hexazinone (Velpar) Herbicide Profile 9/88
Name of Chemical: Hexazinone
Reason for Issuance: Registration Standard
Date Issued: September 1988
Fact Sheet Number: 183
1. DESCRIPTION OF CHEMICAL
- Generic Name: 3-cyclohexyl-6-dimethylamino-1-methyl-1,3,5-triazine-
- Common Name: Hexazinone
- Trade Name: Velpar
- EPA Shaughnessy Code: 51235-04-02
- Chemical Abstracts Service (CAS) Number: 107201
- Year of Initial Registration: 1975
- Pesticide Type: Herbicide
- Chemical Family: Triazine
- U.S. Producer: Dupont
2. USE PATTERNS AND FORMULATIONS
- Registered Uses: Terrestrial food crop use on fruit, sugarcane,
alfalfa,- pastures/rangeland and fallowland;
- Terrestrial nonfood crop use on grasses, rights-of-ways, and other
- Aquatic nonfood crop uses on drainage ditch banks;
- Forestry use on Christmas tree plantation, conifer release, and
conifer forest plantings.
- Predominant Uses: A selective herbicide used to control grasses and
broadleaf and woody plants. Approximately 33% is used on alfalfa, 31%
in forestry, 29% in industrial areas, 4% on rangeland and pastures,
and < 2% on sugarcane.
- Formulation Types Registered: Technical, formulation intermediate,
granular, pelleted/tableted, dry flowable, emulsifiable concentrate,
soluble concentrate/liquid, and ready-to-use liquid.
- Methods of Application: Postemergence, preemergence, layby, directed
spray, or basal soil treatment using ground equipment or where
appropriate, broadcasted using aerial equipment.
- Rates of Application: lb ai/A = pounds active ingredient per acre
Terrestrial food crop - 0.22 - 6.0 lb ai/A
Terrestrial nonfood crop - 0.67 - 13.5 lb ai/A
Aquatic nonfood crop - 1.0 - 13.5 lb ai/A
. Forestry - 0.45 - 6.0 lb ai/A
3. SCIENCE FINDINGS
- Physical State: crystalline solid
- Color: white
- Melting point: 115-117 degrees C
- Solubility: soluble in water, chloroform, methanol, benzene,
dimethylformamide, acetone, toluene, and hexane.
- Vapor Pressure: 2 x 10 minus 7 mmHg, 25 degrees C.
- Stability: Stable in aqueous solutions at pH 5, 7, 9 at temperatures
up to 37 degrees C.
- Acute Toxicity:
- Oral (rat): 1690 mg/kg (males), toxicity category III.
Testing of females is required.
- Dermal (rabbit): > 5278 mg/kg (males), toxicity category IV.
If a gender difference is exhibited in the acute oral test on
females, testing on females may be required.
- Inhalation (rat): 7.48 mg/l (males), toxicity category III.
If a gender difference is exhibited in the acute oral test on
females, testing on females may be required.
- Primary Eye Irritation (rabbit): Corrosive, causing irreversible
eye damage, toxicity category I.
- Primary Dermal Irritation: Not an irritant.
- Subacute Toxicity:
- A 21-day dermal study is required. Two acceptable oral toxicity
studies were reviewed and no additional data are required. In the
90-day dog study, at the Lowest Effect Level (LEL) cf 125 mg/kg
(highest dose tested (HDT)), there was decreased body weight in both
sexes, increased alkaline phosphatase in both sexes, decreased
albumin /globulin values in both sexes, and increased absolute and
relative liver weight in both sexes. There were no compound-related
histopathological effects. The No Observed Effect Level (NOEL) was
- In the 90-day rat study, at the LEL of 250 mg/kg (HDT), there was
decreased body weight in both sexes. There were no compound-related
effects in mortality, toxic signs, food consumption, clinical
pathology, organ weights, and histopathology. The NOEL was 50
- Chronic Toxicity:
- Chronic Oral Toxicity
- One acceptable chronic feeding study in rats has been submitted.
A data gap exists for a chronic nonrodent (dog) feeding study.
- In the rat study, there was increased survival over all test
groups for male rats at 125 mg/kg at 2 years. Survival at 2
years in female rats was comparable between control and treated
groups. The systemic NOEL was 10 mg/kg. At the LEL of 50 mg/kg,
females had a 5% decreased body weight and slight decrease in
food efficiency. At 125 mg/kg, there were significant toxic
effects in both sexes. Males had a 12% body weight decrease, a
4% food consumption decrease, increased white blood cells and
eosinophiles, alkaline urine and organ weight changes. Females
had a 19% body weight decrease, slight food efficiency decrease,
alkaline urine and organ weight changes.
