United Stttat Offlo* of PMfcktai and Toxte SutttwcM
Environmental Protection Offic* of Pertidd* Programs (TS-766C)
Agency Washington. DC 20460
&EPA Pesticide
Fact Sheet
Name of Chemical: AMI-HOLE
Reason for Issuance:
Date Issued: way 14, 1984
Fact Sheet Number: 20
1. Description of chemical;
Generic name: Amitrole
Common name: Amitrole
Trade names: Weedaxole®, Amino Trlazole Weed Killer*, Cytrol«,
Amitrol T», Dooatoie, Voro*&, Ami role*, X-Alie, Ustinex*, AT,
ATA, Aminotrlaxole 90 and Chempar Amitrole
EPA Shaughnessy code: 004401
Chemical abstracts service (CAS) number: 61-82-5
Year of initial registration: 1948
Pesticide type: Herbicide
U.S. and foreign producers: Not produced in U.S., major importers
are Union Carbide, American Cyanamid and Aceto Chemical.
2. Use patterns and formulations;
Application sites: Noncrop sites Including rights-of-way, marshes,
drainage -ditches, ornamentals and around commercial, industrial,
agricultural, domestic and recreational premises.
Types of formulations: Technical (90Z, 95Z); vettable powder (15Z,
25Z); flowable concentrate (0.33 Ib/gal, 0.44 Ib/gal, 1Z);
soluble concentrate/liquid (0.3 Ib/gal, 2 Ib/gal); soluble
concentrate/solid (50Z, 90Z) and pressurized liquid (0.36Z, 1Z)
Types and methods of application: Applied as a spray for broadcast,
spot or directed treatments using aerial or ground equipment.
Application rates: 0.9 to 20 Ibs a.i./A depending upon weed species
and method of application
Usual carriers: water
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3. Science findings :
Su m %ry science statement:
Extensive data gaps exist for Amitrole in product chemistry,
toxicology, ecological effects and environmental fate. A itrole
has demonstrated oncogenic potential and is a candidate for
Special Review. Because of this oncogenic risk, all use patterns
and application techniques (except for homeowner uses) are
classified as restricted.
Chemical characteristics:
Physical state: Crystalline powder
Color: Transparent, colorless
Odor: Odorless
Melting point: 159° C
Solubility: 28g/lOOg water, soluble in some polar solvents
Stability: Stable in heat to 1000 C. Amitrole sublimes under
reduced pressure.
Aqueous solutions are neutral.
Unusual handling characteristics: None
Toxicology characteristics:
Acute toxicology results:
Acute oral LD 50 (rat) > 4.08 gin/kg, Toxicity category I II
Acute dermal LD 50 (rabbit): No mortalities reported, Toxicity
category III
Primary eye irritation (rabbit): Amitrole is slightly irritating,
additional testing is required.
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Chronic toxicology results:
Feeding/Oncogenicity: Am.ttrole has an anti—thyroid effect in
laboratory rats. Dogs fed Amitrole exhibited thyroid and
pituitary changes.
Reproduction: Mitrole does not cause reproductive effects.
Teratology: Additional testing required.
Mutagenicity: Mitrole does not cause mutagenic effects.
Metabolism: Amitrole is rapidly eliminated from the body.
Major routes of exposure: Mixers, loaders and applicators would be
expected to receive the most exposure via skin contact and
inhalation.
Physiological and biochemical behavioral characteristics:
Absorption and translocation: It is readily absorbed and rapidly
translocated in the roots and leaves of higher plants.
Mechanism of pesticidal action: Amitrole interferes with the
metabolism of nucleic acid precursors, disrupts chioroplast
development and regrowth from buds.
Enviro ntal characteristics:
Adsorption and leaching in basic soil types: Amitrole exhibits
intermediate soil mobility.
Microbial breakdown: Microbial metabolism is the expected major
route of degradation.
