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    PESTICIDE RESIDUES IN FOOD - 1982


    Sponsored jointly by FAO and WHO






    EVALUATIONS 1982





    Data and recommendations of the joint meeting
    of the FAO Panel of Experts on Pesticide Residues
    in Food and the Environment and the
    WHO Expert Group on Pesticide Residues
    Rome, 23 November - 2 December 1982

    Food and Agriculture Organization of the United Nations
    Rome 1983

    DIPHENYLAMINE

    CHEMICAL STRUCTURE 1

    Explanation

         Diphenylamine (DPA) was first evaluated by the 1969 JMPR (FAO/WHO
    1970).1 No-effect levels in mouse, rat and dog were determined. An
    ADI was allocated on the basis of the no-effect level observed in a
    2-year study in the dog.

         As new toxicological data had become available, diphenylamine was
    reconsidered by the 1976 JMPR (FAO/WHO 1977), and an ADI was derived
    from a no-effect level observed in a 6-month mouse study.

         Further data have become available and are summarized in the
    following monograph addendum.

    EVALUATION FOR ACCEPTABLE DAILY INTAKE

    TOXICOLOGICAL STUDIES

    Special Studies on Identification of Toxic Impurities in Commercial
    Diphenylamine

         Six samples of commercial diphenylamine (DPA) were subjected to
    investigation for identification of minor components. Combined
    chemical techniques (TLC, GLC/MS, IR,NMR) were used. Only one
    impurity, o-cyclohexylaniline, was found in all the commercial DPA
    samples at levels of 5-93 ppm. p-Cyclohexylaniline was detected in
    only one sample. o-Biphenylamine was found in three samples
    (3.2-32 ppm). p-Biphenylamine, a known carcinogen was found in four
    samples (6.9-94 ppm). Another compound (band 1) was detected, but its
    structure was not precisely determined. This compound was found to be
    remarkably unstable to heat, light and oxygen, and rapidly polymerized
    to give a deep purple, insoluble, resinous material. The components
    E,F,G, isolated in the work of Crocker  et al (1972), were comparable
    to band 1 (unidentified compound), band 3 (o-cyclohexylaniline) and
    band 5 (p-cyclohexylaniline), respectively, of this work (Safe
     et al 1977).

              

    1  See Annex 2 for WHO and FAO documentation.

    Short-Term Studies

         Pregnant Sprague-Dawley rats of known gestation were fed diets
    containing 0, 1.5% or 2.5% diphenylamine of source I (DPA/I) aged
    about 2 years from gestation day 14 to term, 2.5 DPA/I aged 3 months,
    or 2.5% DPA/II aged 2 years. All viable newborn rats were removed from
    mothers shortly after birth and two or three randomly selected
    pairs of kidneys from each litter were prepared for histological
    examination.

         The histology of the kidneys from mothers was normal, and no
    tubular dilatation or other abnormalities were observed. Cystic
    changes in the proximal tubules were regularly induced by feeding 2.5%
    2-year aged DPA/I. Lesions were uncommon and less severe after feeding
    either 1.5% 2-year-aged DPA/I, 2.5% 3-month-aged DPA/I, or 2.5%
    2-year-aged DPA/II.

         In another portion of the study, three trace compounds
    (designated E, F and G) were isolated by thin-layer chromatography
    from 2-year-aged DPA/I, and also purified DPA/I was prepared. Rats
    were given, by gastric tube in 70% ethanol, either 2-year-aged DPA/I
    (20 mg/day), purified DPA/I (20 mg/day), contaminant E (20 g/day),
    contaminant F (20 g/day), or contaminant G (20 g/day).

         Aged DPA/I and the contaminant E frequently induced moderate
    cystic changes in the proximal tubules of the newborn rat.
    Chromatographically pure DPA/I and the two other contaminants F and G
    induced only mild cystic tubular changes (Crocker  et al 1972).

    COMMENTS

         Diphenylamine (DPA) was first evaluated by the 1969 JMPR.
    No-effect levels in mouse, rat and dog were determined. An ADI was
    allocated on the basis of the no-effect level observed in a 2-year
    study in the dog.

         As new toxicological data had become available, diphenylamine was
    reconsidered by the 1976 JMPR and an ADI was derived from a no-effect
    level observed in a six-month mouse study.

         The Meeting considered a study showing that an impurity (not
    fully characterized) in commercial grade diphenylamine (DPA) is the
    active nephrotoxic compound responsible for the  in utero induction
    of cystic tubular lesions in the kidneys of newborn rats of mothers
    fed DPA in dietary concentrations of 2.5%. Another study described the
    identification of some impurities in commercial samples (source not
    specified) of DPA, showing that the level of primary amines is higher
    than that specified (10 ppm) by the 1969 JMPR. The Meeting noted that,
    in general, the purity of DPA used in toxicological studies has not

    been reported, except for the long-term mouse study (FAO/WHO,1977) in
    which 99.5% pure DPA was used. On the other hand, the specification of
    purity (99.9%) reported by the 1969 JMPR appeared unrealistic. The
    Meeting noted that no teratogenicity studies had been evaluated by
    previous Meetings.

         The Meeting decided to change the ADI to temporary status.

    TOXICOLOGICAL EVALUATION

    Level Causing no Toxicological Effect

    Mouse : 10 ppm in the diet, equivalent to 1.5 mg/kg bw.

    Rat : 100 ppm in the diet, equivalent to 5 mg/kg bw.

    Dog : 100 ppm in the diet, equivalent to 2.5 mg/kg bw.

    Estimate of Temporary Acceptable Daily Intake for Man

    0 - 0.02 mg/kg bw.

    FURTHER WORK OR INFORMATION

    Required (by 1984)

    A teratogenicity study.

    Desirable

    1.  Short-term studies with special attention to the formation of
    Heinz bodies (from 1976 JMPR).

    2.   Mutagenicity tests.

    3.   Information on the nature and level of impurities in technical
    grade diphenylamine.

    REFERENCES

    Crocker, J.F.S., Brown, D.M., Borch, R.F., Vernier, R.L. Renal cystic
    1972      disease induced in newborn rats by diphenylamine
              derivatives. Am. J. Pathol. 66(2):343-348.

    Safe, S., Hutzinger, O., Crocker, J.F.S., Digout, S.C. Identification
    1977      of toxic impurities in commercial diphenylamine.
              Bull.Environ.Contam. Toxicol. 17:204-207.


    See Also:
       Toxicological Abbreviations
       Diphenylamine (ICSC)
       Diphenylamine (FAO/PL:1969/M/17/1)
       Diphenylamine (Pesticide residues in food: 1976 evaluations)
       Diphenylamine (Pesticide residues in food: 1979 evaluations)
       Diphenylamine (Pesticide residues in food: 1984 evaluations)
       Diphenylamine (Pesticide residues in food: 1984 evaluations)