Naled is an insecticide
in the organophosphate pesticide
family that is commonly used to
kill adult (flying) mosquitoes.
Naled has been registered for use in the U.S.
since 1959 and is sold under the brand
name Dibrom. AMVAC Chemical Corporation
has been the major manufacturer
of NALED since 1998.
About one million pounds of
naled are used every year in the U.S.
Approximately 70 percent of this is
used for mosquito control; almost
all of this is applied aerially.
30 percent is used in agriculture.
Major agricultural uses are on
cotton in California and Louisiana, on
alfalfa in Idaho and Oregon, and on
grapes in California.
Efficacy of Mosquito Treatments
The U.S. Centers for Disease Control
and Prevention has written that
“adulticiding, application of chemicals
to kill adult mosquitoes by ground or
aerial applications, is usually the least
efficient mosquito control technique.
Naled is no exception.
researchers from the New York Department
of Health showed that 11
years of naled spraying was “successful
in achieving short-term reductions
in mosquito abundance, but populations
of the disease-carrying mosquito
of concern “increased 15-fold over
the 11 years of spraying.
Mode of Action
Like all organophosphate insecticides, NALED (DIBROM)
Naled is an insecticide in the organophosphate pesticide family used primarily for mosquito control. Dibrom is a
common brand name for naled products. About one million pounds are used annually in the U.S.
Like all organophosphates, naled is toxic to the nervous system. Symptoms of exposure include headaches, nausea,
and diarrhea. Naled is more toxic when exposure occurs by breathing contaminated air than through other kinds of exposure. In laboratory tests, naled exposure caused increased aggressiveness and a deterioration of memory and learning.
Naled’s breakdown product DICHLORVOS (another organophosphate insecticide) interferes with prenatal brain
development. In laboratory animals, exposure for just 3 days during pregnancy when the brain is growing quickly reduced brain size 15 percent.
DICHLORVOS also causes cancer, according to the International Agency for Research on Carcinogens. In laboratory tests, it caused leukemia and pancreatic cancer. Two independent studies have shown that children exposed to household “no-pest” strips containing dichlorvos have a higher incidence of brain cancer than unexposed children.
Aerial applications of naled can drift up to one-half mile.
According to the U.S. Environmental Protection Agency, naled is moderately to highly toxic to birds and fish. It also reduced egg production and hatching success in tests with birds and reduced growth in tests with juvenile fish.
convulsions, paralysis, and death.
** Naled breaks down into dichlorvos **
another organophosphate insecticide, in animals and soil. THIS IS DANGEROUS!!!
Effects on Behavior
Exposure to naled has multiple
effects on behavior. In a study conducted
by naled’s manufacturer, naled caused reduced muscle strength, slow
responses to stimulation, and reduced activity in rats.
These behavioral changes occurred at all but the lowest dose level tested in males and all dose
levels tested in females, suggesting that females are more sensitive than
males to naled poisoning.
Exposure to naled’s breakdown product dichlorvos causes increased aggression and impaired memory. The Indian biochemists mentioned above found that fighting aggression was increased about 5 times
Like most pesticides, commercial
naled-containing insecticides contain
ingredients other than naled. Many of
these ingredients, according to U.S.
pesticide law, are called “inert.” Except
for tests of acute effects, toxicology
tests required for the registration
of a pesticide are not conducted with
the combination of ingredients found
in commercial products.
Most inert ingredients are not identified
on product labels, and little information
about them is publicly available.
Symptoms of Exposure
Symptoms of exposure to naled and
all organophosphate insecticides
include headaches, muscle twitching,
nausea, diarrhea, difficult breathing,
naled kills insects by inhibiting acetylcholinesterase
(AChE), an enzyme involved
in the transmission of nerve impulses
from one nerve cell to another.
This causes a “jam” in the transmission
system, resulting in restlessness,depression, seizures, and loss of consciousness.
