FAO Meeting Report No. PL/1965/10/2
    WHO/Food Add/28.65


    The content of this document is the result of the deliberations of the
    Joint Meeting of the FAO Committee on Pesticides in Agriculture and
    the WHO Expert Committee on Pesticide Residues, which met 15-22 March

    Food and Agriculture Organization of the United Nations
    World Health Organization

    1 Report of the second joint meeting of the FAO Committee on
    Pesticides in Agriculture and the WHO Expert Committee on Pesticide
    Residues, FAO Meeting Report No. PL/1965/10; WHO/Food Add./26.65.




    Chemical name



         Nitrochloroform, trichloronitromethane

    Empirical formula


    Structural formula


    Relevant physical and chemical properties

    Physical state (atmospheric pressure, 20°C): colourless liquid

    Boiling-point: 112°C

    Odour: strongly irritating tear-gas

    Lowest concentration in air which is detectable by odour: because of
    irritant effect, a toxic concentration cannot be endured for more than
    a few seconds

    Flash point: non-flammable


         Water: 0.227 g/100 ml

         Organic solvents: infinitely soluble in alcohol and ether

    Specific gravity (liquid): 1.65

    Specific gravity (gas): 5.7


         Chloropicrin is used as an insecticide and sterilizing agent;
    however, cereal grains are the only foodstuffs usually treated. Under
    carefully controlled conditions it has been employed successfully for
    control of insects and micro-organisms in certain seeds (Kennedy,
    1961; Hsin et al., 1959). It is widely used for fumigation of soil to
    control nematodes, micro-organisms, and weed seeds, but the possible
    effect on food crops grown in treated soil has not been considered in
    the present evaluation.

         Chloropicrin has strong lachrymatory effects and is sometimes
    added in small amounts to other comparatively odourless fumigants to
    act as a warning agent.

         A usual treatment for bulk grain is 2 to 2.5 lb per 1000 bushels.


         There appear to be no published quantitative data on residues of
    chloropicrin or its chemical decomposition products in foodstuffs
    subsequent to fumigation.

    Effect of fumigant on treated crop

         If fumigated grain, or flour made from it, still contains
    residual chloropicrin, milling and baking qualities may be affected
    (Cotton, 1956). However, if the material is properly aerated there are
    no adverse effects.


    Biochemical aspects

         In this connexion, the ability of chloropicrin to react with free
    thiol(-SH) groups, which become oxidized to disulfide groups, should
    be stressed (Bacq, 1942a and b; Fischer, 1944; Desreux et al., 1946).
    This blocking of the thiol groups causes, inter alia, a change in
    the proteins (Bacq and Desreux, 1942; Bacq and Fischer, 1943) and
    inhibition of enzyme systems whose activity depends on the presence of
    free-SH groups, including urease (Fischer, 1946), papain (Desreux et
    al., 1946) and succinodehydrogenase (Massart and Peeters, 1941).

         From one study, it was concluded that the reaction of
    chloropicrin with mercaptides at ordinary temperature is

         3 RSH + NO2CCl3 --> (RS)3 - CNO2 + 3 HCl

    but in another it was shown that chloropicrin acts as an oxidizing
    agent with the simplest mercaptans, like ethylmercaptan and
    thiophenol, giving the corresponding disulfides. With mercaptides,
    there is always a considerable evolution of gas consisting of carbon
    dioxide, considerable amounts of nitrogen and approximately equal
    amounts of carbon monoxide and nitric oxide. The main reaction is
    represented by the following equation:

         2(RS)3 - CNO2 --> 3 R-S-S-R + 2 CO2 + N2

    and is accompanied to a smaller extent by the reaction

         2(RS)3 - CNO2 --> 3 R-S-S-R + 2 CO + 2 NO (Jackson, 1934).

