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PANUPS: Bromoxynil Tolerant Cotton
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P A N U P S
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Pesticide Action Network
North America
Updates Service
http://www.panna.org/panna/
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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
applications.
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
becky@edf.org.
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