IPCS INCHEM Home

    ENDOSULFAN       JMPR 1998

    First draft prepared by 
    D.B. McGregor
    International Agency for Research on Cancer
    Lyon, France


         Explanation
         Evaluation for acceptable daily intake
              Biochemical aspects
                   Absorption, distribution, and excretion 
              Toxicological studies 
                   Acute toxicity 
                   Short term studies of toxicity 
                   Long-term studies of toxicity and carcinogenicity
                   Genotoxicity 
                   Reproductive toxicity 
                        Multigeneration reproductive toxicity
                        Developmental toxicity 
                   Special studies 
                        Enzyme induction 
                        Promotion 
                        Immunotoxicity 
                        Neurobehavioural effects and neurotoxicity 
                        Effects on sperm 
                        Endocrine effects 
              Observations in humans 
         Comments 
         Toxicological evaluation 
         References 


    Explanation

         Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-
    methano-2,4,3-benzo-dioxathiepin-3-oxide), an insecticide, has been
    evaluated toxicologically on several occasions by previous Joint
    Meetings (Annex 1, references 2, 4, 8, 10, 38, 44, and 56), the latest
    being the 1989 JMPR (Annex 1, reference 56), when an ADI of 0-0.006
    mg/kg bw was established. Endosulfan was reviewed by the present
    Meeting within the Periodic Review Programme of the Codex Committee on
    Pesticide Residues. In this evaluation, full use was made of the
    review of endosulfan prepared by the Australian National Registration
    Authority, the entire version of which may be obtained at
    http://www.dpie.gov.au/nra/prsendo.html. This monograph summarizes the
    new data and relevant data from the previous monographs and monograph
    addenda on endoslufan (Annex 1, references 4, 9, 11, 39, and 58)

    Evaluation for acceptable daily intake

    1.  Biochemical aspects

     (a)  Absorption, distribution, and excretion

         When radiolabelled endosulfan was administered to mice as a
    single dose of 4 mg/kg bw by gavage, a single dose of 4.7 mg/kg bw in
    the diet, or a 21-day administration of 2.4 mg/kg bw per day in the
    diet, most of the radiolabel was recovered from the faeces. Within
    three weeks after cessation of treatment, a total of 87-100% of the
    administered dose was recovered, with little difference with dosing
    regime. While biliary excretion was not studied, the percent of
    chemical absorbed after oral dosing would appear to have been moderate
    to high. Three weeks after the final administration, the residues in
    tissues were greater in animals fed the compound for 21 days, the
    higher concentrations being found in the liver (about 2 ppm) and
    spleen (about 1.4 ppm) at this time. Little residue was found in the
    kidneys and fat, even after repeated administration, and there was no
    accumulation of radiolabelled endosulfan residues (Christ & Kellner,
    1968).

         Single oral doses of 0.3 mg endosulfan and its two isomers
    administered to male Balb/c mice were not completely absorbed from the
    gastrointestinal tract but were excreted with the metabolites
    endosulfan sulfate and diol in the faeces. Only the diol metabolite
    was excreted via the urine; the sulfate metabolite was the only form
    of endosulfan found in tissues, with relatively large amounts in
    liver, small intestine, and visceral fat and trace amounts in muscle
    and kidney. When endosulfan was fed to Balb/c mice in the diet at a
    concentration of 10 ppm for up to 49 days, the sulfate metabolite was
    detected in the liver and visceral fat of all animals. Both isomers
    and the sulfate and diol metabolites of endosulfan were detected in
    the faeces, while the only endosulfan product detected in the urine of
    these animals in this early study was the diol metabolite. After a
    single dose of up to 0.3 mg 14C-labelled endosulfan to Balb/c mice,
    about 65% of the radiolabel was recovered; the faeces accounted for
    the highest concentrations, followed (in rank order) by visceral fat
    > urine > small intestine > kidney > brain > expired carbon
    dioxide > blood (Deema et al., 1966).

         At the end of a 24-month study in which NMRI mice were given
    diets containing 0, 2, 6, or 18 ppm technical-grade endosulfan (see
    Donaubauer, 1988), the concentrations of endosulfan and its main
    metabolites endosulfan hydroxyether, sulfate, lactone, and diol were
    measured in the liver and kidneys. No endosulfan was detected in
    either the liver or the kidney. In mice given 18 ppm endosulfan, the
    concentrations of the hydroxyether, lactone, and diol metabolites were
    at or below the level of detection (0.02 ppm), while the endosulfan
    sulfate concentrations were 0.1-0.2 ppm in kidney and 0.7-1.1 ppm in
    liver. The tissue concentrations of endosulfan sulfate in mice at 2,
    6, and 18 ppm, respectively, were: kidney, 0.2-0.4 ppm, 0.04 ppm, and

    0.1-0.2 ppm; and liver, 0.06-0.07 ppm, 0.12-0.45 ppm, and 0.7-1.1 ppm
    (Leist, 1989a).

         After oral or intravenous administration of 14C-endosulfan to
    male and female Wistar rats at a dose of 2 or 0.5 mg/kg bw,
    respectively, > 80% (intravenous) or 90% (oral) of the dose was
    eliminated in the urine and faeces within seven days; elimination was
    essentially complete within the first 1-2 days. The half-lives for
    urinary and faecal elimination for males and females were biphasic,
    with an earlier half-life of 6-14 h and a later half-life of 33-67.5
    h. Elimination in urine of the intravenous and oral doses,
    respectively, accounted for 11 and 13% of the dose in males and 2 and
    24% of the dose in females; the corresponding figures for elimination
    in faeces were 65 and 82% in males and 60 and 72% in females. The
    highest tissue concentrations were found in the kidneys (1.8 ppm),
    liver (0.23 ppm in males; 0.48 ppm in females), and retroperitoneal
    fat (0.16 ppm in females). The concentrations of residues were < 0.1
    ppm in all other tissues examined. The absorption of endosulfan was
    estimated to be 60-70% on the basis of a comparison of areas under the
    curve after intravenous and oral administration and about 90% on the
    basis of a comparison of elimination of radiolabel administered by the
    two routes (Table 1; Kellner & Eckert, 1983; Stumf & Lehr, 1993).

         14C-Endosulfan (alpha or ß isomer) was rapidly excreted by
    female rats after a single oral dose of 2 mg/kg bw or administration
    in the diet at a concentration of 5 ppm. After a single oral dose,
    > 85% was excreted within 120 h (> 70% after 48 h), mainly in the
    faeces and to a lesser extent in the urine. After dietary
    administration for 14 days, followed by a 14-day recovery period,
    > 72% of the administered dose was recovered. Biliary excretion of
    radiolabel in male rats given 1.2 mg/kg bw as a single dose approached
    50% for the alpha isomer and 30% for the ß isomer over 48 h. There
    appeared to be little enterohepatic circulation. The tissue
    concentrations of residues were generally highest in the kidneys and
    liver and lower in other tissues, including fat. At the end of the
    14-day recovery period, residues were confined to the kidneys and to a
    lesser extent the liver, with half-lives of about seven days in
    kidneys and three days in liver. By far the largest proportion of the
    radiolabel administered was metabolized to highly polar products, most
    of which could not be extracted from faeces (28%) or tissues (71%). Of
    the extractable fraction, unidentifiable polar metabolites constituted
    6.2% in faeces and 13% in urine. The apolar metabolites of endosulfan
    identified in faeces and urine were the diol, the lactone, the 
    alpha-hydroxyether, and the sulfate. The metabolites occurred at
    similar concentrations, ranging from 3.4 to 9.1% of the radiolabel in
    the urine of rats given single doses and from 2.4 to 4.2% in the urine
    of rats given endosulfan in the diet. The three apolar metabolites
    (endosulfan diol, hydroxyether, and lactone) accounted for 7.5% of the
    single dose and 3.2% of the dietary dose in the urine, 9% of the
    administered dose in bile, and 21% in faeces. No accumulation in fatty
    tissues was found (Dorough et al., 1978). A metabolic scheme is
    presented in Figure 1.


        Table 1. Pharmacokinetics of 14C-endosulfan in rats after oral and intravenous administration

                                                                                                                       

    Pharmacokinetic parameter       Oral (2 mg/kg bw)                    Intravenous (0.5 mg/kg bw)
                                                                                                                       

    Tmax                            Males, 3-8 h; females, 18 h          Males and females, 5 min
    Cmax                            Males, 0.25 ± 0.06 µg/ml;            Males and females, 0.18 ± 0.04 µg/ml
                                    females, 0.18 ± 0.05 µg/ml           
    Elimination half-life           Males (biphasic), 8 h , 110 h        Males (triphasic), 0.77 h, 12.5 h, 157 h
                                    Females (monophasic), 75 h           Females (biphasic), 1.2 h, 47 h
    Faecal excretion                Males, 82%; females, 72%             Males, 66%; females, 59%
    Urinary excretion               Males, 12%; females, 22%             Males, 13%; females, 24%
    Urinary excretion half-life     Males (biphasic), 6.2 h, 67.5 h      Males (biphasic), 7.5 h, 60 h
                                    Females (biphasic), 5.6 h, 33 h      Females (biphasic), 7.6 h, 42 h
    Faecal excretion  half-life     Males (biphasic), 7.7 h, 34 h        Males (biphasic), 8.6 h, 34.5 h
                                    Females (biphasic), 11.4 h, 30 h     Females (biphasic), 13.6 h, 40 h

                                                                                                                       
    

    FIGURE 1

         Groups of 24 male Sprague-Dawley rats received dermal
    applications of [5a,9a14C]-endosulfan at a dose of 0.1, 0.76, or 10
    mg/kg bw, without washing. Four animals from each group were killed at
    0.5, 1, 2, 4, 10, and 24 h, and radiolabel was measured in the
    collected excreta and various organs and tissues, including the
    application site after washing with soapy water. No skin irritation
    was seen at the application site. Adsorption onto the skin was
    essentially complete within 0.5 h at all doses and accounted for
    63-80% of the applied dose. Movement away from the application site
    was slow, with 73, 73, and 89%, respectively, of the adsorbed doses
    remaining at the application site after 24 h. By 10 h, each group had
    excreted less than 1% of the applied dose. By 24 h, the excretion was
    11, 10, and 4% of the applied dose in the groups given 0.1, 0.76, and
    10 mg/kg bw, respectively (Craine, 1986).

         Groups of 16 female Sprague-Dawley rats received dermal
    applications of [5a,9a14C]-endosulfan at 0.09, 0.98, or 11 mg/kg bw,
    and the site was washed with soapy water after 10 h. Four animals from
    each group were killed at 24, 48, 72, and 168 h, and radiolabel was
    measured in the collected excreta and various organs and tissues,
    including the application site. No skin irritation was seen at the
    application site, and there were no signs of systemic toxicity.
    Recovery of radiolabel was 84-115%. The amount of the applied dose
    that was removed by washing was 28, 47, and 69%, respectively, at the
    three doses. After 168 h, 63, 87, and 65%, respectively, of the dose
    that was not removed by washing was either adsorbed on to the skin or
    had penetrated and been distributed and excreted; an average of
    2.4-3.3% of the adhering dose remained at the application site.
    Excretion was maximal between 24 and 48 h, faeces accounting for about
    two-thirds of the label. The total residues at 168 h represented 2.5,
    2.3, and 1.3% of the applied dose (about 3.5, 4.3, and 4.2% of the
    adhering dose) at the doses of 0.09, 0.98, and 11 mg/kg bw,
    respectively, and were present mainly in liver and kidney (Craine,
    1988).

         At the end of a 24-month study in which Sprague-Dawley rats were
    given diets containing 0, 3, 7.5, 15, or 75 ppm technical-grade
    endosulfan (see Ruckman et al., 1989), the concentrations of
    endosulfan and its known metabolites, endosulfan hydroxyether,
    sulfate, lactone, and diol, were measured in the liver and kidneys. As
    no quantifiable residues were detected in organs of rats at 15 ppm,
    the organs of animals at 7.5 and 3 ppm were not investigated further.
    Neither alpha- nor ß-endosulfan, the substances administered in the
    diet, or any of the metabolites was quantifiable in either organ, with
    the exception of endosulfan sulfate in animals at 75 ppm, which was
    found at concentrations of 0.2-0.4 mg/kg in liver. No residues were
    observed in the kidneys of this group (Dorn & Werner, 1989; Leist,
    1989a).

         Twelve lactating goats were given endosulfan (purity unspecified)
    in gelatine capsules at a dose of 1 mg/kg bw per day for 28 days. The
    tissue concentrations of residues were generally low, the highest
    being detected on the first day after cessation of treatment, with

    0.29 ppm in kidney, 0.2 ppm in the gastrointestinal tract, and 0.12
    ppm in liver. The concentrations in the kidney were increased one week
    after treatment, reaching 0.49 ppm on day 8, but no residues were
    detected 21 days after treatment ceased. Endosulfan residues did not
    accumulate in the fat; the concentrations reached 0.06 ppm on day 1
    after the end of treatment, but none were detected by day 8 after
    treatment (Indraningsih, et al., 1993).

         Groups of three lactating Holstein cows were given diets
    containing 0, 0.3, 3, or 30 ppm 14C-endosulfan for 30 days. Between
    days 7 and 29, the average concentrations in milk were 3.4, 40, and
    462 ppb endosulfan equivalents in the three groups. After the dosing
    period, the loss of radiolabel from milk (measured in one cow per
    group) was 81% within seven days in the cow given 0.3 ppm and 96%
    within 14 days in cows given 3 and 30 ppm (Bowman, 1959). The blood
    concentrations rose during the first 21 days, to 0.15 and 1.97 ppm at
    the doses of 3 and 30 ppm, respectively, but were always below the
    detection level (0.06 ppm) in the groups at 0.3 ppm. The
    concentrations of residues found at the three doses were: liver, 0.35,
    2.45, and 25.3 ppm; kidney, 0.05, 0.35, and 6.29 ppm; and omental fat,
    0.07, 0.71, and 7.08 ppm (Keller, 1959a).

          Two lactating East Friesian sheep were given a single oral dose
    of 0.3 mg/kg bw 14C-endosulfan and were killed after 40 days. The
    radiolabel was maximal in blood after 24 h, when it was equivalent to
    0.07 µg/ml. The total radiolabel eliminated in milk over 17 days was
    0.37% and 1.82% of the dose in the two sheep, respectively. Radiolabel
    was excreted mainly via the urine (41%) and faeces (50%). About half
    of the 50% in faeces was unmetabolized endosulfan. Fat, kidney, and
    liver of the sheep contained 0.02-0.03 µg/g endosulfan; all of the
    remaining tissues had considerably lower concentrations. The total
    radiolabel found in organs and tissues accounted for < 1% of the
    administered dose (Gorbach et al., 1965).

         In pigs fed endosulfan at 2 ppm in their diets for up to 81 days,
    the compound was detected in fatty tissue at concentrations of 0.07,
    0.09, and 0.04 ppm after 27, 54, and 81 days of treatment, much less
    than the residues seen after administration of 7 ppm DDT: 8.3, 9.1,
    and 9.7 ppm after 27, 54, and 81 days treatment, respectively. Liver
    and muscle contained about 15-fold less DDT residues than fat. Thus,
    while much less endosulfan was found in fatty tissues, it does not
    appear to bioaccumulate as does DDT (Maier-Bode, 1966).

         The systemic absorption of endosulfan over 96 h after dermal
    administration to two rhesus monkeys of single doses of 2.2-3 mg/kg bw
    of an aqueous suspension of 14C-endosulfan (purity, 94.6%) for 10 h
    was 22% of the administered dose. An additional 11% remained in the
    skin, 10.5% was found in the carcass, and 4.3 and 3.7% of the
    administered dose was excreted in faeces and urine, respectively;
    however, as only 50% of the administered dose was recovered, the
    figures calculated for absorption may not be accurate indications of
    the extent of dermal absorption of endosulfan. A plateau was reached
    in blood and plasma concentrations at 36 h, and there may have been no

    significant additional dermal absorption after that time.
    Concentrations in the liver, kidneys, and fat were highest (0.48,
    0.083, and 0.23 ppm, respectively), while there were negligible
    concentrations in the brain (Lachmann, 1987).

         In a study of the penetration of endosulfan through rat and human
    skin  in vitro, radiolabelled endosulfan formulated as an
    emulsifiable concentrate containing 353 g/L endosulfan, which had been
    diluted to concentrations of 0.4-4 mg/ml in water, was applied at
    nominal doses of 0.01, 0.1, and 1 mg/cm2 to rat and human skin
    mounted in dermal penetration cells. The rate of penetration was, on
    average, 4.3 times greater through rat skin than that of humans. The
    percentage of the applied dose varied with the concentration: 61% of
    the lowest dose applied to human skin and 96% of that applied to rat
    skin penetrated, and 20% of the highest dose applied to human skin and
    40% of that applied to rat skin penetrated. When the skin was washed
    10 h after application, the amount of endosulfan that penetrated
    decreased to 4% in the human and 9% in the rat skin. Endosulfan that
    passed through human skin was metabolized or degraded to a greater
    extent than that which passed through rat skin (Noctor & John, 1995).