Resultant average persistance: AnLitrole residues degrade with a
half—life of <1 to 56 days in non—sterile aerobic soils. The
soil dissipation rate is affected by moisture, temperature,
cation exchange capacity and clay content, but is unaffected by
soil pH. Amitrole is persistent in pond water and hydrosoil.
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Ecological characteristics:
Hazards to fish and wildlife:
Avian dietary LC 50 : Mallard duck > 5,000 ppm
Ring—neck pheasant > 5,000 ppm
Freshwater fish LC : Rainbow trout > 180 mg/i
Bluegill sunfish > 180 mg/i
Aquatic invertebrate LC 50 > 10 ppm
Tolerance assessments: Temporary Maximum Residue Limits for Amitrole
of 0.02 ppm have been established by MO/WHO for those crops where
residues are likely to occur. There are no established tolerances
for Amitrole in the U.S., Canada, and Mexico. There are no food or
feed uses in the U.S. and residues are not permitted on any food or
water intended for irrigation, drinking, or other domestic purposes.
Problems known to have occurred from use: The Pesticide Incident
Monitoring System (PD(S) listed eight incidents resulting from the
use of Amitrole alone from 1972 to 1977. One incident involved
illegal residue on apples and t others involved plant injury
resulting from soil residues. The remaining five incidents involved
pesticide applicators receiving medical attention after exposure.
Symptoms included skin rash, vomiting, diarrhea and nosebleed.
There i re no reported fatalities. PD(S incidents are voluntarily
reported, do not include detailed follow—ups and are not validated
in any way.
4. Sinmn ry of regulatory position and rationale :
Use classification: Restricted (for all uses except for homeowner uses)
Use, formulation, geographical restrictions: Noncropland areas only
Unique label warning statements:
Manufacturing—Use Products:
Products intended for formulation into end—use products must bear
the following statement:
“For formulation only into end—use herbicide products
intended for noncropland, outdoor use.”
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“The use of this product may be hazardous to your health.
This product contains amitrole, which has been determined
to cause cancer in laboratory ant *ls. Products intended
for formulation into restricteduse pesticides at require
on their labeling that a respirator be worn during mixing
and loading. Lightweight waterproof clothing (jumpsuit
(or coverall], boots [ or shoes], gloves, and a vide—br1mm d
plastic hardhat) mist be rn when mixing and loading all
products and when applying all products to control dense,
taU vegetation. Workers applying this product in all
other situations must wear lightweight waterproof gloves
and boots (or shoes). Products intended for formulation
into general—use pesticides must require on their labeling
that waterproof gloves be rn while handling the product.”
All products must bear the following statements:
“Each formulator is responsible for obtaining EPA
registrations for its formulated product(s).”
Do not discharge into lakes, streams, ponds, or public
waters unless in accordance with NPDS permit. For
guidance, contact your Regional Office of the EPA.”
End—Use Products:
All restricted—use products must bear the following statements:
“Restricted Use Pesticide”
“For retail sale to and application only by certified
applicators or personnel under their direct supervision.”
“The use of this product may be hazardous to your health.
This product contains am.ttrole, which has been determined
to cause cancer in laboratory animals. Wear a respirator
during mixing and loading of all products. Wear light-
weight waterproof clothing (jumpsuit [ or coverall], boots
[ or shoes], gloves, and a wide—brimmed plastic hardhat)
when applying all products to control dense, tall
vegetation. Workers applying this product in all other
situations must wear lightweight waterproof gloves and
boots (or shoes).”
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All homeowner products must bear the following statements:
“The use of this product may be hazardous to your health.
This product contains a itrole, which has been determined
to cause cancer in laboratory animals. Wear waterproof
gloves when using this product.”
All products intended for nonaquatic uses must bear the following
statement on the label:
“Do not apply directly to water or wetlands. Do not
contaminate water by cleaning of equipment or disposal
of wastes.”
