WHO Pesticide Residues Series, No. 1
1971 EVALUATIONS OF SOME PESTICIDE RESIDUES IN FOOD
THE MONOGRAPHS
The evaluations contained in these monographs were prepared by the
Joint Meeting of the FAO Working Party of Experts on Pesticide
Residues and the WHO Expert Committee on Pesticide Residues that met
in Geneva from 22 to 29 November 1971.1
World Health Organization
Geneva
1972
1 Pesticide Residues in Food: Report of the 1971 Joint Meeting of
the FAO Working Party of Experts on Pesticide Residues and the WHO
Expert Committee on Pesticide Residues, Wld Hlth Org. techn. Rep.
Ser., No. 502; FAO Agricultural Studies, 1972, No. 88.
These monographs are also issued by the Food and Agriculture
Organization of the United Nations, Rome, as document AGP-1971/M/9/1.
FAO and WHO 1972
CARBON DISULFIDE
This pesticide was previously evaluated in 1965, (FAO/WHO 1965c) and
it was further reviewed in 1967 and 1968 (FAO/WHO 1968b, 1969b).
Reference should be made to Appendix IV where Section 3 of the report
on the 1971 meeting (FAO/WHO 1972a) is reproduced. This appendix also
contains information on some commercial fumigant mixtures.
RESIDUES IN FOOD AND THEIR EVALUATION
Use pattern
Post-harvest use on dry foodstuffs
Carbon disulfide has been used alone and also in mixture with other
compounds. Its use has decreased during recent years. When used alone
there is a very high risk of fire or explosion and mixtures are
usually formulated to reduce this risk to an acceptably low level. A
commonly used mixture contains one volume of carbon disulfide with
four volumes of carbon tetrachloride with or without the addition of
1 or 2% of other fire suppressing or stabilizing compounds such as
sulfur dioxide. There is a continuing use of this mixture in the
United States of America for treating raw cereals in farm bins and in
silos. In the African territories its use is limited to small areas
where it is applied to grain intended for local consumption. In Israel
a mixture containing 26% by volume of carbon disulfide, 5% of carbon
tetrachloride, 37% of chloroform and 32% of trichlorethylene has been
used for treatment of raw grain.
Residues resulting from supervised trials
Previous reports have referred to an extensive series of studies
undertaken in the United States of America (Lynn and Vorhes, 1957) on
the residues of the actual fumigant compounds present in wheat and
milled products after treatment of the raw grain with various liquid
fumigant mixtures including the 20:80% by volume mixture of carbon
disulfide and carbon tetrachloride. Residual carbon disulfide was
recovered by an acid distillation procedure and determined
colorimetrically. Results were reported to 0.1 ppm. In pilot plant
tests the residue of carbon disulfide found in uncleaned wheat treated
at the usual commercial dose was about 1 ppm and in the milled
products this was reduced to around 0.5 ppm. The further reduction in
residue resulting from baking was tested using flour to which about 10
ppm of carbon disulfide had been added. The reported reduction to
below 0.5 ppm (presumably the limit of detection) does not necessarily
represent the behaviour of the residue resulting from fumigation of
the raw grain. Nevertheless, it would be reasonable to expect a
substantial reduction of the residual carbon disulfide on baking or
cooking.
Fate of residues
Investigations into the residues in foodstuffs after treatment with
carbon disulfide have been confined to determination of the amounts of
this compound present. Possible reaction products have not been
sought. Much research has been carried out on the reactions of carbon
disulfide in the higher animals, in particular with peptide and
protein animo groups (FAO/WHO 1965c) but there is little information
on any reactions occurring in plant material.
Evidence of residues in food in commerce or at consumption
In the studies already referred to (Lynn and Vorhes, 1957) amounts of
carbon disulfide found in commercially fumigated wheat were slightly
higher, even after storage for three or four months, than were found
in the pilot-scale trials at comparable dosage levels. This was
probably due to less effective airing during storage and processing
than occurred with the smaller quantities of treated grain. McMahon
(1971) examined seven samples of grain three to eight months after
commercial fumigation with mixtures containing 16.5% by weight of
carbon disulfide. An acid reflux procedure was used for extraction
followed by analysis by gas-chromatography and amounts between 0.84
and 2.16 ppm were found.
Methods of residue analysis
Methods are described only for unreacted carbon disulfide
Determination by gas-chromatography is now preferred to the
colorimetric methods previously used. Of the procedures which have
been described for determining multiple residues of volatile fumigants
by gas-chromatography two appear suitable for carbon disulfide. In the
method of Malone (1969, 1970) which uses an acid reflux extraction
procedure of Heuser and Scudamore (1969) the volatile residues are
extracted by a 5:1 by volume mixture of acetone and water. Using an
electron-capture detector 0.1 ppm can be determined and this would be
the method of choice at the present time.
