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
ZIRAM
This pesticide was 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.
EVALUATION FOR ACCEPTABLE DAILY INTAKES
Short-term studies
Rat. In a reproduction study, rats were given ziram in doses of 10
and 50 mg/kg/day and zineb in doses of 50 and 100 mg/kg/day orally for
2-6 months. Sterility, resorption of fetuses and anomalous tails in
new born rats were observed at the high levels. The lower doses did
not cause any significant changes, compared with a control group
(Ryazanova, 1967).
Long-term studies
Rat. Weanling rats in groups of 25 males and 25 females were fed
diets containing 25, 250 and 2500 ppm of ziram for 2 years. Growth was
reduced at the highest concentration only; life-span was normal in all
groups. Neurological changes were observed in the animals receiving
2500 ppm but not at the lower levels. In some of the males the testes
were atrophied and there was a slight indication of thyroid
hyperplasia, notably in the 2500 ppm group. There was no increase in
tumour incidence in the treated animals (Hodge et al., 1956).
Comments on experimental studies reported
Although ziram was only found in trace amounts in tissues of rats and
dogs fed the compound, storage of metabolites should be investigated
as part of the metabolic studies needed on the dithiocarbamates.
In long-term studies in the rat a level of 250 ppm was without
toxicological effect.
From the one-year study in the dog the daily dose of 5 mg/kg body-
weight was without toxicological effect.
The chemical nature of the residues of ziram in or on the plant has
not been ascertained. Studies are needed on the metabolism of the
dithiocarbamates. While these data are being obtained a temporary ADI,
based on the long-term studies in the rat, is proposed.
TOXICOLOGICAL EVALUATION
Level causing no toxicological effect
Rat. 250 ppm in the diet, equivalent to 12.5 mg/kg body-weight per
day.
Dog. 5 mg/kg body-weight per day.
Estimate of temporary acceptable daily intake for man
0 - 0.025 mg/kg body-weight (alone or in combination with other
dimethyl-dithiocarbamates).
This value is based on experiments carried out with ziram 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
Ziram is used primarily as a pre-harvest spray to protect a number of
agricultural products from plant pathogens.
RESIDUES RESULTING FROM SUPERVISED TRIALS
Twelve applications of equal parts ziram and ferbam at 2 lb/acre to
celery and allowing 7 days for weathering resulted in a residue of 10
ppm (trimmed) and 4.1 ppm (trimmed and washed). Spraying snap beans
with one application at 1 1/2 lb/gal/acre and a 6 day time interval
before sampling resulted in a residue of 3.2 ppm.
RESIDUES IN FOOD AT TIME OF CONSUMPTION
A recent survey of five composite basic 2-week diets for males 14-19
years old showed the presence of 6 dithiocarbamates with values
ranging from 0.4 to 0.8 ppm (Duggan, Barry and Johnson, 1966). No
residues were found in a more recent survey based upon the analyses of
prepared foods (Duggan and Weatherwax, 1967), possibly because the
residues decomposed rapidly as the foods were being prepared.
NATIONAL TOLERANCES
Country Tolerance, ppm Crop Reference
Canada 7 apples, apricots, beans, beets, blackberries, FDD, Canada
black-eyed peas, blueberries, broccoli, (1967)
Brussels sprouts, cabbage, carrots, cauliflower,
celery, cherries, collards, cranberries,
cucumbers, eggplants, gooseberries, grapes, kale,
kohlrabi, lettuce, loganberries, melons, mustard
greens, nectarines, onions, peaches, peanuts,
pears, peas, peppers, pumpkins, quinces, radishes,
raspberries, rutabagas, spinach, squash,
strawberries, summer squash, tomatoes turnips;
U.S. 7 apples, apricots, beans, blackberries, blueberries,
broccoli, cabbage, cantaloupe, carrots, celery,
cherries, citrus fruits, cranberries, cucumbers,
gooseberries, grapes, lettuce, loganberries, peaches,
pears, peppers, plums, potatoes, prunes, raspberries,
squash, strawberries;
West Germany 3 leafy vegetables, fruits and pulses;
METHODS OF RESIDUE ANALYSIS
Residues have been determined by releasing either the dimethylamine
(Barr, Clerk and Jacks, 1957) or the carbon disulfide (Pease, 1957) on
acid treatment of the sample and measuring the intensity of a coloured
copper complex formed. Since the colour formation is critical an
improved modification has been outlined (Cullen, 1964). Better
recoveries from a variety of crops have resulted from changes in the
order of the acid decomposition procedure (Gordon, Schuckert and
Bornak, 1967). Methods using polarographic techniques have also been
developed (Nangniot, 1966; Vogeler, 1967).
RECOMMENDATIONS FOR TOLERANCES
Although some progress has been reported, neither the chemical nature
nor the mode of action of the residues of ziram, in or on the plant
have been ascertained and there is no specific method of analysis
available. Accordingly, no tolerance figures can be recommended.
FURTHER WORK
Further work required
Further work is required on the metabolism of ziram in or on the plant
to include the identification and mode of action of any critical
intermediates. The data on this subject is required prior to 30 June
1971.
REFERENCES PERTINENT TO EVALUATION FOR ACCEPTABLE DAILY INTAKES
Hodge, H.C., Maynard, E.A., Downs, W.L., Coye, R.D. & Steadman, L.T.
(1956) J. Pharmacol. exp. Ther., 118, 174
Ryazanova, R.A. (1967) Gigiena i sanitaria, 2, 26
REFERENCES PERTINENT TO EVALUATION OF TOLERANCES
Barr, H.E., Clark, P.J., Jacks, H. (1957) Determination of
tetramethylthiuram disulfide and dimethyldithiocarbamate sprays on
apples. New Zealand J. Sci. Tech. Sect. B, 38: 425-532.
Cullen, T.E. (1964) Spectrophotometric determination of
dithiocarbamate residues in food crops. Anal. Chem. 36: 221-224.
Duggan, R.E., Barry, H.C., Johnson, L.Y. (1966) Pesticide residues in
total diet samples. Science 151: 101-104.
Duggan, R.E., Weatherwax, J.R. (1967) Dietary intake of pesticide
chemicals, Science 157: 1006-1010.
FDD/Canada. (1967) Food and Drug Directorate, Canada. T. I. L. 290, 15
September
Gordon, C.F., Schuckert, R.J., 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.
Nangniot, P. (1966) L'application des methodes electrochimiques a
l'etude des residus des pesticides. Medel. Landbouwhogeschool
Opzoekingstat. Staat Gent 31: 447-473
Pease, H.L. (1957) Determination of dithiocarbamate fungicide
residues. J. Assoc. Off. Agric. Chem. 40; 1113-1118.
Vogeler, Von K. (1967) Kolorimetrische und polarographische
bestimmungen von ruckstanden in und auf pflanzen nach anwedung von
Antracol. Pflanzenschutz-Nachrichte Bayer.