|Chemical Abstract Number (CAS #)||
|Synonyms||Fensulfothion||Phosphorodithioic acid, O,O-diethyl O-[4-(methyl sulfinyl)phenyl] ester||Dasanit||Daconit||Agricur
||EPA Method 8141A|
Link to the National Library of Medicine's Hazardous Substances
Database for more details
on this compound.
|Use|| INSECTICIDE AGAINST SOIL INSECTS; MOSQUITO LARVICIDE
INSECTICIDE & NEMATOCIDE PRINCIPALLY FOR TOBACCO, CORN, AND
VARIOUS OTHER CROPS
Nematocide-Insecticide that kills by contact action. Effectively controls insects inhabiting soil
and controls in a limited manner attacking insects.
|Consumption Patterns|| ABOUT 80% AS AN INSECTICIDE & NEMATOCIDE FOR TOBACCO; MOST OF
BALANCE AS AN INSECTICIDE & NEMATOCIDE FOR CORN (1974)
|Apparent Color|| BROWN LIQUID; YELLOW OIL
|Boiling Point|| 138-141 DEG C @ 0.01 MM HG
|Molecular Weight|| 308.35
|Density|| 1.202 @ 20 DEG C/4 DEG C
|Sensitivity Data|| EXPT USING 5% GRANULAR FORMULATION APPLIED AIRTIGHT FOR 2 HR
TWICE EACH DAY TO FOREARM OF 3 PERSONS FOR 5 CONSECUTIVE DAYS,
PRODUCED SKIN IRRITATION
|Environmental Impact|| Fensulfothion is a commercially produced insecticide and nematocide. The dominant
source of its release to the environment is likely its application as a pesticide. If released to soil,
fensulfothion will be transformed by microbial degradation and chemical hydrolysis. Adaptation of
soil microbes has been demonstrated to be important which significantly shortens the persistence
of fensulfothion upon annual reapplication. The estimated Koc values of 77 and 105 suggest that
fensulfothion may be susceptible to significant leaching in many soil types. A correlation between
increased adsorption with increasing soil organic content has been demonstrated. In soils of very
high organic content (65%), such as onion fields in which fensulfothion has pesticidal use,
fensulfothion has been shown to be retained in the upper soil layers. Volatilization from soil is not
expected to be significant. The initial persistence half-life of fensulfothion in soil which has not
received previous fensulfothion treatment has been observed to vary from less than one week to
several weeks. If released to the aquatic environment, fensulfothion will hydrolyze; the measured
hydrolysis half-life in pure water at 25 deg C is 58-87 days over the pH range of 4.5 to 8.0.
Microbial degradation in natural water may also be important, especially under anaerobic
conditions. Fensulfothion is not expected to volatilize, bioconcentrate in aquatic organisms, or
adsorb to sediments significantly in natural waters. If released to the atmosphere, vapor-phase
fensulfothion will react rapidly with a resultant estimated half-life of 7.03 hours at 25 deg C in
atmosphere with a typical average concentration of 8X10 5 hydroxyl radicals/cu m. However,
fensulfothion will not react with ozone. If released to air in solid-phase, such as dusts or mists
generated by pesticidal application, fensulfothion is likely to be removed from the air by dry
deposit. Localized removal by rainfall washout may be possible. Occupational exposure by
inhalation and dermal routes related to the use of fensulfothion as a pesticide may be significant.
|Environmental Fate|| AFTER APPLICATION TO PASTURE PLOTS, IN ADDITION TO UNCHANGED
FENSULFOTHION, FENSULFOTHION SULFONE & FENSULFOTHION OXYGEN
ANALOG SULFOXIDE & SULFONE WERE ALSO FOUND.