Toxicity to the Nervous System
A symptom of exposure to naled
that occurs at low doses (whether by
breathing, through the skin, or orally)
is inhibition of acetylcholinesterase
In studies conducted by naled
manufacturers, exposure of rats to
naled in air at a dose of 0.3 milligrams
per kilogram of body weight
(mg/kg) per day for three weeks, skin
exposures of 20 mg/kg per day for 4
weeks, and oral exposure of 10 mg/
kg per day for 4 weeks caused inhibition
Long-term exposure also caused
AChE inhibition; reduced AChE activity
occurred in dogs exposed orally to
2 mg/kg per day for 1 year and in rats
exposed orally to the same dose for 2
In addition, the long-term study with
dogs found that doses of 2 mg/kg per
day also caused mineralization of the
Naled’s breakdown product dichlorvos
inhibits the activity in rats of a nervous system enzyme called neuropathy
In experiments conducted by biochemists at the Postgraduate
Institute of Medical Education and Research (India), doses of 6 mg/kg per day reduced the enzyme’s activity by about 40 percent.
Inhibition of this enzyme causes partial paralysis of the hind legs followed by
Toxicity Caused by Breathing Naled
Naled is more potent when exposure occurs through breathing than when exposure occurs through eating contaminated food or drinking contaminated
Toxicologists at the University of California found that inhalation was 20 times more toxic to rats than oral dosing (dosing through the mouth) of naled.
The U.S. Environmental Protection
Agency (EPA) came to a similar conclusion
based on tests submitted to
the agency by naled’s manufacturer:
the dose required to cause cholinesterase
inhibition through inhalation
exposure was less than 1/6 of the lowest
oral dose causing the same effect.
An additional study by the University
of California researchers mentioned
above found that small droplets
of naled (the size produced by
ultra low volume sprayers often used
in mosquito spraying) were about
four times more acutely toxic than
(EPA Registration No. 5481-480)
contains the inert ingredient aromatic hydrocarbon solvent (Chemical Abstract Services
number 64742-94-5), also called solvent naphtha.
This solvent contains two aromatic hydrocarbons,
naphthalene and 1,2,4- trimethylbenzene. Dibrom 8 Emulsive (EPA Registration No. 5481-479) contains
naphthalene. Dibrom 8 Miscible (EPA Registration No. 34704-351) contains solvents4 whose ingredients can include naphthalene and trimethylbenzene.
Naphthalene has been classified by EPA as a possible human carcinogen because it caused lung tumors
in mice following inhalation.
Naphthalene exposure also causes headaches, restlessness, lethargy, nausea, diarrhea, and anemia.
Anemia in newborns can be caused by exposure during pregnancy.
1,2,4-trimethylbenzene is irritating to eyes and skin. It can depress the central nervous system
and cause headache, fatigue, nausea, and anxiety. It has also caused asthmatic bronchitis.
Exposure to Naled’s Breakdown Product Increases Aggressiveness and Disrupts Learning
In laboratory animals, exposure to naled’s breakdown product dichlorvos causes more frequent
fighting and hinders learning.
Number of fighting episodes (per minute, with standard deviations) ore common among exposed rats
than among unexposed ones.
Exposed animals also required more trials than unexposed ones to learn an avoidance behavior, indicating a “severe deterioration in their memory and learning functions.”
Eye and Skin Irritation
Naled is a “severe” eye irritant and is “corrosive” to skin. All three frequently used commercial Dibrom products pose similar hazards.
Labels of two of the products warn “causes irreversible eye and skin damage and
the third states that it is “corrosive” and “causes eye damage and skin damage.” Skin irritation was documented by physicians soon after naled’s use in the U.S. began.
Effects on the Circulatory System
In a long-term feeding study conducted by naled’s manufacturer, naled
caused anemia in dogs at all but the lowest dose level tested. Exposures of
2 mg/kg per day reduced the number of red blood cells and the amount of hemoglobin (the oxygen-carrying pigment) in the blood.20
Effects on Reproduction
Dichlorvos, naled’s breakdown product, interferes with prenatal brain development.
Biologists at the
University of Oslo found that dosing guinea pigs with 15 mg/kg of dichlorvos twice daily for three days
during pregnancy caused a significant (15 percent) decrease in the offspring’s brain size.
The guinea pigs were dosed with dichlorvos between the 40th and 50th day of their pregnancy,
a time when the fetal brain is undergoing a growth spurt.
In addition, University of Michigan researchers showed that naled exposure causes delays in the development of rat embryos. For example, exposure of pregnant rats on the ninth day of their pregnancy caused a significant delay in the closing of the embryo’s neural tube.
