1967 EVALUATIONS OF SOME PESTICIDE RESIDUES IN FOOD
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
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
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
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).
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
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
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).
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:
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.