December 17, 1997
Urge EPA to Deny Tolerance for Bromoxynil on Genetically
The U.S. Environmental Protection Agency (EPA) is once again
in the process of deciding whether to renew a tolerance for
bromoxynil on cotton genetically engineered to be resistant
to the herbicide. The Union of Concerned Scientists (UCS) is
asking EPA to deny renewal of the tolerance for bromoxynil.
Several months ago, UCS issued a similar action alert asking
individuals and groups to write to the U.S. Environmental
Protection Agency (EPA) to urge the Agency to deny a
tolerance for bromoxynil on cotton. EPA, however, approved a
six-month tolerance for bromoxynil on cotton at that time.
Now that tolerance is again up for renewal.
In 1995, EPA approved a conditional registration for use of
bromoxynil on transgenic bromoxynil-tolerant cotton. The crop
was grown commercially in 1995 and 1996 under this
registration. EPA also established a temporary tolerance -- a
maximum permissible limit for the residues of bromoxynil in
or on cottonseed -- which expired April 1, 1997.
In June 1997, EPA approved six-month tolerances for
bromoxynil and its metabolite DBHA (3,5-dibromo-4-
hydrobenzoic acid) in or on cottonseed, undelinted
cottonseed, cotton gin by-products, and cotton hulls. The
Agency also established or revised tolerances for bromoxynil
in eggs, poultry and other meat, meat by-products and fat.
On November 26, 1997, EPA announced that Rhone-Poulenc,
manufacturer of the herbicide, had filed a petition for a
one-year extension of tolerances for bromoxynil and DBHA in
undelinted cottonseed, cotton gin byproducts, and cotton
hulls; and for an increase from 3% to 10% (1.3 million acres)
of the U.S. cotton acreage to which bromoxynil could be
applied. The Agency granted a 30-day period for the public to
comment on the petition. A decision will be made after
December 26, and no further public comment will be allowed.
UCS is asking that you write to EPA and tell them to deny
Rhone-Poulenc's request for a one-year extension of
bromoxynil and DBHA tolerances:
1) Bromoxynil is a toxic chemical with numerous known adverse
health and environmental effects.
EPA has classified bromoxynil as a possible human carcinogen
because it causes liver cancer in mice. The herbicide is
known to be a developmental toxicant as it causes birth
defects in mammals. Bromoxynil is also highly toxic to
broadleaf plants and fish and thereby poses environmental
threats. These data alone are sufficient to allow EPA to deny
2) The carcinogenic risk of bromoxynil exceeds the one-in-a-
million standard of the Food Quality Protection Act.
The Food Quality Protection Act (FQPA) requires EPA to
implement a new safety standard -- a "reasonable certainty of
no harm" for aggregate exposure using dietary residues and
all other reliable exposure information. The legislative
history of the FQPA establishes the reasonable-certainty-of-
no-harm standard for nonthreshold (cancer) effects at a one-
in-a-million risk level, meaning one additional cancer for
each one million people exposed. EPA's estimate of the
carcinogenic risk of bromoxynil in food sources and drinking
water -- 2.1 in a million -- exceeds the one-in-a-million
3) The Agency lacks sufficient safety data to set tolerances
for DBHA, the metabolite produced by genetically engineered
Bromoxynil-tolerant cotton is able to withstand bromoxynil
because it contains an enzyme that breaks the herbicide down
into a metabolite -- DBHA. The Agency knows that DBHA
accounts for nearly 80% of the residues found in cotton after
bromoxynil application. It expects DBHA residues will be
found in cottonseed oil and meal and in beef, pork, poultry,
and eggs from animals that consume the meal. Though the
Agency and Rhone-Poulenc have known about DBHA for years, the
company has submitted only preliminary data on its toxicity.
EPA has not required DBHA safety data as a condition of
Last spring, the Agency set tolerances for the first time for
the metabolite. Absent data, the Agency relied on the
assumption that DBHA is "toxicologically equal" to the parent
bromoxynil, that is, a carcinogen with the same potency as
bromoxynil. But DBHA may be more potent than bromoxynil or
may act as an endocrine disrupter as well as a carcinogen.
The Agency established tolerances without answering these
questions. It appears from the current petition that Rhone-
Poulenc still has not supplied adequate safety data on DBHA.
The Union of Concerned Scientists feels that given the lack
of data on DBHA, the failure to comply with the FQPA, and
bromoxynil's record on birth defects, the Agency should not
renew tolerances for bromoxynil or DBHA on transgenic cotton.
Send comments to arrive on or before December 26, 1997, to:
Docket Control Number PF-779
Public Information and Records Integrity Branch
Information Resources and Services Division (7502C)
EPA/Office of Pesticide Programs
401 M St., SW, Washington, DC 20460; or
fax: (703) 305-4646; or
(submit as ASCII file and do not use special characters or
Food Quality Protection Act, section 408(b)(2)(A)(ii), 1996.
Environmental Working Group and Natural Resources Defense
Council, "Fact sheet: the impact of the new pesticide law,"
EPA, "PP#3F04233. Extension of conditional registration for
the use of bromoxynil on transgenic cotton," Memo from R.
Griffin et al. to D. Stubbs, Office of Pesticide Programs,
April 8, 1997.
EPA, "PP#3F04233. Assumptions for estimating bromoxynil
exposure from drinking water," Memo from R. Griffin to D.
Stubbs, Office of Pesticide Programs, May 6, 1997.
EPA, November 26, 1997. "Notice of filing of pesticide
petition." Federal Register 62:63170-74.
Contact: Jane Rissler, Ph.D., Union of Concerned Scientists,
1616 P Street NW, Suite 310, Washington DC 20036; phone (202)
332-0900; fax (202) 332-0905; email email@example.com.
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