    2.  Toxicological studies

     (a)  Acute toxicity

         The LD50 of endosulfan varies widely depending on the route of
    administration, species, vehicle, and sex of the animal (see Table 2).
    Certain other reports are available, but it has been argued that most
    of them are not acceptable by current standards (Bremmer & Leist,
    1998). Female rats are clearly more sensitive than male rats, and, on
    the basis of a single study, this sex difference appears to apply to
    mice also. Endosulfan is generally highly toxic after oral and
    inhalation exposure. The lowest oral LD50 value is 9.6 mg/kg bw in
    female Sprague-Dawley rats. 

         The isomers of endosulfan also show high acute toxicity after
    oral administration. The clinical signs of poisoning include
    piloerection, salivation, hyperactivity, respiratory distress,
    diarrhoea, tremors, hunching, and convulsions. Like endosulfan, its
    metabolites were more or less toxic according to the vehicle used and
    the species exposed. In general, the toxicity of the lactone and
    sulfate metabolites was similar to or less than that of the parent
    compound, while the hydroether, ether, and, in particular, the diol
    were far less toxic. The clinical signs of poisoning were similar to
    those induced by the parent compound and included piloerection,
    salivation, hyperactivity, respiratory distress, diarrhoea, tremors,
    hunching, and convulsions.

         Phenobarbital was an effective therapeutic measure against an
    absolute lethal dose of endosulfan in rats, reducing the clinical
    signs of poisoning and the mortality rate. Diazepam was not effective
    (Ebert & Weigand, 1984).


        Table 2.  Acute toxicity of technical-grade endosulfan and its isomers and metabolites

                                                                                                                                  

    Species      Strain               Sex   Route          Vehicle                 LD50            Reference
                                                                                   (mg/kg bw)
                                                                                                                                  

    Technical-grade endosulfan

    Rat          Sprague-Dawley       M     Oral          25% in food              2 800           Bracha (1977)
    Rat          Sprague-Dawley       F     Oral          25% in food              45              Bracha (1977)
    Rat          CD                   M/F   Oral          Maize oil                43              Lightowler & Gardner (1978)
    Rat          Haffkine             M     Oral                                   110             Bhide & Naik (1984a)
    Rat          Haffkine             F     Oral                                   15              Bhide & Naik (1984a)
    Rat          Holtzman             M     Oral          Corn oil                 87              Elsea (1958)
    Rat          Wistar               M     Oral          2% starch                100-160         Diehl & Leist (1988a)
    Rat          Wistar               F     Oral          2% starch                23              Diehl & Leist (1988a)
    Rat          Sprague-Dawley       M     Oral          5% CMC                   40              Reno (1975)
    Rat          Sprague-Dawley       F     Oral          5% CMC                   9.6             Reno (1975)
    Mouse        Kasauli              M     Oral          Tween 80                 35              Bhide & Naik (1984b)
    Mouse        Kasauli              F     Oral          Tween 80                 14              Bhide & Naik (1984b)
    Dog          Mongrel              M/F   Oral          Gelatin capsule          77              Nogami (1970)

    Rat          HoeWISKf             M     Dermala                                > 4 000         Diehl & Leist (1988b)
    Rat          HoeWISKf             F     Dermala                                500             Diehl & Leist (1988b)
    Rabbit       NWS                  M     Dermala                                290             Bhide & Naik (1984c)
    Rabbit       New Zealand          M     Dermala                                500-1 000       Bracha (1977)
    Rabbit       New Zealand          F     Dermala                                1 000-2 000     Bracha (1977)

    Rat          Sprague-Dawley       M/F   Inhalation                             > 21 000        Bracha (1977)
                                                                                   mg/m3 for 1 h
    Rat          Wistar               M     Inhalation    Ethanol + PEG            35 mg/m3        Hollander & Weigand (1983)
                                                                                   for 4 h
    Rat          Wistar               F     Inhalation    Ethanol + PEG            13 mg/m3        Hollander & Weigand (1983)
                                                                                   for 4 h

    Table 2.  (continued)

                                                                                                                                  

    Species      Strain               Sex   Route          Vehicle                 LD50            Reference
                                                                                   (mg/kg bw)
                                                                                                                                  

    Endosulfan alpha isomer

    Rat                                     Oral                                   76              Goebel et al. (1982)
    Mouse        Albino               F     Oral          Tween 80                 11              Dorough et al. (1978)

    Endosulfan ß isomer

    Rat                                     Oral                                   240             Goebel et al. (1982)
    Mouse                             F     Oral          Tween 80                 36              Dorough et al. (1978)

    Endosulfan sulfate

    Mouse        Albino               F     Oral          Tween 80                 8               Dorough et al. (1978)
    Rat          Wistar               F     Oral          Starch suspension        76              Hollander & Kramer (1975a)
    Rat          Wistar               M     Oral                                   570             Ehling & Leist (1991a)
    Rat          Wistar               F     Oral                                   40              Ehling & Leist (1991a)
    Dog          Beagle               M     Oral          Starch suspension        15              Hollander & Kramer (1975b)
    Rat          Wistar               M     Dermal                                 2 700           Ehling & Leist (1991b)
    Rat                               F     Dermal                                 280             Ehling & Leist (1991b)

    Endosulfan diol

    Mouse        Albino               F     Oral          Tween 80                 > 2 000         Dorough et al. (1978)
    Rat                               F     Oral          Starch suspension        > 1 500         Hollander & Kramer (1975c)
    Rat          Albino               F     Oral                                   > 15 000        Weigand (1982a)
    Rat          Wistar               M/F   Oral                                   > 5 000         Ehling & Leist (1991c)
    Mouse        Albino               F     Oral          Tween 80                 120             Dorough et al. (1978)
    Rat                               F     Oral          Starch suspension        1 750           Hollander & Kramer (1975d)
    Rat          Wistar               M/F   Dermal                                 > 2 000         Ehling & Leist (1991d)

    Table 2.  (continued)

                                                                                                                                  

    Species      Strain               Sex   Route          Vehicle                 LD50            Reference
                                                                                   (mg/kg bw)
                                                                                                                                  

    Endosulfan ether

    Mouse        Albino               F     Oral          Tween 80                 270             Dorough et al. (1978)
    Rat                               F     Oral          Starch suspension        > 15 000        Hollander & Kramer (1975c)
    Rat          Albino               F     Oral                                   > 15 000        Weigand (1982b)

    Endosulfan hydroxyether

    Mouse        Albino               F     Oral          Tween 80                 120             Dorough et al. (1978)
    Rat                               F     Oral          Starch suspension        1 750           Hollander & Kramer (1975d)

    Endosulfan lactone

    Mouse        Albino)              F     Oral          Tween 80                 120             Dorough et al. (1978)
    Rat          Wistar               F     Oral          Starch suspension        290             Hollander & Kramer (1975e)
    Rat          Wistar               M     Oral          Starch suspension        160             Hollander & Kramer (1975f)
    Rat                               M/F   Oral          Sesame oil               100/120         Kramer & Weigand (1971)
                                                                                                                                  

    M, male; F, female; CMC, carboxy methyl cellulose; PEG, polyethylene glycol
    a 24 h on intact skin
    

         The dermal irritancy of technical-grade endosulfan (purity,
    98.6%) was tested in three New Zealand white rabbits by clipping the
    hair from a dorsal area of about 25 cm2 and 24 h later applying 500
    mg endosulfan moistened with deionized water on a 6.25-cm2 cellulose
    patch, which was then covered with a semi-occlusive bandage. Exposure
    was for 4 h, after which the test material was removed with warm
    tap-water. The exposed area was examined 0.5-1, 24, 48, and 72 h after
    removal of the patch. On the basis of the evaluation system defined by
    EEC guideline B.4 ('Acute toxicity skin irritation' of Directive
    92/69/EEC), the overall mean scores for dermal irritation were 0 for
    both erythema and eschar formation and oedema formation. No signs of
    systemic toxicity were observed (Bremmer, 1997a).

         The ocular irritancy of technical-grade endosulfan (purity,
    98.6%) was tested in three New Zealand white rabbits by applying 100
    mg to the conjunctival sac of one eye of each rabbit; the other,
    untreated eye served as the control. The eyes were exposed for 24 h,
    after which the endosulfan was washed out, and the eyes were examined
    for ocular lesions 1, 24, 48, and 72 h later. On the basis of the
    evaluation system defined by EEC guideline B.5 ('Acute toxicity eye
    irritation' of Directive 92/69/EEC), the overall mean scores for
    irritation were 0.66 for redness of conjunctiva, 0 for chemosis of
    conjunctiva, 0 for opacity of cornea, and 0.11 for irritation of the
    iris. No signs of systemic toxicity were observed. Endosulfan was not
    irritating to the eye (Bremmer, 1997b).

         The cutaneous allergenic potential of endosulfan (purity, 98.6%)
    was examined in 20 treated and 10 control male albino guinea-pigs. The
    maximal tolerated concentration of endosulfan suitable for the
    induction phase of the main study and a suitable non-irritating
    concentration of topically applied endosulfan were identified for the
    challenge application in a preliminary study. For intradermal
    induction, injection of 0.1 ml of a 0.5% solution in corn oil
    emulsified 1:1 (v:v) with Freund's complete adjuvant was selected. One
    week after these injections, a 6-cm2 patch of filter paper saturated
    with about 0.3 ml of a 50% solution of endosulfan in corn oil was
    applied to the shaved skin of each guinea-pig, and the area was
    occluded with aluminium foil secured by impermeable adhesive tape,
    which was left in position for 48 h. Irritation was assessed 24 and 48
    h later. On test day 22, the guinea-pigs were challenged with the
    non-irritating 50% endosulfan in corn oil applied as during the
    induction phase. The dressing was left in position for 24 h. The
    application sites were assessed for erythema and oedema 24 and 48 h
    later. On the basis of the evaluation system defined by EEC guideline
    B.6 ('Acute toxicity -- Skin sensitization' of Directive 92/69/EEC),
    none of the treated guinea-pigs developed skin reactions. Endosulfan
    was therefore considered to be non-sensitizing for guinea-pig skin
    (Arcelin, 1996).

     (b)  Short-term toxicity

     Mice

         Groups of 10 male and 10 female Hoe:NMRKf mice were fed diets
    containing endosulfan at a concentration of 0 or 18 ppm for six weeks,
    equal to 0 or 3.7 mg/kg bw per day for males and 0 or 4.6 mg/kg bw per
    day for females, to determine whether 18 ppm was the NOAEL in this
    strain, as it was found to be in CD-1 mice in a three-month study
    (Barnard et al., 1984). There were no clinical signs attributable to
    treatment. The mean food intake of mice receiving endosulfan was
    slightly decreased in males and slightly increased in females. Mean
    body-weight gain was reduced in treated males during the second half
    of the experiment but was slightly increased in females throughout the
    experiment. Two treated females died, on days 28 and 38; the causes
    were not established, but no histological changes were found in the
    mouse that was not autolysed. The absolute and relative weights of the
    liver of males and females at 18 ppm were higher than those of
    controls and statistically significantly so in females (17 and 12%,
    respectively). A NOAEL was not identified, as an increase in liver
    weights was seen in females at the only dose tested (Donaubauer et
    al., 1985).

         Groups of 20 CD-1 mice of each sex were fed diets containing
    endosulfan (purity, 97.2%) at a concentration of 0, 2, 6, 18, or 54
    ppm for three months, equal to 0, 0.24, 0.74, 2.1, and 7.3 mg/kg bw
    per day for males and 0, 0.27, 0.8, 2.4, and 7.5 for females. Clinical
    signs attributable to treatment, consisting of convulsions and
    salivation, were seen in one male and one female at the high dose.
    There was a marked treatment-related decrease in the survival rate
    (about 50%) of male and female mice at the high dose; the mean food
    intake of these animals was significantly reduced for the first two
    weeks of the study, and the mean body-weight gain of males at the high
    dose was reduced during the first week of treatment. A significant
    reduction in neutrophil count was observed in males at 54 ppm at week
    6 (72%,  p < 0.01), and a lower count (62%), which was not
    statistically significant, was also observed at week 13. The blood
    glucose concentration was reduced by about 11% in females at all doses
     (p < 0.01) at week 6, and the serum lipid concentration was
    increased by 15% in females at 54 ppm at week 13. The NOAEL was
    18 ppm, equivalent to 2.1 mg/kg bw per day, on the basis of
    convulsions and salivation, decreased survival, and increased serum
    lipid concentrations at 7.3 mg/kg bw per day (Barnard et al., 1984).

         Groups of 10 four-week-old ddY mice of each sex were fed diets
    containing technical-grade endosulfan (purity, 91.4%) at
    concentrations of 0, 10, 30, 100, or 300 ppm, equal to 0, 1.2, 4.1,
    15, and 42 mg/kg bw per day in males and 0, 1.4, 4.7, 14, and 42 mg/kg
    bw per day in females, for 12 months. There were no apparent
    treatment-related clinical signs or deaths. Males at the high dose
    showed a small (1%) but significant decrease in mean corpuscular
    volume, and transient, non-dose-related increases in haemoglobin
    (11%), haematocrit (4%), and eosinophil counts (33%) were seen in

    males at 30 ppm. A significant decrease in serum aspartate
    aminotransferase activity was seen in males at 100 and 300 ppm and a
    decrease in bilirubin concentration in males at the high dose. The
    only change in organ weights was a dose-related increase in the
    relative weight of the adrenals in females, which was about 30% and
    statistically significant at 300 ppm. There were no treatment-related
    changes on gross pathological examination; the histopathological
    effects consisted of dose-related granulomatous changes in the liver
    and lymph nodes. In the liver, granuloma, giant-cell infiltration,
    and/or large histiocytic cells filled with brown pigment were found in
    treated mice; these effects were significant at 100 and 300 ppm. In
    the lymph nodes, giant-cell infiltration and/or reticuloendothelial
    cell proliferation were found at the same doses. Testicular atrophy
    was seen erratically, with incidences of 30, 70, 33, 50, and 80% in
    the five groups, respectively, but was not considered to be related to
    treatment. The NOAEL was 30 ppm, equal to 4.1 mg/kg bw per day, on the
    basis of histological findings in the liver and lymphatic system (Arai
    et al., 1981).

     Rats

         Groups of male albino rats were given endosulfan in peanut oil by
    gavage at a dose of 0 or 11 mg/kg bw per day for 30 days. In addition,
    the possible interaction between endosulfan and the chemosterilant,
    metepa, was investigated in groups of rats receiving either metepa
    alone at 30 mg/kg bw per day for 30 days or in combination with
    endosulfan at 11 mg/kg bw per day. There were three deaths in the
    endosulfan-treated group. Endosulfan alone had no significant effect
    on body weights, organ weights, blood chemistry, or histopathological
    appearance. No potentiation of the toxicity of metepa was seen (Nath
    et al., 1978).

         Groups of 100 male SPF Wistar rats were fed diets containing
    technical-grade endosulfan (purity, 97.9%) at concentrations of 360 or
    720 ppm, equal to 34 and 68 mg/kg bw per day for four weeks. Twenty
    control rats received diet alone. Fifty treated and 10 control animals
    were maintained for an additional four-week withdrawal period. The
    objective of the experiment was to determine the toxicological
    significance of yellow, granular deposits observed in the proximal
    convoluted renal tubules in a 13-week and a two-generation feeding
    study. One rat in each treated group died, with no signs of poisoning.
    The behaviour and general condition of the rats and their food and
    water consumption were unaffected by treatment, and body-weight gains
    were comparable in treated and control groups. Enlargement of the
    liver was observed in rats at 360 and 720 ppm at the end of the
    treatment period, and the kidney and brain weights were significantly
    elevated in those at 720 ppm; these treatment-related changes in organ
    weights had, however, disappeared by the end of the withdrawal period.
    The kidneys of treated rats were darkly discoloured, but their
    appearance had returned to normal by the end of the withdrawal period.
    Histopathological examination by light and electron microscopy showed
    granular pigmentation and larger, more numerous lysosomes in renal
    proximal tubule cells after treatment; these changes had decreased by

    the end of the withdrawal period, and no lysosomal changes were found
    in brain or liver. Analysis of residues showed that storage of
    alpha-endosulfan was dose-dependent, temporary, and confined to the
    kidney, where it was detected as endosulfan sulfate and endosulfan
    lactone. The amount of ß-endosulfan was 230 times less than that of
    alpha-endosulfan. The concentrations of the sulfate and lactone
    metabolites were many times lower in liver, and only traces of
    endosulfan remained in the kidney at the end of the withdrawal period
    (Leist & Mayer, 1987).

