United States
Environmental Protection
Agency
Prevention, Pesticides
And Toxic Substances
(7508W)
EPA-738-F-97-008
August 1997
R.E.D. FACTS
Pesticide
Reregistration
Use Profile
Regulatory
History
Diflubenzuron
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 reregi strati on, 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 reregi strati on, 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
reregi strati on case 0144, diflubenzuron.
Diflubenzuron is an acaricide/insecticide (insect growth regulator)
used to control many leaf eating larvae of insects feeding on agricultural,
forest and ornamental plants (e.g. gypsy moths, mosquito larvae, rust
mites). Diflubenzuron is used primarily on cattle, citrus, cotton,
mushrooms, ornamentals, standing water, forestry trees and in programs to
control mosquito larvae and gypsy moth populations. Formulations include
a soluble concentrate, flowable concentrate, wettable powder and a
pelleted/tableted. Diflubenzuron is applied by airblast, aircraft and
hydraulic sprayers.
Diflubenzuron was first registered as a pesticide in the U.S. in 1976.
EPA issued a Registration Standard for diflubenzuron in September 1985
(PB86-176500). A November 1991 Data Call-In (DCI) required additional
residue chemistry and ecological effects data. Currently, 29 diflubenzuron
products are registered.
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Human Health
Assessment Toxicity
In studies using laboratory animals, diflubenzuron generally has been
shown to be slightly toxic on an acute basis. It is absorbed by the dermal
route and has been placed in Toxicity Category III (the second lowest of
four categories). It has also been placed in Toxicity Category IV (the
lowest of four categories) for ingestion by the oral and inhalation routes.
Dietary Exposure
People may be exposed to residues of diflubenzuron through the diet.
Tolerances or maximum residue limits have been established for
diflubenzuron (please see 40 CFR 180.377). All tolerances for
diflubenzuron residues are currently expressed in terms of diflubenzuron
per se [40 CFR §180.377(a) and (b) and §186.2000]. The Agency has
concluded that the tolerance expression should be changed to address
combined residues of diflubenzuron and metabolites convertible to
parachloroaniline (PCA), expressed as diflubenzuron. EPA has reassessed
the diflubenzuron tolerances and found that data for cotton gin by-products,
cottonseed, grass forage, liver, milk, mushrooms, pasture grass hay,
soybeans and walnuts are required for the continued registration of
diflubenzuron.
EPA has assessed the dietary risk posed by diflubenzuron. For the
overall U.S. population and 22 subgroups, exposure from all current
diflubenzuron tolerances represents less than 1% of the Reference Dose
(RfD), or amount believed not to cause adverse effects if consumed daily
over a 70-year lifetime. The exposure level of the most highly exposed
subgroup, children (aged 1-6), represents 1% of the RfD. Therefore, it
appears that chronic dietary risk is minimal.
Occupational and Residential Exposure
Based on current use patterns, handlers (mixers, loaders, and
applicators) may be exposed to diflubenzuron during and after normal use
of applications in agricultural and other settings. The Agency is
establishing a short-term (1 to 7 days) toxicological endpoint of
sulfhemoglobinemia and intermediate-term (1 week to several months)
toxicological endpoint of methemoglobinemia.
Human Risk Assessment
Diflubenzuron generally is of low acute toxicity, but affects the
hemoglobin of animal in studies. Although the Agency has determined that
there is no evidence of carcinogenicity for diflubenzuron/>er se (Group E);
p-chloroaniline (PCA), a metabolite of diflubenzuron, is a probable human
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carcinogen (Group B2). The Agency has also determined that p-
chlorophenylurea (CPU), a metabolite of diflubenzuron that is closely
related to PCA but has no adequate carcinogen!city data, is considered as
having the same carcinogen!city potential (Ql*) as PCA. The total cancer
risk estimate for PCA and related metabolites for the overall U.S.
population is 1 X 1CT6. The Rfd is 0.02 mg/kg/day, based on the NOEL of
2.0 mg/kg/day in the 52-week chronic oral study in dogs with a safety
factor of 100 to account for interspecies extrapolation and intraspecies
variability.
Of greater concern is the risk posed to diflubenzuron handlers,
particularly mixers/loaders/applicators. The risk for short-term
occupational exposure is acceptable for handlers wearing long-sleeved
shirts, long pants and chemical-resistant gloves. The risk for intermediate-
term occupational exposure is also acceptable, provided dust/mist
respirators (TC-21C) are required for mixers, loaders and applicators when
working with diflubenzuron for certain higher risk application methods.
Post-application reentry workers will be required to observe a 12-hour
Restricted Entry Interval, as set by the WPS.
