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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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and the Institute for Environmental Toxicology, Michigan State
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EXTOXNET primary files maintained and archived at Oregon State
Revised June 1996
Trade and Other Names:
Trade names include Altosid, Apex, Diacan, Dianex, Kabat, Minex,
Pharorid, Precor, and ZR-515.
Methoprene is a slightly to practically nontoxic compound in EPA
toxicity class IV. It is a General Use Pesticide (GUP). Labels
for containers of products containing methoprene must bear the
Signal Word CAUTION.
Chemical Class: Not
Methoprene is a compound which mimics the action of an insect
growth regulation hormone. It is used as an insecticide because
it interferes with the normal maturation process. In a normal
life cycle, an insect goes from egg to larva, to pupa, and
eventually to adult. Methoprene artifically stunts the insects'
development, making it impossible for insects to mature to the
adult stages, and thus preventing them from reproducing.
To be effective, it is essential that this growth inhibitor be
administered at the proper stage of the target pest's life cycle.
Methoprene is not toxic to the pupal or adult stages. Treated
larvae will pupate but adults do not hatch from the pupal stage.
Methoprene is also considered a larvicide since it is effective
in controlling the larval stage of insects. Methoprene is used in
the production of a number of foods including meat, milk, eggs,
mushrooms, peanuts, rice, and cereals. It is also used in aquatic
areas to control mosquitoes and several types of ants, flies,
lice, moths, beetles, and fleas. It is available in suspension,
emulsifiable and soluble concentrate formulations, as well as in
briquette, aerosol, and bait form.
Formulation: It is
available in suspension, emulsifiable and soluble concentrate
formulations, as well as in briquette, aerosol and bait form.
- Acute toxicity: Methoprene is
practically nontoxic when ingested or inhaled and
slightly toxic by dermal absorption. The oral LD50 for
methoprene in rats is greater than 34,600 mg/kg, and in
dogs is greater than 5000 mg/kg . It is slightly toxic
by skin exposure, with reported dermal LD50 values of
greater than 2000 to 3000 mg/kg in rabbits .
Methoprene is not an eye or skin irritant, and it is not
a skin sensitizer . The inhalation LC50 for methoprene
in rats is greater than 210 mg/L . No overt signs of
poisoning have been reported in incidents involving
accidental human exposure to methoprene .
- Chronic toxicity: No methoprene-related
effects were observed in 2-year feeding trials with rats
given doses of 250 mg/kg/day, nor in mice given 30
mg/kg/day . Liver changes were observed in mice fed 50
to 250 mg/kg/day of methoprene during an 18-month study
. Increased liver weights occurred in rats fed 250
mg/kg/day for 90 days, but not during a 24-month feeding
study in which rats were fed 125 mg/kg/day .
- Reproductive effects: Experimental data
indicate that no reproductive hazards are associated with
methoprene . No methoprene-related effects were
observed in three-generation reproduction studies in rats
receiving dietary doses of 125 mg/kg/day .
- Teratogenic effects: There have been no
teratogenic effects in animals dosed with methoprene;
teratogenic effects were not seen in rats at doses of
about 25 mg/kg/day, or in rabbits at doses of about 15
mg/kg/day [156,157]. Methoprene does not appear to be
- Mutagenic effects: Methoprene does not
appear to be mutagenic. No methoprene-related mutagenic
effects were observed in rats following a single dose of
2000 mg/kg .
- Carcinogenic effects: No tumors were
seen in an 18-month feeding study with mice, or in a
24-month oncogenicity study with rats . These data
suggest that methoprene is not carcinogenic.
- Organ toxicity: The target organ
primarily affected by methoprene after long-term exposure
is the liver.
- Fate in humans and animals: In mammals,
methoprene is rapidly and completely broken down and
excreted, mostly in the urine and feces . Some
evidence suggests that methoprene metabolites are
incorporated into natural body components .
Methoprene is excreted unchanged in cattle feces in
amounts that are sufficient to kill some larvae that
breed in dung .
