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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 of this product include Basudin, Dazzel, Gardentox,
Kayazol, Knox Out, Nucidol, and Spectracide. Diazinon may be
found in formulations with a variety of other pesticides such as
pyrethrins, lindane, and disulfoton.
Diazinon is classified as a Restricted Use Pesticide (RUP) and is
for professional pest control operator use only. In 1988, EPA
canceled registration of diazinon for use on golf courses and sod
farms because of die offs of birds that often congregated in
these areas. It is classified toxicity class II - moderately
toxic, or toxicity class III - slightly toxic, depending on the
formulation. Products containing diazinon bear the Signal Word
WARNING or CAUTION.
Diazinon is a nonsystemic organophosphate insecticide used to
control cockroaches, silverfish, ants, and fleas in residential,
non-food buildings. Bait is used to control scavenger yellow
jackets in the western U.S. It is used on home gardens and farms
to control a wide variety of sucking and leaf eating insects. It
is used on rice, fruit trees, sugarcane, corn, tobacco, potatoes
and on horticultural plants. It is also an ingredient in pest
strips. Diazinon has veterinary uses against fleas and ticks. It
is available in dust, granules, seed dressings, wettable powder,
and emulsifiable solution formulations.
Formulation: It is
available in dust, granules, seed dressings, wettable powder, and
emulsifiable solution formulations.
- Acute toxicity: Toxic effects of
diazinon are due to the inhibition of
acetylcholinesterase, an enzyme needed for proper nervous
system function. The range of doses that results in toxic
effects varies widely with formulation and with the
individual species being exposed. The toxicity of
encapsulated formulations is relatively low because
diazinon is not released readily while in the digestive
tract. Some formulations of the compound can be degraded
to more toxic forms. This transformation may occur in
air, particularly in the presence of moisture, and by
ultraviolet radiation. Most modern diazinon formulations
in the U.S. are stable and do not degrade easily . The
symptoms associated with diazinon poisoning in humans
include weakness, headaches, tightness in the chest,
blurred vision, nonreactive pinpoint pupils, salivation,
sweating, nausea, vomiting, diarrhea, abdominal cramps,
and slurred speech. Death has occurred in some instances
from both dermal and oral exposures at very high levels
[2,8]. The LD50 is 300 to 400mg/kg for technical grade
diazinon in rats (2,13). The inhalation LC50 (4-hour) in
rats is 3.5 mg/L . In rabbits, the dermal LD50 is
3600 mg/kg .
- Chronic toxicity: Chronic effects have
been observed at doses ranging from 10 mg/kg/day for
swine to 1000 mg/kg/day for rats. Inhibition of red blood
cell cholinesterase, and enzyme response occurred at
lower doses in the rats. Enzyme inhibition has been
documented in red blood cells, in blood plasma, and in
brain cells at varying doses and with different species
- Reproductive effects: No data are
- Teratogenic effects: The data on
teratogenic effects due to chronic exposure are
inconclusive. One study has shown that injection of
diazinon into chicken eggs resulted in skeletal and
spinal deformities in the chicks. Bobwhite quail born
from eggs treated in a similar manner showed skeletal
deformities but no spinal abnormalities. Acetylcholine
was significantly affected in this latter study .
Tests with hamsters and rabbits at low doses (0.125 0.25
mg/kg/day) showed no developmental effects, while tests
with dogs and pigs at higher levels (1.0 10.0 mg/kg/day)
revealed gross abnormalities .
- Mutagenic effects: While some tests have
suggested that diazinon is mutagenic, current evidence is
- Carcinogenic effects: Diazinon is not
considered carcinogenic. Tests on rats over a 2-year
period at moderate doses (about 45 mg/kg) did not cause
tumor development in the test animals .
- Organ toxicity: Diazinon itself is not a
potent cholinesterase inhibitor. However, in animals, it
is converted to diazoxon, a compound that is a strong
enzyme inhibitor .
- Fate in humans and animals: Metabolism
and excretion rates for diazinon are rapid. The half-life
of diazinon in animals is about 12 hours. The product is
passed out of the body through urine and in the feces.
The metabolites account for about 70% of the total amount
excreted. Cattle exposed to diazinon may store the
compound in their fat over the short term . One study
showed that the compound cleared the cows within 2 weeks
after spraying stopped. Application of diazinon to the
skin of cows resulted in trace amounts in milk 24 hours
after the application .
- Effects on birds: Birds are quite
susceptible to diazinon poisoning. In 1988, the EPA
concluded that the use of diazinon in open areas poses a
"widespread and continuous hazard" to birds.
Bird kills associated with diazinon use have been
reported in every area of the country and at all times of
the year. Canadian geese and mallard ducks may be exposed
to LC50 concentrations in very short periods of time
after application (from 15 to 80 minutes depending on the
application rate of the pesticide). Birds are
significantly more susceptible to diazinon than other
wildlife. LD50 values for birds range from 2.75 mg/kg to
40.8 mg/kg .
- Effects on aquatic organisms: Diazinon
is highly toxic to fish. In rainbow trout, the diazinon
LC50 is 2.6 to 3.2 mg/L . In hard water, lake trout
and cutthroat trout are somewhat more resistant. Warm
water fish such as fathead minnows and goldfish are even
more resistant with diazinon LC50 values ranging up to 15
mg/L . There is some evidence that saltwater fish are
more susceptible than freshwater fish. Bioconcentration
ratios range from 200 in minnows to 17.5 for guppies.
These studies show that diazinon does not bioconcentrate
significantly in fish .
- Effects on other organisms: Diazinon is
highly toxic to bees .
- Breakdown in soil and groundwater:
Diazinon has a low persistence in soil. The half-life is
2 to 4 weeks . Bacterial enzymes can speed the
breakdown of diazinon and have been used in treating
emergency situations such as spills . Diazinon seldom
migrates below the top half inch in soil, but in some
instances it may contaminate groundwater. The pesticide
was detected in 54 wells in California and in tap water
in Ottawa, Canada, and in Japan .
- Breakdown in water: The breakdown rate
is dependent on the acidity of water. At highly acidic
levels, one half of the compound disappeared within 12
hours while in a neutral solution, the pesticide took 6
months to degrade to one half of the original
- Breakdown in vegetation: In plants, a
low temperature and a high oil content tend to increase
the persistence of diazinon . Generally the half-life
is rapid in leafy vegetables, forage crops and grass. The
range is from 2 to 14 days. In treated rice plants only
10% of the residue was present after 9 days .
Diazinon is absorbed by plant roots when applied to the
soil and translocated to other parts of the plant .
- Appearance: Diazinon is a colorless to
dark brown liquid. It has a flashpoint of 180 F .
- Chemical Name: O,O-diethyl
- CAS Number: 333-41-5
- Molecular Weight: 304.35
- Water Solubility: 40 mg/L @ 20 C 
- Solubility in Other Solvents: petroleum
ether v.s.; alcohol v.s.; benzene v.s. 
- Melting Point: Decomposes @ >120 C
- Vapor Pressure: 0.097 mPa @ 20 C 
- Partition Coefficient: Not Available
- Adsorption Coefficient: 1000 (estimated)
- ADI: 0.002 mg/kg/day 
- MCL: Not Available
- RfD: 9 x 10-5 mg/kg/day 
- PEL: Not Available
- HA: 6 x 10-4 mg/L (lifetime) (8)
- TLV: 0.1 mg/m3 (8-hour) 
P.O. Box 18300
Greensboro, NC 27419-8300
- Phone: 800-334-9481
- Emergency: 800-888-8372
References for the information in this PIP can be found in
Reference List Number 5
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