Naled and dichlorvos can be passed from mothers to their offspring through nursing. German researchers found both insecticides in milk from cows that had been treated with naled.
Ability to Cause Genetic Damage (Mutagenicity)
Naled damaged bacteria’s genetic material in laboratory tests conducted
by geneticists at Monash University (Australia)24 as well as biologists at Texas Tech University.
Naled’s breakdown product DICHLORVOS also causes genetic damage.
A team of Greek and Dutch scientists found that injections of dichlorvos at weekly intervals in
mice caused a 3-fold increase in the number of mutations in liver cells.
A team of geneticists from the National Research Centre (Egypt) found that oral doses of dichlorvos given to mice, or feeding mice diclorvos-treated beans, increased the incidence of chromosome abnormalities in both spleen and sperm cells.
Ability to Cause Cancer (Carcinogenicity)
EPA classifies naled as a “Group E” chemical. Group E chemicals have
demonstrated “evidence of noncarcinogenicity” in laboratory tests.
Naled’s breakdown product
DICHLORVOS however, is classified as “possibly carcinogenic to humans,” with “sufficient evidence in experimental animals” for its carcinogenicity by the International Agency for Research on Carcinogens.
The agency gave dichlorvos this classification because it caused forestomach tumors, leukemia, and pancreatic tumors in laborators tests with rats and mice.
In children, exposure to dichlorvos has been linked with increased cancer risks. Researchers at the University of North Carolina found an association between exposure to dichlorvos “no-pest” strips during pregnancy or during childhood and the incidence of three types of childhood cancer: leukemias, brain tumors, and lymphoma.
Missouri Department of Health researchers found similar results for childhood brain cancer.
Effects on the Immune System
Both naled and its breakdown product
DICHLORVOS inhibited an enzyme in white blood cells called monocyte esterase, according to a study conducted by researchers at the Technicon Science Center.
Monocyte esterases are an “integral component”33 of the process by which white blood cells eliminate virus-infected cells from our bodies and monitor for precancerous cells.
A study submitted to EPA by Shell Chemical Co. showed that “the toxic effects of naled were potentiated by co-administration of Ciodrin, malathion, and methyl parathion. All three are insecticides in the organophosphate family.
Malnourished individuals may be particularly susceptible to naled poisoning. Researchers from the Institute
of Hygiene and Occupational Health (Bulgaria) studied naled’s effects on rats that were fed a low-protein diet and found that naled was almost twice as toxic to them as it was to rats fed a normal diet.
In addition, the rats fed a low-protein diet developed liver damage from their naled exposure.
Contamination of Food
The U.S. Department of Agriculture documented contamination of strawberries, peppers, and beans with naled’s breakdown product dichlorvos.
Insecticides in naled’s chemical family, the organophosphates, are com-
Malnutrition Increases Naled’s Toxicity
Naled inhibits the activity of an immune system enzyme. It is also more toxic to malnourished animals than animals fed a normal diet.
Median lethal dose
(milligrams per kilogram of body weight in rats)
mon contaminants of urban streams
However, neither naled
or its breakdown product dichlorvos
were included in the national water
quality monitoring program currently
being conducted by the U.S. Geological
This means that no systematic
information is available about
naled contamination of U.S. streams,
rivers, or wells.
EPA also does not
have monitoring data for naled or its
breakdown products in ground or surface
Naled can persist in air up to several
days after treatment. University of
California, Davis toxicologists measured
both naled and its breakdown product
dichlorvos in the air around a naledtreated
orange grove for three days
Aerial applications of naled drift (move from the target site during application) for significant distances. Entomologists from the University of
Florida measured naled contamination
750 meters (2400 feet) downwind from
sprayed areas. They suggest that nospray
buffer zones greater than 750
meters in width “be placed around ecologically
Effects on Beneficial Insects
Because it is a broad spectrum insecticide,
it is not surprising that naled
impacts beneficial insects, those that
provide important economic benefits
to farmers. In a study submitted as
part of naled’s registration process,
naled was “highly toxic”42 to honey
bees. Follow-up studies found that this
toxicity decreased rapidly during the
first day after treatment.42 Naled’s
toxicity to other species of bees
(alfalfa leafcutting bees and alkali
bees) is more persistent than for honey
bees.43 It can “mimic long residual
[persistent] materials,” reducing
leafcutting bee numbers 48 hours after
Parasitoid wasps (wasps that lay
their eggs in juvenile stages of other
insects, which then are killed as the
wasps hatch and develop) can also be
poisoned by low-level exposure to naled.
