| Chemical Abstract Number (CAS #) |
121755
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| Synonyms | Malathion |
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Succinic acid, mercapto-, diethyl ester, S-ester with O,O-dimethyl phosphorodithioate | Sumitox | Phosphothion |
| Analytical Method |
EPA Method 8141A |
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| Molecular Formula | C10H19O6PS2 |
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| Use | MEDICATION: PEDICULICIDE; MEDICATION (VET): ECTOPARASITICIDE
Insecticide used for many insects including aphids, spider mites, scale insects, house fly, &
mosquitoes as well as large number of other sucking & chewing insects attacking fruits,
vegetables, ornamentals, & stored products; Adult mosquito control in public health programs
INSECTICIDE FOR NON AGRICULTURAL USES-EG, AQUATIC USES, LIVESTOCK,
POULTRY, HOME & GARDEN USES, LAWNS, TURF & ORNAMENTALS,
COMMERCIAL, HOUSEHOLD & INDUSTRIAL USES, COTTON, VEGETABLES, &
CITRUS, OTHER FIELD CROPS-EG, CORN & SORGHUM, DECIDUOUS FRUITS/NUTS
& WHEAT, STORAGE BINS & TRANSPORTATION EQUIPMENT ACARICIDE
Insecticide to control fruit flies
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| Consumption Patterns | INSECTICIDE FOR AQUATIC USES, 15%; LIVESTOCK/POULTRY, 7%; OTHER
NON AGRICULTURAL USES-EG, HOME & GARDEN, LAWN, TURF, ORNAMENTAL,
COMMERCIAL, HOUSEHOLD & INDUSTRIAL USES, 33%; COTTON, 14%;
VEGETABLES, 10%; ALFALFA, 4%; TOBACCO, 3%; CITRUS, 1%; OTHER FIELD
CROPS-EG, CORN, DECIDUOUS FRUITS/NUTS, SORGHUM & WHEAT, 11% (1982)
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| Apparent Color | Clear colorless liquid when pure ; DEEP BROWN TO YELLOW LIQUID
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| Odor | SKUNK-LIKE ODOR
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| Boiling Point | 156-157 DEG C AT 0.7 MM HG
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| Melting Point | 2.9 DEG C
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| Molecular Weight | 330.36
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| Density | 1.23 AT 25 DEG C/4 DEG C
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| Odor Threshold Concentration | 1.00 ppm (detection in water, purity not stated)
Odor thresholds: 13.5000 mg/cu m (low); 13.5000 mg/cu m (high)
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| Sensitivity Data | Irritating to the eyes.
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| Environmental Impact | Release of malathion to the environment will occur as a result of its manufacture and use
as a broad spectrum insecticide and acaricide. If malathion is released to soil, it should moderately
bind to the soil, and will be subject to significant biodegradation and hydrolysis. Reported half
lives in soil range from approximately 4 days to a reported literature avg of 6 days. If malathion is
released to water it may moderately sorb to sediment, but will not be expected to bioconcentrate
in aquatic organisms. It should be subject to biodegradation and may be subject to
photodegradation at the surface of water. Hydrolysis in water may be an important fate process
based on reported half life range of 0.2 weeks at pH 8.0 to 21 weeks at pH 6.0. Volatilization
from water should not be an important fate process. If malathion is released to the atmosphere it
may be subject to direct photolysis. The estimated vapor phase half life in the atmosphere is 1.50
days as a result of hydrogen abstraction by photochemically produced hydroxyl radicals.
Occupational exposure to malathion will occur mainly from dermal contact and inhalation of
contaminated air as a result of its use as an insecticide and acaricide. General exposure may result
from the consumption of contaminated food. Minor exposure may occur from the consumption of
contaminated water.
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| Environmental Fate | TERRESTRIAL FATE: If malathion is released to soil, it may moderately sorb to the soil.