TERRESTRIAL FATE: Fensulfothion degraded rapidly in a sandy loam soil to the moderately
persistent metabolite fensulfothion sulfone . Field application of 50 ppm fensulfothion was
reduced to 5 ppm after 120 days in the first year of application; however, in the second year of
application, less than 0.2 ppm remained after 60 days, which was attributed to microbial
adaptation . In laboratory studies, the initial half-life of fensulfothion in a sandy loam soil
(organic matter 2.9%) and in an organic soil (organic matter 48.7%) was less than one week and
one week, respectively, but was greater than 24 weeks in the same soils which had been sterilized
by autoclaving . Initial fensulfothion concn of 50-175 ppm persisted for 50-60 days in a
laboratory soil, whereas initial concn of 250-500 ppm persisted for up to 900 days . In a
greenhouse study using an organic soil containing 65% organic matter, the initial half-life of
fensulfothion applied at normal insecticidal concn was about 3-5 weeks with a slightly faster
disappearance exhibited in wetter soil . Persistence of fensulfothion (as measured by larvae
mortality) varied from 3-10 weeks in greenhouse and field studies of a sandy loam soil(6). Based
on the available data, microbial degradation appears to be a major transformation process for
fensulfothion in soil; chemical hydrolysis in moist soils may also contribute to its
transformation. The estimated Koc value of 77 and 105 suggest that fensulfothion may be
susceptible to significant leaching in many soil types; however, in soils of very high organic
content (65%), fensulfothion has been shown to be tightly retained in the upper soil layers . A
correlation of stronger adsorption of fensulfothion to soils of increasing organic content has been
demonstrated(7). Based on a calculated vapor pressure of 6.82X10-7 mm Hg at 25 deg C (8) and
an expectation of tight adsorption in high organic matter soils, fensulfothion is not expected to
volatilize significantly from soil.
AQUATIC FATE: The persistence of fensulfothion in both sterile and non-sterile natural water
at 20 deg C was approximately the same with a half-life of about 16 weeks; under anaerobic
conditions, the fensulfothion disappeared from the non-sterile natural water in 8-12 weeks with
almost complete conversion to fensulfothion sulfide . The hydrolysis half-life of fensulfothion in
pure water at 25 deg C has been measured to be 58 to 87 days over the pH range of 4.5 to 8.0.
Based on estimated Koc values of 77 and 105, fensulfothion adsorption to aquatic sediment is not
expected to be significant. Volatilization and bioconcentration are also not expected to be
significant process in water. Based on the available data, hydrolysis and biodegradation are
expected to be the important aquatic removal mechanisms for fensulfothion.
ATMOSPHERIC FATE: Vapor-phase fensulfothion will react rapidly with photochemically
produced hydroxyl radicals with a resultant estimated half-life of 7.03 hours at 25 deg C, but will
not react with ozone. Fensulfothion dusts or mists released to the air by insecticidal applications
are likely to be removed from the air by dry deposition, with the time required for deposition
dependent on particle size and climate. Localized removal by rainfall wash-out may be possible.
Fensulfothion is among the most persistent nematocides, but significant carry-over in soil from
year to year is unlikely. Persistence in soil at 10 ppm initial concentration was 50% in > 24 weeks
for sterile sandy loam and organic soil; 5% in about 5 weeks for non-sterile sandy loam and
organic soil. One year after fensulfothion application, the residues of both fensulfothion and its
oxidative metabolite had disappeared.
Laboratory studies were conducted to assess fensulfothion persistence in soil. Persistence varied
from 50-60 days with concentrations of 50-175 ppm. At concentrations of 250 ppm or more,
fensulfothion persisted for more than 900 days in soil.
Greenhalgh R; Read DC; Persistence of Fensulfothion in a Sand-Loam Soil and Uptake by
Rutabagas, Carrots and Radishes Using Microplots; Field microplots were treated with 141 and
282 ppm fensulfothion (FSO) and 37.1 and 74.2 ppm fensulfothion sulfone (FSO2). The soil in
the microplots consisted of 67.1% sand, 25.1% silt, 7.8% clay, and 2.6% organic matter. The pH
of the soil was 5.7. The water content of the air-dried soil samples ranged from 0.9 to 1.8%.
The calculated half-life values for FSO were 35 and 39 days, respectively for the 8.48 and 16.96
kg AI/ha treatments in 1978, and 31 and 30 days in 1979. A calculated half-life of 14-23 days
was found for FSO2, which was less than that of the parent insecticide.
|Drinking Water Impact|| GROUNDWATER: No residues of fensulfothion were detected at the minimum
detectable level of 5.0 ppb in 27 wells sampled in areas of agricultural usage in California .
Methods (gas chromatog and HPLC) were developed for the detn of >50 pesticides in
wastewaters. A detection limit of apprx 1.5 ug/l was achieved for Fensulfothion/.
EFFL: Fensulfothion has been detected (no concentration available) in run-off water from
agricultural fields treated with the insecticide .