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
- 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.
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. 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.
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)
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."
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
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.
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
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.
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
Conditional registration of Firebrake ZB will expire on July 31, 1992.
5. CONTACT PERSON AT EPA
Susan T. Lewis
Product Manager (21)
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.