National tolerances
The following statements form the basis for regulatory action on
residues of carbon disulfide in the countries specified.
Australia Carbon disulfide is included in a group of
volatile, post-harvest fumigants which when used
as directed on stored products, will disappear
before the food reaches the consumer. Residues of
the unchanged compound must not be present in or
upon foods consumed.
Canada Carbon disulfide is included in a group of
agricultural chemicals which when used according
to recommendations for post-harvest application to
stored food products, disappear during the
subsequent processing of the food or do not have
harmful or poisonous residues so that when the
food reaches the consumer, no hazard is considered
to remain.
United States Carbon disulfide is exempted from the requirements
of America of a tolerance for residues, when used as a
fumigant after harvest for the following grains:
barley, corn, oats, popcorn, rice sorghum (milo),
wheat.
Appraisal
Carbon disulfide has been in limited use in many countries over
several decades as an insecticidal fumigant for cereals and other
products. This use is much less than formerly. In the United States of
America, it is commonly used in a 20:80% by volume mixture with carbon
tetrachloride for raw cereals in farm bins and in silos. Some other
mixtures with aliphatic chlorohydrocarbons such as 1,2-dichloroethane,
chloroform and trichloro-ethylene are also in use. These mixtures are
formulated to reduce the fire risk with carbon disulfide. There is
some small-scale use of carbon disulfide alone by farmers on grain
intended for local consumption.
Sorption by cereals is relatively low and this physically held
material is substantially removed when airing occurs during storage
and handling. Amounts found in commercially treated cereals after
storage have been reported as around 1 or 2 ppm. This residue is
further reduced by milling and after baking residues greater than the
limits of the analytical methods used (usually 0.5 ppm) have not been
found.
Much research has been carried out on the reactions of carbon
disulfide in the higher animals, in particular with peptide and
protein amino groups but there is little information on any reactions
occurring in plant material. Investigations into the residues in
foodstuffs after treatment with carbon disulfide have been confined to
determination of the amount of the parent compound present.
Residual carbon disulfide can be determined in food samples by
gas-chromatography after separation by a distillation procedure or by
solvent extraction. Using an electron-capture detector 0.1 ppm can be
determined.
From the available information on the occurrence of unchanged carbon
disulfide in or on raw cereals or cereal products after fumigation in
accordance with good practice it appears that the following amounts
need not be exceeded. It is recommended that these levels be used as
guidelines of the amounts which should not be exceeded following use
of the fumigant in commercial practice.
In raw cereals at point of entry into a
country or when supplied for milling,
provided that the commodity is freely
exposed to air for a period of at least
24 hours after fumigation before sampling 10 ppm
In milled cereal products which will be
subjected to baking or cooking 2 ppm
In bread and other cooked cereal products
(i.e. at or about the present limit of
determination) 0.5 ppm
Further work desirable
1. Additional data on residues of unchanged carbon disulfide
occurring in food in commercial practice.
2. Studies on the nature of the reaction products, if any, of carbon
disulfide with foodstuffs.
REFERENCES
Lynn, G. E. and Vorhes, F. A. (1957) Symposium: Residues in foods and
feeds resulting from fumigation of grains with the commoner liquid
formulations of carbon disulfide, carbon tetrachloride, ethylene
dichloride, and ethylene dibromide. J. Ass. Offic. Agr. Chem.,
40: 163-209
McMahon, B. Malone (1971) Analysis of commercially fumigated grains
for residues of organic fumigants. J. Ass. Offic. Chem., 54. 964-965
Malone, B. (1969) Analysis of grains for multiple residues of organic
fumigants. J. Ass. Offic. Anal. Chem., 52: 800-805
Malone, B. (1970) Method for determining multiple residues of organic
fumigants in cereal grains. J. Ass. Off. Anal. Chem., 53: 742-746
Heuser, S. G. and Scudamore, K. A. (1969) Determination of fumigant
residues in cereals and other foodstuffs: a multi-detection scheme for
gas-chromatography of solvent extracts. J. Sci. Food Agr.,
20: 565-572
See Also:
Toxicological Abbreviations
Carbon disulfide (EHC 10, 1979)
Carbon disulfide (ICSC)
Carbon disulfide (PIM 102)
Carbon disulfide (FAO Meeting Report PL/1965/10/2)
Carbon disulfide (FAO/PL:1967/M/11/1)
Carbon disulfide (FAO/PL:1968/M/9/1)
Carbon Disulfide (CICADS 46, 2002)