Potential Exposure
Methoprene is a natural insect growth
regulator (IGR) that mimics juvenile hormone(s) and is
used against a variety of insects including horn flies, mosquitoes, beetles, tobacco moths, sciarid flies, fleas (eggs
and larvae), fire ants, pharoah ants, midge flies and Indian
meal moths. Controlling some of these insects, methoprene
is used in the production of a number of foods including
meat, milk, mushrooms, peanuts, rice and cereals. It also
has several uses on domestic animals (pets) for controlling
fleas and to control insects in wastewater, sludge beds and
ponds. For oral use in dogs, 9 weeks of age and older and
4 lb body weight or greater, for the prevention and control
of flea populations
First aid
If this chemical gets into the eyes, remove any
contact lenses at once and irrigate immediately for at least
15 minutes, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the
skin, remove contaminated clothing and wash immediately
with soap and water. Seek medical attention immediately.
If this chemical has been inhaled, remove from exposure,
begin rescue breathing (using universal precautions) if
breathing has stopped, and CPR if heart action has stopped.
Transfer promptly to a medical facility. When this chemical
has been swallowed, get medical attention. Give large
quantities of water and induce vomiting. Do not make an
unconscious person vomit. Do not induce vomiting when
formulations containing petroleum solvents are ingested
Shipping
UN3082 Environmentally hazardous substances,
liquid, n.o.s., Hazard class: 9; Labels: 9-Miscellaneous hazardous material, Technical Name Required
Description
Methoprene is the common name for a racemic mixture of two
enantiomers (R and S in a ratio of 1:1). The activity of the
compound as a juvenile hormone (JH) mimic is restricted to
the S enantiomer. Methoprene was the first insect growth
regulator approved in the 1970s by the US Environmental
Protection Agency after extensive studies showing low toxicity
to vertebrates and rapid natural chemical degradation in the
environment and through organism metabolism. Nowadays, it
is one of the most widely used and successful insect growth
regulators. Different products containing methoprene (e.g.,
pesticides, veterinary drugs) are commercially available in
different forms (emulsifiable concentrates, granules, pellets,
briquettes, aerosols, or sustained-release formulations). Some
of these are applied to water for mosquito control whereas
others are sprayed in areas where foods are stored to prevent
insect infestations. Methoprene may be used in combination
with other active insecticides to optimize pest control.
Chemical Properties
Amber colored liquid. Faint fruity odor.
Waste Disposal
It is the responsibility of chemical waste generators to
determine if a discarded chemical is classified as a hazardous waste. See 40 CFR Parts 261.3 for United States
Environmental Protection Agency guidelines for the classification determination. In addition, in order to ensure complete and accurate classification, waste generators must
consult state and local hazardous waste regulations.
Incineration might be an effective disposal procedure
where permitted. If an efficient incinerator is not available, the product should be mixed with large amounts of
combustible material and contact with the smoke should
be avoided. In accordance with 40CFR165, follow recommendations for the disposal of pesticides and pesticide
containers
Agricultural Uses
Insect growth hormone: Methoprene is an insect growth regulator (IGR) used
against a variety of insects including horn flies, mosquitoes,
beetles, tobacco moths, sciarid flies, fleas (eggs and larvae), fire ants, pharoah ants, midge flies and Indian meal moths.
Controlling some of these insects, methoprene is used in
the production of a number of foods including meat, milk,
mushrooms, peanuts, rice and cereals. It also has several
uses on domestic animals (pets) for controlling fleas and to
control insects in wastewater, sludge beds and ponds. For
oral use in dogs, 9 weeks of age and older and 4 pounds
body weight or greater, for the prevention and control of
flea populations [21 CFR 520.1390]. Not approved for use
in EU countries
. Registered for use in the U.S.
Trade name
ALTOSID®; APEX®; DIACON®;
DIANEX®; ENT 70,460®; EXTINGUISH®;
FLEATROL®; KABAT®; MANTA®; MOORMAN’S®
IGR CATTLE CONCENTRATE; OVITROL®;
PHARORID®; PRECOR®; ZR-515®
Environmental Fate
Methoprene may be degraded by demethylation, hydrolysis,
oxidative cleavage, and photodegradation, resulting in the
formation of a series of metabolites that include methoprene
acid and citronellic acid. The primary modes of degradation are
photodegradation and degradation by aquatic microorganisms.
It is metabolized rapidly in soil under both aerobic and
anaerobic conditions (half-life = 10–14 days). The major
microbial degradation product is carbon dioxide. Degradation
in both freshwater and saltwater is also quite rapid with a halflife
of 10–35 days at 20 ℃. Methoprene is not very soluble in
water (<2 ppm) and as a result is not highly mobile in soil.
Because of this and its rapid biodegradation, methoprene does
not persist for long periods in soil and is unlikely to contaminate
groundwater. When released into water, methoprene is
expected to adsorb to suspended solids and sediment. A high
potential for bioconcentration in aquatic organisms has been
suggested, with an estimated bioconcentration factor of 3400.
However, studies with bluegill sunfish, showed no significant
bioconcentration of methoprene in fish tissues as a result of
aquatic exposure.
Methoprene rapidly degrades in plants, with a half-life of
1–2 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
reported to be 3–7 weeks, depending on the level of moisture
in the plant.
Metabolic pathway
Methoprene is readily degraded biologically by hydrolysis of the ester
group, O-demethylation and oxidative cleavage of the bond at the
4-position.
Degradation
Methoprene (1) is stable in water and in the presence of aqueous acids and
alkalis. It is sensitive to UV light. Isomerisation of the double bond is
facile. In sunlight (S)-methoprene decomposes to a number of products.
These include trans,trans-( S)-methoprenic acid, 2-cis,4-trans-( S)-methoprenic
acid, and 2-cis,4-trans-(S)-methoprene.
When [5-14C]methoprene was irradiated in direct sunlight in Pyrex
vessels in aqueous solutions (0.01 ppm and 0.50 ppm) the DT50 was less
than one day. Initially decomposition was rapid, but after one week 12%
and 5% 1 remained in the 0.5 and 0.01 ppm solutions, respectively.
Carbon dioxide was collected and total 14C recovered was not less than
94% during a 21-day experiment. Five products were characterised as
oxygenated products but could not be positively identified. For product
identification, an aqueous emulsion of methoprene was irradiated in
sunlight and four photoproducts (24% yield) were characterised as methoxycitronellal
dimethyl acetal(3,3.9%), methoxycitronellic acid (4,4.7%),
an epoxide of methoprene (5,4%) and a methyl ketone (6,4%). In addition
to unreacted methoprene there were at least 46 other photoproducts
of which none represented more than 2% yield. Rose Bengal and
anthraquinone increased the rate of photocatalysed breakdown of
methoprene and the profile of products was similar to that obtained by
irradiation of a thin film. The extent of decomposition in the presence
of anthraquinone was 86% after 6 hours and the predominant product
was methoxycitronellal (2, l0-14%). Photosensitised oxidation was slow
and 47% of the original was unreacted and a single major product
(12%) was identified as the dihydrofuranol (7) (Quistad et al., 1975a)
(see Scheme 1).
Toxicity evaluation
Acute oral LD50 for rats: >34,600 mg/kg
