United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508W) ,
EPA-738-F-98-011
September 1998
R.E.D. FACTS
Pesticide
Reregistration
Use Profile
***BROMOXYNIL***
All pesticides sold or distributed in the United States must be registered
by EPA, based on scientific studies showing that they can be used without
posing- unreasonable risks to people or the environment. Because of advances
in scientific knowledge, the law requires that pesticides which were first
registered before November 1,1984, be reregistered to ensure that they meet
today's more stringent standards.
In evaluating pesticides for reregistration, EPA obtains and reviews a
complete set of studies from pesticide producers, describing the human health
and environmental effects of each pesticide. The Agency develops any
mitigation measures or regulatory controls needed to effectively reduce each
pesticide's risks. EPA then reregisters pesticides that can be used without
posing unreasonable risks to human health or the environment.
When a pesticide is eligible for reregistration, EPA explains the basis for
its decision in a Reregistration Eligibility Decision (RED) document. This
fact sheet summarizes the information in the RED document for reregistration
case 2070, bromoxynil. ,
Bromoxynil is a selective contact foliage applied herbicide used to
control a variety of grasses and broadleaf weeds. Agricultural crop use sites
include: food crops (e.g., garlic/onions); food and feed crops (e.g., mint, flax,
spearmint, peppermint, barley, oats, rye, triticale, wheat, sorghum, cotton, and
field, sweet, and pop corn); and feed crops (e.g., fodder/hay, grass, millet
(proso), alfalfa, sudangrass). Non-food uses include: fallow/idleland; outdoor
industrial areas; nonagricultural uncultivated areas/soils; ornaniental
herbaceous plants; commercial/industrial lawns; ornamental (non-residential)
lawns and turf; golf course turf; and sod farms. Bromoxynil is formulated as
an emulsifiable concentrate, soluble concentrate, and a gel formulation (in
water soluble packages). The application rates for crop uses range from 6.25
Ib ai/acre to 0.5 Ib ai/acre. There are no residential uses for this herbicide.
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Regulatory
History
Bromoxynil was first registered in the United States in 1965 for use as
a herbicide to control grassy and broadleaf weeds on wheat and barley. In
1972, tolerances were established for field and fodder crops, meat, and meat
byproducts of cattle, goats, hogs, horses and sheep. Throughout the 1980's,
a series of additional tolerances were established for a variety of vegetable,
field and fodder crops.
When the reregistration case for bromoxynil was opened, case 2070,
bromoxynil phenol, butyrate, heptanoate and octanoate were all incorpo-
rated. Subsequently, bromoxynil butyrate registrations were voluntarily
canceled by the registrant hi 1989 due to concerns related to developmental
toxicity. Therefore, bromoxynil butyrate is not included as a part of this
reregistration decision. At that tune, the Agency also had concerns for
potential risks to workers mixing, loading, and/or applying bromoxynil
products. To reduce these exposures, the registrant undertook several
actions. These included label amendments, development of a new jug (to
prevent splashing) and the supply of gloves included in product packaging.
Further changes to the reregistration case came when the registrant
decided not to support the heptanoate. However, hi 1993, the registrant
applied for a new heptanoate registration, which was g;ranted. Since only
those pesticides registered prior to 1984 are subject to reregistration, the
bromoxynil heptanoate is not considered a reregistration chemical and is not
specifically incorporated for this reregistration action. However, there are
two products which include both the heptanoate and the octanoate forms of
bromoxynil. All esters of the chemical are considered to be lexicologically
similar to the phenol and, hi fact, rapid conversion of ithe esters to the
phenol occurs hi the environment. The exposure estimates, therefore,
incorporate exposure to the octanoate and the heptanoate included hi the two
combined labels. The percent crop treated used hi the dietary exposure
considers all esters of bromoxynil.
In May 1995 (60 FR 27414), the Agency established a tune-limited
tolerance under section 408 of the Federal Food, Drug and Cosmetic Act
(FFDCA), for residues of bromoxynil on cottonseed. This tolerance expired
on April 1, 1997. On May 13, 1998, the Agency issued a tolerance for
cotton use. In that Notice, the maximum allowable cotton acreage that can
be treated with bromoxynil was increased from 400,000 acres (3 % of cotton
acreage) to 1.3 million acres (10% of cotton acreage). This document
incorporates the information published hi the May 13, 1998 Federal Register
Notice.
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Human Health Toxicity
Assessment Bromoxynil phenol is in Toxicity Category E for acute effects via the
oral and inhalation routes and Toxicity Category HI for acute dermal effects.
Bromoxynil octanoate is Toxicity Categpry E for acute oral and derrnal
effects and Toxicity Category El for acute inhalation effects. Bromoxynil
phenol has been classified as a Group C, possible human carcinogen. Rapid
1 conversion of the ester forms of the chemical (heptanoate and octanoate)
permit the risk assessment to be based on exposure to the phenol.
Bromoxynil is considered to be developmentally toxic. This concern is
considered below under, FQPA Assessment.
