Endosulfan
PESTICIDE NAME: Endosulfan
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Trade name(s): Thiodan, Tiovel
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Manufacturer(s): FMC Corp.
Agricultural Chemicals Group
2000 Market Street
Philadelphia, PA. 19103
Velsicol Chemical Corp.
341 E. Ohio Street
Chicago, IL. 60611
I. Basic information
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A. Molecular structure: C9H6Cl6O3S
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B. Chemical name: 6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-
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hexahydro-6,9-methano-2,4,3-benzodioxathiopin-3-oxide
C. Derivatives: endosulfan sulfate, alpha and beta isomers in 4:1
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ratio
D. Molecular weight: 406.95 g/mole
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E. Solubility in water: <1.0 mg/l
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F. Common physical appearance: brownish crystalline solid
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G. Oral LD50(rat): 18-43 mg/kg
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H. Pesticide classification: organochlorine insecticide
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I. Restricted use list (N.Y.): yes
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EPA priority pesticide list: yes
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J. Crop use: apple, pear, peach, apricot, grape, strawberry
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cabbage, cauliflower, broccoli, Brussels sprouts, cucurbits, leafy
greens, peppers, potato, eggplant, tomato
II. Text
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Endosulfan is a broad spectrum, non-systemic organochlorine
insecticide used on a variety of fruit and vegetable crops. It
undergoes rapid transformation to its metabolites which are then fairly
stable in soil. The degradation, transformation, transport and
adsorption of endosulfan is widely investigated in the scientific
literature. It has been found to be resistant toleaching even at high
concentrations over a long time period under elevated temperature
regimes.
III. Soils information
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A. Degradation and transformation
The transformation of endosulfan to its alpha and beta isomers is
rapid and complete. An initial concentration of endosulfan in soil of
8.2ppm declined to 1ppm after 3wks and 0.25ppm in 7wks(4). The
cultivation practices can influence this somewhat. Endosulfan was
found to persist 30d when applied broadcast and 45d with furrow
application(5). The metabolites then undergo degradation in all types
of soils. In a sandy loam, with an initial application of 6.7 kg/ha
endosulfan, the alpha isomer had degraded to 50% of the original
concentration in 60d while the beta isomer was at the 50% level in
800d(8). Another study utilized clay loam soil with a normal pesticide
treatment in wet soil and high/low treatments in dry soil. The alpha
and beta isomers were shown to undergo rapid fall-off in all soils. The
initial loss in wet was greater than that in dry soil; however, after
30d all treatments were equal. In the high treatment, dry soil,
endosulfan alcohol converted to ether which after 50d converted to the
sulfate; conversion took place after 5d with the low treatment, dry
soil. Sulfate conversion occurred after 15d in the wet soil and it
was, therefore, determined that persistance was dependent upon initial
concentration(6). The degradation of the alpha isomer is thought to be
by both bacteria and fungi whereas the beta isomer is degraded only by
bacteria(1).
The table below presents data dealing with degradation of
endosulfan metabolites. The reference is given in parentheses at the
end of the title.
Percent recovery of alpha and beta endosulfan at 42d and 37deg C in
loam soil(1)
alpha beta
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unautoclaved 50.6 +a3.3 29.7 +a0.2
autoclaved 63.6 +a0.8 65.3 +a0.7
B. Adsorption and transport
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Endosulfan is not considered to be subject to physical
leaching(2,3,6,8). The level of endosulfan in any given soil layer was
found to remain consistent throughout the course of one study which
reported that 90% of the residue remained in the 0-15cm layer, 9% in
the 15-30cm layer and 1% in the 30-45cmlayer(8). In a clay loam soil,
100d after application, 95% of the endosulfan+sulfate was in the top
3in with no penetration below 4in. There was a trace of alpha and beta
isomers in the 3-4in layer. Rainfall for this experiment totaled
620mm(6). Another study, using sandy clay loam leached with water at
10d intervals for 300d, reported no leaching past 17cm even at high
concentrations of endosulfan and thus concluded that concentration has
no marked effect on adsorption(2). This was reaffirmed in a subsequent
study by the same authors who found endosulfan to be resistent to
physical leaching at concentrations as high as 100ug/g soil over a 60d
time period with soil at 45deg C(3). These researchers reported that
adsorption decreases as temperature increases and hypothesized that
such a phenomenon could be due to 1)increased temperature causing
increased water movement, 2)increased temperature resulting in
increased evaporation and degradation, and 3)increased temperature
leading to decreased adsorption because adsorption is exothermic and
there is a resultant release of heat(3).
The following tables present data concerning adsorption and
leaching of endosulfan. The reference is given in parentheses at the
end of each title.
Pesticide retention in glass columns on sandy clay loam soil at
differing initial concentrations(2)
ALPHA: 1ug/g 2.7ug/g 5.2ug/g 2.8ug/g
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depth(cm)
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4 40% 40% 35% 50%
8 55 65 40 60
12 65 65 50 65
16 75 70 60 69
BETA: 0.6ug/g 1.4ug/g 2.8ug/g 15.1ug/g
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depth(cm)
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4 45 60 40 35
8 65 65 50 40
12 70 65 55 50
16 75 65 55 55
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Adsorption of the isomers of endosulfan as a function of time and soil
temperature (alpha=a, beta=b)(units=% of a or b applied)(3)
2 25 45 (deg C)
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10d 79a,80b 68a&b 50a,60b
70d 60a,48b 50a&b 10a&b
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IV. References (*denotes key references)
*1.El Beit, I.O.D., J.V. Wheelock, D.E. Cotton. 1981. Int.J. Environ.
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Stud. 16.171-96.
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*2.El Beit, I.O.D., J.V. Wheelock, and D.E. Cotton. 1981.(II). Int. J.
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Environ. Stud. 16.171-96.
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*3.El Beit, I.O.D., J.V.Wheelock, and D.E. Cotton. 1981 (III) Int. J.
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Environ. Stud. 16.171-96.
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4.El Zorgani, G.A. 1976. Bull Environ. Contam. Toxicol. 15:3. 378-82.
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5.Gupta, H.C.L., B.L. Pareek, K.P. Sharma. l977. Entomon. 2:2. 161-2.
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*6.Rao, D.M.R., A.S. Murty. l980. J. Agric.Food Chem. 28. 1099-1101.
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7.Srivastava, K.P., M.G. Jotwani. 1979. J.Ent. Res. 3:2. 148-56.
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*8.Stewart, D.K.R., K.G. Cairns. 1974. J. Agr. Food Chem. 22:6.984-6.
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