- Oncogencity: Mouse study - The oncogenic potential is incon-
clusive due to a possible ambiguity in the classification of liver
neoplasia in both sexes. The systemic NOEL is 30 mg/kg. The
liver slides must be rereviewed by the Agency.
- Rat Study - There were no oncogenic effects up to and
including 125 mg/kg (HDT).
- The Agency will reassess hexazinone's oncogenic potential
after rereview of the mouse study.
- Teratoloqy: Rat study - At 900 mg/kg/day (HDT), developmental
toxicity was evidenced by decreased fetal body weight, and partial
ossification, kidney anomalies, and misaligned sternebrae. The
LEL was 400 mg/kg and the NOEL was 100 mg/kg/day for
developmental. For maternal toxicity, the NOEL was 100 mg/kg/day.
- Rabbit study - NOEL for developmental and maternal
toxicity was 50 mg/kg/day.
- The Agency has determined that hexazinone is not a teratogen.
- Reproduction: The Agency is requiring that additional information
be submitted on a rat study that exhibited a NOEL of 50 mg/kg.
Not a mutagen in a gene mutation, an unscheduled DNA synthesis or in a
chromosomal aberration study in rats. However, a chromosomal
aberration study with the Chinese hamster showed a positive response.
The Agency has determined that hexazinone is not a mutagenic agent.
- The Agency has reviewed one acceptable rat metabolism study. C14 was
excreted as an average of 97% of the total dosed radioactivity via the
urine (ca. 77%) and feces (ca. 20%) during the collection period. The
results were comparable for each treatment regimen. Very low levels
of radioactivity were detected in the GI tract, hide, excised organs,
muscle, blood, and fat. Hexazinone was metabolized primarily by
hydroxylation and demethyl- ation resulting in eight major
metabolites. No additional data are required.
- Major Routes of Exposure:
- The major routes of exposure are dermal and occular during mixing,
loading, and application.
Physiological and Behavioral Characteristics:
- Foliar Absorption: Hexazinone is absorbed through the roots and/or
leaves depending upon the type of formulation and method of
- Translocation: Following root absorption, hexazinone translocates
upward through the xylem.
- Mechanism of Pesticide Action: Hexazinone acts as photosynthesis
- Persistence in Water: Hexazinone is persistent in water at pH 5,7,
- Mobility in soil: Hexazinone is mobile in soil.
- Bioaccumulation: Hexazinone does not accumulate in fish.
- Environmental Fate and Groundwater:
- Contamination Concerns: Hexazinone belongs to the triazine family
of pesticides. Some of these pesticides have been found in ground
water. Because hexazinone has been identified as being persistent in
water and mobile in soils, there is concern for groundwater
contamination. Data are required to address this concern.
- Nontarget Organisms: The Agency is requiring Droplet Spectrum and
.Spray Drift Evaluation tests because of the phytotoxicity of
hexazinone, its aerial method of application, and the potential
exposure of off-site plants to the pesticide.
- Exposure of Humans:
- Hexazinone has not been reported to be associated with any death or
hospitalized cases since 1976. The voluntary accident reporting system
reported one accidental ingestion.
- Technical grade hexazinone is corrosive to the eye and causes
irreversible eye damage. Use of protective goggles, face shield, or
safety glasses are required for mixers, loaders, and applicators.
- Exposure during Reentry Operations: The Agency has not received
adequate toxicological or epidemiological evidence to indicate that
residues of hexazinone can cause adverse effects on persons entering
treated sites. No reentry data are required and no reentry interval
has been imposed.
- LD = lethal dose
- LC = lethal concentration
- EC = effect concentration
- Avian Toxicity: Acceptable data indicate that technical hexazinone is
practically nontoxic to birds.
- Acute oral (Bobwhite) LD50 = 2258 mg/kg
- Dietary Toxicity (Mallard) LC50 = >10,000 ppm
(Bobwhite) LC50 = >5,000 ppm
- Fish Toxicity: Acceptable data indicate that technical hexazinone is
practically nontoxic to fish.
- Fish Acute (Rainbow trout) LC50 = >320 ppm
(Bluegill sunfish) LC50 = >370 ppm
(Fathead minnow) LC50 = >274 ppm
(Bluegill sunfish) LC50 = >505 ppm
- Freshwater Invertebrate Toxicity: Acceptable data indicate that
technical hexazinone is practically nontoxic to freshwater
Daphnia magna EC50 = 145.3 ppm
- Estuarine and Marine Organisms Toxicity: Acceptable data
indicate that hexazinone is practically nontoxic to
molluscs and slightly toxic to crustaceans.
Oyster 48-hr EC50 = >320 pm
Shrimp 96-hr LC50 = 78 ppm
Crab 96-hr LC50 = >1000 ppm
- Nontarget Insects: There is insufficient information to determine
that use patterns of hexazinone are nontoxic to honeybees. Therefore
a honey bee acute study is required.