         Groups of 15 male and 15 female Wistar rats were exposed by
    inhalation to technical-grade endosulfan (purity, 97.2%) at a
    concentration of 0, 0.5, 1, or 2 mg/m3 air for 6 h/day, five days per
    week for 29 days, for a total of 21 exposures. One male rat at the
    high dose was emaciated, had a pale skin, and adopted a high-legged
    position; no other clinical signs were seen in the treated animals. No
    neurological disturbances, opacity of the refractive media, impairment
    of dental growth, or changes in the oral mucosa were seen. The
    body-weight gain of males at the high dose tended to be depressed from
    day 20 of exposure until day 29, the end of the recovery period, but
    no other changes in body-weight gain or food consumption were seen.
    Non-dose-related increases in erythrocyte and haemoglobin
    concentrations were seen at the end of exposure, but not at day 29;
    these concentrations were reported to be within normal ranges for this
    strain of rat. Apart from a transient, non-dose-related increase in
    creatinine concentration and a decrease in serum aspartate
    aminotransferase activity in females at the high dose, no
    treatment-related change in blood chemistry was noted, and no
    histological changes were seen in any of the rats (Hollander et al.,
    1984)

         Technical-grade endosulfan (purity, 97.2%) was applied in a
    solution in sesame oil to the shaved skin of the nape of groups of six
    Wistar rats of each sex 21 times over 30 days, for 6 h/day on five
    days per week under an occlusive bandage. Males were given a dose of
    0, 12, 48, 96, or 190 mg/kg bw per day, and females received 0, 3, 6,
    12, or 48 mg/kg bw per day. In males, deaths and clinical signs of
    poisoning consisting of tremors, tonoclonic convulsions, and/or
    hypersalivation were observed only at the highest dose. In females,
    clinical signs of poisoning were observed at > 2 mg/kg bw per day;
    deaths occurred mainly in the group receiving 48 mg/kg bw per day,
    although single animals died on day 18 after receiving 3, 6, or 12
    mg/kg bw per day, none having shown signs of poisoning. Serum
    cholinesterase activity was 33% lower in males at 192 mg/kg bw per
    day, whereas the activities of the erythrocyte and brain enzymes were
    reduced by 12 and 7%, respectively. In females at 48 mg/kg bw per day,
    serum cholinesterase activity was 21% lower than in controls, and
    there were no effects in the activities of erythrocyte and brain
    enzymes. The NOAEL was 6 mg/kg bw per day (Ebert et al., 1985a,b). 

         Technical-grade endosulfan (purity, 97.2%) as a solution in
    sesame oil was applied to the shaved skin of the nape of groups of six
    male and six female Wistar rats 21 times over 30 days, for 6-h periods
    under an occlusive bandage, at doses of 0, 1, 3, 9, 27, or 81 (males
    only) mg/kg bw per day. No signs of toxicity were observed in males or
    females at 1 and 3 mg/kg bw per day, but two males at 9 mg/kg bw per
    day died, one on day 5 with no previous signs of poisoning and the
    other on day 8 after piloerection, hypersalivation, blood-encrusted
    nose, stagger, and dyspnoea. There were no deaths among males at 27
    mg/kg bw per day, but three at 81 mg/kg bw per day died. None of the
    females at 9 mg/kg bw per day died and no clinical signs of toxicity
    were observed, but five females at 27 mg/kg bw per day died between
    days 2 and 6 with no previous clinical signs of toxicity. Microscopic
    changes were seen in the livers of animals at > 9 mg/kg bw per day,
    consisting of enlargement of parenchymal cells in the periphery and
    loss of cytoplasmic basoplilia. Serum cholinesterase activity was
    statistically significantly reduced by treatment, by 70-80% in males
    at doses of 9-81 mg/kg bw per day but in females by only about 40% at
    9 mg/kg bw per day. Brain acetylcholinesterase activity was
    statistically significantly reduced in males at 9 (21%), 27 (28%), and
    81 (24%) mg/kg bw per day and in all treated females by 13-18%. The
    responses were not dose-related, and the observations in females are
    probably not biologically significant. Since a later study did not
    demonstrate a direct inhibitory effect of endosulfan on rat brain
    acetylcholinesterase activity  in vitro, the reduced brain enzyme
    activity found in this study was difficult to interpret. It is also
    noted that serum enzyme activity was inhibited only at much higher
    doses in the study of Ebert et al. (1985a,b). The two males at 9 mg/kg
    bw per day that died had reduced or immature testes and/or sex organs,
    and the livers of these animals has accentuated lobular markings. The
    authors reasoned that these effects resulted from a
    non-substance-related developmental disturbance already present before
    treatment. No mechanism was proposed for these effects, which were not
    seen at higher doses. The NOAEL was 3 mg/kg bw per day on the basis of
    inhibition of serum and brain cholinesterase activity and microscopic
    changes in the liver (Ebert et al., 1985b,c).

         Endosulfan (purity not stated) as a solution in acetone was
    applied daily to the shaved abdominal skin of groups of 24 albino rats
    of each sex for 30 days at doses of 0, 19, 38, or                
    63 mg/kg bw per day for males and 0, 10, 20, or 32 mg/kg bw per day
    for females. There were no deaths. All doses produced
    hyperexcitability, tremor, dyspnoea, and salivation, which disappeared
    after one week. No significant changes in organ:body weight ratios
    occurred, and there were no treatment-associated effects on
    histological, haematological, or blood chemical parameters. Liver
    alanine and aspartate aminotransferase activities were reduced in
    animals of each sex at the lowest dose, but there were no further
    reductions with increasing dose. Liver alkaline phosphatase and
    lactate dehydrogenase activities were increased in females but not in
    males, again with no increase with dose. Cholinesterase activities
    were not measured. A NOAEL was not identified (Dikshith et al., 1988).

         Groups of 25 CD Sprague-Dawley rats of each sex were fed diets
    containing technical-grade endosulfan (purity, 97.9%) at
    concentrations of 0, 10, 30, 60, or 360 ppm, equal to 0, 0.64, 1.9,
    3.8, and 23 mg/kg bw per day for males and 0, 0.75, 2.3, 4.6, and
    27 mg/kg bw per day for females,  for three months. Five animals of
    each sex per group were maintained for an additional four-week
    recovery period. Three females died, one each at 0, 60, and 360 ppm.
    Slight but statistically significant, dose-related reductions in
    erythrocyte counts and haemoglobin concentrations were seen in males
    at > 30 ppm and in females at > 60 ppm, but were within the
    reported normal range for this strain and age of rat (Leist & Bremmer,
    1998); increased mean corpuscular volume was also seen at these doses.
    Females at 360 ppm had statistically significant decreases in plasma
    and erythrocyte cholinesterase activities (measured by the Ellman
    method) at week 12 (by 41 and 12%, respectively), while increased
    brain acetylcholinesterase activity was observed at 60 and 360 ppm (19
    and 20%, respectively). In males at 360 ppm, urinalysis showed a
    number of reversible changes, including increased urine volume and
    urinary protein concentrations and decreased specific gravity. Gross
    examination revealed enlargement of the liver in males at 360 ppm and
    of the kidneys at 60 and 360 ppm; increases in the absolute weights of
    the liver (18%), kidney (29%), and epididymides (8%) were seen in
    males and of the liver (21%) and kidneys (10%) in females. The kidney
    weights remained significantly elevated in male rats at 360 ppm (15%,
     p < 0.01) at the end of the withdrawal period. 

         Histopathological examination revealed traces of brown pigment in
    scattered hepatocytes in 25% of male rats and minimal centrilobular
    enlargement of hepatocytes in 25% of females at 360 ppm. These changes
    were not observed in rats at the end of the withdrawal period.
    Yellowish discolouration of renal proximal tubular cells was seen in
    males at all doses and in females at 30-360 ppm, the degree of
    pigmentation increasing in a dose-related manner; however, no cell
    death was associated with this finding. In addition, granular
    pigmentation was seen in straight portions and occasionally in
    proximal tubular cells in males at 60 and 360 ppm. The yellow
    discolouration of the renal tubules in male rats had decreased by the
    end of the withdrawal period, but trace or minimal pigmentation was
    still evident. In females at > 60 ppm, the traces of pigmentation
    persisted. Males at 360 ppm also had yellow protein aggregation in the
    proximal convoluted with intracytoplasmic eosinophilic droplets in the
    tubules. The increase in incidence and degree of the yellowish
    discolouration of the proximal tubular cells appeared to be
    treatment-related, since it did not develop in control rats; however,
    no adverse effects were reported that might be associated with these
    findings alone. All rats at 30 ppm showed either trace or minimal
    discolouration and signs of granular or clumped pigment. Other
    investigations suggest that the yellow pigmentation is no more than an
    indication that endosulfan and some of its metabolites are being
    temporarily stored before urinary excretion, and that it is therefore
    an indicator of exposure rather than an expression of toxicity.
    Consequently, this effect was not considered in the evaluation. At
    doses of 60 and 360 ppm, other treatment-related effects were also

    seen when the pigmentation was present, including enlarged kidneys and
    centrilobular hepatocytes. No treatment-related increase in the
    incidence of other renal effects was reported in animals at 10 ppm.
    The NOAEL was thus 10 ppm, equal to 0.64 mg/kg bw per day, on the
    basis of haematological changes (Barnard et al., 1985).

     (c)  Long-term studies of toxicity and carcinogenicity

     Mice

         Groups of 50 six- to seven-week-old B6C3F1 mice of each sex were
    fed diets containing technical-grade endosulfan (purity, 98.8%) at
    time-weighted average concentrations of 3.5 or 6.9 ppm for males and 2
    or 3.9 ppm for females for 78 weeks. Groups of 20 controls received
    untreated diet. There were no clear compound-related effects on
    appearance or behaviour in the treated groups, and the body weights of
    both males and females were unaffected by treatment. The mortality
    rate of males at the high dose was increased early in treatment so
    that, at the end of the experiment, the survival rates were 3/20
    controls, 19/50 at the low dose, and 5/50 at the high dose. The
    mortality rates of female mice were not affected by treatment. No
    treatment-related clinical signs were recorded, and no
    treatment-related neoplastic lesions were seen in the females. Owing
    to the high early mortality rates, no conclusion could be drawn about
    the carcinogenic potential of endosulfan in males. None of the
    non-neoplastic changes seen in the kidneys and sex organs of male and
    female mice could be attributed to treatment. The NOAEL for female
    mice was 3.9 ppm, equal to 0.58 mg/kg bw per day (US National Cancer
    Institute, 1978).

         Groups of 60 NMRI mice of each sex were fed diets containing
    technical-grade endosulfan (purity, 97.2%) at concentrations of 0, 2,
    6, or 18 ppm, equal to 0.28, 0.84, and 2.5 mg/kg bw per day for males
    and 0.32, 0.97, and 2.9 mg/kg bw per day for females,  for up to 24
    months. Ten mice of each sex per dose were killed at 12 and 18 months.
    The behaviour and general health of the animals were not affected by
    treatment. The mortality rate of females at 18 ppm was statistically
    significant decreased at the end of the experiment: control, 45%; 18
    ppm, 28%  (p < 0.05); at week 78, the rates in these two groups of
    female mice were 82 and 62%. Survival among treated male mice was not
    statistically different from that of controls. The body weights of
    males receiving 18 ppm were slightly but significantly lower than
    those of controls during the first third of the study and remained
    slightly but not significantly low throughout the remainder of the
    study. In the other treated groups, there was a tendency to increased
    body-weight gains, especially in the satellite groups killed at 12 and
    18 months. No statistically significant changes were observed in
    haematological or clinical chemical parameters, and macroscopic
    examination did not reveal any findings that were related to
    treatment. No statistically significant changes in organ weights were
    seen in treated animals at the end of the experiment; however, slight
    but statistically significant changes in organ weights were observed
    in animals at 18 ppm at 12 and 18 months, consisting of decreased lung

    and ovary weights in females at 12 months and decreased liver weights
    in males and decreased ovary weights in females at 18 months.
    Histopathological examination did not reveal any effects that were
    related to treatment. No increase in the incidence of neoplastic or
    non-neoplastic lesions was observed. The NOAEL was 6 ppm, equal to
    0.84 mg/kg bw per day, on the basis of decreased body weights in males
    at 24 months and decreased weights of the liver, ovaries, and lung in
    males and females at 12 and/or 18 months (Donaubauer, 1988, 1989; Hack
    et al., 1995).

     Rats

         Groups of 50 male and 50 female Osborne-Mendel rats were fed
    diets containing technical-grade endosulfan (purity, 98.8%) at
    time-weighted average doses of 220, 410, or 950 ppm for males and 220
    or 400 ppm for females for 78 weeks, with a return to control diets
    for a further four weeks. Groups of 20 rats of each sex received
    untreated diet. A highly significant morbidity rate was seen in male
    rats and, by week 54, 52% of those at the high dose had died. A
    dose-related reduction in body weight was found in males at all doses.
    Histopathological examination showed a high incidence of toxic
    nephropathy (> 90%) in males at the low and high doses and in
    females, but in none of the controls. Chronic renal inflammation was
    observed in 40% of control males and 80% of treated males. The toxic
    nephropathy observed was characterized as degenerative changes in the
    proximal convoluted tubules at the junction of the cortex and medulla,
    with associated cloudy swelling, fatty degeneration, and necrosis of
    the tubular epithelium. Some tubules had hyaline casts, and enlarged,
    dark-staining regenerative tubular epithelial cells were observed
    infrequently. In treated males, parathyroid hyperplasia was observed,
    as were calcium deposits in the stomach, kidney, testis, aorta, and
    mesenteric artery. A dose-related increase in the incidence of
    testicular atrophy was seen in treated males, characterized by
    degeneration and necrosis of the germinal cells lining the
    seminiferous tubules and multinucleated cells (fusion bodies),
    resulting in aspermatogenesis. No treatment-related effects were noted
    in the reproductive organs of female rats. No treatment-related
    neoplastic lesions were seen in female rats; owing to the high
    mortality rate in males, no valid conclusion can be drawn about
    carcinogenicity. A NOAEL was not identified, as treatment-related
    changes occurred in the kidneys and the testis at all doses (US
    National Cancer Institute, 1978) 

         Groups of 50 five-to-six-week-old Sprague-Dawley rats of each sex
    were fed diets containing endosulfan (purity, 97.1%) at concentrations
    of 0, 3, 7.5, 15, or 75 ppm, equal to 0, 0.1, 0.3, 0.6, and 2.9 mg/kg
    bw per day for males and 0, 0.1, 0.4, 0.7, and 3.8 mg/kg bw per day
    for females, for 104 weeks. Satellite groups of 20 animals of each sex
    were retained for blood sampling and examination at 104 weeks.
    Reductions in body weights and body-weight gains were observed in
    males (group mean, 17% at 104 weeks) and females (group mean, 18% at
    104 weeks) at 75 ppm, but no clinical signs of poisoning were seen at
    any dose. No increase in mortality rates was observed in treated

    groups. Increased incidences of enlarged kidneys in females and of
    aneurysms and enlarged lumbar lymph nodes in males were seen at 75
    ppm. Histopathological examination showed that males at 75 ppm had an
    increased incidence of aneurysm and marked progressive
    glomerulonephrosis (controls, 20/70; 75 ppm, 30/70). The commonest
    neoplasms were pituitary tumours in males and females and mammary
    tumours in females, but the increased incidences did not appear to be
    related to treatment. The NOAEL was 15 ppm, equal to 0.6 mg/kg bw per
    day, on the basis of reduced body weights and pathological findings at
    higher doses (Ruckman et al., 1989; Gopinath & Cannon, 1990; Hack et
    al., 1995).

         Groups of 25 Wistar rats of each sex were fed diets containing
    technical-grade endosulfan (purity unspecified) at doses of 0, 10, 30,
    or 100 ppm for up to 104 weeks; groups of five of each sex were killed
    at 52 weeks. There were no treatment-related clinical signs, and the
    body weights were unaffected, except for a nonsignificant decrease in
    the body weights and food consumption of males at the high dose. The
    survival rate of treated females was reduced, the deaths being
    associated predominantly with respiratory infections. The weights of
    the testes of males at 10 ppm were reduced by 7% with respect to
    controls at 104 weeks  (p < 0.05), and the kidney weights were
    significantly  (p < 0.001) increased (by 16%) in males at the high
    dose at 104 weeks. Histopathological changes observed in males at the
    high dose at 104 weeks consisted of enlarged kidneys, mild-to-severe
    renal tubular dilatation (12/12), mild-to-moderate formation of
    irregular albuminous casts (10/12), pronounced focal nephritis (7/12),
    and mild-to-severe degeneration (11/12) of the renal tubular
    epithelium. At 104 weeks, female rats at the high dose showed minimal
    degeneration of renal tubules (2/3) and some focal nephritis (1/3).
    The low survival rate precluded a clear conclusion about the renal
    changes in female rats. Microscopic alterations in the liver were seen
    in 50% of males at the high dose at week 104, consisting of focal
    areas of hydropic cells, which were pale and swollen; the nuclei were
    surrounded by a clear zone, and a few cells appeared to have
    eosinophilic cytoplasmic inclusions. Few females at the high dose
    showed changes in liver cells. A few tumours developed during the
    experiment, but their occurrence was not dose-related. The NOAEL was
    30 ppm, equal to 1.5 mg/kg bw per day, on the basis of effects on the
    kidney (Keller, 1959c). 

