WHO Pesticide Residues Series, No. 1



    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



    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


    This pesticide was previously evaluated at the Joint Meetings in 1965
    (FAO/WHO 1965c) and was further considered in 1967 and 1968 (FAO/WHO
    1968b, 1969b).

    Reference should be made to Appendix IV. It includes Section 3 of the
    report of the 1971 meeting (FAO/WHO 1972a); also information on some
    commercially available fumigant mixtures.


    Use pattern

    Post-harvest use on dry foodstuffs

    Carbon tetrachloride is used in many countries as a fumigant either
    alone, or, more usually, mixed with other more toxic fumigants
    including 1,2-dibromoethane, carbon disulfide, 1,2-dichloroethane and
    methyl bromide. The main use is in the disinfestation of bulks of
    grain in bins or on floors and there is probably relatively little use
    on other foodstuffs except for small-scale treatments. A recent
    small-scale fumigation development in West Africa uses gelatine
    capsules of carbon tetrachloride to treat individual bags of grain or
    pulses, each enclosed in a bag made of polyethylene. The proportion of
    carbon tetrachloride in commercially available mixtures varies between
    5 and 80% by volume. The most widely used mixture is a 75:25% by
    volume mixture of 1,2-dichloroethane and carbon tetrachloride
    ("3:1 mixture"). Other mixtures are listed in Appendix IV. The
    toxicity of carbon tetrachloride to insects is low in comparison with
    that of other fumigants and relatively long treatment periods such as
    one or two weeks are required for effective disinfestation when it is
    used alone. In mixtures it serves to reduce the fire and explosion
    hazards from the use of fumigants such as carbon disulfide or ethyline
    dichloride (i.e. 1,2-dichlorethane), or it is used to assist the
    distribution of the more toxic ingredients of the mixture.

    Residues resulting from supervised trials

    Laboratory and larger scale supervised trials previously reported, in
    which carbon tetrachloride was applied to raw cereal grains at normal
    commercial dosages either alone or in mixtures containing a
    substantial proportion of this fumigant, indicated that the amount of
    unchanged compound to be found shortly after treatment is typically in
    the range of 100 to 200 ppm. After storage without specifically airing
    the grain, after a few months this usually falls to below 50 ppm. The
    effect of processing to flour and bread has been studied in the
    Netherlands by Wit et al. (1969). There were some discrepancies
    between the results reported by the different participating
    laboratories but the general picture emerged that, starting with grain

    which had been aired for several weeks after fumigation and which then
    contained 20 to 60 ppm of carbon tetrachloride, the amounts found in
    white flour were usually between 2 and 10 ppm and in bread were
    usually below 0.05 ppm and part of these small residues in bread may
    have resulted from impurities in analytical reagents.

    Scudamore and Heuser (1971) give some interim results from an
    extensive investigation of the amounts of carbon tetrachloride in
    wheat and maize after fumigation under controlled conditions. This
    investigation was still in progress when the current review was
    conducted but the results already demonstrate the persistent character
    of the residue of carbon tetrachloride during storage after treatment.
    On milling there was an immediate loss of residue with a further loss
    during subsequent storage of the ground grains under freely exposed
    conditions but a proportion of the residue (around 10%) was still very
    firmly held. The initial loss of residual carbon tetrachloride was
    more rapid from grain fumigated at 10 than from grain fumigated at
    25 but in each case storage under freely exposed conditions at 25
    caused a more rapid loss than similar storage at 10. These results
    are at variance with those of Alumot and Bielorai (1971) who
    unexpectedly reported that ventilation was more effective in removing
    fumigant at lower than at higher temperatures.

    Fate of residues

    In the light of earlier work it was concluded (FAO/WHO 1965c) that
    there was no evidence of chemical reaction with food constituents.

    Evidence of residues in food in commerce or at consumption

    In the period 1964 to 1966 a number of cereals imported into the
    Netherlands were analysed and nearly half of the samples contained a
    detectable amount of carbon tetrachloride (Wit 1968, summarized in
    FAO/WHO 1968b). In about 20% of all samples the residue range was 0.1
    to 0.5 ppm, in 5% the range was 0.5 to 1 ppm, and in 8% the range was
    1 to 5 ppm. Three per cent. of the samples investigated exceeded the
    5 ppm level. The maximum residue found was 58 ppm. Seven lots of grain
    (wheat, corn and milo) commercially fumigated in the United States of
    America with liquid fumigants containing either 70.5 or 82.2% by
    weight of carbon tetrachloride were sampled after storage for one to
    three months in bins and analysed (McMahon, 1971). Amounts of carbon
    tetrachloride ranged from 2.9 to 20.4 ppm.

