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zinc borate (Firebreak ZB) EPA Pesticide Fact Sheet 10/91

AMENDED VERSION:  10/1/91                           EPA Pesticide Fact Sheet

Name of Chemical:  Zinc Borate (2ZnO.3B2O3.3.5H20)
Reason for Issuance:  New Chemical Registration  (AMENDED VERSION)
Date Issued:  7/15/91
Fact Sheet Number:  225.1

                             1. DESCRIPTION

- Generic Names:  Zinc Borate (2ZnO.3B2O3.3.5H20)
- Trade Name:  Firebrake ZB
- EPA Shaughnessy Code:  128859
- Year of Initial Registration:  1991
- Pesticide Type:  Fungicide
- U.S. and Foreign Producers:  U.S. Borax & Chemical Corp.
                               3075-Wilshire Blvd.
                               Los Angeles, CA 90010

                     2. USE PATTERNS AND FORMULATIONS

Application sites:  Interior uses, such as PVC carpet backing, shower
   curtains, wall coverings, etc., and exterior uses, such as PVC tenting and
   awnings, polyolefin wire and cable coverings, etc.

Type of formulation:  100 manufacturing grade formulation.

Types and methods of application:  Granular product can be fed into an
   extruder, calender machine, or injection molding machine for plastics or
   incorporated during pigment dispersion cycle for coatings.

Application rates:  The effective additive level varies depending on fungal
   susceptibility of the product and ultimate conditions for the use of the
   product.  For protection of plastics, a rate range of 3-30 parts product
   per hundred parts resin is used.  For coatings, rates range from 1.25 to
   3.0 lb/gal.

                            3. SCIENCE FINDINGS

Summary Science Statement

     The toxicological data submitted for this active ingredient included the 
full complement of acute studies.  Results of these studies show that zinc 
borate is in the toxicity category III (CAUTION) based on acute dermal and 
primary eye irritation studies with rabbits.

     Zinc borate did not induce either genotoxic effects or chromosomal 
aberrations in mutagenicity studies.

     Environmental fate data were waived because there is no direct or 
indirect discharge resulting from production of this chemical.

Chemical Characteristics

   Color:  White
   Physical State:  Granular
   Melting Point:  Greater than 550 degrees C
   Particle Size:  8-20 um (mean)
   Density:  40 to 50 lbs/cu. ft. (bulk)
   pH:  7.6 (In deionized H20)

Toxicological Characteristics

Acute effects:

   1. Acute Oral (LD50) in Rats - The LD50 in rats (males) was found to
      be greater than 10 g/kg.  Zinc borate did not produce severe signs of
      toxicity in treated rats.
   2. Acute Dermal Toxicity (LD50) in Rabbits - The LD50 was estimated to be
      greater than 10 g/kg in both male and female albino rabbits.
   3. Primary Eye Irritation in Albino Rabbits - Zinc borate was shown to be
      an eye irritant producing mild conjunctivitis in albino rabbits.
   4. Primary Dermal Irritation/Corrosivity in Albino Rabbits - The Primary
      Irritation Index of zinc borate in rabbits was found to be 0.
      Therefore, it is not considered to be an irritant or corrosive.

     Data from acute oral and acute dermal toxicity tests place the chemical 
in Toxicity Categories IV and III, respectively.  These results were 
duplicated in the primary eye and primary dermal irritation studies.  In a 
dermal sensitization study involving guinea pigs, zinc borate showed no 
evidence of adverse dermal effects.  Precautionary labeling language as 
follows is required for this product:

     "Avoid skin and eye contact.  Avoid inhalation.  Wash after handling."

Mutagenic effects:

     In the Salmonella/microsomal Assay (Ames Bioassay) for bacterial 
mutagenic activity, zinc borate did not elicit any mutagenic response in 
Salmonella tester strains when tested either with or without a metabolic 
activation system.

