review Report for the Active Substance 2,4-D Re-evaluation. 7599/VI/97-final. 1 October
2001.

<http://europa.eu.int/eur-lex/pri/en/oj/dat/2001/l_313/l_31320011130en00370039.pdf>

9 PMRA. (2005). Proposed Acceptability for Continuing Registration; Re-evaluation of the Lawn and Turf
Uses of (2,4-Dichlorophenoxy)acetic Acid [2,4-D]. <www.pmra-arla.gc.ca/english/consum/2,4-D-e.html>