Dietary Exposure and Risk
The Reference Dose (RfD) for bromoxynil phenol is 0.015
mg/kg/day based on the threshold NOEL/LOEL of 1.5'mg/kg/day hi a 12
month-chronic oral toxicity study hi dogs. Chronic non-cancer dietary risk
is estimated to occupy less than one percent (1%) of thechronic 'RfD. The
aggregate dietary risk of cancer to the general population from residues hi
food and water, associated with long-term exposure to bromoxynil, was
estimated to be 1.7x10^. The estimated aggregate acute dietary risk,
calculated as Margins of Exposure (MOE), all exceed 10,000. Therefore,
significant concerns related to acute and chronic dietary exposure are not
predicted.
Occupational and Residential Exposure and Risk
The handler dermal risk assessment based on the Pesticide Handler's
Exposure Database (PHED) data for mixers/loaders/applicators indicates mat
short- and intermediate-term dermal risks and cancer risks are acceptable (i.e.,
greater than 100) if such handlers wear chemical-resistant gloves in addition
to baseline attire (long-sleeve shirt, long pants, shoes, and socks) while
performing mixing and loadingtasks and baseline attire while performing
applicator tasks. For all other tasks, the risks are acceptable for handlers
wearing baseline attke. The cancer risk for the non-commercial handlers
(grower) is 2 x 10'6 or lower for all scenarios with baseline attire, except that
mixers and loaders must also wear chemical-resistant gloves. The cancer risk
for commercial handlers is 1.9 x 10"5 dr lower for all scenarios with baseline
attire, except that mixers and loaders must also wear chemical-resistant
gloves. The highest cancer risk estimate from these particular scenarios was
1.9 X 10'5 (commercial mixer/loaders for aerial applications and sprinkler
irrigation). However, these mixer/loader risk estimates do not account for the
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potential exposure reduction from the use of "wide-mouth" containers (de-
signed to reduce spillage) for mixer/loaders. At the present time the PHED
database does not allow the Agency to quantify this risk: mitigation measure,
however the use of the "wide-mouth" containers would likely reduce the
reported risk further. In addition, to provide an additional margin of safety,
EPA has required mixers and loaders to wear a chemical-resistant apron.
Although EPA has no data to specifically assess the exposure reduction to
mixers/loaders afforded by a chemical-resistant apron, the Agency is per-
suaded that the exposure reduction would be significant. Available data
indicate that the preponderance of non-hand exposure to mixers/loaders is to
the front torso.
FQPA Assessment
In accordance with the Food Quality Protection Act of 1996, the
Agency uses a weight-of-evidence approach to determine whether to retain,
reduce, or remove the 10X safety factor required for possible enhanced
sensitivity to infants and children. The database for the developmental
toxicity of bromoxynil is robust. Developmental effects (supernumerary ribs
being the most sensitive indicator) have been observed hi developmental and
reproductive studies. The Agency concluded that reliable data support using
a 100-fold uncertainty factor to assess bromoxynil dietary risk for all
populations with the exception of females 13 + . Upon review of the
' extensive developmental lexicological database for this chemical, a concern
for in utero developmental effects was noted. In order to provide a suffi-
cient margin of safety for the developing fetus, the 10-fold safety factor for
enhanced sensitivity to infants and children was retained for females 13 +
thus requiring a 1000-fold uncertainty factor for this population subgroup.
All MOEs calculated exceeded 10,000 and, therefore, developmental effects
to any sub-population are not predicted.
Environmental
Assessment Environmental Fate
Bromoxynil octanoate was found to be chemically and-physically
similar to bromoxynil heptanoate. Both esters rapidly degrade to
bromoxynil per se. Bromoxynil octanoate is mobile and non-persistent. It
dissipates in the environment by abiotic hydrolysis, photolytic degradation,
and microbially-mediated metabolism in both the aerobic and anaerobic
environments. Bromoxynil octanoate readily hydroly2:es to bromoxynil
phenol and then further degrades to COj. The hydrolysis half-life for
degradation of bromoxynil octanoate ranges from 1 day up to 34 days.
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Degradation is increased by exposure to sunlight and aerobic and anaerobic
degradative processes. ,
Based on the available data, the Agency concludes that the potential for
ground water contamination from bromoxynil octanoate is low; it does not
exhibit the mobility or persistence characteristics of pesticides that are
normally found hi ground water. Environmental fate studies indicate that
bromoxynil (phenol and octanoate) should not persist hi surface waters. The
aerobic aquatic metabolism study shows rapid degradation with a half-life of
<12 hours.
Ecological Effects
The overall risk to birds (and to insects) exposed to bromoxynil
octanoate is expected to be low. For mammals the calculated risk ranges
.from medium to high, based on known developmental effects. However,
exposure levels high enough to cause chronic developmental effects are
believed to be unlikely to occur. The acute risk to both freshwater and '
estuarine fish is expected to be low; chronic risk is expected to be minimal.
The overall acute risk to freshwater invertebrates is expected to be medium.
