The information in this profile may be out-of-date. It was last revised
in 1996. EXTOXNET no longer updates this information, but it may be useful
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E X T O X N E T
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EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
Trade names for products containing hexazinone are DPX 3674,
Pronone, and Velpar. It may be used in combination with other
herbicides such as bromacil and diuron.
Hexazinone is a slightly toxic compound in EPA toxicity class I.
Labels for products containing hexazinone bear the Signal Word
DANGER - POISON due its ability to cause serious and irreversible
eye irritation. It is a General Use Pesticide (GUP).
Hexazinone is a triazine herbicide used against many annual,
biennial, and perennial weeds, as well as some woody plants. It
is mostly used on non-crop areas; however, it is used selectively
for the control of weeds among sugar cane, pineapples, and
lucerne. Hexazinone is a systemic herbicide that works by
inhibiting photosynthesis in the target plants. Rainfall or
irrigation water is needed before it becomes activated. It is
available in soluble concentrate, water-soluble powder, or
Formulation: It is
available in soluble concentrate, water-soluble powder, or
- Acute toxicity: Hexazinone is slightly
toxic via the oral route, with a reported LD50 of 1690
mg/kg in rats, and 860 mg/kg in male guinea pigs [6,15].
Via the dermal route, it is practically nontoxic, with a
reported dermal LD50 in rabbits of greater than 5278
mg/kg [6,15]. Hexazinone does not cause significant skin
irritation or sensitization in guinea pigs or rabbits,
but it does cause severe eye irritation in rabbits .
Hexazinone's inhalation toxicity is very low, its 1-hour
inhalation LC50 is greater than 7.48 mg/L in rats .
Effects due to acute exposure may include irritatation
the eyes, nose and throat, as well as nausea and vomiting
- Chronic toxicity: Over a 2-week period,
male rats receiving dietary doses of 300 mg/kg/day showed
no evidence of cumulative toxicity . Male rats
receiving doses of 50 mg/kg/day over 90 days showed no
effects, but higher doses caused decreased body weights.
Body weight gain was seen in dogs at doses of about 35
mg/kg/day and higher over 1 year . Very high doses
for 8 weeks did not affect hamsters and caused only
increased liver weights in mice .
- Reproductive effects: Female rats, fed
moderate to high doses (up to 150 mg/kg) over two
generations, showed no effects on reproduction or milk
production, but only reduced offspring weight [15,29].
Available evidence suggests that hexazinone is unlikely
to cause reproductive effects in humans.
- Teratogenic effects: Pregnant female
rats receiving doses up to 100 mg/kg/day during
gestation, and rabbits receiving up to 125 mg/kg/day,
evidenced no fetal abnormalities . Teratogenic
effects were observed in rats only at maternal doses
greater than 400 mg/kg/day during gestation . It is
unlikely that hexazinone would pose a teratogenic effects
in humans under normal conditions.
- Mutagenic effects: Hexazinone showed no
mutagenic activity in the Ames assay and tests using
Chinese hamster ovary cell cultures . In living
animal tests, no changes in chromosomal structure
occurred. In other laboratory analyses of its capacity to
induce genetic disruption, results were inconclusive
. The evidence suggests hexazinone is either slightly
- Carcinogenic effects: Rats, mice, and
dogs have been tested for 1 to 2 years on diets
containing up to 500 mg/kg. Hexazinone was not
carcinogenic in rats, and was only carcinogenic in mice
at dietary levels of over 300 mg/kg. At these levels in
mice, liver adenomas were observed . These studies
suggest that hexazinone is unlikely to be carcinogenic to
humans under normal circumstances.
- Organ toxicity: Target organs affected
in lab animals by chronic hexazinone exposure include the
- Fate in humans and animals: Hexazinone
is fairly rapidly processed and excreted by animal
systems. Rats typically excrete hexazinone almost
completely within 3 to 6 days, the majority in urine
. Long-term exposure does not diminish this rapid
processing and elimination; rats given prior exposure for
2 weeks excreted almost all of the product within 3 days
. Less than 1% of the parent hexazinone was detected
in urine and feces. There does not appear to be any
significant tissue accumulation . Dairy cows given
small amounts of hexazinone in their diets for 30 days
had no detectable residues in milk, fat, liver, kidney,
or lean muscle, but did have minute amounts of a
hexazinone metabolite in their milk . Lactating goats
given small amounts of hexazinone for 5 days also had
small amounts of the compound in their milk and livers
- Effects on birds: Hexazinone is slightly
to practically nontoxic to birds. The acute oral LD50 of
hexazinone in bobwhite quail is 2258 mg/kg . The 5-
to 8-day dietary LC50 in bobwhite quail and mallard
ducklings is greater than 10,000 ppm .
- Effects on aquatic organisms: Hexazinone
is slightly toxic to fish and other freshwater organisms.
Some of the reported 96-hour LC50 values include: rainbow
trout, 320 mg/L; bluegill, 370 mg/L; fathead minnow, 274
mg/L [6,15]. The 48-hour LC50 for hexazinone in the water
flea, Daphnia magna, is 151 mg/L . The
bioconcentration factor in bluegill sunfish is only seven
times the ambient water concentration, indicating very
low bioaccumulation in fish .
- Effects on other organisms: Hexazinone
is nontoxic to honey bees. The herbicide is toxic to
larch trees (Larix spp.), and should not be used for weed
control in forested areas .
- Breakdown in soil and groundwater:
Hexazinone is of moderate to high persistence in the soil
environment. Measured field half-lives range from less
than 30 to 180 days, with a representative value of about
90 days . Hexazinone is broken down by soil microbes,
which release carbon dioxide in the process .
Sunlight may also break down the compound via
photodegradation . The rate of breakdown under
natural field conditions will depend on many
site-specific variables, including sunlight, rainfall,
soil type, and rate of application. Hexazinone does not
evaporate to any appreciable extent from soil .
Hexazinone is very poorly adsorbed to soil particles,
very soluble in water, and slowly degraded, so it is
likely to be mobile in most soils and has the potential
to contaminant groundwater.
- Breakdown in water: Photodecomposition,
biodegradation, and dilution are the prime mechanisms for
loss of hexazinone activity in aquatic systems .
- Breakdown in vegetation: Hexazinone is
readily absorbed in the root zone and translocated
throughout the plant. It is less mobile following uptake
from the foliage. It is converted in non-susceptible
plants to less phytotoxic compounds. In susceptible
plants, it is more persistent and can result in
disruption of photosynthesis and chloroplast damage .
- Appearance: Hexazinone is a colorless,
odorless crystal at room temperature .
- Chemical Name:
- CAS Number: 51235-04-2
- Molecular Weight: 252.32
- Water Solubility: 33,000 mg/L @ 25 C 
- Solubility in Other Solvents: v.s. in
acetone, hexane, and methanol 
- Melting Point: 115-117 C 
- Vapor Pressure: 0.03 Pa @ 25 C 
- Partition Coefficient: -4.40
- Adsorption Coefficient: 54 
- ADI: Not Available
- MCL: Not Available
- RfD: 0.033 mg/kg/day 
- PEL: Not Available
- HA: 0.20 mg/L (lifetime) 
- TLV: Not Available
DuPont Agricultural Products
Walker's Mill, Barley Mill Plaza
P.O. Box 80038
Wilmington, DE 19880-0038
- Phone: 800-441-7515
- Emergency: 800-441-3637
References for the information in this PIP can be found in
Reference List Number 8
information in this profile does not in any way replace or
supersede the information on the pesticide product labeling or
other regulatory requirements. Please refer to the pesticide