     Dogs

         Groups of six beagle dogs of each sex were fed diets containing
    technical-grade endosulfan (purity, 96.5%) at concentrations of 0, 3,
    10, or 30 ppm for one year, calculated by the authors to be equivalent
    to 0, 0.23, 0.77, and 2.3 mg/kg bw per day. In addition, one group was
    given a diet containing 30-60 ppm endosulfan, increasing in stages
    from 30 ppm for 54 days, to 45 ppm for 52 days, and 60 ppm for 19-40
    days; these dogs were killed  in extremis before the scheduled
    completion of the experiment and showed a number of signs of
    poisoning, including tonic contraction and increased sensitivity to
    noise and optical stimuli. Some animals given endosulfan at 30 ppm

    throughout the 12-month study had violent contractions of the
    abdominal muscles (without vomiting), and males at this dose had
    reduced body-weight gains throughout the study and slightly reduced
    body weights in the latter stages of the study, in comparison with
    control animals. Cholinesterase activity was measured in serum,
    erythrocytes, and brain, but difficulty appears to have been
    experienced in measuring these activities, and there were large
    variations within groups for the brain enzyme, the group mean of which
    was increased in dogs at 30 ppm. No other effects related to treatment
    were observed, and no increase in the incidence of neoplastic or non-
    neoplastic lesions was observed in treated animals. The NOAEL was 10
    ppm, calculated by the authors to be equivalent to 0.57 mg/kg bw per
    day, on the basis of clinical signs and reductions in body weight
    (Brunk 1989, 1990).

         Groups of two male and two female mongrel dogs were given
    technical-grade endosulfan in gelatin capsules at doses of 0, 3, 10,
    or 30 ppm, equivalent to 0, 0.075, 0.25, or 0.75 mg/kg bw per day, on
    six days per week for one year. The group receiving 3 ppm was given
    100 ppm for the first three days of treatment, but clinical signs of
    vomiting, tremors, convulsions, rapid respiration, mydriasis,
    salivation, and tonic-clonic convulsions in one male and both females
    led to a reduction in the dose for the remainder of the study. No
    clinical signs or treatment-related effects on body-weight gain were
    seen. Clinical chemical and haematological end-points were within
    normal limits, and kidney function was unaffected by treatment. No
    gross or histopathological changes associated with treatment were
    noted. The NOAEL was 30 ppm, equivalent to 0.75 mg/kg bw per day, on
    the basis of clinical signs at the initial high dose (Keller, 1959b).

     (d)  Genotoxicity

         Endosulfan was tested for genotoxicity in a wide range of assays,
    both  in vitro (with and without metabolic activation) and  in vivo 
    (Table 3). There was no evidence of genotoxicty in most of these
    assays. In an assay for dominant lethal mutation in male Swiss mice
    given endosulfan of a purity of 97.3%, there was a significant change
    in the result of mating during the sixth mating week in the group at
    16.6 mg/kg bw per day. The total numbers of implants per pregnancy
    were 9 in controls and 4.5 at the high dose; the numbers of live
    implants per pregnancy were 9 in controls and 2.2 at the high dose;
    and the numbers of dead implants per pergnancy were none in controls
    and 2.25 at the high dose (Pandey et al., 1990). While there is no
    doubt about the statistical significance of these results, it is
    unusual to find a true dominant lethal effect appearing so late in an
    experimental mating schedule; however, it is not unknown, since a
    reproducible effect of this type was demonstrated with some glycol
    ethers (McGregor et al., 1983). In a later assay for dominant lethal
    mutation (Dzwonkowska & Hübner, 1991), much lower doses were used, so
    the results cannot be used as evidence for a non-reproducible effect.
    Significant increases in the proportion of morphologically abnormal
    sperm were also observed in the study of Pandey et al. (1990), as well


        Table 3. Results of assays for the genotoxicity of endosulfan

                                                                                                                              

    End-point               Test object                            Dose                 Result       Reference
                                                                   (LED or HID)a
                                                                                                                              

    In vitro

    Differential toxicity   B. subtilis rec strains H17 and M45    2000 µg/disc         Negativea    Shirasu et al. (1978)

    Reverse mutation        S. typhimurium TA100, TA1535,          5000 µg/plate        Negativeb    Shirasu et al. (1978)
                            TA1537, TA1538, TA98; 
                            E. coli WP2 uvrA

    Gene conversion         S. cerevisiae, D4                      5000 µg/ml           Negativeb    Mellano & Milone (1984b) 
    Forward mutation        S. pombe                               500 µg/ml            Negativeb    Mellano & Milone (1984a) 
    Unscheduled DNA         Male F344 rat primary hepatocytes      51 µg/ml             Negativea    Cifone & Myhr (1984b)
    synthesis

    Gene mutation           Mouse lymphoma L5178Y cells,           75 µg/ml [?]         Negativeb    Cifone & Myhr (1984a)
                            tk locus

    Chromosomal             Human lymphocytes                      200 µg/ml            Negativeb    Asquith & Baillie (1989)
    aberration

    Chromosomal             Human lymphocytes                      200 µg/ml            Negativeb    Pirovano & Milone (1986)
    aberration

    In vivo

    Micronucleus            NMRI mouse bone-marrow cells           5 mg/kg bw,          Negative     Jung et al. (1983)
    formation                                                      po × 1

    Micronucleus            NMRI mouse bone-marrow cells           10 mg/kg bw,         Negative     Müller (1988)
    formation                                                      po × 1

    Table 3. (continued)

                                                                                                                              

    End-point               Test object                            Dose                 Result       Reference
                                                                   (LED or HID)a
                                                                                                                              

    Chromosomal             Albino rat bone-marrow cells           55 mg/kg, po × 5     Negative     Dikshith & Dotta (1978)
    aberration

    Dominant lethal         Male Swiss mice                        16.6 mg/kg bw,       Equivocal    Pandey et al. (1990)
    mutation                                                       ip × 5

    Dominant lethal         Male Balb/c mice                       0.64 mg/kg bw,       Negative     Dzwonkowska & Hübner 
    mutation                                                       ip × 1 and ip × 5                 (1991)

    Sperm morphology        Mice                                   16.6 mg/kg bw,       Positive     Pandey et al. (1990)
                                                                   ip × 5

    Sperm morphology        Mice in vivo                           3 mg/kg bw,          Positive     Khan & Sinha (1996)
                                                                   ip × 35
                                                                                                                              

    LED, lowest effective dose; HID, highest ineffective dose; po, oral; ip, intraperitoneal
    a In the absence of exogenous metabolic activation; not tested in the presence of exogenous metabolic activation
    b In the absence and presence of exogenous metabolic activation
    

    as in a later study (Khan & Sinha, 1996) at lower daily doses of a 35%
    emulsifiable concentrate. 

     (e)  Reproductive toxicity

    (i)   Multigeneration reproductive toxicity

         A preliminary investigation was conducted to determine the doses
    of endosulfan to be used in a two-generation study of reproductive
    toxicity. Four groups of 10 male and 10 female seven-week-old Crl:
    COBS CD Sprague-Dawley rats were given diets containing
    technical-grade endosulfan (purity, 97%) at concentrations of 0, 50,
    75, or 100 ppm for two weeks and subsequently throughout mating and
    the rearing of offspring to weaning. Food consumption and body weights
    were decreased in adults at 75 and 100 ppm. At terminal autopsy, the
    mean weights of the livers were significantly higher than the control
    value in all treated groups. Mating performance, pregnancy rate, and
    the duration of gestation were unaffected by treatment. The litter
    weights of dams were significantly decreased at 75 ppm and to a
    greater extent at 100 ppm from day 4  post partum. No
    treatment-related abnormalities were found in the young (Edwards et
    al., 1982).

         In a two-generation study of reproductive toxicity with two
    matings in each generation,  four groups of six-week-old
    Sprague-Dawley rats were fed diets containing technical-grade
    endosulfan (purity, 97%) at concentrations of 0, 3, 15, or 75 ppm,
    equal to 0.2-0.23, 1-1.2, and 5-5.7 mg/kg bw per day for males and
    0.24-0.26, 1.2-1.3, and 6.2-6.9 mg/kg bw per day for females. The
    group sizes were 32 of each sex for the F0 generation and 28 of each
    sex for the F1b generation. No clinical signs or deaths related to
    treatment were observed during the study. Single deaths occurred among
    F0 females at 0, 3, and 15 ppm and among F1b control females. Mating
    performance and pregnancy rates were not affected by treatment.
    Statistically significant decreases in litter weight were occasionally
    seen, but there was no effect on mean pup weights or on litter size.
    No treatment-related effect on sex ratios was seen at any dose. 

         Statistically significantly increased relative kidney weights
    were seen at 75 ppm in F0 and F1b males, and statistically
    significantly increased relative liver weights were observed in F0
    males and females at 75 ppm and in F1b females at 15 and 75 ppm. The
    effect at 15 ppm in F1b dams was not seen at this dose in any other
    matings. Yellowish discolouration of cells in the proximal convoluted
    tubules were observed in male F1b rats at 3, 5, and 75 ppm and in
    female F1b rats at 75 ppm. The incidence and extent of this effect
    was dose-related; traces of discolouration were seen at all doses, and
    minimal discolouration was seen in male rats at 15 and 75 ppm.
    Granular or clumped pigment was seen in proximal convoluted tubular
    cells in males at the high dose, but these findings were not
    associated with histopathological evidence of renal damage. While the
    increased incidence of cellular discolouration was related to

    treatment, the finding is considered not to be toxicologically
    significant as no adverse effects were seen on cells and the yellow
    pigment was considered likely to be due to storage of endosulfan and
    its metabolites in lysosomes before excretion (Annex 1, reference 58).
    The presence of the pigment is thus an indication of exposure to
    endosulfan rather than of toxicity. The NOAEL for maternal toxicity
    was 15 ppm, equal to 1 mg/kg bw per day, on the basis of increased
    relative liver and kidney weights at higher doses. The NOAEL for
    reproductive effects was 75 ppm, equal to 6 mg/kg bw per day, the
    highest dose tested (Edwards et al., 1984; Offer, 1985).

     (ii)  Developmental toxicity

     Rats

         Groups of mated female albino rats (strain and age unspecified)
    were given oral doses of 0 (20 rats), 5 (26 rats), or 10 (32 rats)
    mg/kg bw per day of endosulfan (purity unspecified) on days 6-14 of
    gestation. No marked changes in behaviour or appearance were reported,
    and the body weights of treated animals were similar to those of
    controls. The numbers of pregnancies were 18, 20, and 21,
    respectively. The dams were killed on day 21 of gestation. No
    abortions occurred, but there was a significant increase in the
    percent of litters with resorptions (5.5% in controls, 20% at 5 mg/kg
    bw per day, and 23% at 10 mg/kg bw per day) and increased fetal
    mortality, although this effect was slight and was not dose-related
    (0, 2, and 1 in the three groups, respectively). Slight increases in
    the incidences of cerebral hypoplasia and enlargement of the renal
    pelvis were observed on visceral examination, but these effects were
    not considered to be related to treatment as they were also seen in
    control animals and the increases were small and were not
    dose-dependent. No other increase in the incidence of visceral
    abnormalities was reported. Skeletal examination showed statistically
    significant increases in the incidences of absent fifth sternebrae and
    of fetuses with incomplete ossification. A slight increase in the
    incidence of absent fifth metacarpus, although not statistically
    significant, was also seen in treated animals. These effects were not
    considered to be related to treatment, as their magnitude was small
    and they were not dose-dependent. No maternal toxicity was seen at any
    dose. The level of reporting in this published paper was inadequate
    for identifying a NOAEL for developmental toxicity (Gupta et al.,
    1978).

         Groups of 25 mated CD Sprague-Dawley rats were given
    technical-grade endosulfan (purity, 97.3%) in corn oil by gavage on
    days 6-19 of gestation at a dose of 0, 0.66, 2, or 6 mg/kg bw per day.
    The clinical signs in dams at 6 mg/kg bw per day included flaccidity,
    rough coat, alopecia, and hyperactivity. A dose-related decrease in
    maternal body-weight gain was seen at 2 and 6 mg/kg bw per day. The
    number of implantations and litter size were unaffected, but there was
    a slight reduction in the weight and length of fetuses of dams at the
    high dose. A non-dose-related reduction in the percent of live fetuses
    and an increase in the number of resorbed fetuses were seen at 2 mg/kg

    bw per day. No statistically significant treatment-related effect on
    the sex ratio was observed. No external variations or malformations
    were seen at 0.66 or 2 mg/kg bw per day; at the high dose, 5/405
    fetuses exhibited lordosis (anteroposterior curvature of the spine)
    and six had oedema. All five of the fetuses with lordosis and five of
    those with oedema were from a single litter. In one fetus from the
    same litter, the skin of the upper forelimb was webbed to the chest.
    No significant treatment-related effects were seen on soft-tissue
    development. Common minor skeletal variations were present in all
    groups. The incidence of poorly ossified sixth sternebrae was
    significantly greater in animals at the high dose than in the control
    group, and two fetuses at this dose had clubbed left hindlimbs. The
    five fetuses from the same litter that had oedema and lordosis also
    had wide, thickened vertebral arches, ribs, and clavicles, and the
    clavicles were shortened, curved, and twisted. Four of these fetuses
    had shortened pubes, and two had an unossified hyoid bone. The
    incidence of these effects was generally < 1%, and the effects were
    largely related to delayed development and confined mainly to a single
    litter from a single dam that showed numerous signs of poisoning
    related to administration of endosulfan, including face rubbing,
    alopecia, flaccidity, and hyperactivity. The developmental effects are
    therefore probably related to the maternal toxicity of the high dose.
    The NOAEL for maternal toxicity was 0.66 mg/kg bw per day on the basis
    of decreased body-weight gain and clinical signs at higher doses. The
    NOAEL for developmental toxicity was 2 mg/kg bw per day on the basis
    of delayed development and a low incidence of isolated skeletal
    variations (Mackenzie, 1980).

         Groups of 20-24 mated female Wistar rats were given
    technical-grade endosulfan (purity, 97.3%) dissolved in sesame oil by
    gavage on days 7-16 of gestation at doses of 0, 0.66, 2, or 6 mg/kg bw
    per day. No clinical signs of toxicity were reported in females at
    0.66 or 2 mg/kg bw per day; four dams at 6 mg/kg bw per day died after
    6-10 doses of endosulfan, three of these rats having tonic-clonic
    convulsions for several days before death. Thirteen of the surviving
    animals had tonic-clonic convulsions for a number of days, generally
    around day 10 of gestation. Some of these rats also showed
    hypersalivation on a number of days during treatment. Statistically
    significant decreases in body weight and body-weight gain were
    observed at 6 mg/kg bw per day. No statistically significant changes
    in reproductive or pup parameters were observed at any dose, and the
    fetal sex ratio was relatively well balanced. No statistically
    significant increase in the incidence of abnormalities was observed in
    fetuses. A single oedematous, retarded fetus at 6 mg/kg bw per day
    presented with superior brachygnathia and a relatively small alveolar
    cavity in the upper jaw, combined with cleft palate, bending of both
    hind feet in the tarsal joint, wavy clavicles, and bent and shortened
    scapulae. These effects were considered to be spontaneous, as no other
    limb or head defects were observed in any pup in any of the litters at
    this dose. Skeletal examination revealed a statistically significant
    increase in the incidence of fragmented thoracic vertebral centra at 6
    mg/kg bw per day. This effect was considered to be treatment-related
    and reflects the frank maternal toxicity of endosulfan at the high

    dose. No treatment-related major malformations were observed. The
    NOAEL for maternal toxicity was 2 mg/kg bw per day on the basis of
    deaths, clinical signs, and decreased body weights at higher doses.
    The NOAEL for developmental toxicity was 2 mg/kg bw per day on the
    basis of the increased incidence of fragmented thoracic vertebral
    centra (Albrecht & Baeder, 1993).