    Analytical studies in Israel conducted on three commercial samples of
    flour showed residues of 0.2 to 0.3 ppm. All eight samples of bread
    tested were free from detectable carbon tetrachloride (less 0.005
    ppm). Biscuits appeared to contain 0.004 ppm (Bondi et al., 1971 as
    reported by Kenaga 1971).

    Methods of residue analysis

    Methods of determination based on gas liquid chromatography are now
    preferred to earlier methods involving dry or wet aeration or
    distillation, hydrolysis and determination of chloride (Winteringham,
    1944, Mapes and Shrader, 1957, Conroy, Munsey and Ramsey, 1957) or
    direct colorimetric determination of the carbon tetrachloride (Ramsey
    1957). Four basic methods of extraction have been used in preparation
    for determination by gas-chromatography.

    (a)  A steam distillation procedure adapted by Bielorai and Alumot
    (1966) from the method of Kennet and Huelin (1957). This procedure was
    used in later studies by Alumot and Bielorai (1969) and was also
    followed by Wit et al. (1969).

    (b)  A sweep co-distillation method based on the procedures of Ragelis
    et al. (1968) and Storherr et al. (1967).

    (c)  The acid reflux method of Ramsey (1957). Malone (1969) compared
    these three methods and, whilst all were then considered suitable, the
    acid reflux method was preferred and was further evaluated (Malone,
    1970) and used in residue studies (McMahon 1971). The sensitivity of
    the method for carbon tetrachloride in cereal grains using an electron
    capture detector was 0.04 ppm. In the tests with all three of these
    methods of extraction on grain fumigated with carbon tetrachloride
    Malone (1970) reported finding chloroform. It would appear that this
    was formed by conversion of carbon tetrachloride during the hot
    extraction. This conversation was more severe when whole grains were
    extracted. No chloroform was found when cold solvent extraction was

    (d)  In the solvent extraction method of Heuser and Scudamore (1968)
    the substrate is soaked in a 5:1 acetone water mixture at room
    temperature and an aliquot of the supernatant liquid injected into the
    gas-chromatograph. The method was later developed into a multi-residue
    scheme (Heuser and Scudamore 1969) when drying and partial clean-up of
    the extract was introduced as an additional step. Normally an
    extraction period of 48 hours is allowed for whole cereal grains and
    four hours for flour but recent studies (Scudamore and Heuser 1971)
    have shown that a longer period may be required to extract the last
    fraction of residual carbon tetrachloride in materials which have been
    aired for some months after fumigation. Using an electron-capture
    detector, a residue of 0.01 ppm can readily be detected.

    It would appear that methods for extraction of carbon tetrachloride
    from cereals which employ a heating step are less preferable than the
    cold solvent extraction procedure because of the partial conversion to
    chloroform caused by the former. Procedure (d) therefore is the
    preferred method.

    National tolerances (as reported to the meeting)

    The following statements form the basis for regulatory action on
    residues of carbon tetrachloride in the countries specified.

    Australia           Residues of the unchanged compound must not be
                        present in or upon foods ready for consumption.
                        Carbon tetrachloride is included in a group of
                        volatile, post-harvest fumigants which when used
                        as directed on stored products are held to meet
                        this requirement.

    Canada              When used according to recommendations for stored
                        food products, is held to disappear during the
                        subsequent processing and not to have harmful

    United States       For similar reasons, is exempted from the
    of America          requirements of a tolerance for the following
                        grains: barley, corn, oats, popcorn, rice sorghum
                        (milo), wheat.


    The fumigant is quite widely used on stored cereal grains and to a
    much smaller extent on other stored foods. It is frequently used in
    mixtures with more insecticidally active fumigants.

    There is no evidence of significant reaction with food constituents
    but airing off of some of the residue may be slow. The residue is
    greatly reduced on milling. The amount found in bread baked from flour
    containing the residues persisting under commercial conditions after
    milling of fumigated grain is below 0.05 ppm. Satisfactory analytical
    methods are available, using gas-chromatography, capable of detecting
    residues of 0.01 ppm.

    From the available information on the occurrence of unchanged carbon
    tetrachloride in or on raw cereal products after fumigation in
    accordance with good practice it appears that the following amounts
    need not be exceeded and it is recommended that these residue levels
    be used as guidelines.

         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 and before sampling         50 ppm

         In milling cereal products which will be
         subjected to baking or cooking                        10 ppm

         In bread and other cooked cereal products
         (i.e. at or about the present limit of
         determination)                                      0.05 ppm

    Further work desirable

    Further information from supervised trials and commercial treatments
    on the amount of residues of unchanged carbon tetrachloride occurring
    after fumigation of raw cereals showing the rate of disappearance
    during subsequent storage or processing.


