| Chemical Abstract Number (CAS #) |
563122
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| Synonyms | Ethion |
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Phosphorodithioic acid, S,S'-methylene O,O,O',O'-tetraethyl ester | Bladan | Nialate |
| Analytical Method |
EPA Method 8141A |
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| Molecular Formula | C9H22O4P2S4 |
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| Use | INSECTICIDE AND ACARICIDE FOR CITRUS FRUIT, APPLES, NUTS, OTHER
FRUIT, & COTTON
It is used as a cattle dip for ticks and as a treatment for buffalo flies.
/IT IS USED FOR CONTROL OF APHIDS, MITES (INCLUDING ERIOPHYD MITES),
SCALES, THRIPS, LEAFHOPPERS, MAGGOTS, AND FOLIAR FEEDING LARVAE. ON A
WIDE VARIETY OF FOOD, FIBER, & ORNAMENTAL CROPS.
ETHION IS A NON-SYSTEMIC INSECTICIDE & ACARICIDE USED ON APPLES,
PARTICULARLY WITH PETROLEUM OILS ON DORMANT TREES, TO KILL EGGS &
SCALES. IT IS ALSO USED IN CONTROL OF BOOPHILUS SPP ON CATTLE IT
IS NON-PHYTOTOXIC EXCEPT TO APPLE VARIETIES MATURING WITH OR BEFORE
EARLY MCINTOSH.
A series of pesticides were classified as follows: those which are non-toxic to both spores and
mycelia of Trichoderma viride (group I), those which are moderately toxic to spores and mycelia,
or toxic either to spores or mycelia (group II), and those which are toxic both to spores and to
mycelia (group III). Ethion was found to be a member of group I and could be used with T viride
in soil-borne fungal pathogen control.
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| Consumption Patterns | 70% AS AN INSECTICIDE & ACARICIDE ON CITRUS FRUIT; 30% AS AN
INSECTICIDE & ACARICIDE ON OTHER FRUIT, NUTS, & COTTON (EST) (1974)
Applied to melons, 50.1%; Tree fruits, 2.6%; Citrus, 12.8%; Grapes, 4.5%; Other vegetables,
nuts, and fruits account for remainder (1984) California use, calculated from table
(1984) 4.68X10 7 g used in California
(1984) 4.68X10 7 g used in California
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| Apparent Color | COLORLESS TO AMBER-COLORED LIQUID
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| Melting Point | -12 TO -13 DEG C
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| Molecular Weight | 384.48
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| Density | 1.220 @ 20 DEG C/4 DEG C
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| Environmental Impact | Ethion is released directly into the environment in its application as an insecticide and
acaricide. If released to soil, microbial degradation may be an important process for the removal
of ethion based on degradation studies with sterile versus nonsterile soils. Ethion is susceptible to
slow aqueous hydrolysis at acidic and neutral conditions with the hydrolysis becoming relatively
rapid at pHs approaching 9 and above; therefore, hydrolysis may be the dominant transformation
mechanism in very alkaline moist soils. Based on measured Koc values of 6451 to 15435, ethion
is not expected to leach in soil. The persistence half-life of ethion in various soils under laboratory
conditions has been found to vary from 1.3 to 8 weeks. Greenhouse and field studies with an
organic soil have found half-lives of 16 to 49 weeks and significant carry-over from one planting
season to the next. If released to water, microbial degradation may not be important in relation to
abiotic processes based on degradation studies with natural waters versus sterilized natural
waters. The hydrolysis half-lives of ethion at 25 deg C are 63, 58, 25, and 8.4 weeks at pHs 5, 6,
7, and 8, respectively, with a half-life of 1 day at pH 10 and 30 deg C. Ethion may be susceptible
to some photooxidation in sunlit natural water. The high measured Koc values suggest that
adsorption to sediment will be an important transport process. Based on a measured log Kow of
5.073, bioconcentration is potentially significant. Volatilization of ethion from water is not
expected to be important, with the possible exception of rapidly moving shallow streams. The
persistence half-life of ethion in three different natural waters under laboratory conditions was
found to vary from 4 to 22 weeks; it was suggested that the faster rate of degradation in one of
the natural waters was due to the presence of dissolved ions which caused an unidentified
catalytic effect. If released to the atmosphere, ethion will exist in both the vapor-phase and
adsorbed-phase, although the adsorbed-phase may dominate. In the vapor-phase, ethion will react
rapidly with photochemically produced hydroxyl radicals at an estimated half-life rate of 6.95
hours. Ethion in the adsorbed-phase will be subject to wet and dry deposition. General population
exposure to ethion may occur through ingestion of contaminated food, particularly fruits and root
vegetables. Occupational exposure may occur through inhalation and dermal routes associated
with the insecticidal use of ethion.
