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 was evaluated by the 1965 Joint Meeting of the FAO
Committee on Pesticides in Agriculture and the WHO Expert Committee on
Pesticide Residues (FAO/WHO, 1965). A re-evaluation of the
toxicological data and an evaluation for tolerances is given in the
following monograph addendum.
EVALUATION FOR ACCEPTABLE DAILY INTAKES
In long-term studies in rats toxic effects were seen at a level of 300
ppm in the diet with questionable effects at 100 ppm. In a study that
extended over three generations, a dietary level of 48 ppm was without
toxicological affect. Chicks appear to be especially susceptible to
thiram brut confirmation and extension of these experiments are
The biochemical investigations on the homologue, tetra ethyl thiuram
disulfide, are considered relevant to the evaluation of thiram.
It is known that tetra methyl thiuram disulfide in a dose of 0.5 to
1.5 per day can be taken by man for many weeks without ill-effect
unless alcohol is consumed.
While additional data are being obtained, a temporary ADI, based on
the long-term studies in rat, is proposed.
Level causing no toxicological effect
Rat. 48 ppm in the diet, approximately equivalent to 2.5 mg/kg
body-weight per day.
Dog. 5 mg/kg body-weight/day
Estimate of temporary acceptable daily intake for man
0 - 0.025 mg/kg body-weight (alone or in combination with other
This value is based on experiments carried out with thiram 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
Thiram is used primarily as a pre-harvest spray to protect a number of
agricultural products from plant pathogens.
RESIDUES IN FOOD AT TIME OF CONSUMPTION
A recent survey of five composite basic 2-week diets for males 14-19
years showed the presence of six 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.
METHODS OF RESIDUE ANALYSIS
Residues have been determined by releasing either the dimethylamine
(Barr, Clark 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).
Thiram is registered for use in Canada on apples, celery, peaches,
strawberries and tomatoes at a residue level of 7 ppm (FDD/Canada,
1967). The United States use at the same level also includes bananas
(1 ppm in pulp), while no tolerance has been set for a number of
agricultural pesticide chemical uses (USDA, 1967). The West German
tolerance has been set at 3 ppm for leafy vegetables, and fruits.
RECOMMENDATIONS FOR TOLERANCES
Although some progress has been reported, neither the chemical nature
nor the mode of action of the residues of thiram 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 required by 30 June 1971
Further work is required on the metabolism of thiram in or on the
plant to include the identification and mode of action of any critical
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
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 de pesticides. Mededel. Landbouwhogeschool
Opzoekingstat. Staat Gent 31: 447-473.
Pease, H.L. (1957) Determination of dithiocarbamate fungicide
residues. J. Assoc. Off. Agric. Chem. 40: 1113-1118.
USDA. (1967) Summary of registered agricultural pesticide chemical
uses. 2nd ed., Suppl.III.
Vegeler, von K. (1967) Kolorimetrische und polarographische
bestimmungen von ruckstanden in und auf pflanzen nach anwendung von
Antracol. Pflanzenschutz-Nachrichte Bayer.