All products intended for aquatic uses must bear the following
statement on the label:
“Consult your state Fish and Game Agency before applying
this product to public waters. Permits may be required
before treating such waters.
All products must bear the following statements, regardless of
classification:
“Do not allow spray or spray drift to contaminate edible
crops or water intended for irrigation, drinking or
other domestic purposes.”
“Do not allow livestock to graze or feed in treated noncrop
areas.”
Suii mary of preliminary risk/benefit review:
Risks:
Amitrole is not used on food crops and there is no dietary
exposure to amitrole. Deruial exposure is the major source of
exposure, with inhalation furnishing only a minor contribution
to the total body burden. Human exposure, in some circumstances,
occurs at doses which resulted in antithyroid effects in
laboratory animals.
Conservatively assuming 100% dermal penetration, the oncogenic
risk associated with some use patterns and application techniques
is high. Lightweight waterproof clothing and a respirator are
expected to reduce exposure and risk for all uses except the
power wagon application.
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Benefits:
The largest use site by production volume, the highway rights—
of—wey site wee selected for this limited analysis. Mitrole is
not produced in the United States, with under 800 thousand pounds
being imported by Union Carbide, American Cyanamid and Aceto
Chemical. Mitrole, in combination with other chemicals, offers
low cost, broad spectrum control of both newly emerged or
established broadleaf weeds as well as seasonal control by
residual chemicals with which it is mixed. Alternatives include
contact herbicides and mechanical cutting.
5. Stt ’miary of major data gaps :
Generic data requirements:
Product chemistry: data due 6 months after receipt of Standard
Statement of composition
Discussion of formation of unintentional ingredients
Preliminary analysis
Density, bulk density, or specific gravity
Solubility
Vapor pressure
Dissociation constant
Octanol/Water partition coefficient
Submittal of samples
Toxicology:
Acute lesting: data due 6 months after receipt of Standard
Primary eye irritation
Primary skin irritation
Derma.1 sensitization
Subchronic testing: data due 24 months after receipt of Standard
90—day dermal
90—day inhalation
Chronic testing: data due 24 months after receipt of Standard
Teratogenicity — 2 species
Special testing: data due 6 months after receipt of Standard
Dermal absorption study
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Wildlife and aquatic organisms: data due 24 months after receipt of
Standard
Avian oral 5O
Freshwater fish LC 50
Acute LC 50 freshwater invertebrates
Acute LC 50 estuarine and marine organisms
Environmental fate:
Data due 6 months after receipt of Standard:
Hydrolysis studies
Photodegradation studies in water
Photodegradation studies on soil
Leaching and adsorption/desorption
Special exposure study — Protective clothing effectiveness
Data due 24 months after receipt of Standard:
Aerobic soil metabolism study
Anaerobic aquatic metabolism study
Aerobic aquatic metabolism study
Soil dissipation study — field
Aquatic (sediment) dissipation study — field
Forestry dissipation study — field
Soil, long—term dissipation study (field) — reserved, depending
upon results of field dissipation study
Acct ulation studies — irrigated crops
Product specific data requirements for manufacturing—use products
containing Amitrole:
Product chemistry: data due 6 months after receipt of Standard
Statement of composition
Discussion of formation of unintentional ingredients
Preliminary analysis
Certification of limits
Analytical methods for enforcement of limits
Density, bulk density, or specific gravity
pH
Oxidizing or reducing action
FlRmmability
Explodability
Storage stability
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Toxicology:
Acute testing: data due 6 months after receipt of Standard
Primary eye irritation — rabbit
Primary dermal irritation
Derma]. sensitization
6. Contact person at EPA :
Robert J. Taylor
Product Manager (25), TS—767C
Environmental Protection Agency
401 N Street, S.W.
Washington, D.C. 20460
(703) 557—1800
DIScLAIMER: The information presented in this Chemical Information Fact
Sheet is for informational purposes only and may not be used to fulfill
data requirments for pesticide registration and reregistration.
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