     Rabbits

         Groups of 20-26 mated New Zealand white rabbits were given
    technical-grade endosulfan (purity, 97.3 %) in corn oil by gavage on
    days 6-28 of gestation at doses of 0, 0.3, 0.7, or 1.8 mg/kg bw per
    day. There were no changes in mean body weight. None of the does at
    0.3 or 0.7 mg/kg bw per day aborted, and there were no signs of
    toxicity and no deaths. The high dose was associated with signs of
    maternal toxicity that included noisy, rapid breathing, hyperactivity,
    and convulsions. The does were killed on day 29 of gestation. The
    number of implantations, litter size, sex ratio, mean fetal weight and
    length, and the numbers of live and resorbed fetuses were unaffected
    by treatment. There were no dead fetuses in any group, and no gross
    external alterations were reported. The only soft-tissue anomalies
    occurred in 6/167 fetuses (2/20 litters examined) at the high dose and
    consisted of the left carotid arising from the innominate; 1/141
    control fetuses (1/18 litters examined) also showed this abnormality.
    Common skeletal variations and minor anomalies occurred at similar
    incidences in control and treated fetuses. Endosulfan did not have
    teratogenic or developmental effects even at the maternally toxic dose
    of 1.8 mg/kg bw per day. The NOAEL for maternal toxicity was 0.7 mg/kg
    bw per day on the basis of clinical signs at higher doses (Dickie et
    al., 1981).

     (f)  Special studies

    (i)   Enzyme induction

         Endosulfan was one of 16 organochlorine pesticides tested for
    their ability to induce hepatic microsomal enzyme activities. Wistar
    rats were given diets containing endosulfan at concentrations of 0,
    20, 50, or 200 ppm for two weeks. No difference from control enzyme
    activity was observed at 20 or 50 ppm; at 200 ppm group, the
    activities in comparison with the control were 123% for aniline
    hydroxylase (statistically significant, one experiment), 191% for
    aminopyrene demethylase (statistically significant, one experiment),
    and 124% for hexobarbital oxidase (not significant, one experiment)
    (den Tonkelaar & van Esch, 1974).

         ICR mice given endosulfan at 5 mg/kg bw per day by oral gavage
    for three days and killed on the fourth day showed no increase in
    liver weight or total hepatic cytochrome P450 content. The dearylation
    of  O-ethyl  O- para-nitrophenyl phenylphosphorothioate and
    parathion and NAD(P)H-dependent reductase activity were
    nonsignificantly increased (Robacker et al., 1981).

    (ii)   Promotion

         Enhancement of gamma-glutamyl transpeptidase-positive foci in rat
    liver was studied as an indicator of promotion. Young male
    Sprague-Dawley rats were partially hepatectomized and injected
    intraperitoneally 24 h later with  N-nitrosodiethylamine at 30 mg/kg
    bw. One week after the partial hepatectomy, the rats were randomized
    to groups of 10 or 11 and dosed orally by gavage on five days per week
    for 10 weeks with endosulfan in corn oil at 0, 1, or 5 mg/kg bw per
    day. The numbers and volume of enzyme-altered foci were not increased
    in the treated groups in comparison with controls. 

         In the same study, inhibition of intercellular communication was
    studied in Chinese hamster lung V79 cells in a metabolic cooperation
    assay and in rat liver WB epithelial cells in a scrape loading,
    dye-transfer assay. At nontoxic concentrations, technical-grade
    endosulfan, analytical-grade ensosulfan (alpha and ß isomers and a
    mixture of the two), and endosulfan sulfate inhibited gap-junctional
    intercellular communication in both systems. In addition, endosulfan
    ether was effective in the rat liver WB cell system (Flodström et al.,
    1988). 

     (iii)  Immunotoxicity

         In two published studies, endosulfan was administered to male
    Wistar rats at dietary doses of up to 50 ppm for six weeks (Banarjee &
    Hussain, 1987) or up to 20 ppm for 22 weeks (Banarjee & Hussain, 1986)
    to evaluate humoral and cell-mediated immune responses. In the
    six-week study, a significant decrease in total serum antibody titre
    to tetanus toxoid was seen at 30 and 50 ppm, with a slight decrease
    (not statistically significant) at 10 ppm. A decrease in both
    immunoglobulin (Ig)M and IgG and in the total gamma-globulin content
    of rat serum was observed at 50 ppm. Cellular immunity was assayed by
    measuring inhibition of migration of activated leukocytes and
    macrophages. Rats exposed to endosulfan and subsequently immunized
    with tetanus toxoid showed a significant decrease in inhibition of
    leukocyte and macrophage migration in a dose-dependent pattern, the
    decrease becoming statistically significant at 30 and 50 ppm. These
    results indicate that both humoural and cellular immunity was
    depressed as a result of exposure to endosulfan at 30 and 50 ppm, with
    no effect at 10 ppm, equivalent to 0.5 mg/kg bw per day. In the
    22-week study, the specific response of serum antibody titre to
    tetanus toxoid showed a marked decrease in rats exposed to 10 or 20
    ppm endosulfan throughout the experiment, in a dose- and
    time-dependent pattern. Treatment at 10 or 20 ppm diminished the
    inhibition of migration of both leukocytes and macrophages throughout
    the study. 

         The effect of endosulfan on the immune system did not appear to
    be secondary to other toxic effects, since the body weights of the
    animals were unaffected by treatment and endosulfan is not known to
    affect the hormonal system. Immune responses were unaffected by
    treatment at 5 ppm, equivalent to 0.25 mg/kg bw per day. The Committee

    noted that the method used to assess cellular immunity in these
    studies is far from ideal as it is flawed by large inherent errors,
    lack of objectivity, and, except in very experienced hands, lack of
    accuracy. Less subjective tests of cellular immunity, such as
    cytotoxic T cell response to a virus, would have provided more
    reliable results.

         Technical-grade endosulfan (purity, 96%) was administered in
    sesame oil on 10 occasions by gavage to groups of eight female Wistar
    rats at doses of 0.5, 1.5, or 4.5 mg/kg bw per day from two days
    before until seven days after infection by gavage with approximately
    500  Trichonella spiralis larvae. As a positive control, prednisolone
    was administered by subcutaneous injection at a dose of 25 mg/kg bw
    per day two days before and three days after infection. Three rats
    from each group were killed seven days after infection so that the
    number of adult worms in the intestine could be counted; the remaining
    rats were killed 54 days after infection in order to count the number
    of larvae in the tongue. Thymus and spleen weights and the percentage
    lymphocytes in the white cell count were measured at both times. Body
    weights were measured weekly. There were no differences between
    endosulfan-treated and untreated rats, whereas the
    prednisolone-treated group had a sevenfold higher tongue larval count
    and, at seven days, a 25% reduction in thymus weight, a 50% reduction
    in spleen weight, and lymphocyte counts < 50% of the control value
    (Hack & Leist, 1988).

         Endosulfan was included in the first part of a study to screen
    for immunotoxicity, but because no effect was observed it was not
    examined in greater detail. Groups of six male, weanling Wistar rats
    were given endosulfan in the diet at concentrations of 20, 100, or 250
    ppm for three weeks. Body weights and food intake were recorded
    weekly. At autopsy, the weights of the liver, kidneys, spleen, thymus,
    pituitary, adrenals, thyroid, testis, and mesenteric and popliteal
    lymph nodes were recorded, these organs were also examined
    histologically. Haematological examination consisted of total and
    differential leukocyte counts. Serum IgM and IgG were determined by
    enzyme-linked immunosorbent assay. The only effects induced by
    endosulfan were considered to be expressions of general toxicity, and
    there was no evidence for any specifically immunotoxic effects. The
    most sensitive parameter for the toxicity of endosulfan was a
    reduction in body-weight gain, which was observed at 100 ppm (Vos et
    al., 1982).

     (iv)  Neurobehavioural effects and neurotoxicity

         In a number of studies conducted by the same group of
    investigators, endosulfan (purity, 95%) was given by gavage to rats at
    a dose of 2 mg/kg bw per day for 90 days (Paul et al., 1993, 1994) or
    up to 6 mg/kg bw per day for 30 days (Paul et al., 1995), and
    behavioural and biochemical changes were determined. Signs of frank
    toxicity (reduced body weights, reduced food consumption, death,
    increased intensity of tremors, and increased liver enzyme activity)
    were observed in all studies, and some changes in behaviour were

    noted, including increased motor activity and inhibition of
    conditioned and unconditioned escape and avoidance responses.

         Groups of adult domestic hens were given a single oral dose of 96
    mg/kg bw endosulfan, the LD50, in corn oil, observed for 21 days,
    re-dosed, and again observed for 21 days. As was to be expected, a
    number of deaths occurred that were related to treatment. No signs of
    ataxia and no treatment-related changes in nervous tissue were seen in
    vehicle control or endosulfan-treated hens. Seven of 10 hens in a
    concurrent positive control group given tri- ortho-cresyl phosphate
    developed ataxia and signficant spinal cord and peripheral nerve
    degeneration (Roberts et al., 1983).

         No inhibition of rat brain acetylcholinesterase activity was
    observed in a preparation incubated with 10 µmol/L alpha-endosulfan
    for up to 75 min.. A similar concentration of aldicarb produced 15%
    inhibition within 5 min and 80% inhibition within 75 min (Müllner,
    1989).

         Technical-grade endosulfan (purity, 98.6%) was administered to
    groups of 10 rats as a single dose of 25, 50, or 100 mg/kg bw to males
    and 3, 6, or 12 mg/kg bw to females. Deaths occurred at the highest
    doses, and there was a dose-related increase in the frequency of
    clinical signs, which were reversible and apparent only on the day of
    dosing. These were assumed to be due to the known affinity of
    endosulfan for the gamma-aminobutyric acid receptors in the brain. At
    50 and 100 mg/kg bw in males and 6 and 12 mg/kg bw in females, various
    serious neuropharmacological effects were seen, including coarse
    tremor and tonic-clonic convulsions. At 25 mg/kg bw in males and
    3 mg/kg bw in females, the clinical signs seen were typical of general
    discomfort, such as stilted gait, squatting posture, and irregular
    respiration. No compound-related effects on motor activity were
    observed at non-lethal doses. No effects were seen on the rearing
    frequency, fore- or hindlimb grip strength, or on landing foot-spread.
    No histopathological effects were found in the central or peripheral
    nervous system. The study was carried out in accordance with
    prevailing OECD testing guidelines (April 1996) and the OECD
    principles of good laboratory practice (12 May 1981 [C(81)30(Final)])
    (Bury, 1997).

     (v)  Effects on sperm

         In a study of biochemical changes induced by endosulfan in the
    testis of Druckrey rats, the authors postulated that endosulfan
    impairs testicular function by altering the enzyme activities
    responsible for spermatogenesis, thus affecting the intratesticular
    spermatid count and resulting in low sperm production and increased
    sperm deformities. The data presented support the notion that
    administration of endosulfan at relatively high doses (> 2.5 mg/kg
    bw per day) for several months increases the activity of a number of
    enzymes in the testes, including lactate dehydrogenase, sorbitol
    dehydrogenase, gamma-glutamyl transpeptidase, and glucose-6-phosphate
    dehydrogenase. At doses of 5 mg/kg bw per day and higher, there was a

    marked reduction in sperm count (up to 47%) in comparison with
    controls. In the absence of historical control data, it is unclear
    whether the decrease in sperm count seen at 2.5 mg/kg bw per day (22%)
    was within the normal biological range for the test animals. The sperm
    abnormalities and the reductions in spermatid count and sperm
    production, while statistically significantly different from those in
    concurrent controls, were only slight. In the absence of consistent
    dose-response relationships for these effects, they were considered
    not biologically significant (Sinha et al., 1995).

         The effects of endosulfan on gonadal hormones, measured as plasma
    and testicular testosterone, plasma follicle-stimulating and
    luteinizing hormones, and plasma and testicular 3ß- and
    17ß-hydroxysteroid dehydrogenases, was investigated in Wistar rats
    given endosulfan in peanut oil at doses up to 10 mg/kg bw per day for
    up to 30 days. Significant inhibition of 3ß- and 17ß-hydroxysteroid
    dehydrogenases occurred in the testes of treated animals after 30 days
    of treatment, and the plasma follicle-stimulating hormone, luteinizing
    hormone, and testosterone concentrations were significantly
     (p < 0.05) reduced in rats treated for 15 or 30 days at either
    dose. Plasma and testicular testosterone concentrations were not
    significantly reduced after 15 days of treatment at 7.5 mg/kg. A
    significant decrease in the content or activity of microsomal
    cytochrome P450 and related mixed-function oxidases was observed in
    the testes of treated animals, with marked inhibition of the activity
    of glutathione- S-transferase at both doses. The latter changes were
    reversed when endosulfan was withdrawn, but the testicular
    testosterone concentrations remained significantly reduced (Singh &
    Pandey, 1990).

     (vi)  Endocrine effects

         An estrogen is a substance that can induce estrus or a biological
    response associated with estrus; one such effect is proliferation of
    cells in the female genital tract. In recent years, naturally
    occurring and man-made substances in the environment that may be
    estrogenic have come under increasing scrutiny. Suspicion that
    endosulfan may have estrogenic properties was stimulated by
    observation of the reduced sperm counts described above and of
    testicular atrophy in rats given endosulfan in the diet in long-term
    studies. 

         Perhaps the first study of estrogenic effects  in vivo was
    conducted by Raizada et al. (1991), who treated groups of eight
    ovariectomized Wistar rats, weighing an average of 100 g, with
    endosulfan at 1.5 mg/kg bw per day by gavage, estradiol dipropionate
    intraperitoneally (dose unspecified), or a combination of these
    treatments for 30 days. Endosulfan did not change the weights of the
    uterus, cervix, or vagina, whereas estradiol propionate produced large
    increases. The increased weights seen with the combined treatment were
    similar to those with estradiol propionate alone.

         Concern that endosulfan might be estrogenic persisted as a result
    of the findings of an 'E-screen' assay, which was developed to assess
    the estrogenic effects of environmental chemicals by observing their
    proliferative effect on a target cell. The numbers of cells present
    after similar inocula of the human breast cancer cell line, MCF-7,
    were compared in the absence of estrogens (negative control), in the
    presence of estradiol-17ß (positive control), and with a range of
    concentrations of endosulfan. In this assay, endosulfan was estrogenic
    at concentrations of 10-25 µmol/L, with a proliferative effect about
    80% that of 17ß-estradiol at 10 µmol/L; the relative proliferative
    potency (i.e. the ratio of the doses of endosulfan and estradiol-17ß
    required to produce the maximum effect) was 0.0001%. In addition,
    endosulfan competed with estradiol-17ß for binding to the estrogen
    receptor and increased the concentrations of progesterone receptor and
    pS2 in MCF-7 cells, as would be expected for a compound that mimics
    estrogens (Soto et al., 1994, 1995).

         As part of a study to optimize investigations of estrogenic
    activity, endosulfan and nine other chemicals (17ß-estradiol,
    diethylstilbestrol, tamoxifen, 4-hydroxytamoxifen, methoxychlor, 
    the methoxychlor metabolite
    2,2-bis (para-hydroxyphenyl)-1,1,1-trichloroethane, nonylphenol,
     ortho, para'-DDT, and kepone) with known or suspected estrogenic
    activity were tested in three assays: competitive binding to the mouse
    uterine estrogen receptor, transcriptional activation in HeLa cells
    transfected with plasmids containing an estrogen receptor and a
    response element, and  the uterotropic assay in mice. The results of
    the three assays were consistent with respect to the known estrogenic
    activities of the chemicals tested and their requirements for
    metabolic activation. There was no evidence from any of these tests
    that endosulfan is estrogenic (Shelby et al., 1996). 

         A much publicized report indicated that even estrogens of low
    potency, such as endosulfan, could have important effects because of
    interaction with other chemicals. The estrogenic potencies of
    combinations of chemicals were screened in a system in which the human
    estrogen receptor sequence is incorporated into the yeast genome.
    Combinations of two weak environmental estrogens, such as dieldrin,
    endosulfan, and toxaphene, were 1000 times more potent in human
    estrogen receptor-mediated transactivation than any chemical alone
    (Arnold et al., 1996). This result was not reproduced in another
    laboratory in which the same assay was used or in a uterotropic assay
    in which sexually immature rats were treated with endosulfan or
    dieldrin alone or in a combination on three successive days and the
    uterine mass weighed on the following day. The highest doses used in
    the human estrogen receptor assay were determined by the solubility of
    the compounds, and the highest doses in the uterotropic assay were 100
    mg/kg bw for endosulfan or dieldrin alone and 75 mg/kg bw of each in
    combination. Both chemicals were inactive in both assays, and there
    was no evidence of synergism (Ashby et al., 1997). In a further study
    with the human estrogen receptor assay, however, 0.1 mmol/L endosulfan
    increased the activity of ß-galactosidase (Ramamoorthy et al., 1997).