- Effects on birds: Methoprene is slightly
toxic to birds [1,158]. The reported 5- to 8-day LC50
values for Altosid, a methoprene formulation, are greater
than 10,000 ppm in mallard ducks and bobwhite quail, and
the acute oral LD50 for Altosid is greater than 4640 ppm
in chickens [1,158]. In mallards an acute oral LD50 of
greater than 2000 mg/kg was determined . Nonlethal
effects that may affect survival of the birds did appear
at acute oral doses of 500 mg/kg. These effects appeared
as soon as 2 hours after treatment and persisted for up
to 2 days and included slowness, reluctance to move,
sitting, withdrawal, and incoordination . These
effects may decrease bird survival by making them
temporarily more susceptible to predation. No effects
were observed in the reproduction of bobwhite quail and
mallard ducks at 30 ppm constant feeding of Altosid
- Effects on aquatic organisms: Methoprene
is slightly to moderately toxic to fish . The
reported 96-hour LC50 values for the methoprene
formulation Altosid were 4.6 mg/L in bluegill sunfish,
4.4 mg/L in trout, and greater than 100 mg/L in channel
catfish and largemouth bass [1,8]. Methoprene residues
may have a slight potential for bioconcentration in
bluegill sunfish and crayfish . Methoprene is very
highly toxic to some species of freshwater, estuarine,
and marine invertebrates, while the acute LC50 values are
greater than 100 mg/L in freshwater shrimp, and it is
greater than 0.1 mg/L in estuarine mud crabs .
Altosid had very little effect, if any, on exposed
non-target aquatic organisms including waterfleas,
damselflies, snails, tadpoles, and mosquito fish .
- Effects on other organisms: Tests with
earthworms showed little if any toxic effects on contact
. It is nontoxic to bees .
- Breakdown in soil and groundwater:
Methoprene is of low persistence in the soil environment;
reported field half-lives are up to 10 days . In
sandy loam, its half-life was calculated to be about 10
days . When Altosid was applied at an extremely high
application rate of 1 pound per acre, its half-life was
less than 10 days . In soil, microbial degradation
is rapid and appears to be the major route of its
disappearance from soil [155,157]. Methoprene also
readily undergoes degradation by sunlight .
Methoprene is rapidly and tightly sorbed to most soils
. It is slightly soluble in water . These
properties, along with its low environmental persistence
make it unlikely to be significantly mobile. In field
leaching studies, it was observed only in the top few
inches of the soil, even after repeated washings with
- Breakdown in water: Methoprene degrades
rapidly in water . Studies have demonstrated
half-lives in pond water of about 30 and 40 hours at
initial concentrations of 0.001 mg/L and 0.01 mg/L,
respectively . At normal temperatures and levels of
sunlight, technical Altosid is rapidly degraded, mainly
by aquatic microorganisms and sunlight [159,49].
- Breakdown in vegetation: Altosid is
biodegradable and nonpersistent, even in plants treated
at very high rates. It has a half-life of less than 2
days in alfalfa when applied at a rate of 1 pound per
acre . In rice, the half-life is less than 1 day
. In wheat, its half-life was estimated to be 3 to 7
weeks, depending on the level of moisture in the plant
. Plants grown in treated soil are not expected to
contain methoprene residues.
- Appearance: Technical methoprene is a
amber or pale yellow liquid with a faint fruity odor 
- Chemical Name:
- CAS Number: 40596-69-8
- Molecular Weight: 310.48
- Water Solubility: 1.4 mg/L @ 25 C 
- Solubility in Other Solvents: Miscible
in organic solvents 
- Melting Point: Not Available
- Vapor Pressure: 3.15 mPa @ 25 C 
- Partition Coefficient: Not Available
- Adsorption Coefficient: Not Available
- ADI: 0.1 mg/kg/day 
- MCL: Not Available
- RfD: Not Available
- PEL: Not Available
- HA: Not Available
- TLV: Not Available
12005 Ford Rd., Suite 800
Dallas, TX 75234
- Phone: Not Available
- Emergency: 708-699-1616
References for the information in this PIP can be found in
Reference List Number 10
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