Environmental Fate

     The Agency reviewed available data on fate and transport of zinc and 
boron in the environment and concluded that no additional data were warranted 
for the proposed pesticidal use.  The following were among factors 
contributing to this position:

1. According to the registrant, there is no direct or indirect discharge of
   zinc borate into the environment from manufacturing this chemical.
2. The water solubility for zinc borate at 23 degrees C (average temperature
   under natural conditions) is very low (0.1 at pH 5 and 7, and 0.03 at
   pH 9).  The zinc borate will be incorporated into some synthetic matrix to
   act as an antifungal agent.  To be effective over time, the chemical must
   not have a propensity to solubilize and leach out of the matrix.  Any
   movement of the chemical out of the matrix will either be by abrasion
   (wear) or leaching as solubilized ions.  Therefore it is highly unlikely
   that large amounts of the chemical will get into the the environment
   through its pesticidal use.  Leaching studies are being required to confirm
   that ion levels in the leachate would be of no toxicological concern.
3. When reformulated into other products where it serves as a fire retardant
   and fungicide , i.e. in PVC products, ceramics, other chemicals, cosmetics,
   etc., zinc borate becomes chemically incorporated into the finished
   products and loses its identity.
4. The chemical reactions of zinc borate can form a composite of oxides of
   zinc and boron.  Both these chemicals occur naturally in soil and are
   essential micronutrients for plants.  Moreover, both zinc and boron are
   used extensively in agriculture as soil amendments to improve the vigor of
   plants.  As soil amendments these chemicals are applied at levels
   substantially higher than would be anticipated from their use in plastics
   as a fungicide.  The Agency is unaware of any lasting adverse effects on
   the environment from the soil amendment uses of zinc and boron.  The Agency
   concluded that additional data requirements would not add any substantive
   information to the available scientific data base.

     Based on these facts, the registrant was granted a waiver from all 
environmental fate data requirements including hydrolysis data.

Ecological Characteristics

     In avian dietary studies, the LC50 value of zinc borate in the mallard 
ducklings (Anas platyrhynchos) is estimated to be greater than 5,620 ppm.  No 
mortality occurred in either the control or treated groups.  A slight 
reduction in body weight was observed at the 6,520 ppm concentration during 
the exposure period.  There was no effect on feed consumption at any 
concentration tested.

     The acute toxicity of zinc borate to bluegill sunfish (Lepomis 
macrochirus) was tested under static conditions at mean concentrations of 94, 
137, 182, 248, and 335 ppm.  The 96hr LC50 for bluegill sunfish was shown to 
be greater than 335 ppm.  These results indicate that zinc borate is 
practically nontoxic to the fish species tested.


     Potential advantages to the general public appear to exist by having 
Firebrake ZB available as a fungicide in view of the following:

- Zinc borate has a relatively low toxicity with no demonstrated adverse
  public health effects following extensive long-term use as a fire retardant
  in applications including carpet backing, fabric coating, wall covering,
  urethane foam, roofing PVC tenting and awnings, etc.

- Zinc borate is a broad-spectrum fungicide with no demonstrated adverse
  environmental effects. This chemical would provide protection of a variety
  of plastic products and may decrease the environmental burden of more toxic
  pesticides by acting as an alternative for protection of plastics.

Tolerance Assessment

     There are no proposed direct food or feed uses of zinc borate, therefore, 
EPA has not established tolerances or exemptions from tolerances in raw 
agricultural commodities or processed food and feed products under the Federal 
Food, Drug and Cosmetic Act (FFDCA).

                       4. SUMMARY OF MAJOR DATA GAPS

     A leachability study is being required as a condition of registration.  
This study must be submitted within nine (9) months of registration approval 
of Firebrake ZB

Expiration Date

    Conditional registration of Firebrake ZB will expire on July 31, 1992.

                          5. CONTACT PERSON AT EPA

Susan T. Lewis
Product Manager (21)
Fungicide-Herbicide Branch
Registration Division (H7505C)
Environmental Protection Agency
401 M St., S.W.
Washington, D.C.  20460


DISCLAIMER:  The information presented in this Pesticide Fact Sheet is for 
informational purposes only and may not be used to fulfill data requirements 
for pesticide registration and reregistration.