         More doubt was cast upon the thesis of synergism by an
    independent study in which endosulfan and dieldrin showed no additive
    effect in displacing 3H-17ß-estradiol from rat uterine estrogen
    receptors or in inducing the proliferation of MCF-7 breast cancer
    cells. The weak proliferative potential described by Soto et al.
    (1994, 1995) was, however, confirmed in this assay  in vitro. 
    Endosulfan or dieldrin alone at 3 mg/kg bw per day or in combination,
    injected intraperitoneally daily for three days, did not stimulate
    uterotrophic activity and had no effect on pituitary prolactin or
    other endocrine-related end-points in immature female rats, indicating
    that these weakly estrogenic compounds do not interact in a
    synergistic fashion in binding to estrogen receptors or in activating
    estrogen receptor-dependent responses in mammalian tissues or cells
    (Wade et al., 1997). The paper in which synergism was originally
    proposed was later withdrawn, since the results could not be
    reproduced, even in the same laboratory (McLachlan, 1997). Overall,
    these results suggest that concomitant exposure to weakly estrogenic
    compounds probably does not result in reproductive toxicity related to
    estrogen action.

    3.  Observations in humans

         In general, the doses of endosulfan involved in cases of
    poisoning have been poorly characterized. In a summary of case reports
    (Lehr, 1996), the lowest reported dose that resulted in death was 35
    mg/kg bw; deaths have also been reported after ingestion of 295 and
    467 mg/kg bw, within 1 h of ingestion in some cases. Intensive medical
    treatment within 1 h was reported to be successful after ingestion of
    doses of 100 and 1000 mg/kg bw. The clinical signs in these patient
    were consistent with those seen in laboratory animals, dominated by
    tonic-clonic spasms. In a case in which a dose of 1000 mg/kg bw was
    ingested, neurological symptoms requiring anti-epileptic therapy were
    still required one year after exposure. 

    Comments

         More than 90% of an oral dose of endusulfan was absorbed in rats,
    with maximum plasma concentrations occurring after 3-8 h in males and
    about 18 h in females. Elimination occurs mainly in the faeces and to
    a lesser extent in the urine, more than 85% being excreted within 120
    h. The highest tissue concentrations were in the kidneys. The
    metabolites of endosulfan include endosulfan sulfate, diol,
    hydroxy-ether, ether, and lactone but most of its metabolites are
    polar substances which have not yet been identified. Endosulfan would
    not be expected to accumulate significantly in human tissues. No data
    on plant metabolites were available to the Meeting.

         A battery of tests for acute toxicity in several species with
    technical-grade endosulfan showed that it is highly toxic after oral
    or dermal administration, with respective LD50 values of 10-160 mg/kg
    bw and 45-135 mg/kg bw. The LC50 value for rats in a single study was
    13 mg/m3 in females and 35 mg/m3 in males. Endosulfan, administered
    by any route, is more toxic to female than to male rats. Clinical

    signs of acute intoxication include piloerection, salivation,
    hyperactivity, respiratory distress, diarrhoea, tremors, hunching, and
    convulsions.

         WHO has classified endosulfan as moderately hazardous (WHO,
    1996).

         The kidney is the target organ for toxicity. The renal effects
    include increased renal weights and granular pigment formation after
    short-term administration and progressive, chronic glomerulo-nephrosis
    or toxic nephropathy after long-term exposure, although the
    observation of progressive glomerulonephrosis is complicated by the
    fact that this is a common lesion in ageing laboratory rats and occurs
    at high incidence in control rats.

         In a 90-day feeding study in rats, the cytoplasm of isolated
    cells in the renal proximal convoluted tubules had a yellowish colour,
    particularly in males, at all dietary concentrations from 10 ppm. The
    presence of this yellow pigmentation was largely reversible during a
    four-week recovery period, and it did not appear to indicate
    nephrotoxicity. A darker, more particulate, granular and/or clumped
    pigment was also observed, predominantly in cells of the straight
    portions and occasionally in the proximal convoluted tubules, at
    dietary concentrations of 30 ppm and above. This darker pigment was
    more persistent than the yellow one, and urinalysis revealed darker
    urine and marginally more ketones at doses from 60 ppm, and marginally
    more protein, particularly in males, indicating renal damage at doses
    of 360 ppm and above. Similar findings emerged from a multigeneration
    study but not from a two-year study of carcinogenicity in rats. The
    changes in pigmentation were considered to be due to the presence of
    endosulfan and/or its metabolites in the enlarged lysosomes. To test
    this hypothesis, a four-week feeding study was conducted in which male
    rats were given dietary concentrations of 360 or 720 ppm endosulfan.
    Light and electron microscopy of the kidneys of these animals clearly
    showed increases in the number of lysosomes and the size of cells in
    the convoluted tubule, probably as a result of accumulation of the
    test material and/or its metabolites. Lysosomal changes were not
    observed in either brain or liver, and the renal changes receded
    appreciably during a 30-day recovery period. Chemical analysis of the
    kidneys indicated the presence of alpha-endosulfan and, to a lesser
    extent ß-endosulfan sulfate, and endosulfan lactone. The
    concentrations of the dominant alpha-endosulfan in the kidneys were
    about 50 times those in the liver. The concentrations in blood were
    usually below the level of detection. After the 30-day recovery
    period, renal alpha-endosulfan was detected only in traces and ß-
    endosulfan not at all. Similar analysis of tissues from rats in the
    two-year study of toxicity and carcinogenicity did not reveal the
    presence of these substances in the kidney, although measurable alpha-
    endosulfan was found in the liver at 75 ppm. The yellow colour
    therefore indicates the presence of endosulfan and/or its metabolites,
    rather than either a stage in the pathogenesis of nephropathy or an
    independent expression of toxicity. It was postulated that in longer

    studies its removal from lysosomes is accelerated by enzyme induction,
    which has not been investigated.

         In a 78-week study, exposure of rats to endosulfan at a high dose
    of 20 mg/kg bw per day resulted in testicular atrophy, characterized
    by degeneration and necrosis of the germinal cells lining the
    seminiferous tubules. In addition, decreased sperm counts accompanied
    by an increased incidence of sperm abnormalities have been reported in
    mice, again at high doses of endosulfan. Reductions in the activities
    of some testicular xenobiotic-metabolizing enzymes and some hormones
    that are necessary for normal testicular function were also seen in a
    30-day study in rats at 10, but not at 7.5 mg/kg bw per day. The
    functional significance of these findings was not clear, as studies of
    reproductive and developmental toxicity in rats and rabbits showed
    neither impaired fertility nor any increase in the incidence of
    defects or abnormalities in offspring. Given the high doses at which
    these testicular effects were observed, it would appear that they are
    of little human significance.

         No genotoxic activity was observed in an adequate battery of
    tests for mutagenicity and clastogenicity  in vitro and  in vivo. 
    The Meeting concluded that endosulfan is not genotoxic.

         No carcinogenic effect was observed in mice at 18 ppm for 24
    months, in female rats at 445 ppm for 78 weeks in one study or in male
    or female rats at 75 ppm or 100 ppm for two years in two other
    studies. The Meeting noted the differences in the dietary
    concentrations used in these studies, but non-neoplastic responses
    were seen even at the lower doses.

         Endosulfan at dietary concentrations of 0, 3, 15, or 75 ppm did
    not affect reproductive performance or the growth or development of
    the offspring of rats over the course of a two-generation study. The
    NOAEL was 75 ppm, the highest dose tested, equal to 5 mg/kg bw per day
    for males and 6.2 mg/kg bw per day for females. The NOAEL for parental
    toxicity was 15 ppm, equal to 1 mg/kg bw per day for males and 1.2
    mg/kg bw per day, on the basis of increased liver and kidney weights
    at 75 ppm.

         In two studies of developmental toxicity in rats given oral doses
    of 0, 0.66, 2, or 6 mg/kg bw per day, the NOAEL for maternal toxicity
    was 0.66 mg/kg bw per day in one study and 2 mg/kg bw per day in the
    other. In the first case, the basis was decreased body-weight gain at
    2 mg/kg bw per day and decreased body-weight gain and clinical signs
    of toxicity at 6 mg/kg bw per day; in the second case, the basis was
    mortality, clinical signs of toxicity, and decreased body-weight gain
    at 6 mg/kg bw per day. In both studies, the NOAEL for developmental
    toxicity was 2 mg/kg bw per day, in the first case on the basis of
    delayed development and a low incidence of skeletal variations seen at
    6 mg/kg per day and in the second on the basis of an increased
    incidence of fragmented thoracic vertebral centra seen at 6 mg/kg bw
    per day. In neither study was there any treatment-related major
    malformation.

         In a study of developmental toxicity in rabbits given oral doses
    of 0, 0.3, 0.7, or 1.8 mg/kg bw per day, the NOAEL for maternal
    tocicity was 0.7 mg/kg bw per day on the basis of clinical signs of
    toxicity at 1.8 mg/kg bw per day. The NOAEL for developmental toxicity
    was 1.8 mg/kg bw per day, the highest dose tested.

         Several recent studies have shown that endosulfan, alone and in
    combination with other pesticides, may bind to estrogen receptors and
    may perturb the endocrine system. The available studies show only very
    weak binding to hormone receptors  in vitro, and the evidence for
    their relevance to adverse physiological effects  in vivo is
    extremely limited. Long-term assays of toxicity and studies of
    reproductive and developmental toxicity in experimental mammals did
    not indicate that endosulfan induces functional aberrations that might
    result from loss of endocrine homeostasis.

         The absence of immunotoxic effects in a large number of bioassays
    with endosulfan suggested that it does not have an adverse effect on
    the immune function of laboratory animals. However, in two studies,
    rats given endosulfan in the diet at 30 or 50 ppm for 6 weeks or 20
    ppm for 22 weeks had reduced serum titres of tetanus toxoid antibody
    and reduced immunoglobulins G and M, and inhibition of migration of
    both leukocytes and macrophages. These findings have not been
    confirmed.

         In a summary of case reports of human poisoning incidents, the
    lowest reported dose that caused death was 35 mg/kg bw. Higher doses
    caused death within 1 h. The clinical signs in these patients were
    dominated by tonic-clonic convulsions, consistent with the
    observations in experimental animals.

         An ADI of 0-0.006 mg/kg bw was established on the basis of the
    NOAEL of 0.6 mg/kg bw per day in the two-year dietary study of
    toxicity in rats and a safety factor of 100. The ADI is supported by
    similar NOAEL values in the 78-week dietary study of toxicity in mice,
    the one-year dietary study of toxicity in dogs, and the study of
    developmental toxicity in rats.

         An acute RfD of 0-0.02 mg/kg was established on the basis of the
    NOAEL of 2 mg/kg bw per day in the study of neurotoxicity in rats and
    a safety factor of 100.

    Toxicological evaluation

     Levels that cause no toxic effect

         Mouse:    3.9 ppm, equal to 0.58 mg/kg bw per day (females in a
                   78-week study of toxicity)

         Rat:      15 ppm, equal to 0.6 mg/kg bw per day (two-year dietary
                   study of toxicity)
                   75 ppm, equal to 6 mg/kg bw per day (reproductive
                   toxicity)
                   0.66 mg/kg bw per day (maternal toxicity in a study of
                   developmental toxicity)
                   2 mg/kg bw per day (fetotoxicity in a study of
                   developmental toxicity)

         Rabbit:   0.7 mg/kg bw per day (maternal toxicity in a study of
                   developmental toxicity)

         Dog:      10 ppm, equivalent to 0.57 mg/kg bw per day (one-year
                   study of toxicity)

     Estimate of acceptable daily intake for humans

              0-0.006 mg/kg bw

     Estimate of acute reference dose for humans

              0.02 mg/kg bw

     Studies that would provide information useful for continued 
     evaluation of the compound

         1.   Studies of immunotoxicity with standard test protocols

         2.   Studies of the significant sex difference in acute toxicity,
              particularly in rats

         3.   Further observations in humans

        List of end-points relevant for setting guidance values for dietary and non-dietary exposure
                                                                                                 

     Absorption, distribution, excretion, and metabolism in mammals 

    Rate and extent of absorption             Rat: oral, > 90% absorption; max. concentration at 
                                              3-8 h (males) 18 h (females)
    Distribution                              Mainly in kidney and liver
    Potential for accumulation                Low
    Rate and extent of excretion              Biphasic; urinary half-life was 6 h for 1st phase, 
                                              33-68 h for 2nd phase; faecal half-life was 10 h and 
                                              30 h; > 85% excretion within 120 h 
    Metabolism in animals                     Oxidation and hydrolysis; unidentified polar 
                                              metabolites
    Toxicologically significant               Parent; no data on plant metobolites 
    compounds (animals, plants and 
    environment)

    Acute toxicity

    Rat: LD50 oral                            10 mg/kg bw (female)
    Rat: LD50  dermal                         500 mg/kg bw (female)
    Rat: LC50 inhalation                      13 mg/m3 4 h (female)
    Skin irritation                           Not irritating
    Eye irritation                            Not irritating
    Skin sensitization                        Not sensitizing

    Short-term toxicity

    Target/critical effect                    Reduced survival, convulsions, salivation
    Lowest relevant oral NOAEL                Rat: 0.64 mg/kg bw per day, dietary
    Lowest relevant dermal NOAEL              Rat: 3 mg/kg bw per day
    Lowest relevant inhalation NOAEL          Rat: 2 mg/m3, no effect (highest concentration)

    Genotoxicity                              Not genotoxic

    Long-term toxicity and carcinogenicity

    Target/critical effect                    Kidney
    Lowest relevant NOAEL                     Rat: 0.6 mg/kg bw per day, 2-year study
    Carcinogenicity                           Not carcinogenic

    Reproductive toxicity

    Reproduction target: critical effect      None identified
    Lowest relevant reproductive NOAEL        Rat: 6 mg/kg bw per day
    Developmental target /critical effect     Fetoxicity at maternally toxic doses
    Lowest relevant developmental NOAEL       Rat: 2 mg/kg bw per day

    Neurotoxicity/Delayed neurotoxicity       Rat: 1.5 mg/kg bw (female); 12.5 mg/kg bw (male) 
                                              no effect

    Other toxicological studies               Immunotoxicity in certain special assays, not 
                                              confirmed in sensitization test or histologically

                                              Some conflicting evidence of interaction with 
                                              estrogen receptors in vitro; none in vivo

    Medical data                              Lowest lethal dose: 35 mg/kg bw, oral

    Summary                  Value                Study                         Safety factor
    ADI                      0-0.006 mg/kg bw     Several different species     100
                                                  and end-points
    Acute reference dose     0.02 mg/kg bw        Study of neurotoxicity in     100
                                                  rats  
                                                                                                 
    
    References

    Albrecht, M. & Baeder, C. (1993) Hoe 002671-substance technical (code:
    Hoe 002671 00 ZD98 0005). Testing for embryotoxicity in the Wistar rat
    after oral administration. Unpublished report No. 93.0716, document
    A51695. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Arai, M., Hiromori ,T., Ho, S., Okuno, Y. & Miyamoto, J. (1981) Life
    span chronic toxicity study of endosulfan in mice -- 12 month report.
    Unpublished report No. 0285, at-10 from Sumitomo Chemical Co Ltd,
    Japan, 28 April 1981. Submitted to WHO by Hoechst Schering AgrEvo
    GmbH, Frankfurt-am-Main, Germany.

    Arcelin, G. (1996) Contact hypersensitivity to endosulfan (Code: Hoe
    002671 00ZD99 0008) in albino guinea pigs maximumization test.
    Unpublished report No. 630753 from RCC, Itingen, Switzerland. Hoechst
    document A58132.A51695. Submitted to WHO by Hoechst Schering AgrEvo
    GmbH, Frankfurt-am-Main, Germany.

    Arnold, S.F., Klotz, D.M., Collins, B.M., Vonier, P.M., Guilette, L.J.
    & McLachlan, J.A. (1996) Synergistic activation of oestrogen receptor
    with combinations of environmental chemicals.  Science, 272,
    1489-1492.

    Ashby, J., LeFevre, P.A., Odum, J., Harris, C.A., Routledge, E.J. &
    Sumpter, J.P. (1997) Synergy between synthetic oestrogens?  Nature, 
    385, 494. 

    Asquith, J.C. & Baillie, J.H. (1989) Endosulfan substance technical
    (code Hoe 002671 0I ZD95 0005). Metaphase analysis of human
    lymphocytes. Unpublished report No. m/hl/1307 from Toxicol
    Laboratories, United Kingdom, 16 March 1989. Hoechst document A40411.
    Submitted to WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main,
    Germany.

    Banarjee, B.D. & Hussain, Q.Z. (1986) Effect of subchronic endosulfan
    exposure on humoral and cell-mediated immune responses in albino rats.
     Arch. Toxicol., 59, 279-284.

    Banarjee, B.D. & Hussain, Q.Z. (1987) Effects of endosulfan on humoral
    and cell-mediated immune responses in rats.  Bull. Environ. Contam. 
     Toxicol., 38, 438-441.

