| Chemical Abstract Number (CAS #) |
86500
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| Synonyms | Azinphos-methyl |
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Guthion | Phosphorodithioic acid, O,O-dimethyl ester, S-ester with
3-(mercaptomethyl)-1,2,3-benzotriazin-4(3H)-one | Gusathion |
| Analytical Method |
EPA Method 8141A |
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| Molecular Formula | C10H12N3O3PS2 |
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| Use | Nonsystemic insecticide and acaricide
Organosphosphate insecticide, acaricide, moluscicide
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| Consumption Patterns | INSECTICIDE FOR DECIDUOUS FRUITS & NUTS, 53%; COTTON, 17%;
SOYBEANS, 10%; VEGETABLES, 10%; CITRUS, 3%; OTHER FIELD CROPS, 7% (1982)
(1978) 1.09X10 9 G (CONSUMPTION-INCL IMPORTS)
(1982) 1.36X10 9 G (CONSUMPTION-INCL IMPORTS)
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| Apparent Color | Colorless crystals ; BROWN WAXY SOLID
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| Melting Point | 73-74 DEG C
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| Molecular Weight | 317.34
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| Density | 1.44 @ 20 DEG C/4 DEG C
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| Odor Threshold Concentration | Detection: 0.0002 mg/kg water
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| Sensitivity Data | Irritating to eyes and skin.
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| Environmental Impact | Azinphosmethyl is used as a nonsystemic insecticide and acaricide on citrus, cotton,
grapes, corn, and some ornamentals, top fruit, and vegetables. Azinphosmethyl released to soil
surfaces will probably not be persistent. In one field study, 50% of the azinphosmethyl applied as
an emulsion was lost in 12 days. Biodegradation and volatilization are most likely the primary
degradation and transport processes, respectively, for azinphosmethyl released to soil surfaces or
incorporated in the upper several inches of soil. Azinphosmethyl will be relatively immobile in soil
and thus is not expected to leach extensively. Chemical hydrolysis is probably not important
except possibly in alkaline soils. If released to water, azinphosmethyl will have a low to medium
tendency to sorb to sediments and suspended solids or to bioconcentrate. Volatilization from
water is probably not an important transport process since the estimated Henry's Law constant is
very low. Biodegradation is probably the most important degradative process for azinphosmethyl
in natural waters while chemical hydrolysis is probably not significant except in alkaline waters
(half life 28 days in pH 8.6 and 25 deg C). No information was found on photolysis. An estimated
half-life for reaction of azinphosmethyl with photochemically generated hydroxyl radicals in the
vapor phase of the atmosphere is 6.1 hours. Azinphosmethyl has been found in unspecified fruits
and vegetables and in beans. No other monitoring information was available. Exposure to
azinphosmethyl may occur through its use as an insecticide and from the consumption of fruits
and vegetables that contain it.
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| Environmental Fate | AZINPHOS METHYL WAS APPLIED TO SUGARCANE RUNOFF PLOTS AT 0.22
KG/HA, 4 TIMES/YR IN 1980 AND 1981 AS PART OF AN INSECT INTEGRATED PEST
MANAGEMENT SYSTEM RESEARCH EVALUATION OF SEASON LONG CONTROL OF
THE PRIMARY SUGARCANE INSECT PEST, THE SUGARCANE BORER (DIATRAEA
SACCHARALIS). RUNOFF SAMPLES (WATER SEDIMENT) WERE COLLECTED
WITHIN 8 HR AFTER EACH STORM AND ANALYZED BY GAS CHROMATOGRAPHY.
IN 1980, RUNOFF LOSSES WERE 0.02% OF THE AMOUNT APPLIED. RUNOFF IN 1981
WAS TWICE THAT IN 1980, PARTIALLY ACCOUNTING FOR LARGER INSECTICIDE
RUNOFF LOSSES MEASURED, 0.56% OF THAT APPLIED. THE LARGER 1981 LOSSES
ALSO WERE ATTRIBUTED TO SHORTER TIME INTERVALS BETWEEN INSECTICIDE
APPLICATIONS AND RUNOFF EVENTS. AZINPHOS METHYL CONCENTRATIONS IN
RUNOFF ARE NOT HARMFUL TO SURROUNDING AQUATIC HABITATS.
