United States
Environmental Protection
Agency
Pesticides And
Toxic Substances
(7508W)
738-F-91-104
March 1991
R.E.D. FACTS
Pesticide
Reregistration
Methoprene
All pesticides sold or used in the United States must be registered by
EPA, based on scientific studies showing that they can be used without
posing unreasonable risks to people or the environment. Because of
advances in scientific knowledge, the law requires that pesticides which
were first registered years ago be reregistered to ensure that they meet
today's more stringent standards.
In evaluating pesticides for reregistration, EPA obtains from pesticide
producers and reviews a complete set of studies showing the human health
and environmental effects of each pesticide. The Agency imposes any
regulatory controls that are needed to effectively manage each pesticide's
risks. EPA then reregisters pesticides that can be used without posing
undue hazards to human health or the environment.
Methoprene
When a pesticide is eligible for reregistration, EPA announces this and
explains why in a Reregistration Eligibility Document, or RED. This fact
sheet summarizes the information in the RED for methoprene.
Methoprene, which is sold under the trade name Altosid, is an insect
growth regulator. It is considered a biochemical pesticide because rather
than controlling target pests through direct toxicity, methoprene interferes
with an insect's life cycle and prevents it from reaching maturity or
reproducing. 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 flies, moths,
beetles and fleas. All pesticide products that contain methoprene as the sole
active ingredient are eligible for reregistration except the briquette or slow-
release formulation.
Regulatory Methoprene was first registered by EPA as a conventional, chemical
History pesticide in 1975. EPA issued a Registration Standard for methoprene in
February 1982. Subsequently, the Agency reclassified methoprene as a
biochemical pesticide.
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Health Methoprene is a biochemical pesticide, and its health-related data base
Effects consists mainly of a group of screening studies designed to show its toxicity
and developmental effects in people and other nontarget organisms. If these
studies indicated potential adverse effects, further studies on environmental
fate, ecological effects and food residues would have been required.
The results of these screening tests and other available studies on
methoprene indicate that it is of low toxicity and poses little risk to people
and other nontarget species, with one exception. Methoprene is highly
acutely toxic to estuarine invertebrates. Use of the briquette or slow-release
formulation of methoprene in aquatic environments could pose an undue risk
to these species. Further study of this formulation is being required, as
described further below.
Methoprene showed no significant adverse toxicological effects in any
human health effects screening studies. The pesticide has very low acute
oral and inhalation toxicity potential, and is not an eye or skin irritant (it has
been placed in toxicity category IV, the least toxic category, for these
effects). It also is not a human skin sensitizer. Methoprene is of low acute
dermal toxicity (it has been placed in toxicity category III).
In subchronic studies, methoprene showed some evidence of causing
increased liver weights in test animals, at high dose levels. However, in
chronic effects and oncogenicity studies, no effects were observed even at
the highest dose levels. Other studies show that methoprene does not cause
developmental or reproductive effects, is not mutagenic, and metabolizes
rapidly and completely in mammals.
Routes Through the Diet
Of Exposure People may be exposed to small amounts of methoprene through the
food supply. However, the amount of methoprene in the U.S. consumer's
diet is well below the level at which any adverse health effects could occur.
Tolerances, or legal residue limits, have been established for residues
of methoprene in or on a number of raw agricultural commodities (also see
40 CFR 180.359). Several international Codex Maximum Residue Levels
(MRLs) and Canadian tolerances also have been established, as listed below:
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Methoprene Tolerances
Canadian
Commodity
U.S. Codex
Tolerance MRL Tolerance
(ppm) (ppm)
(ppm)
Cattle, fat
Cattle, meat
Cattle, meat byproducts
Eggs
Goats, fat
Goats, meat
Goats, meat byproducts
Hogs, fat
Hogs, meat
Hogs, meat byproducts
Horses, fat
Horses, meat
Horses, meat byproducts
Milk
Mushrooms
Peanuts
Peanut hulls
Poultry, fat
Poultry, meat
Poultry, meat byproducts
Sheep, fat
Sheep, meat
Sheep, meat byproducts
Meat, fat
Cattle milk
Edible offal (mammalian)
0.3
0.1
0.1
0.05
0.3
0.1
0.1
0.3
0.1
0.1
0.3
0.1
0.1
0.05
1.0
2.0
40.00
0.5
0.5
0.5
0.3
0.1
0.1
0.05
0.2
2.0
0.1
0.05
0.1
0.1
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EPA has reassessed the existing tolerances and finds that they are set at
appropriate levels. Although the U.S. tolerances for mushrooms and meat
fat are higher than the Codex and Canadian limits, EPA is not lowering the
U.S. tolerances at this time. These tolerances are set at levels that
accommodate current methoprene use practices in this country. No changes
are needed to adequately protect the public health.
No new tolerances are required to cover the existing methoprene uses.
