Environmental Fate
Soil. Metabolites of endosulfan identified in soils were endosulfandiol (1,4,5,6,7,7-
hexachlorobicyclo[2.2.1]hept-5-ene-2,3-dimethanol), endosulfan ether, endosulfan lactone
(4,5,6,7,8,8-hexachloro-1,3,3a,4,7,7a-hexahydro-4,7-methane-isobenzofuran-1-one) and
endosulfan sulfate (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,3,4-
benzodioxathiepin-3,3-dioxide) (Martens, 1977; Dreher and Podratzki, 1988). These compounds,
including endosulfan ether, were also reported as metabolites identified in aquatic
systems (Day, 1991). Endosulfan sulfate was the major biodegradation product in soils
under aerobic, anaerobic and flooded conditions (Martens, 1977). In flooded soils, endolactone
was detected only once whereas endodiol and endohydroxy ether were identified in
all soils under these conditions. Under anaerobic conditions, endodiol formed in low
amounts in two soils (Martens, 1977).
Indigenous microorganisms obtained from a sandy loam degraded a-endosulfan to
endosulfandiol. This diol was converted to endosulfan a-hydroxy ether and trace amounts
of endosulfan ether and both were degraded to endosulfan lactone (Miles and Moy, 1979).
Using settled domestic wastewater inoculum, a-endosulfan (5 and 10 mg/L) did not
degrade after 28 days of incubation at 25°C (Tabak et al., 1981).
Plant. Endosulfan sulfate was formed when endosulfan was translocated from the
leaves to roots in both bean and sugar beet plants (Beard and Ware, 1969). In tobacco
leaves, a-endosulfan is hydrolyzed to endosulfandiol (Chopra and Mahfouz, 1977). Stewart
and Cairns (1974) reported the metabolite endosulfan sulfate was identified in potato peels
and pulp at concentrations of 0.3 and 0.03 ppm, respectively. They also reported that the
half-life for the conversion of a-endosulfan to b-endosulfan was 60 days. On apple leaves,
direct photolysis of endosulfan by sunlight yielded endosulfan sulfate (Harrison et al.,
1967).
In carnation plants, the half-lives of a-endosulfan stored under four different conditions,
non-washed and exposed to open air, washed and exposed to open air, non-washed
and placed in an enclosed container and under greenhouse conditions were 6.79, 6.38,
10.45 and 4.22 days, respectively (Céron et al., 1995).
Surface Water. Endosulfan sulfate was also identified as a metabolite in a survey of
11 agricultural watersheds located in southern Ontario, Canada (Frank et al., 1982). When
endosulfan (a- and b- isomers, 10 mg/L) was added to Little Miami River water, sealed
and exposed to sunlight and UV light for 1 week, a degradation yield of 70% was observed.
After 2 and 4 weeks, 95% and 100% of the applied amount degraded. The major degradation
product was identified as endosulfan alcohol by IR spectrometry (Eichelberger and
Lichtenberg, 1971).
Photolytic. Thin films of endosulfan on glass and irradiated by UV light (l >300 nm)
produced endosulfandiol with minor amounts of endosulfan ether, a lactone, an a-hydroxyether
and other unidentified compounds (Archer et al., 1972). When an aqueous solution
containing endosulfan was photooxidized by UV light at 90–95°C, 25, 50 and 75%
degraded to carbon dioxide after 5.0, 9.5 and 31.0 hours, respectively (Knoevenagel and
Himmelreich, 1976).
Chemical/Physical. Endosulfan slowly hydrolyzes forming endosulfandiol and
endosulfan sulfate (Kollig, 1993; Martens, 1976; Worthing and Hance, 1991). The hydrolysis
rate constant for a-endosulfan at pH 7 and 25°C was determined to be 3.2 ′ 10–3/hour,
resulting in a half-life of 9.0 days (Ellington et al., 1988). The hydrolysis half-lives are
reduced significantly at varying pHs and temperature. At temperatures (pH) of 87.0 (3.12),
68.0 (6.89) and 38.0°C (8.69), the half-lives were 4.3, 0.10 and 0.08 days, respectively
(Ellington et al., 1986). Greve and Wit (1971) reported the hydrolysis half-lives of a-
endosulfan at 20°C and pH values of 7 and 5.5 were 36 and 151 days, respectively.
Emits toxic fumes of chlorides and sulfur oxides when heated to decomposition (Lewis,
1990).