    The possibility of formation of residual nitrites and even
    nitrosamines by action of chloropicrin on food cannot be excluded,
    particularly when it is remembered that chloropicrin can undergo
    photochemical decomposition in accordance with the equation:

         CCl3 - NO2 --> COCl2 + NOCl

    In the presence of water, nitrosyl chloride (NOCl) gives hydrochloric
    acid and nitrous acid:

         NOCl + H2O --> HNO2 + HCl

    Acute toxicity

    Animal      Route             LD mg/kg              References

    Rabbit  Intravenous               10                Gildemeister &
            (aqueous emulsion      (minimal             Heubner, 1921
            in the presence        lethal dose)
            of lecithin)

    Cat     Subcutaneous           About 10             Negherbon, 1959

    Dog     Inhalation (30         0.8 mg/litre         Negherbon, 1959
            minute exposure       (120 ppm) (LC50)

         Chloropicrin emits very irritating vapours which are lacrimatory,
    and cause coughing and suffocation, as well as vomiting and

         In man, a concentration of 2.4 g per m3 can cause death from
    acute pulmonary oedema in a minute (Hanslian, 1921).

         The maximal tolerable concentration of chloropicrin in air has
    been fixed at 0.1 ppm.

    Short-term studies

         Cat.    During two weeks a cat received a diet containing
    approximately 1175 ppm of chloropicrin. A decrease in appetite was
    noted, but no toxic symptoms were found (Gildemeister and Heubner,

         Dog. A dog weighing 21.8 kg was fed on meat containing a total
    amount of chloropicrin in excess of 1.5 g. The animal was reluctant to
    eat the meat, but no symptoms of poisoning were seen (Gildemeister and
    Heubner, 1921).

    Long-term studies

         No information.

    Comments on the experimental studies reported

         The short-term stidies are extremely limited (one cat, one dog),
    while long-term ones are completely lacking. Moreover, the fate of
    chloropicrin residues, if any, in treated food has not yet been


         The very scanty data available do not make it possible to
    estimate any acceptable daily dose for man.

    Further work required

         If it proves essential to continue using chloropicrin for the
    fumigation of certain foods, it will be necessary to carry out

    (1) to define the nature and the amount of the residues present in
        treated foods;

    (2) to determine the long-term effects, in at least two animal
        species, of chloropicrin and the degradation or reaction products 
        to which it may give rise in foods submitted to its action.


    Bacq, Z. M. (1942a) Acta biol. belg., 2, 430

    Bacq, Z. M. (1942b) Bull. Acad. roy. Méd. Belg., 7, 500

    Bacq, Z. M. & Desreux, V. (1942) Acta biol. belg., 3, 369

    Bacq, Z. M. & Fischer, P. (1943) Bull. Soc. roy. Sci. Liège, 575 and

    Cotton, R. T. (1956) Pest of stored grain and grain products, (rev.
    ed.) Burgess Publ., Minneapolis

    Desreux, V., Frèdèricq, E. & Fischer, P. (1946) Bull. Soc. Chim.
    biol. (Paris), 28, 493

    Fischer, P. (1944) Compt. Rend. Soc. biol (Paris), 138, 870

    Fischer, P. (1946) Bull. Soc. Chim. biol. (Paris), 28, 240

    Gildemeister, M. & Heubner, W. (1921) Z. ges. exp. Med., 13, 291

    Hanslian, R. (1921) Ber. dtsch. pharm. gesell., 31, 222

    Hsin, K. L., Hsueh, C. F., Liang, L. J., Dai, Z. S. & Chen, L. C.
    (1959) Chem. Abstr., 54, 3831 c and d

    Jackson, K. E. (1934) Chem. Rev., 14, 251

    Kennedy, J. (1961) J. Sci. Food Agri., 12, 96

    Massart, L. & Peeters, G. (1941) Acta biol. Belg., 1, 42

    Negherbon, W. O. (1959) Handbook of Toxicology, vol. 3, Saunders,

    See Also:
       Toxicological Abbreviations