Under the Food Quality Protection Act of 1996, the Agency has
determined that there is a reasonable certainty that no harm will result to
infants and children from aggregate exposure to diflubenzuron. The total
dietary cancer risk for the published tolerances for the overall U.S.
population is approximately 1 x 10"6. Since there are no detections of
diflubenzuron in ground water, dietary risk from drinking water are
expected to be negligible. Based on very low residues detected in forestry
dissipation studies, a low dermal absorption rate, and extremely low dermal
and inhalation toxicity, occupational uses of diflubenzuron in residential
locations, parks, or forests treated with diflubenzuron are expected to result
in insignificant risk.
Environmental
Assessment
Environmental Fate
Diflubenzuron appears to be relatively non-persistent and immobile
under normal use conditions. The major route of dissipation appears to be
biotic processes (half-life of approximately 2 days for aerobic soil
metabolism). Diflubenzuron is stable to hydrolysis and photolysis.
Available data indicate that it is unlikely that diflubenzuron will
contaminate ground water or surface water. Additional data are needed to
confirm this conclusion.
Ecological Effects
Diflubenzuron is practically non-toxic to avian species, small
mammals, freshwater fish and marine/estuarine fish on an acute oral dietary
basis, while it is slightly toxic to avian species on a subacute dietary basis.
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Diflubenzuron is non-toxic to bees. The results indicate that diflubenzuron
is very highly toxic to freshwater aquatic invertebrates, including
marine/estuarine Crustacea, while it is highly toxic to marine/estuarine
mollusks. The results indicate that diflubenzuron affects reproduction,
growth and survival in freshwater invertebrates as well as reproduction in
marine/estuarine invertebrates.
Ecological Effects Risk Assessment
The risk assessment conducted using available data indicates that
levels of concern are not exceeded for avian species, mammals, insects or
freshwater fish. Although the use of diflubenzuron is expected to cause
some adverse chronic effects to estuarine/marine fish at the highest
application rate (forestry), these effects are not as widespread as those
associated with freshwater and estuarine/marine invertebrates. The use of
diflubenzuron is expected to cause adverse acute and chronic effects to both
freshwater and estuarine/marine invertebrates, including endangered
species.
The risk to aquatic invertebrates is also expected to be substantial
when diflubenzuron is applied to control mosquito larvae. Since this use
involves direct application to water and/or near water, no mitigation is
currently proposed.
Risk Mitigation To lessen the environmental risks posed by diflubenzuron, EPA is requiring
the following risk mitigation measures:
° row crops and orchard uses must include a 150 foot buffer zone for
aerial applications and a 25 foot vegetative buffer strip to decrease
runoff in all cases (buffer strip will also serve as a buffer zone for
spray drift from ground applications);
° aerial applications must include the most current spray drift language;
and
o all products must bear a hazards statement warning about possible
adverse effects to aquatic organisms.
Additional Data
Required
EPA is requiring the following additional generic studies for
diflubenzuron to confirm its regulatory assessments and conclusions:
ecological effects, toxicity, residue chemistry, and occupational and
residential exposure.
The Agency also is requiring product-specific data including product
chemistry and acute toxicity studies, revised Confidential Statements of
Formula (CSFs), and revised labeling for reregi strati on.
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Product LabGling All diflubenzuron end-use products must comply with EPA's current
Changes Required pesticide product labeling requirements. For a comprehensive list of
labeling requirements, please see the diflubenzuron RED document.
Regulatory
Conclusion
For More
Information
The use of currently registered products containing diflubenzuron in
accordance with approved labeling will not pose unreasonable risks or
adverse effects to humans or the environment. Therefore, all uses of these
products are eligible for reregi strati on.
Diflubenzuron products will be reregistered once the required product
specific data, revised Confidential Statements of Formula, and revised
labeling are received and accepted by EPA.
EPA is requesting public comments on the Reregi strati on Eligibility
Decision (RED) document for diflubenzuron during a 60-day time period,
as announced in a Notice of Availability published in the Federal Register.
To obtain a copy of the RED document or to submit written comments,
please contact the Pesticide Docket, Public Response and Program
Resources Branch, Field Operations Division (7506C), Office of Pesticide
Programs (OPP), US EPA, Washington, DC 20460, telephone
703-305-5805.
Electronic copies of the RED and this fact sheet can be downloaded
from the Pesticide Special Review and Reregi strati on Information System
at 703-308-7224. They also are available on the Internet on EPA's gopher
server, GOPHER.EPA.GOV, or using ftp on FTP.EPA.GOV, or using
WWW (World Wide Web) on WWW.EPA.GOV.
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 diflubenzuron RED document
also will be available from the National Technical Information Service
(NTIS), 5285 Port Royal Road, Springfield, VA 22161, telephone 703-487-
4650.
For more information about EPA's pesticide reregi strati on program,
the diflubenzuron RED, or reregi strati on of individual products containing
diflubenzuron, please contact the Special Review and Reregi strati on
Division (7508W), 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-
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free 1-800-858-7378, between 9:30 am and 7:30 pm Eastern Standard
Time, Monday through Friday.
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