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    FAO Meeting Report No. PL/1965/10/1
    WHO/Food Add./27.65

    EVALUATION OF THE TOXICITY OF PESTICIDE RESIDUES IN FOOD

    The content of this document is the result of the deliberations of the
    Joint Meeting of the FAO Committee on Pesticides in Agriculture and
    the WHO Expert Committee on Pesticide Residues, which met in Rome,
    15-22 March 19651

    Food and Agriculture Organization of the United Nations
    World Health Organization
    1965

                
    1 Report of the second joint meeting of the FAO Committee on
    Pesticides in Agriculture and the WHO Expert Committee on Pesticide
    Residues, FAO Meeting Report No. PL/1965/10; WHO/Food Add./26.65

    CHLORBENSIDE

    Chemical name

         4-chlorobenzyl 4-chlorophenyl sulfide.

    Synonyms

         Chlorparaside; chlorsulfacide.

    Empirical formula

         C13H10Cl2S

    Structural formula

    CHEMICAL STRUCTURE 

    BIOLOGICAL DATA

    Biochemical aspects

         After 13 weeks of feeding at a 10-ppm dose level there was no
    appreciable chlorbenside in any tissue of the rats except fat and
    possibly liver. At 100 ppm there were measurable concentrations in
    liver, kidney and fat but not in the blood or brain; whilst at 1000
    ppm there were measurable concentrations in all organs, although the
    amount in the blood was barely detectable. The greatest amount of
    chlorbenside found in any one animal was 184 g in a whole rat which
    had received the highest dose level of 1000 ppm. This was about one
    fiftieth of the daily intake. The total body load fell to about one
    sixth within 2 weeks of stopping treatment (Boots, 1957).

         Rabbits were given chlorbenside orally in a dose of about 300
    mg/kg body-weight and the excretion of sulfide (chlorbenside),
    sulfoxide and sulfone in urine and faeces was followed. 97.4% of the
    dose was recovered unchanged from the faeces, and traces of sulfoxide
    were present in the urine (Boots, 1957).

    Acute toxicity

                                                              
    Animal    Route         LD50 mg/kg              References
                           body-weight
                                                              

    Mouse     Oral     > 3 000 pure sulfide         Boots, 1957
                       > 3 000 pure sulfoxide
                       > 3 000 pure sulfone

                       >10 000 technical sulfide    Boots, 1957
                       >10 000 technical sulfone

    Rat       Oral     >10 000 technical sulfide    Boots, 1957
                                                              

    Short-term studies

         Mouse. Each of 3 pure samples (sulfide, sulfoxide, sulfone) was
    given daily by stomach tube to a group of 10 male mice at a dose of
    1000 mg/kg body-weight 6 times a week for 14 days (12 doses total):
    enlargement of the liver was observed and a few deaths occurred
    (Boots, 1957).

         Rat. Daily oral doses of 50 mg/kg body-weight of technical
    sulfide or sulfone were given to rats for a period of 3 weeks; no
    toxic effects resulted. Daily doses of 250 mg/kg body-weight for the
    same period caused enlargement of the liver without any histological
    evidence of liver damage. There was no other toxic effect (Boots,
    1957).

         Several small groups of rats, each consisting of 2 males and 2
    females, were given daily oral doses of chlorbenside in aqueous acacia
    suspensions for 3 to 4 weeks at dose levels up to 10 000 mg/kg
    body-weight. Doses were administered by stomach-tube. Doses of 5000
    mg/kg body-weight and over were sub-divided in 2 half-doses daily. The
    only systemic effect of the 10 000 mg/kg body-weight daily dose was
    the liver enlargement. There were mild cellular changes in the liver,
    consisting of vacuolation of the lobular cells. The increase in
    liver-weight occurred at all doses, and was graded according to dose.
    The reduction of growth occurred only on doses of 5000 mg/kg
    body-weight and above, and the vacuolation of liver cells was marked
    at the highest dose level of 10 000 mg/kg body-weight daily (Boots,
    1957).

         Additional experiments in rats showed that the major part of the
    liver hypertrophy occurs in the first few weeks of feeding
    chlorbenside and continued feeding after this point has little further
    effect.

         The liver hypertrophy is reversible, and the liver-weight returns
    nearly to normal within two weeks of stopping treatment (Boots, 1957).

         Breeding rats (4 groups and 2 control groups each of 6 breeding
    pairs) were maintained throughout 3 generations on diets containing
    100 ppm or 20 ppm of technical sulfide, 20 ppm of pure sulfoxide or 20
    ppm of technical sulfone. The treatment had no effect on fertility
    through 3 generations (Boots, 1957).

         Rabbit. Daily oral doses of 250 mg/kg body-weight of technical
    sulfide or sulfone given to rabbits for a period of 4 weeks had no
    toxic effects (Boots, 1957).

    Long-term studies

         Rat. Groups of 10 albino rats, 5 of each sex, were maintained
    on diets containing 20, 100 and 1000 ppm of technical sulfide, and the
    same 3 concentrations of technical sulfone. Three similar groups were
    maintained on the basic diet as controls. They were placed on the
    experimental diets when the rats were 5-6 weeks of age. With the
    exception of 3 animals of each sex which were killed after 6 months or
    after 1 year for pathological examination, the remaining 4 animals in
    each group were maintained on their respective diets for 2 years, and
    the survivors were killed at the end of this time. The main organs
    were taken for histological examination. No deaths occurred which
    could be attributed to the effects of treatment, and there was no
    effect on the length of life-span, weight gain and blood picture. The
    livers were enlarged in both sexes fed 1000 ppm of either compound and
    in females fed 100 ppm. There was no significant enlargement in males
    fed 100 ppm or in either sex fed 20 ppm. There was no microscopic
    abnormality of the liver. The kidneys of males fed 1000 ppm of either
    compound showed a slight increase in weight. There was no effect on
    the kidneys of males on the two lower doses, nor in any of the
    females. There were no other gross or microscopic pathological changes
    that could be attributed to treatment (Boots, 1957).

         Dog. Eight mongrel females approximately one to one-and-a-half
    years old were maintained for one year on daily oral doses of 60 mg of
    technical sulfide, pure sulfoxide or technical sulfone. This is
    equivalent to approximately 5 mg/kg body-weight daily. There were no
    toxic effects on growth, appetite, general health, blood picture,
    liver function or kidney function and no gross or microscopic
    pathological changes were found (Boots, 1957).

    Comments on experimental studies reported

         Long-term studies of two years' duration in rats and one year in
    dogs were carried out. Other studies in mice, rats and rabbits of
    shorter duration were reported. Tissue residue and excretion studies
    showed that the pesticide is not cumulative.

    EVALUATION

    Level causing no significant toxicological effect in the rat

         Twenty ppm in the diet of the rat is equivalent to 1 mg/kg
    body-weight; in the dog 5 mg/kg body-weight.

    Estimate of acceptable daily intakes for man

         0-0.01 mg/kg body-weight.

    Further work desirable

         Additional long-term studies in the rat and the dog.

    REFERENCE

    Boots Pure Drug Co. Ltd., Nottingham, England (1957) Unpublished
    Report
    


    See Also:
       Toxicological Abbreviations