TERRESTRIAL FATE: Half-lives (days) for azinphosmethyl in a dry (2-3% moisture content)
and wet (50% moisture content) soil were: 484 and 64 (6 deg C), 88 and 13 (25 deg C), and 32
and 5 (40 deg C) . When azinphosmethyl was applied as an emulsion to a soil surface in the
field, 50% of it was lost in 12 days and when incorporated in granular form into the upper 4-5
inches of the soil, 50% was lost within 28 days . In this Wisconsin field study, soil samples
collected in May, one year after the insecticide application, contained residue levels of
azinphosmethyl that were similiar to those determined in October of the previous year. Although
the soil had been rototilled to a depth of 4-5 inches, 90-100% of the total recovered insecticide
from a 9 inch deep sample were located in the upper 3 inch soil layer. Two years after
azinphosmethyl application, no residues were detected in a 6 inch deep soil sample; however,
from 0.01-0.03 ppm were found in the upper 3 inch soil layer . In 1980 and 1981, runoff losses
were 0.02% and 0.56% of the amount applied respectively(9). Azinphosmethyl will not leach
extensively in soils(3,4,5,6). One study estimated that azinphosmethyl will leach < 20 cm per cm
of annual rainfall in a loam soil at 25 deg C . An estimated Koc for methyl is 638.
Azinphosmethyl will biodegrade in soil(7,8). Chemical hydrolysis is probably not important except
in alkaline soils.
AQUATIC FATE: Azinphosmethyl released to waters will have a low to medium tendency to
sorb to sediments and suspended solids or to bioconcentrate. Volatilization from water is probably
no important because of the low Henry's Law constant. The most important removal mechanism
for azinphosmethyl in water, based on available soil studies and screening tests, will probably be
biodegradation. Studies with aquatic water/sediment microcosms at 5 mg/1 and pH 6.7 indicate
half-lives of 3.3 days in microcosms compared to 2.7 days in field studies . Chemical hydrolysi
is probably not important except in alkaline waters. No information was found o photolysis.
ATMOSPHERIC FATE: An estimated half-life for vapor phase azinphosmethyl is 1.3 hours due
to reaction with hydroxyl radicals .
AQUATIC FATE: BEHAVIOR OF AZINPHOS METHYL IN WATER ITS HALF LIFE
IN BOTH LAB & NATURAL WATER SYSTEMS WAS FOUND TO BE 30-70 DAYS @ PH
OF 5.1-8.4. THE HIGHER THE PH, THE LESS PERSISTENT THE CMPD SEEMED TO BE.
TERRESTRIAL FATE: KINETICS OF AZINPHOS METHYL PERSISTENCE IN SOIL WAS
STUDIED. LOSSES OF INSECTICIDE FOLLOWED FIRST ORDER KINETICS.
MOISTURE & TEMP AFFECTED PERSISTENCE OF AZINPHOS METHYL. HALF LIFE
VARIED FROM 5 DAYS (40 DEG C AND WET) TO 484 DAYS (6 DEG C WET OR DRY).
HALF-LIFE 36.4 DAYS IN WATER @ 6 DEG C WITH PH 8.6.
TERRESTRIAL FATE: Field tests with azinphosmethyl indicated that on treated apple trees the
half-life of this pesticide was about 2.6 to 6.3 days.
Half life in a nonsterile soil is 21 days under aerobic condition and 68 days under anaerobic
conditions in sterile conditions half life of 355 days/. Under aerobics conditions metabolites
were oxygen analog residues, mercaptomethyl benzazimide, benzazimide, hydroxymethyl
benzazimide, and bis-(methyl benzazimide)sulfide.
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| Drinking Water Impact | SURFACE WATER: Lake Pamvotis, Greece azinphosmethyl concentrations run from no
data to 16 ng/l, highest concentrations are found in the summer months near the city of
Ioannina . Canal concentrations were only detected in June samples ranging from 7-17 ng/l .
River concentrations were highest during summer months, values ranged from no data to 25 ng/l
over a year's time . High summer pesticide concentrations are accountable because of a lower
volume of water and spring application of pesticides to fields .
GROUNDWATER: Azinphosmethyl was not detected in farm wells in Canada: 11 wells in 1981
and 1982; 91 wells in 1984 and 179 wells in 1986 and 1987 .
EFFL: Air emissions of 0.16 kg of sulfur dioxide, 0.13 kg of nitrous oxide, 0.75 kg of
hydrocarbons and 0.5 kg of guthion per metric ton of pesticide produced have been reported.
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