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| Environmental Fate | Aquatic Fate: Degradation of ethion in irrigation canal waters draining a citrus grove in
South Florida occurred readily by hydrolysis with a half-life of 26 days. The reaction was pH
independent from pH 4-7 with a pseudo-1st-order rate constant of 4.8/days. Adsorption to canal
sediments was negligible and desorption was rapid. Ethion did not accumulate in the sediment and
water sample levels, never exceeded 0.017 mg/l in the water or 0.03 mug/g (dry wt) in the
sediments. Hydrolysis may have been a significant mechanism in the loss of ethion from irrigation
canal waters.
Terrestrial Fate: Ethion, fonofos, fensulfothion, carbofuran, or chlorpyrifos were applied as a
commercial granular formulations at rates equivalent to 2.24, 1.12, 1.12, 1.68, and 1.68 kg AI
(active ingredient)/ha, respectively, to furrows in a greenhouse and subjected to 4 different
watering schedules (normal, 0.5, 1.0, and 1.5 ml/sq cm). Persistence & movement were measured.
Ethion moved slightly faster in the 2 wetter soils. Unretained water did not contain significant
concn of pesticides. Plots were treated with insecticide & seeded with onions for 3 successive yr.
Residue (ethion) in the soil after 3 yr was 7.6 ppm.
TERRESTRIAL FATE: Under laboratory conditions, the half-lives of ethion in a sandy loam soil
and organic soil were found to be 7 and 8 weeks, respectively , while the half-life in red, black,
and laterite soil was 9.0-15.5 days in the laboratory . In greenhouse tests using an organic soil,
the half-life of ethion varied from 16 to 49 weeks depending upon the degree of watering ; field
tests using the same organic soil over a 3-year period (with ethion application in the spring of
each year) found a significant carry-over of ethion residue from the autumn to the following
spring with eventual accumulation of ethion in the soil in the 2nd and 3rd year . When applied
to an organic soil in granular form in the spring, about 25% of the ethion was carried over to the
following spring in field tests in Ontario . Microbial degradation of ethion may be an important
process in its removal from soil based on degradation studies with nonsterile versus sterile soils.
Ethion is susceptible to slow aqueous hydrolysis at acidic and neutral conditions with the
hydrolysis becoming relatively rapid at pHs approaching 9 and above; therefore, in very alkaline
moist soils, hydrolysis will probably be the dominant removal mechanism. Based on measured
Koc values of 6451 to 15435, ethion is not expected to leach in soil. .
AQUATIC FATE: Degradation studies with natural waters versus sterilized natural waters have
suggested that microbial degradation of ethion is not important in relation to abiotic processes.
The hydrolysis half-lives of ethion at 25 deg C are 63, 58, 25, and 8.4 weeks at pHs 5, 6, 7, and 8,
respectively, with a half-life of 1 day at pH 10 and 30 deg C. Since ethion is susceptible to rapid
photooxidation in the vapor-phase and slow oxidation in the solid-phase, photooxidation in sunlit
natural water may be possible, although the relative significance of this process has not been
estimated. Based on high measured Koc values (6451-15435), adsorption to sediment and
particulate organic matter in water is expected to be a significant fate process. The volatilization
half-life from a river one meter deep flowing 1 m/sec with a wind velocity of 3 m/sec has been
estimated to be 14.6 weeks, however, adsorption to sediment may significantly attenuate the
potential rate of volatilization. In addition, the rate of volatilization will be significantly slower in
deeper bodies of water or in more stagnant bodies of water; therefore, ethion volatilization is not
expected to be an important fate process, with the possible exception of shallow, rapidly moving
streams. Based on a measured log Kow of 5.073, bioconcentration is potentially significant. The
persistence half-life of ethion in three different natural waters under laboratory conditions was
found to vary from 4 to 22 weeks(1,2,3). It was suggested that the faster rate of degradation in
one of the natural waters was due to the presence of dissolved ions which caused an unidentified
catalytic effect(1,SRC).
ATMOSPHERIC FATE: Based on a vapor pressure of 1.5X10-6 mm Hg at 25 deg C , ethion
will exist in both the vapor-phase and adsorbed-phase in the ambient atmosphere, although the
adsorbed-phase may dominate(2,SRC). In the vapor-phase, ethion will react rapidly with
photochemically produced hydroxyl radicals at an estimated half-life rate of 6.95 hours. Ethion in
the adsorbed-phase will be subject to wet and dry deposition .
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| Drinking Water Impact | DRINKING WATER: Ethion has reportedly been identified in German drinking
water .
SURFACE WATER: Ethion was detected in 0.1% of 2823 water samples collected at 174
stations of the US Geological Survey-USEPA Pesticide Monitoring Network between 1975 and
1980 . Ethion has been qualitatively identified in tributaries feeding Lake Erie, Lake Huron and
Lake St. Clair . Ethion was detected to 0.4% of all water samples collected from 11 agricultural
watersheds in Ontario in 1975-1976 monitoring and had a maximum concn of 0.04 ppb; it was not
detected in 1976-1977 monitoring .
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