United States
                 Environmental Protection
                      Prevention, Pesticides
                      And Toxic Substances
August 1997
                  R.E.D.   FACTS
   Use Profile
     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.

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
                         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

                     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
                          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  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.

                      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
                            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;
                      o     all products must bear  a hazards statement warning about possible
                            adverse effects to aquatic organisms.
Additional Data
     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.

 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.
           For More
     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
     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-
     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-
     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.