FAO/PL:1967/M/11/1
    WHO/Food Add./68.30

    1967 EVALUATIONS OF SOME PESTICIDE RESIDUES IN FOOD

    THE MONOGRAPHS

    The content of this document is the result of the deliberations of the
    Joint Meeting of the FAO Working Party of Experts and the WHO Expert
    Committee on Pesticide Residues, which met in Rome, 4 - 11 December,
    1967. (FAO/WHO, 1968)

    FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
    WORLD HEALTH ORGANIZATION
    Rome, 1968

    NABAM

    This pesticide wan evaluated toxicologically by the 1965 Joint Meeting
    of the FAO Committee on Pesticides in Agriculture and the WHO Expert
    Committee on Pesticide Residues (FAO/WHO, 1965). Additional
    toxicological information, together with information for evaluation
    for tolerances, is summarized and discussed in the following monograph
    addendum.

    IDENTITY

    Other relevant chemical properties

    The standard formulation contains 19 per cent of active ingredient (27
    per cent as the hexahydrate) and is formulated to be used as a liquid
    spray after addition of an equimolar amount of zinc sulphate.
    Occasionally a zinc-iron sulphate mixture is added.

    The water soluble salt under aeration conditions has been shown to
    yield a number of products including ethylenethiuram monosulfide and
    its polymer, ethylene thiourea disulfide and ethylene thiourea (Thorn
    and Ludwig, 1962). Addition of zinc sulphate to the aqueous solution
    of the tank mix of the soluble sodium salt yields the relatively
    insoluble zinc ethylene bisdithiocarbamate. Therefore except for
    possible by-products formed initially from the sodium salt, the
    properties of the final spray are essentially those of zineb and for
    further discussion reference should be made to the monograph on zineb.

    EVALUATION FOR ACCEPTABLE DAILY INTAKES

    Biochemical aspects

    Nabam, in vitro, completely inhibited dopamine beta hydroxylase,
    prepared from beef adrenals, at a concentration of 4 × 10-6M. Partial
    inhibition occurs at a concentration of 1 × 10-6M. In rat brain, in
    vivo, this inhibitory effect is produced only by relatively high
    doses (300 mg/kg body-weight) (Truhaut et al, 1967).

    Comment

    No long-term studies on nabam have been reported. There is no basis
    for estimating an acceptable daily intake for this compound. Where
    nabam in used in combination with zinc sulfate prior to spraying, it
    is converted to zineb and hence residues of nabam would not be present
    as a result of this use. For this method of use, there is no need for
    an ADI for nabam, per se, and the ADI estimated for zineb would be
    applicable.

    TOXICOLOGICAL EVALUATION

    Temporary acceptable daily intake for man

    0 - 0.025 mg/kg body-weight (as zineb alone or in combination with
    other ethylene bisdithiocarbamates)

    This value is based on experiments carried out with zineb and does not
    take account of chemical alterations after application.

    Further work required

    Studies of the compound in plants to determine the chemical nature of
    the residues followed by appropriate toxicological studies.

    Results of the above work should be made available not later than 30
    June 1971 after which a re-evaluation of this compound will be made.
    The re-evaluation may be made at an earlier meeting should relevant
    information become available.

    EVALUATION FOR TOLERANCES

    USE PATTERN

    Pre-harvest treatments

    The nabam-zinc sulphate tank mix is used as a pre-harvest spray to
    protect a number of agricultural crops from invasion by fungal plant
    pathogens. Residues are reduced as outlined under zineb.

    METHODS OF RESIDUE ANALYSIS

    The method is identical with that for zineb involving the colorimetric
    measurement of the carbon disulfide liberated on acid treatment of the
    residue. (Gordon, Schuckert and Bornak, 1967).

    NATIONAL TOLERANCES

    Nabam is registered for use in Canada on the same crops as for zineb
    except wheat, collards, mustard greens, lettuce and spinach, with a
    tolerance limit of 7 ppm (Canada, 1967). In the United States, except
    for lettuce, mustard greens, Swiss chard and spinach with a tolerance
    limit of 25 ppm, the numerous other vegetables and fruit have a limit
    of 7 ppm (USDA, 1966)

    RECOMMENDATIONS FOR TOLERANCES

    No tolerances for nabam per se are necessary, since this compound is
    converted to zineb. See monograph on latter compound.

    REFERENCE PERTINENT TO EVALUATION FOR ACCEPTABLE DAILY INTAKES

    Truhaut, R., Baquet, A., Bohnon, C. and Guirinot F. (1967) Paper given
    at IUPAC Congress, Prague, September, 1967 (in press)

    REFERENCES PERTINENT TO EVALUATION FOR TOLERANCES

    Canada. (1967) Food and Drug Directorate, T.I.L. 290, Sept. 15.

    FAO/WHO. (1965) Evaluation of the toxicity of pesticide residues in
    food. FAO Meeting Rept. PL/1965/10/1; WHO/Food Add./27.65.

    Gordon, C.F., Schuckert, R.J., and Bornak, W.E. (1967) Improved method
    for the determination of ethylenebisdithiocarbamate residues in
    plants, fruits and vegetables. J. Assoc. Off. Anal. Chem. 50:
    1102-1108.

    Thorn, G.D. and Ludwig, R.A. (1962) The dithiocarbamates and related
    compounds. Amsterdam, Elsevier Pub. Co. 234 p.

    USDA. (1966) Summary of Registered Agricultural Pesticide Chemical
    Uses, 2nd ed. Suppl. 2 and 3.
    

    See Also:
       Toxicological Abbreviations
       Nabam (FAO Meeting Report PL/1965/10/1)