PANUPS: Bromoxynil Tolerant Cotton

                         P A N U P S
                   Pesticide Action Network 
                        North America
                       Updates Service

April 1, 1997

Urge EPA to Deny Tolerance Enabling Use of Bromoxynil on 
Transgenic Cotton

The U.S. Environmental Protection Agency (EPA) is in the 
process of deciding whether to renew a tolerance on cotton 
genetically engineered to tolerate the herbicide bromoxynil 
(trade name Buctril). According to the Environmental Defense 
Fund (EDF), new evidence indicates that this chemical is even 
more hazardous than previously recognized. EDF feels that EPA 
should deny renewal of the tolerance for bromoxynil, thus 
sending a strong signal to industry that the Agency will not 
permit use of genetically engineered herbicide-tolerant crops 
to promote expanded use of hazardous herbicides.

Bromoxynil is normally toxic to cotton, a broadleaf plant, 
and is used on grass-like crops, such as corn, sorghum and 
small grains, to kill broadleaf weeds. However, several years 
ago Rhone-Poulenc, the manufacturer of the herbicide, and 
Calgene, a small California biotechnology company, teamed up 
to engineer cotton so that it would tolerate the toxic 
effects of bromoxynil, thus making it possible to apply the 
weed killer to cotton.

In 1995, EPA approved a conditional registration for 
bromoxynil on transgenic bromoxynil-tolerant cotton under 
which the crop was grown commercially in 1995 and 1996. EPA 
also established a temporary tolerance -- a maximum 
permissible limit for the residues of bromoxynil in or on 
cottonseed, which will expire April 1, 1997. Sometime within 
the next week or so, EPA will decide whether to renew the 
tolerance. If it is renewed, the herbicide could continue to 
be applied to transgenic cotton. If not, bromoxynil could not 
be sold for use on cotton and there would be no reason to 
market bromoxynil-tolerant cotton.

Bromoxynil is a toxic chemical with numerous adverse health 
and environmental effects. A committee of EPA staff has 
concluded that bromoxynil should retain its classification as 
Group C, a possible human carcinogen, based on a new study 
submitted by Rhone- Poulenc showing that bromoxynil causes 
malignant liver tumors in both female and male mice. Evidence 
of bromoxynil's mutagenicity and information from a 
structural analog, 2,4,6-tricholorophenol, a known 
carcinogen, provided additional support for the 
carcinogenicity classification.

In addition, bromoxynil causes birth defects in laboratory 
mammals (rats, mice, and rabbits) and has been classified by 
the Agency as a developmental toxicant. In 1989, EPA canceled 
all registrations of pesticides containing one form of 
bromoxynil -- bromoxynil butyrate -- because of the risk of 
developmental toxicity in pesticide handlers. At that time, 
EPA also imposed new measures, since relaxed somewhat, 
limiting occupational exposure to avoid cancellation of other 
bromoxynil formulations (e.g., octanoate).

Bromoxynil also poses environmental threats -- it is highly 
toxic to broadleaf plants and fish. Because it is a low-dose 
herbicide, even a small amount accidentally misapplied or 
blown from the site of application threatens wildlife 
habitats near fields. A study in ponds in the prairie-pothole 
region of Canada demonstrated bromoxynil's toxicity to fish 
and showed that the herbicide in water is readily converted 
to a toxic derivative which persists for weeks after spray 

Given the new carcinogenicity data and the record on birth 
defects, the Agency should not renew the tolerance for 
bromoxynil on transgenic cotton. Also, this decision is being 
made by the Agency as it is implementing the new Food Quality 
Protection Act (FQPA). This far reaching statute requires a 
new tougher standard of safety, aggregate risk assessments, 
and special protections for infants and children. The FQPA 
demands serious consideration of chemicals that pose as many 
health and environmental hazards as bromoxynil, and may 
facilitate EPA for the first time to say "no" to expanded use 
of an herbicide on an herbicide-tolerant crop.

EDF urges you to write to EPA as soon as possible (a decision 
is likely within a week) and ask the Agency to deny the 
renewal of the tolerance for bromoxynil on cotton because 1) 
the herbicide presents a significant cancer risk and is a 
developmental toxicant, and 2) expanding use of bromoxynil 
with a bromoxynil-tolerant crop violates the Food Quality 
Protection Act's safety standard of "reasonable certainty of 
no harm from aggregate exposure."

Address your letters to: Dr. Lynn Goldman, Assistant 
Administrator, OPPTS, EPA, 401 M Street, SW, #642, 
Washington, DC  20460; fax (202) 260-1847.

Sources: "Carcinogenicity peer review of bromoxynil phenol 
(4th)," Memo from E.R. Budd and E. Rinde to R. Taylor, K. 
Davies, and T. Luminello, Jr., Office of Prevention, 
Pesticides, and Toxic Substances, EPA, Washington DC, March 
12, 1997. "Fifth developmental toxicity peer review of 
bromoxynil." Memo from G.J. Burin and A. Clevenger to J. 
McQueen. Office of Pesticide Programs, EPA, Washington DC, 
April 21, 1992. "Order canceling registration for pesticide 
products containing bromoxynil butyrate," Federal Register 
54:24949-50, June 12, 1989. "EPA imposes risk reduction 
measures for bromoxynil pesticide," Office of Public Affairs, 
EPA, Washington DC, May 9, 1989. "Suspended, cancelled, and 
restricted pesticides," Office of Pesticides and Toxic 
Substances, EPA, 20T-1002, Washington, DC, February 1990. 
Letter from R. Taylor, EPA Registration Division to N. Somma, 
Rhone-Poulenc Registration Manager, Washington DC, May 21, 
1992. "Fish and agricultural chemicals: safeguarding your 
pond," Extension Division, University of Missouri, Columbia, 
1989. "Fate and acute toxicity of bromoxynil esters in an 
experimental prairie wetland," Muir, D.C.G. et al., 
Environmental Toxicology and Chemistry 10: 395-406, 1991.

Contacts: Rebecca Goldburg, Ph.D., Senior Scientist, 
Environmental Defense Fund, 257 Park Avenue South, New York, 
NY 10010; phone (212) 505-2100; fax (212) 505-2375; email 

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