Hydrolysis may be important based on the hydrolysis rate in water with a reported degradation of
50-90% in 24 hr in both sterile and non sterile soils . Biodegradation may be an important fate
process, especially in soils at < pH 7 where the rate of hydrolysis may be slow relative to the rate
of biodegradation. The major metabolite in soil is malathion beta monoacid. Reported half lives in
soil range from approximately 4 days to a reported literature avg of 6 days . Percent
degradation, range (avg), in 4 West Bengal soils between 3 and 7 days after treatment with
malathion in dry, moist, waterlogged soils, respectively, were: 33-86%(70%), 15-40%(33%), and
20-54%(37%); 100% overall degradation reported within 20 days for all 3 conditions . Based
on the range of Koc reported and the rapid degradation of malathion in soils, it should not leach
to the groundwater.
AQUATIC FATE: If malathion is released to water it may moderately sorb to sediment but will
not be expected to bioconcentrate in aquatic organisms. Hydrolysis half lives in water range from
0.2 weeks at pH 8.0 to 21 weeks at pH 6.0 . Products of hydrolysis include malaoxon,
malathion alpha and beta monoacid, O,O-dimethylphosphorodithioic acid, diethyl fumarate,
diethyl thiomalate, O,O-dimethylphosphorothionic acid. Photodegradation may compete with
hydrolysis as an important degradation process in certain waters; however, photolysis has been
shown to be sensitized only in water from 1 river, half life 16 hr , compared to a half life of 6
weeks in distilled water . Malathion sorbed by algae was photodegraded > 25 times faster than
malathion in distilled water . Biodegradation may be an important process, especially in waters
< pH 7.0 where the rate of hydrolysis may be slow relative to the rate of biodegradation. Products
of biodegradation include malathion, beta monocarboxylic acid and dicarboxylic acid, diethyl
thiomalate. malathion. Persistence of malathion in water from 4 rivers ranged from 52% still
present after 11 days to 21% after 14 days . Degradation of 90% malathion within 2 weeks in
raw river water (pH 7.3-8.0) compared to no change in distilled water over 3 weeks suggests that
degradation was biological(6). The major metabolite in soil was malathion beta monoacid.
Volatilization from water should not be an important fate process.
ATMOSPHERIC FATE: If malathion is released to the atmosphere it may be subject to direct
photolysis. The estimated vapor phase half life in the atmosphere is 1.50 days as a result of
hydrogen abstraction by photochemically produced hydroxyl radicals.
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| Drinking Water Impact | DRINKING WATER: Not detected in 54 of 54 California wells near areas where telone
or D-D had been applied for several years . Ottawa, Ontario, Canada, not detected (detection
limit 10-15 pg) . Malation was detected in 4 of 91 ground wells at an average concn of 0.1
ug/L . Malation was detected in 5 of 28 county water supplie in CA .
SURFACE WATER: National surface water monitoring program, 1976-80, 0.3% pos samples,
max concn 0.18 ppb . USA Pesticide Monitoring Network, 1975-80, 174 stations, 0.6% pos,
2,85 samples, 0.1% pos . Lake Erie watershed, 1971-72, 157 river water and bottom sediment
samples, not detected(nd) . Ontario, Canada, 11 agricultural watersheds, 0.8% samples pos
1975-76, nd, 1976-77, nd-1.80 ppt, overall avg < 0.01 parts per trillion max avg 1.80 . Raw
bank filtered Rhine water, West Germany, occasionally detected, not quantified . Malathion was
detected at 0.6% of 174 sampling stations of the nations river(6). Malathion was listed in the
waters of Lake Erie(7).
In Virgin Islands, where malathion is used extensively only 2 of 49 water samples taken from
cisterns contained malathion, at levels of 0.14 & 0.01 ug/kg.
EFFL: Conc within 800 m of 2 formulation plants in Arkansas: 1970, 66 samples, 33.3% pos,
0.6-5.7 ng/cu m, avg 1.9 ng/cu m; 1971, 60 samples, 18.3% pos, 0.4-4.1 ng/cu m, avg 1.6 ng/cu
m; 1972, 64 samples, 17.2% pos, 0.8-38.1 ng/cu m, avg 10.4 ng/cu m . Concn within 275 m of
formulation plant in Tennessee, 1971, 56 samples, 46.4% pos, 0.8-198.2 ng/cu m, avg 10.9 ng/cu
m .
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