    Barnard, A.V., Atkinson, J.S., Heywood, R., Street, A.E, Gibson, W.A.,
    Rao, R., Offer, J.M. & Gopinath, A.R.H. (1984) 13 week toxicity study
    in mice. Unpublished report No. Hst 229/831052, 25 September 1984 from
    Huntingdon Research Centre, Huntingdon, Cambridgeshire, United
    Kingdom. Hoechst document A29663. Submitted to WHO by Hoechst Schering
    AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Barnard, A.V., Jones, D.R., Powell, L.A.J., Heywood, R., Street, A.E.,
    Gibson, W.A., Gopinath, C., Majeed, S.K. & Almond, R.H. (1985) 13-week
    toxicity study in rats followed by a 4-week withdrawal period.
    Unpublished report No. Hst 230/84176, 25 March 1985 from Huntingdon
    Research Centre, Huntingdon, Cambridgeshire, United Kingdom. Hoechst
    document A30700 Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt- am-Main, Germany.

    Bhide, M.B. & Naik, P.Y. (1984a) The acute oral toxicity (LD50) of
    Excel Industries Ltds endosulfan technical No. 2 to the albino rats.
    Unpublished report from Indian Institute of Toxicology (report No. and
    date not given). Submitted to WHO by the National Registration
    Authority for Agricultural and Veterinary Chemicals, Australia.

    Bhide, M.B. & Naik, P.Y. (1984b) The acute oral toxicity (LD50) of
    Excel Industries Ltds endosulfan technical No. 1 to the albino mice.
    Unpublished report from Indian Institute of Toxicology (report No. and
    date not given). Submitted to WHO by the National Registration
    Authority for Agricultural and Veterinary Chemicals, Australia.

    Bhide, M.B. & Naik, P.Y. (1984c) The acute dermal toxicity (LD50) of
    Excel Industries Ltds endosulfan technical No. 2 to the albino
    rabbits. Unpublished report from Indian Institute of Toxicology
    (report No. and date not given). Submitted to WHO by the National
    Registration Authority for Agricultural and Veterinary Chemicals,
    Australia.

    Bowman, J.S. (1959) Preliminary report: Subacute feeding -- dairy
    cows. Unpublished report from Hazleton Laboratories, USA. Hoechst
    document No. A14205. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Bracha, P. (1977) Thionex tech: Acute oral toxicity study in rats,
    skin irritation study in rabbits, acute dermal toxicity study in
    rabbits, eye irritation study in rabbits and acute inhalation study in
    rats. Unpublished report No. 6111820 from Warf Institute Inc. Madison,
    Wisconsin, USA. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Bremmer, J.N. (1997a) Endosulfan: Substance technical (code: Hoe
    002671 00 ZD99 0008) Testing for primary dermal irritation in the
    rabbit. Unpublished Hoechst Marion Roussel preclinical development
    study No. 96.0837. Hoechst document A58442. Submitted to WHO by
    Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Bremmer, J.N. (1997b) Endosulfan: Substance technical (code: Hoe
    002671 00 ZD99 0008) Testing for primary eye irritation in the rabbit.
    Unpublished Hoechst Marion Roussel preclinical development study No.
    96.0838. Hoechst document A58443. Submitted to WHO by Hoechst Schering
    AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Bremmer, J.N. & Leist, K.-H. (1998) Endosulfan (AE F002671, substance
    technical). Evaluation of the acute oral and dermal toxicity.
    Unpublished report No. TOX98/003 from Hoechst Schering AgrEvo GmbH.
    Hoechst document A59823. Submitted to WHO by Hoechst Schering AgrEvo
    GmbH, Frankfurt-am-Main, Germany.

    Brunk, R. (1989) Endosulfan-substance technical (code: Hoe 002671 00
    ZD96 0002). Testing for toxicity by repeated oral administration
    (1-year feeding study) to beagle dogs. Unpublished report No. 87.0643
    from Pharma Research Toxicology and Pathology. Hoechst report No.
    89.0188; document No. A40441 Submitted to WHO by Hoechst Schering
    AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Brunk, R. (1990) Addendum to Hoechst report 89.0188; document No.
    A44605. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Bury, D. (1997) Endosulfan; substance, technical (code: Hoe 002671 00
    ZD99 0008). Neurotoxicological screening in the male and female Wistar
    rat. Acute toxicity. Unpublished report No. 96.0373 from Hoechst
    Marion Roussel Preclinical Development, Germany. Hoechst report No.
    A59088. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Christ, O. & Kellner, H.M. (1968) Investigations with endosulfan-14C
    in mice. Unpublished report No. ch/he-8412 from Hoechst Radiochemical,
    Frankfurt, 31 December 1968. Hoechst document A53842, translation of
    document A14217. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Cifone, A.M. & Myhr, B.C. (1984a) Evaluation of Hoe 002671-substance
    technical in the rat primary hepatocyte unscheduled DNA synthesis
    assay. Unpublished LBI project No. 20991 from Litton Bionetics Inc.,
    USA, November 1984. Hoechst document No. A29800. Submitted to WHO by
    Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Cifone, A.M. & Myhr, B.C. (1984b) Mutagenicity evaluation of Hoe
    002671-substance technical in the mouse lymphoma forward mutation
    assay. Unpublished LBI project No. 20980 from Litton Bionetics Inc.,
    USA, November 1984. Hoechst document No. A29801. Submitted to WHO by
    Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany. 

    Craine, E.M. (1986) A dermal absorption study in rats with
    14C-endosulfan. Unpublished project No. Wil-39028, 11 December 1986
    from Wil Research Lab, USA. Wil-39028. 11 Decemnber, 1986. Hoechst
    document No. A35730. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Craine, E.M. (1988) A dermal absorption study in rats with
    14C-endosulfan with extended test duration. Unpublished project No.
    Wil-39029 from Wil Research Lab, USA. Hoechst document No. A39677.
    Submitted to WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main,
    Germany.

    Deema, P. Thompson, E. & Ware, G. (1966) Metabolism, storage and
    excretion of 14C-endosulfan in the mouse.  J. Econom. Entomol., 59,
    546-550.

    Dickie, S.M., Mackenzie K.M. & Rao, G.N. (1981) Teratology study with
    FMC 5462 in rabbits. Unpublished study No. 80070, 27 July 1981 from
    Raltech Scientific Services. Hoechst document No. A23192. Submitted to
    WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Diehl, K.H. & Leist, K.H. (1988a) Hoe 002671: Active ingredient
    technical (code: Hoe 002671 0I ZD96 0002). Testing for acute oral
    toxicity in the male and female Wistar rat. Unpublished study No.
    88.0551, 27 July 1988, from Pharma Research Toxicology and Pathology,
    Frankfurt, Germany. Hoechst document No. A39680. Submitted to WHO by
    Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Diehl, K.H. & Leist, K.H. (1988b) Endosulfan-active ingredient
    technical (code: Hoe 002671 0I ZD96 0002). Testing for acute dermal
    toxicity in the male and female Wistar rat. Unpublished study No.
    88.0552, 22 August 1988, from Pharma Research Toxicology and
    Pathology, Germany. Hoechst document A39397, 1 September 1988.
    Submitted to WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main,
    Germany.

    Dikshith, T.S. & Datta, K.K. (1978) Endosulfan: Lack of cytogenetic
    effects in male rats. Unpublished document No. A17140 from Industrial
    Toxicology Research Centre. Submitted to WHO by Hoechst Schering
    AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Dikshith, T.S.S., Raizada, R.B., Kumar, S.N., Srivastava, M.K.,
    Kaushal, R.A., Singh, R.P. & Gupta, K.P. (1988) Effect of repeated
    dermal application of endosulfan to rats.  Vet. Hum. Toxicol., 30,
    219-224.

    Donaubauer, H.H. (1988) Endosulfan-substance technical (code: Hoe
    002671 OI ZD97 0003). Carcinogenicity study in mice: 24 months feeding
    study. Unpublished study No. 745 from Pharma Research Toxicology and
    Pathology, Germany. Hoechst document No. A38008. Submitted to WHO by
    Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Donaubauer, H.H. (1989) Amendment to the report No. 88.0278
    endosulfan-substance technical (code: Hoe 002671 OI ZD97 0003).
    Carcinogenicity study in mice: 24 months feeding study. Unpublished
    study No. 745 from Pharma Research Toxicology and Pathology, Germany.
    Hoechst document No. A41617. Submitted to WHO by Hoechst Schering
    AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Donaubauer, H.H., Leist, K. & Kramer, M. (1985) Endosulfan-substance
    technical (code: Hoe 002671 01 ZD97 0003). 42-Day feeding study in
    mice. Unpublished study No. 744 from Pharma Research Toxicology,
    Germany. Hoechst document No. A38104. Submitted to WHO by Hoechst
    Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Dorn, E. & Werner, H.-J. (1989) Endosulfan (Hoe 002671 OI ZD97 0003):
    Determination of residues in the liver and kidneys of rats after
    chronic (2-years) feeding (week 104). Unpublished Produktentwicklung,
    GB-C Ökologie II Hoechst AG Study No. (Analytical part) CR065/88.
    Hoechst document No. A41265. Submitted to WHO by Hoechst Schering
    AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Dorough, M.W., Huhtanen, K., Marshall, T.C. & Bryant, H.E. (1978) Fate
    of endosulfan in rats and toxicological considerations of apolar
    metabolites.  Pest. Biochem. Physiol., 8, 241-252.

    Dzwonkowska, A. & Hübner, H. (1991) Studies on commercial insecticides
    with the dominant lethal mutations test.  Polish J. Occup. Med. 
     Environ. Health, 4, 43-53.

    Ebert, E. & Weigand, W. (1984) Testing of the therapeutic effect of
    diazapam (Valium R) and phenobarbital (Luminal R) in the event of
    acute poisoning with endosulfan-active ingredient technical (code: Hoe
    002671 oi ZD97 0003) in Wistar rats. Unpublished report No. 84.0062
    from Pharma forschung Toxikologie. Hoechst document A29211. Submitted
    to WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Ebert, E., Weigand, W. & Kramer, P. (1985a) Endosulfan-active
    ingredient technical (code: Hoe 002671 01 ZD97 0003). Testing for
    subchronic dermal toxicity (21 applications over 30 days) in SPF
    Wistar rats. Unpublished study No. 83.0118 from Pharma forschung
    Toxicologie. Hoechst document No. A30754, translation of document
    A30751. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Ebert, E., Leist, K.H. & Kramer, P. (1985b) Endosulfan-active
    ingredient technical (code: Hoe 002671 01 ZD97 0003). Testing for
    subchronic dermal toxicity (21 applications over 30 days) in Wistar
    rats. Toxicological review of studies 721 and 729 (reports 84.0321 and
    84.0223). Unpublished Hoechst document No. A30755, translation of
    A30752. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Ebert, E., Leist ,K.H. & Kramer, P. (1985c) Endosulfan-active
    ingredient technical (code: Hoe 002671 01 ZD97 0003). Testing for
    subchronic dermal toxicity (21 applications over 30 days) in Wistar
    rats. Unpublished study No. 83.0508 from Pharma forschung Toxicologie.
    Hoechst document No. A30753, translation of document A30750. Submitted
    to WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Edwards, J.A., Hughes, E.W. & Almond, R.H. (1982) Preliminary
    investigation of the effect of endosulfan (code, Hoe 02671 OI AT 209)
    on reproduction of the rat. Unpublished report No. Hst 203/82252 from
    Huntingdon Research Centre, Huntingdon, Cambridgeshire, United
    Kingdom. Hoechst document No. A29563. Submitted to WHO by Hoechst
    Schering AgrEvo GmbH, Frankfurt-am-Main, Germany. 

    Edwards, J.A., Reid, J.Y., Offer, M.J., Almond, H.R. & Gibson, A.W.
    (1984) Effect of endosulfan-technical (code, Hoe 02671OI AT209) on
    reproductive function of multiple generations in the rat. Unpublished
    report No. Hst 204/83768 from Huntingdon Research Centre, Huntingdon,
    Cambridgeshire, United Kingdom. Hoechst document No. A29428. Submitted
    to WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany. 

    Ehling, G. & Leist, K.-H. (1991a) Hoe 051327: substance technical
    (code HOE 051327 00 ZB99 0002): Testing for acute oral toxicity in the
    male and female Wistar rat. Pharma Research Toxicology, Germany.
    Hoechst document No. A46286. Submitted to WHO by Hoechst Schering
    AgrEvo GmbH, Frankfurt-am-Main, Germany. 

    Ehling, G. & Leist, K.-H. (1991b) Hoe 051327: substance technical
    (code HOE 051327 00 ZB99 0002): Testing for acute dermal toxicity in
    the male and female Wistar rat. Pharma Research Toxicology, Germany.
    Unpublished Hoechst document No. A45783. Submitted to WHO by Hoechst
    Schering AgrEvo GmbH, Frankfurt-am-Main, Germany. 

    Ehling, G. & Leist, K.-H. (1991c) Hoe 051329: substance technical
    (code HOE 051329 00 ZD98 0001): Testing for acute oral toxicity in the
    male and female Wistar rat. Pharma Research Toxicology, Germany.
    Unpublished Hoechst document No. A45783. Submitted to WHO by Hoechst
    Schering AgrEvo GmbH, Frankfurt-am-Main, Germany. 

    Ehling, G. & Leist, K.-H. (1991d) Hoe 051329: substance technical
    (code HOE 051329 00 ZD98 0001): Testing for acute dermal toxicity in
    the male and female Wistar rat. Pharma Research Toxicology, Germany.
    Unpublished Hoechst document No. A45829. Submitted to WHO by Hoechst
    Schering AgrEvo GmbH, Frankfurt-am-Main, Germany. 

    Elsea, J.R. (1958) Thiodan technical: Acute oral administration: Rats.
    Hazleton Laboratories, USA, 28 February, 1958. Unpublished Hoechst
    document No. A13686. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Flodström, S., Wärngård, L., Hemming, H., Fransson, R. & Ahlborg, U.G.
    (1988) Tumour promotion related effects by the cyclodiene insecticide
    endosulfan studies  in vitro and  in vivo. Pharmacol Toxicol., 62,
    230-235.

    Goebel, H., Gorbach, S., Knauf, W., Rimpau, R.H. & Uttenbach, H.
    (1982) Properties, effects, residues and analytics of the insecticide
    endosulfan.  Res. Rev., 83, 41. Submitted to WHO by the National
    Registration Authority for Agricultural and Veterinary Chemicals,
    Australia. 

    Gopinath, C. & Cannon, M.W.J. (1990) Photomicrographic addendum to
    histopathology report No. Hst/289 Endosulfan, active ingredient
    technical (code: Hoe 002671 OI ZD97 0003) combined chronic
    toxicity/carcinogenicity study (104-week feeding in rats). Huntingdon
    Research Centre Ltd, Huntingdon, Cambridgeshire, United Kingdom.
    Unpublished Hoechst document No. A44604. Submitted to WHO by Hoechst
    Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Gorbach, S., Christ, O., Kellner, H.M., Kloss, G. & Börner, E. (1968)
    The metabolism of endosulfan in milk sheep.  J. Agric. Food Chem., 
    16, 950-953. 

    Gupta, P.K., Chandra, S.V. & Saxena, D.K. (1978) Teratogenic and
    embryotoxic effects of endosulfan in rats.  Acta Pharmacol. 
     Toxicol., 42, 150-152.

    Hack, R. & Leist, K.-H. (1988) Endosulfan-substance technical (code:
    Hoe 002671 0I ZD96 0002) Testing of host resistance in the female
    Wistar rat (immunological screening with  Trichonella spiralis). 
    Unpublished study No. 87.1125 from Pharma Research Toxicology and
    Pathology, Germany. Hoechst report A43829. Submitted to WHO by Agrevo
    GmbH, Frankfurt-am-Main, Germany.

    Hack, R., Ebert, E. & Leist, K.H. (1995) Chronic toxicity and
    carcinogenicity studies with the insecticide endosulfan in rats and
    mice.  Food Chem. Toxicol., 33, 941-950.

    Hollander, H. & Kramer, P. (1975a) Endosulfan sulfate = NIA 7985.
    Acute oral toxicity in female SPF-Wistar rats (vehicle: starch
    suspension). Unpublished Hoechst document No. A06966. Submitted to WHO
    by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Hollander, H. & Kramer, P. (1975b) Endosulfan sulfate = NIA 7985.
    Acute oral toxicity in male beagle dogs. Unpublished Hoechst document
    No. A06965. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Hollander, H. & Kramer, P. (1975c) Comparative test on the acute
    toxicity of endosulfan ether and endosulfan alcohol in female
    SPF-Wistar rats (vehicle: starch suspension). Unpublished Hoechst
    document No. A07170; translation of A05271. Submitted to WHO by
    Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Hollander, H. & Kramer, P. (1975d) 1-Hydroxy endosulfan ether. Acute
    oral toxicity in female SPF-Wistar rats (vehicle: starch suspension).
    Unpublished Hoechst document No. A06967; translation of A05276
    Submitted to WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main,
    Germany.