    Alumot, E. and Bielorai, R. (1969) Residues of fumigant mixture in
    cereals fumigated and aired at two different temperatures. J. Agr.
    Food Chem., 17: 869

    Bielorai, B. and Alumot, E. (1966) Determination of residues of a
    fumigant mixture in cereal grain by electron-capture gas
    chromatography. J. Agr. Food Chem., 14: 622

    Bondi, A. and Alumot, E. (1971) As reported by Kenaga, E. E., 1971,
    IUPAC Meeting

    Conroy, M. W., Munsey, V. E. and Ramsey, L. L. (1957) Total volatile
    organic halide determination of aggregate residue of carbon
    tetrachloride, ethylene dichloride, and ethylene dibromide in
    fumigated cereal products. 2. Ethanolamine-sodium reduction procedure.
    J. Ass. Offic. Agr. Chem., 40: 185-189

    Heuser, S. C. and Scudamore, K. A. (1967) Determination of ethylene
    chlorohydrin, ethylene dibromide and other volatile fumigant residues
    in flour and whole wheat. Chem. Ind., 16 September: 1557-1560

    Heuser, S. G. and Scudamore, K. A. (1968b) Determination of residual
    acrylonitrile, carbon disulfide, carbon tetrachloride and ethylene
    dichloride after fumigation. Chem. Ind., 24 August: 1154-1157

    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 Agric.,
    20: 565-572

    Kennet, B. H. and Huelin, F. E. (1957) Determination of
    ethylenedibromide in fumigated fruit. J. Afr. Food Chem., 5: 201

    Kolthoff, I. M. and Yutzy, M. (1937) Volumetric determination of
    bromide in the presence of much chloride. Ind. Eng. Chem. (Anal. Edn.)
    9: 75

    Lindgren, D. L., Sinclair, W. B. and Vincent, L. E. (1968) Residues in
    raw and processed food resulting from post-harvest insecticidal
    treatments. Residue Reviews, 21: 1-121

    Lynn, G. E. and Vorhes, F. A. (1957) Symposium: Residues in food and
    feeds resulting fumigation of grains with the commoner liquid
    formulations of carbon disulfide, carbon tetrachloride, ethylene
    dichloride and ethylene dibromide. J. Ass. Offic. Agr. Chem., 40:

    Mapes, D. A. and Shrader, S. A. (1957) Determination of total and
    inorganic bromide residues in fumigated products. J. Ass. Offic. Agr.
    Chem., 40: 189-191

    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. Offic. Anal. Chem., 53: 742-746

    Nachtomi, E., Alumot, E, and Bondi, A. (1968) Biochemical changes in
    organs of chicks and rats poisoned with ethylene dibromide and carbon
    tetrachloride. Israel J. Chem., 6: 803-811

    Ragelis, E. P. Fisher, B. S. and Klimeck, B. A. (1966) Note on
    determination of chlorohydrins in foods fumigated with ethylene oxide
    and with propylene oxide. J. Ass. Offic. Anal. Chem., 49: 963

    Ramsey, L. L. (1957) Colorimetric determination of carbon
    tetrachloride in fumigated cereal products. J. Ass. Offic. Agr. Chem.,
    40: 175-180

    Scudamore, K. A. and Heuser, S. G. (1971b) Progress report on an
    investigation of the behaviour of residues of carbon tetrachloride in
    cereals during storage. (Unpublished report to FAO)

    Storrherr, R. W., Murray, E. J., Klein, I. and Rosenberg, L. A. (1967)
    Sweep co-distillation clean-up of fortified edible oils for
    determination of organophosphate and chlorinated hydrocarbon
    pesticides. J. Ass. Offic. Anal. Chem., 50: 605-615

    Winteringham, F. P. W. (1944) Determination of fumigants XI.
    Determination of chlorohydrocarbons in air by reaction in
    monoethanolamine. J. Sci. Chem. Ind., 61: 186-187

    Wit, S. L. (1968) Residues of insecticides in cereals and related
    products incorporated in the Netherlands, 1964/66. Report No. 17/68
    Tox. (CCPR 68/2 Report)

    Wit, S. L., Besemer, A. F. H., Das, H. A., Goedkoop, W., Loosjes, F.
    E. and Meppelink, E. R. (1969) Results of an investigation on the
    regression of three fumigants (carbon tetrachlorine, ethylene
    dibromide and ethylene dichloride) in wheat during processing to
    bread. Report No. 36/69

    See Also:
       Toxicological Abbreviations
       Carbon Tetrachloride (EHC 208, 1999)
       Carbon Tetrachloride (HSG 108, 1998)
       Carbon tetrachloride (ICSC)
       Carbon tetrachloride (FAO Meeting Report PL/1965/10/2)
       Carbon tetrachloride (FAO/PL:1967/M/11/1)
       Carbon tetrachloride (FAO/PL:1968/M/9/1)
       Carbon tetrachloride (Pesticide residues in food: 1979 evaluations)
       Carbon Tetrachloride (IARC Summary & Evaluation, Volume 71, 1999)