(Please note that a petition is pending to establish additional methoprene
tolerances for cereal grains, grain milled fractions and rice hulls.)
During Application
People can be exposed to methoprene while mixing, loading or applying the
pesticide, and while working among treated crops. However, since
methoprene is of such low acute toxicity, and poses no risk of oncogenic,
reproductive, developmental or neurotoxic effects, EPA is satisfied that
methoprene poses no risks to people who are occupationally exposed to the
pesticide.
Environmental All the environmental fate data requirements for methoprene are satisfied.
Hazards The information available to EPA indicates that methoprene will not result
in unreasonable adverse effects to the environment. However, the
ecological effects studies on methoprene suggest that use of the briquette or
slow-release formulation in estuarine areas may cause undue risks to
estuarine invertebrates, since the pesticide is highly acutely toxic to these
organisms. EPA is therefore requiring further study of this methoprene
use.
Environmental Fate
Methoprene degrades rapidly in sunlight, both in water and on inert
surfaces. The pesticide also is metabolized rapidly in soil and does not
leach. Thus, it should not persist in soil or contaminate ground water.
Ecological Effects
Methoprene has been shown to be practically non-toxic to mallard ducks,
and had no effect on quail reproduction. However, the pesticide is
moderately toxic to warm water, freshwater fish, and is slightly toxic to
cold water, freshwater fish.
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Methoprene is very highly toxic to freshwater invertebrates, as seen in
studies with crayfish and Daphnia magna. The pesticide also can be very
highly acutely toxic to estuarine and marine invertebrates, as seen in studies
with grass shrimp and mud-crabs. Marine organisms are not likely to be
exposed to methoprene, but estuarine organisms are likely to be exposed as
a result of the use of methoprene as a mosquito larvicide.
Additional Data
Required
Product Labeling
Changes Required
Methoprene degrades rapidly in water so the use of most formulations in
estuaries is not of concern. However, the slow-release briquette
formulation is of concern to EPA because it causes estuarine organisms to
be exposed to methoprene over an extended period of time. An estuarine
invertebrate life cycle toxicity study is being required to adequately
characterize the chronic toxicity of methoprene to estuarine organisms.
EPA has a sufficient battery of studies to support the reregistration of most
uses of methoprene. The only use of concern is the aquatic, mosquito
larvicide use involving the briquette formulation. An estuarine invertebrate
life cycle study is being required to determine whether long term exposure
of these species to methoprene through the briquette formulation poses
adverse effects. In addition, an octanol/water partition coefficient study is
being required to complete the product chemistry data base for methoprene.
End-use products containing methoprene must bear a statement warning the
applicator that improper use could harm aquatic invertebrates. These
products also must bear an updated water contamination warning. Please
see the Reregistration Eligibility Document for a detailed list of labeling
requirements.
Regulatory * The studies available to EPA indicate that the biochemical insect growth
Conclusion regulator methoprene is of low toxicity and poses very little hazard to
people and most other nontarget species.
* Methoprene is highly acutely toxic to estuarine invertebrates, however,
and these organisms may be exposed to sufficient amounts of methoprene
through its aquatic, slow-release, briquette formulation to experience
adverse effects. An estuarine invertebrate life cycle toxicity study must be
completed before the briquette formulation of methoprene will be eligible
for reregistration.
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* All other registered methoprene products can be used without causing
unreasonable adverse effects in people or the environment. Therefore, all
pesticide products containing methoprene as the sole active ingredient,
except the briquette formulation, are eligible for reregistration.
* EPA will reregister individual products containing methoprene once
product specific data and revised product labeling are submitted to and
accepted by the Agency.
For More EPA requests public comments on the Reregistration Eligibility Document
Information for methoprene, and will consider comments received during the next
several months. To obtain a copy of the RED, or to submit written
comments, please contact the Public Response and Program Resources
Branch, Field Operations Division (7506C), Office of Pesticide Programs,
U.S. EPA, Washington, D.C. 20460. Call 703-557-4436, or FAX to 703-
557-1884.
To obtain a copy of the Registration Standard for methoprene, please
contact the National Technical Information Service (NTIS), 5285 Port Royal
Road, Springfield, VA. 22161. Call 703-487-4650, and request document
#PB87-109443.
For more information about methoprene or about EPA's pesticide
reregistration program, please contact the Special Review and Reregistration
Division (7508W), Office of Pesticide Programs, U.S. EPA, Washington,
D.C. 20460. Call 703-808-8000, or FAX your request to 703-308-8005.
For information about the health effects of pesticides, or for assistance in
recognizing and managing pesticide poisoning symptoms, please contact the
National Pesticides Telecommunications Network (NPTN). Call toll-free 1-
800-858-7378, 24 hours a day, seven days a week, or FAX your inquiry to
806-743-3094.
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