    Hollander, H. & Kramer P. (1975e) Endosulfan lactone: Acute oral
    toxicity in female SPF-Wistar rats (vehicle: starch suspension).
    Unpublished Hoechst document No. A07171; translation of A05273.
    Submitted to WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main,
    Germany.

    Hollander, H. & Kramer, P. (1975f) Endosulfan lactone. Acute oral
    toxicity in male SPF-Wistar rats. Unpublished Hoechst document No.
    A06964.25. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Hollander, H. & Weigand, W. (1983) Acute aerosol toxicity in male and
    female SPF Wistar rats 4 hours-LC50. Unpublishd Hoechst report No.
    83.0397; document No. A32087. Submitted to WHO by Hoechst Schering
    AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Hollander, H., Weigand, W. & Kramer, P. (1984) Endosulfan-active
    ingredient technical (code: Hoe 002671 0I ZD97 0003) Testing for
    subchronic inhalation toxicity--21 exposures in 29 days -- in SPF
    Wistar rats. Unpublished study No. 762; document No. A29823,
    translation of A29766. Submitted to WHO by Hoechst Schering AgrEvo
    GmbH, Frankfurt-am-Main, Germany.

    Indraningsih, McSweeney, C.S. & Ladds, P.W. (1993) Residues of
    endosulfan in the tissues of lactating goats.  Aust. Vet. J., 70,
    59-62. 

    Jung, Weigand, W. & Kramer, P. (1983) Mouse micronucleus test
    following oral administration. Unpublished Hoechst AG report No.
    83.0458; document No. A31628. Submitted to WHO by Hoechst Schering
    AgrEvo GmbH, Frankfurt-am-Main, Germany. 

    Keller, J.G. (1959a) Subacute feeding--dairy cows. Hazleton
    Laboratories, USA. Unpublished Hoechst document No. A14206. Submitted
    to WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Keller, J.G. (1959b) One-year oral study in dog. Hazleton
    Laboratories, 12 May 1959. Unpublished Hoechst document No. A13924.
    Submitted to WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main,
    Germany.

    Keller, J.G. (1959c) 2 year dietary study in rats. Hazleton
    Laboratories, USA, 22 May 1959. Unpublished Hoechst document No.
    A14037. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Kellner, H.M. & Eckert  (1983) Hoe 02671-14C. Pharmacokinetics and
    residue determinations after oral and intravenous administration to
    rats. Unpublished study No. tep 74/1; bereich c/analytisches project
    oe 87/45; Hoechst report 01-l42-0382-83, 15 February 1983; document
    No. A49475, translation of document A27971. Submitted to WHO by
    Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Khan, P.K. & Sinha, S.P (1996) Ameliorating effect of vitamin C on
    murine sperm toxicity induced by three pesticides (endosulfan,
    phosphamidon and mancozeb).  Mutagenesis, 11, 33-36 

    Kramer, P. & Weigand, W. (1971) Endosulfan lactone (vehicle: sesame
    oil). Acute oral toxicity in male and female SPF-Wistar K-rat.
    Unpublished Hoechst document No. A18276, 21 May 1971; translation of
    A14326. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Lachmann, G. & Siegemund, B. (1987) Hoe 002671-(5a, 9a-14C). Dermal
    absorption of 14C- endosulfan in rhesus monkeys. Battelle-Institut,
    Frankfurt. Unpublished Hoechst document No. A36685. Submitted to WHO
    by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Lehr, W (1996) Summary of intoxications with endosulfan. Clinical
    cases and poisoning incidents. Unpublished Hoechst report No. psr
    96/006, 12 March 1996; document A56361. Submitted to WHO by Hoechst
    Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Leist, K.H. (1989a) Endosulfan-substance technical (code: Hoe 002671
    oi ZD97 0003). Carcinogenicity study in mice, 24 months feeding study
    -- Residue determination. Pharma Research Toxicology and Pharmacology.
    Unpublished Hoechst document No. A41284. Submitted to WHO by Hoechst
    Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Leist, K.-H. (1989b) Amendment to report No. HST 289/881067.
    Endosulfan, active ingredient technical (code: Hoe 002671 OI ZD97
    0003). Combined chronic toxicity/carcinogenicity study (104-week
    feeding in rats). Residue determination. Unpublished Hoechst report
    No. 89.1105; document No. A41265. Submitted to WHO by Hoechst Schering
    AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Leist, K.-H. & Bremmer, J. (1998) Endosulfan (AE F002671, substance
    technical). Re-evaluation of the NOAEL in the 90-day subchronic
    toxicity study in rats. Unpublished AgrEvo document No. 59825.
    Submitted to WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main,
    Germany. 

    Leist, K.-H. & Mayer, D. (1987) Endosulfan-active ingredient technical
    (code: Hoe 002671 01 ZD97 0003). 30-Day feeding study in adult male
    Wistar rats. Unpublished study No. 84 0585 from Pharma Research
    Toxicology and Pharmacology. Hoechst report No. 87.0129, 27 March
    1987; document No., A37112. Submitted to WHO by Hoechst Schering
    AgrEvo GmbH, Frankfurt-am-Main, Germany. 

    Lightowler, J.E. & Gardner, J.R. (1978) Acute oral toxicity study in
    rats. Unpublished report No. 78/mak1/428. 20 November 1978 from Life
    Science Research. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Mackenzie, K.M. (1980) Teratology study with FMC 5462 in rats. Raltech
    Scientific Services, study No. 79041, 2 October 1980. Hoechst document
    No. A21393. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Maier-Bode, H. (1966) Investigations on the persistence of the
    insecticide endosulfan in the vegetable and animal organism.
    Pharmakologisches Institut der Rheinischen Friedrich Wilhelms
    Universität. Unpublished Hoechst document No. A4047. Submitted to WHO
    by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    McGregor, D.B., Willins, M.J., McDonald, P., Holström, M., McDonald,
    D. & Niemeier, R.W. (1983) Genetic effects of 2-methoxyethanol and
    bis(2-methoxyethyl)ether.  Toxicol. Appl. Pharmacol., 70, 303-316.

    McLachlan, J.A. (1997) Synergistic effect of environmental estrogens:
    Report withdrawn.  Science, 277, 462-463.

    Mellano, D. & Milone, M.F. (1984a) Mutagenic activity of the compound
    endosulfan-technical with  Saccharomyces cerevisiae gene
    conversion-DNA repair test. Instituto di Recherche Biomediche.
    Unpublished Hoechst document No. A29313. Submitted to WHO by Hoechst
    Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Mellano, D. & Milone, M.F. (1984b) Mutagenic activity in vitro of the
    compound endosulfan-technical with  Schizosaccharomyces pombe. 
    Unpublished experiment No. M 708, 18 June 1984, from Instituto di
    Recherche Biomediche. Hoechst document No. A29312. Submitted to WHO by
    Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Müller, W. (1988) Endosulfan-substance technical (code: Hoe 002671 0I
    ZD95 0005). Micronucleus test in male and female NMRI mice after oral
    administration. Pharma Research Toxicology and Pathology. Unpublished
    Hoechst document No. A38059. Submitted to WHO by Hoechst Schering
    AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Müllner, H. (1989) Effects of endosulfan and aldicarb on rat brain
    acetylcholinesterase. Unpublished Hoechst report 16 June 1989;
    document No. A43395. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Nath, G., Datta, K.K., Dikshith, T.S.S., Tandon, S.K. & Pandya, K.P.
    (1978) 30 day oral administration in rats. Interaction of endosulfan
    and metepa in rats. Industrial Toxicology Research Centre. Unpublished
    Hoechst document No. A17906. Submitted to WHO by Hoechst Schering
    AgrEvo GmbH, Frankfurt-am-Main, Germany. 

    Noctor, J.C. & John, S.A. (1995) (14C)-Endosulfan: Rates of
    penetration through human and rat skin determined using an in vitro
    system. Hazleton Europe, United Kingdom. Unpublished Hoechst document
    No. A54103. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Nogami, K. (translator, no other name available) (1970) Testing report
    on the toxicity of endosulfan (Malix) to dogs through acute oral
    administration (LD50). Unpublished Hoechst document No. A13834.
    Submitted to WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main,
    Germany.

    Offer, J.M. (1985) Addendum to HST 204. Effect of endosulfan-technical
    (code: Hoe 02671 OI AT209) on the reproductive function of multiple
    generations in the rat. Histopathological review of the kidneys in
    adult rats of the F1b generation and in weanling rats of the F2b
    generation. Huntingdon Research Centre, Huntingdon, Cambridgeshire,
    United Kingdom. Unpublished Hoechst document No. A30757. Submitted to
    WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Pandey, N., Gundevia, F., Prem, A.S. & Ray, P.K. (1990) Studies on the
    genotoxicity of endosulfan, and organochlorine insecticide, in
    mammalian germ cells.  Mutat. Res., 242, 1-7.

    Paul, V., Sheela, S., Balasubramaniam, E. & Kazi ,M. (1993)
    Behavioural and biochemical changes produced by repeated oral
    administration of the insecticide endosulfan in immature rats. 
     Indian J. Physiol. Pharmacol., 37, 204-208.

    Paul, V., Easwaramoorthy, B. & Kazi, M. (1994) The neurobehavioural
    toxicity of endosulfan: A serotonergic involvement in learning
    impairment.  Eur.J. Pharmacol. Environ. Toxicol. Pharmacol., 270,
    1-7.

    Paul, V., Easwaramoorthy, B., Arumugam, R.J. & Kazi, M. (1995) A
    sex-related difference in the neurobehavioural and hepatic effects
    following chronic endosulfan treatment in rats.  Eur. J. Pharmacol. 
     Environ. Toxicol. Pharmacol., 293, 355-360.

    Pirovano, R. & Milone, M.F. (1986) Study of the capacity of the test
    article endosulfan, substance technical to induce chromosome
    aberrations in human lymphocytes cultured in vitro. Unpublished RBM
    experiment No. m 822, 20 March 1986. Hoechst document A33127.
    Submitted to WHO by Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main,
    Germany.

    Raizada, R.B., Srivastava, M.K. & Dikshith, T.S.S. (1991) Lack of
    estrogenic effects of endosulfan: An organochlorine insecticide in
    rat.  Natl Acad. Sci. Lett., 14, 103-107.

    Ramamoorthy, K., Wang, F., Chen, I.-C., Norris, J.D., McDonnel, D.P.,
    Leonard, L.S., Gaido, K.W., Bocchinfuso, W.P., Korach, K.S. & Safe, S.
    (1997) Estrogenic activity of a dieldrin/toxaphene mixture in the
    mouse uterus, MCF-7 human breast cancer cells, and yeast-based
    estrogen receptor assays: No apparent synergism.  Endocrinology, 138,
    1520-1527.

    Robacker, K.M., Kulkarni, A.P. & Hodgson, E. (1981) Pesticide induced
    changes in the mouse hepatic microsomal cytochrome P-450-dependent
    monooxygenase system and other enzymes.  J. Environ. Sci. Health, 
    B16, 529-545.

    Reno, F.E. (1975) Acute oral toxicity study in rats. Endosulfan
    technical. Unpublished final report, 18 December 1975, from Hazleton
    Laboratories America. Hoechst document No. A33732. Submitted to WHO by
    Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Roberts, N.L., Phillips, N.K. & Gopinath, C. (1983) Acute delayed
    neurotoxicity study with endosulfan-technical (code: Hoe 002671 OI
    ZD97 0003) in the domestic hen. Huntingdon Research Centre,
    Huntingdon, Cambridgeshire, United Kingdom. Unpublished Hoechst
    document No. A32153. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany.

    Ruckman, S.A., Waterson, L.A., Crook, D., Gopinath, C., Majeed, S.K.,
    Anderson, A. & Chanter, D.O. (1989) Endosulfan, active ingrediant
    technical (code: Hoe 002671 OI ZD97 0003). Combined chronic
    toxicity/carcinogenicity study (104-week feeding study in rats).
    Huntingdon Research Centre, Huntingdon, Cambridgeshire, United
    Kingdom. Unpublished Hoechst document No.A40440. Submitted to WHO by
    Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Shelby, M.D., Newbold, R.R., Tully, D.B., Chae, K. & Davis, V.L.
    (1996) Assessing environmental chemicals for estrogenicity using a
    combination of in vitro and in vivo assays.  Environ. Health 
     Perspectives, 104, 1296-1300.

    Shirasu, Y., Moriya, M. & Ohta, T. (1978) Microbial mutagenicity
    testing on endosulfan. Institute of Environmental Toxicology, Japan.
    Unpublished Hoechst document No. A21215, 1978. Submitted to WHO by
    Hoechst Schering AgrEvo GmbH, Frankfurt-am-Main, Germany.

    Singh, S.K. & Pandey, R.S. (1990) Effect of sub-chronic endosulfan
    exposures on plasma gonadotrophins, testosterone, testicular
    testosterone and enzymes of androgen biosynthesis in rat.  Indian J. 
     Exp. Biol., 28, 953-956.

    Sinha, N., Narayan, R., Shanker, R. & Saxena, D.X. (1995)
    Endosulfan-induced biochemical changes in the testis of rats.  Vet. 
     Hum. Toxicol., 37, 547-549.

    Soto, A.M., Chung, K.L. & Sonnenschein, C. (1994) The pesticides
    endosulfan, toxaphene and dieldrin have oestrogenic effects on human
    oestrogen-sensitive cells.  Environ. Health Perspectives, 102,
    380-383.

    Soto, A.M., Sonnenschein, C., Chung, K.L., Fernandez, M.F., Olea, N. &
    Serrano, F.O. (1995) The E-screen assay as a tool to identify
    estrogens: An update on estrogenic environmental pollutants. 
     Environ. Health Perspectives, 103 (Suppl. 7), 113-122. 

    Stumf, K. & Lehr, W. (1993) Amendment to document A49584. Unpublished
    Hoechst document A49584, 2 February 1993. Submitted to WHO by Hoechst
    Schering AgrEvo GmbH, Frankfurt-am-Main, Germany. 

    den Tonkelaar, E.M. & van Esch, G.J. (1974) No-effect levels of
    organochlorine pesticides based on induction of microsomal liver
    enzymes in short-term toxicity experiments.  Toxicology, 2, 371-380.

    US National Cancer Institute (1978) 78-week dietary study in
    Osborne-Mendel rats and B6C3F1 mice. NCI study No. NCI-CG-TR62,
    Technical Report Series No. 62, Bethesda, Maryland, USA.

    Vos, J.G., Krajnc, E.I., Beekhof, P.K. & van Logten, M.J. (1982)
    Methods for testing immune effects of toxic chemicals: Evaluation of
    the immunotoxicity of various pesticides in the rat. In: Matsunaka,
    S., Hutson, D.H. & Murphy, S.D., eds,  Pesticide Chemistry: Human 
     Welfare and the Environment, Oxford, Pergamon Press, pp. 497-504.

    Wade, M.G., Desaulniers, D., Leingartner, K. & Foster, W.G. (1997)
    Interactions between endosulfan and dieldrin on estrogen-mediated
    processes  in vitro and  in vivo. Reprod. Toxicol., 11, 791-798. 

    Weigand, W. (1982a) Acute oral toxicity of Hoe 51329 in albino rats.
    Pharma Research Toxicology, Germany. Unpublished Hoechst document No.
    A23296. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany (in German).

    Weigand, W. (1982b) Acute oral toxicity of Hoe 51330 in albino rats.
    Pharma Research Toxicology, Germany. Unpublished Hoechst document No.
    A23297. Submitted to WHO by Hoechst Schering AgrEvo GmbH,
    Frankfurt-am-Main, Germany (in German).

    WHO (1996)  The WHO Recommended Classification of Pesticides by 
     Hazard and Guidelines to Classification 1996-1997 (WHO/PCS/96.3),
    International Programme on Chemical Safety, Geneva.
    


    See Also:
       Toxicological Abbreviations
       Endosulfan (EHC 40, 1984)
       Endosulfan (HSG 17, 1988)
       Endosulfan (PIM 576)
       Endosulfan (FAO Meeting Report PL/1965/10/1)
       Endosulfan (FAO/PL:1967/M/11/1)
       Endosulfan (FAO/PL:1968/M/9/1)
       Endosulfan (WHO Pesticide Residues Series 1)
       Endosulfan (WHO Pesticide Residues Series 4)
       Endosulfan (WHO Pesticide Residues Series 5)
       Endosulfan (Pesticide residues in food: 1982 evaluations)
       Endosulfan (Pesticide residues in food: 1989 evaluations Part II Toxicology)