- Potential Problems Related to Endangered Species: Because of the
aerial use pattern of hexazinone on forests and/or rangelands, there
is a threat to endangered plant species around these use sites.
- Tolerances Established: Tolerance regulations have been established
for residues of hexazinone and its metabolites in a variety of
commodities (refer to 40 CFR 180.396).
- Results of Tolerance Assessment: The nature of the residue in plants
is adequately understood. However, the metabolism of hexazinone in
animals is not. Studies characterizing the total terminal residue of
hexazinone in ruminants and poultry are required. Storage stability
data and analysis of hexazinone residues on certain crops must be
submitted. Additional residue analytical data are required. Processing
data are needed for certain commodities. PHI's must also be
established for some commodities. The adequacy of the established
tolerances will be reassessed when the required data is reviewed.
4. SUMMARY OF REGULATORY POSITION AND RATIONALE
- Hexazinone does not meet any of the criteria specified in 40 CFR
154.7; therefore a Special Review is not being initiated at this time.
- The Agency will not require restricted use classification for
hexazinone end-use products.
- The Agency is not classifying hexazinone as an oncogen pending
rereview of certain data from previously submitted studies.
- Additional data are needed to thoroughly evaluate the potential of
hexazinone to contaminate groundwater.
- The Agency is requiring that a tolerance for pasture/rangeland hay be
proposed so that the impractical restriction against the cutting of
hay from these sites be removed from the label.
- The Agency is requiring that the tolerance for alfalfa hay be revised
so that the impractical feeding restriction of alfalfa hay be removed
from the label.
- EPA is developing a program to reduce or eliminate exposure to
endangered plant species from the use of hexazinone to a point where
use does not result in jeopardy and will issue notice of any labeling
revisions when the program is developed. Endangered species labeling
is not required at this time.
- While the data gaps are being filled, currently registered
manufacturing-use products and end-use products containing hexazinone
as the sole active ingredient may be sold, distributed, formulated,
and used in the United States, subject to the terms and conditions
specified in this Standard. Registrants must provide or agree to
develop additional data, required in the Registration Standard.
5. STATEMENTS REQUIRED ON LABELS
- The following pesticide disposal statement must appear on hexazinone
"Do not discharge effluent containing this product into
lakes, streams, ponds, estuaries, oceans, or public
waters unless this product is specifically identified
and addressed in an NPDES permit. Do not discharge
effluent containing this product to sewer systems without
previously notifying the sewage treatment plant authority.
For guidance, contact your State Water Board or Regional
Office of the EPA."
- The Following Must Appear on End-Use Products:
- In the Precautionary Statements:
"Corrosive, causes irreversible eye damage. Harmful if
swallowed. Do not get in eyes or clothing. Mixers,
loaders, and applicators must wear goggles, face shield,
or safety glasses. Wash thoroughly with soap and water
after handling. Remove contaminated clothing and wash
- Environmental Hazard Statement:
"Do not apply directly to water or wetlands (swamps,
bogs, marshes, and potholes). Do not contaminate water
when disposing of equipment washwaters."
- In the Directions for Use Section:
"Do not enter or allow entry into treated areas until
sprays have dried to perform hand tasks. A person may
enter the areas to perform other tasks only if the
person is wearing the personal protective eye equipment
listed on the label."
- As appropriate, the following grazing statements should appear on the
- For sugarcane: "Do not feed sugarcane forage to live.stock."
- For conifer release and forest plantings (reforestation site
preparation): "Do not graze domestic animals on treated areas
within 30 days after treatment."
6. SUMMARY OF MAJOR DATA GAPS
- The following data are required for hexazinone. Specific requirements
are detailed in the Data Tables, Appendix I of the Hexazinone
Registration Standard, which can be obtained from National Technical
Information Service (NTIS) in Springfield, Virginia.
Study Due Date - From Date
Product Chemistry 6 - 15 Months
Residue Chemistry 18 - 24 Months
Magnitude of the Residue
Toxicology 9 - 50 Months
Subchronic 21 day Dermal
Ecological Effects 9 - 18 Months
Freshwater Fish LC50
Fish Early Life Stage
Freshwater Invertebrate Acute EC50
Aquatic Invertebrate Life-Cycle
Honey bee Acute Contact LD50
Environmental Fate 9 - 50 Months
Soil Dissipation Studies
Accumulation Studies (Irrigated crop and Rotational Crops)
7. CONTACT PERSON AT EPA:
Mr. Richard Mountfort
Product Manager (Team 23)
Registration Division (TS-767C)
Office of Pesticide Programs, EPA
Washington, DC 20460
Telephone: (703) 557-1830
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.