Naled (and Dichlorvos)Inhibit the Immune System
According to U.S. Department
of Agriculture researchers, a wasp that
parasitizes fruit flies was killed by a
naled and protein bait mixture designed
to kill fruit flies.
Naled is also highly toxic to a
A University of Florida zoologist
studied areas in Florida where regular
mosquito spraying occurred with
Dibrom and another insecticide. He
found a “major loss” in insect diversity
in sprayed sites. Wasps showed
“some of the most dramatic drops in
species diversity.”47 Scale insects,
whose populations are normally controlled
by parasitic wasps, increased.
Effects on Birds
According to EPA, naled is moderately
to highly toxic to birds. The most sensitive
species tested by naled’s manufacturer
during the registration process
was the Canada goose, killed by 37
mg/kg of naled.
According to tests conducted by
naled’s manufacturer, this insecticide
also affects bird reproduction. Mallard
ducks eating food treated with naled
laid fewer eggs, produced fewer viable
eggs, and hatched fewer ducklings
than unexposed mallards.
Effects on Fish
According to EPA, naled is very
highly toxic to lake trout; highly toxic
to rainbow trout, cutthroat trout, and
catfish; and moderately toxic to sunfish,
minnow, and bass. The most
sensitive species in tests submitted
to EPA by naled’s manufacturer was
lake trout, with an LC50 (median lethal
concentration; the dose required
to kill 50 percent of test animals) of
87 parts per billion (ppb).
Naled also causes effects on fish
other than death. In a test conducted
by naled’s manufacturer, a concentration
of 15 ppb impaired the growth of
Effects on Other Aquatic Animals
Ecologically important insects are
killed by naled. According to a naled
manufacturer, a concentration of 8 ppb
kills stoneflies.50 Research conducted
by the Arctic Health Research Center
(Alaska) showed that water striders
were killed 300 feet from a naled
Stoneflies are important nutrient
cyclers in streams and water striders
are scavengers and predators.
Aquatic arthropods are also impacted
by naled. Waterfleas are killed
by less than 0.5 ppb of naled in tests
conducted by naled’s manufacturer,
and less than 0.2 ppb disrupts
waterflea growth. Shrimp are killed
by less than 10 ppb.
According to EPA, naled is “very
highly toxic” to oysters.
Sea urchins are also sensitive to
naled exposure. University of Miami
researchers showed that concentrations
of less than 4 ppb disrupt normal
development of embryos.
Effects on Endangered Species
Evaluations by both EPA and the
U.S. Fish and Wildlife Service have
concluded that use of naled puts endangered
mammals, fish, mussels, and
other species at risk.
In addition, there is field evidence
of naled’s hazards for endangered
Dibrom spraying (along with
spraying of another insecticide) was
“directly correlated with the precipitous
decline in the Schaus Swallowtail
populations on Key Largo [FL], according
to a University of Florida zoologist.
This swallowtail is listed as an
endangered species under both Florida
and federal law.
A University of Florida entomologist
studying a different rare butterfly,
the Florida lacewing, found higher
populations in unsprayed areas than
in sprayed areas. (See Figure 7.) He
concluded that “it is likely that chemical
applications play an important role
in affecting the population size and
behavior of these species.
Effects on Plants
Insecticides are typically not expected
to damage plants. However,
University of California researchers
showed that naled treatment caused
brown lesions in celery and bronzing
of strawberries.The strawberry
damage was accompanied by reduced
photosynthesis (using sunlight to produce
sugars) and closing of leaf openings
(stomata).60 Brazilian researchers
found that naled also “drastically reduced”
tomato pollen germination.
In aquatic plants, naled reduces
photosynthesis. In laboratory tests, a
naled concentration of 1 ppm reduced
photosynthesis by estuary algae by
over 50 percent.
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