The overall risk to both endangered and non-endangered terrestrial and semi-
aquatic plants is expected to be medium. And finally, the risk to aquatic
vascular plants is uncertain at this time due to a lack of data, while risk to
nonvascular plants is expected to be minimal. Additional testing for aquatic
vascular plants is required.
Risk Mitigation
As a result of this RED, the Agency does not have concerns relative to
dietary exposure (including food and water), for the general population to
bromoxynil. There are no residential uses of the chemical. However, based
on calculations made for occupational uses, the Agency is requiring that
chemical resistant gloves, hi addition to baseline attire, be worn by handlers
involved in mixing, loading and/or applying bromoxynil. In order to
provide an additional margin of safety, mixers and loaders will also be
required wear a chemical resistant apron. Finally, given the concern that the
Agency identified for increased fetal susceptibility, the Agency is requiring
that scouting activities be specifically included on labels for the restricted
entry timeframes.
Additional Data
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Required The Agency is requiring the submission of two confirmatory studies
(aquatic plant toxicity and chronic estuarine/marine fish and invertebrates) to
complete the database for bromoxynil. Also, in the case of one of the
technicals, EPA is requiring that acute toxicity information be submitted. In
addition, product-specific data including product chemistry and acute
toxicity studies, product efficacy data, revised Confidential Statements of
Formula (CSFs), and revised labeling for reregistration are being requested
in this document. Additionally, in order to allow moire precise estimates of
exposure to bromoxynil in drinking water, the Agency herein reiterates the
requirement of the submission of an acceptable surface water monitoring
program as specified in the FR Notice, 63FR26473.
Product Labeling (1) Plantback intervals. Pending receipt of limited field rotational crop
Changes Required studies for cotton, labels must restrict rotation of treated cotton fields,
treated with more than 0.5 a.i./A/season, to transgenic cotton (BXN cotton).
(2) The following language must be placed on registered labels: "The
restricted-entry interval (REI) for cotton is 4 days and includes scouts and
crop advisors. The exemption in the Worker Protection Standard for certified
crop advisors does not apply to bromoxynil. Scouts and crop advisors are
prohibited from entering the treated area during the entire 4-day REI for
bromoxynil. Applicators and other users must inform crop advisors and
scouts of this requirement."
(3) EPA is establishing a 4-day REI for uses ofbromoxynilon cotton and a
26-day REI for uses of bromoxynil on turf grown for transplanting (e.g., on
sod farms). EPA believes that measures to reduce short- and intermediate-
term risks also will reduce cancer risks. These REIs reconfirm the REIs of 4
days for cotton and 26 days for sod established in the Federal Register Notice
published May 13,1998, in conjunction with the cotton use registration
action.
(4) EPA has required mixers and loaders to wear a chemical-resistant apron.
Although EPA has no data to specifically assess the exposure reduction to
mixers/loaders afforded by a chemical-resistant apron,, the Agency is per-
suaded that the exposure reduction would be significant.
Regulatory Based on the reviews of the generic data for the active ingredient
Conclusion bromoxynil, the Agency has sufficient information on the health effects of
bromoxynil and on its potential for causing adverse effects hi fish and
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wildlife and the environment. The Agency has determined that bromoxynil
products, labeled and used as specified in the Reregistration Eligibility
Decision, will not pose unreasonable risks to humans or the environment.
Therefore, the Agency concludes that products containing bromoxynil for all
uses are eligible for reregistration, provided the registrant follows all
requirements as set forth in the RED.
For More EPA is requesting public comments on the Reregistration Eligibility
Information Decision (RED) document for BROMOXYNIL during a 60-day tune period,
as announced in a Notice of Availability published hi the Federal Register.
To obtain a copy of the RED document or to submit written comments,
please contact the Pesticide Docket, Information and Record Integrity ,
Branch, Information Resources Services Division (7502C), Office of Pesti-
cide Programs (OPP), US EPA, Washington, DC 20460, telephone 703-305-
5805.
Electronic copies of the RED and this fact sheet are available on the
internet. See http://www.epa.gov/REDs. , .
Printed copies of the RED and fact sheet can be obtained from EPA's
National Center for: Environmental Publications and Information
, (EPA/NCEPI), PO Box 42419, Cincinnati, OH 45242-0419, telephone 513-
489-8190, fax 513-489-8695,
Following the comment period, the BROMOXYNIL RED document
also will be available from the National Technical Information Service
(NTIS), 5285 Port Royal Road, Springfield, VA 22161? telephone 703-605-
. 6000 or 800-553-6847.
. For more information about EPA's pesticide reregistration program,
the BROMOXYNIL RED, or reregistration of individual products contain-
ing bromoxynil, please contact the Special Review and Reregistration
Division (75Q8W), OPP, US EPA, Washington, DC 20460, telephone 703-
308-8000. .
For information about the health effects of pesticides, or for assistance
in recognizing and managing pesticide poisoning symptoms, please contact
the National Pesticides Telecommunications Network (NPTN). Call
toll-free 1-800-858-7378, between 9:30 am and 7:30 pm Eastern Standard
Time, Monday through Friday.
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