Arising out of the list of requirements published in the Report of the
    1976 Joint Meeting (FAO/WHO, 1977a) some information on the stability
    of residues of maleic hydrazide during the cooking of potatoes has
    been referred to the Meeting. Data, on residues observed in tobacco
    were also made available. The new information is reviewed below.

    No new toxicological data have been provided. It was therefore
    impossible to complete a evaluation or to establish an ADI for humans.




    Information was available to the FAO Panel of Experts relating to
    residues of maleic hydrazide Observed in tobacco and cigarettes in the
    USA during the years 1961-75 Uniroyal chemical, 1977b). Data concerned
    flue cured and Burley tobaccos, influence of harvest time, influence
    of application rate, effect of curing, residues in stored tobacco, and
    residues in tobacco products.

    The data from supervised trials collected over 15 years from almost
    100 locations clearly indicated extensive variability in observed
    residue levels and a high probability of finding an occasional high
    level in cured tobacco The average residue was 52 mg/kg in flue cured
    and Burley tobaccos; however, the, data were strongly skewed towards
    residues in the range 15-60 mg/kg. It would appear that as a guideline
    level, 100 mg/kg would cover about 96% of all tobaccos examined; 95%
    would be covered by 200 mg/kg but levels approaching 500 mg/kg were

    The limited data available showed that neither air curing nor flue
    curing appeared to alter the level of maleic hydrazide residues found
    in freshly harvested tobacco leaves; it also appeared unlikely that
    prolonged storage would lead to any notable reduction in residue
    levels. Thus, the levels of maleic hydrazide found in freshly
    harvested or recently cured tobacco leaves can serve as reliable
    indicators of likely levels at all stages of trade in unblended leaf.

    The effects of blending, however, are such that the variability of
    residue level, as well as the levels themselves, are much reduced
    during the manufacture of cigarettes, cigars, snuff etc. Examination
    of 16 brands of cigarettes gave a range of residue levels from 22 to
    52 mg/kg, with a mean value of 39 mg/kg. Residue levels observed in
    limited samples of cigars, small cigars, smoking tobacco, chewing
    tobacco and snuff were, in general, less than those found in
    cigarettes; the highest level observed was 38 mg/kg, in smoking

    tobacco. For such tobacco products a guideline level of 50 mg/kg
    should suffice.

    Tobacco samples from several countries were analysed by Nesemann,
    Rabitz and Seehofer (1974). Tobaccos from the USA showed residues of
    maleic hydrazide ranging from 35 to 94 mg/kg with an average of 65
    mg/kg. Two 1969 samples from Italy contained 4 and 11 mg/kg,
    respectively but other samples from that country and from Argentine,
    Brazil, Bulgaria, China, Mexico, Philippines and Thailand contained
    less than 2 mg/kg. Liu and Hoffmann (1973) determined maleic hydrazide
    in tobacco smoke. They found that cigarettes containing about 30 µ of
    maleic hydrazide each, yielded smoke containing an average of 1.2 µ g,
    ie about 4% of the total originally present; hydrazine was not
    detected in the smoke.

    A full review of data concerning pesticide residues, including maleic
    hydrazide, in tobacco and tobacco products was completed recently as
    part of a study programme of the Directorate-General for Agriculture
    of the Commission of the European Communities (Anonymous, 1976a,b,c).
    A draft method for the determination of residues of maleic hydrazide
    in tobacco and tobacco products is under discussion by the ISO
    Committee TC 126. Consideration of this procedure has reached an
    advanced stage and early publication is anticipated.


    In cooking

    Commercially treated potatoes (3.4 kg a.i./ha) were sampled and
    analysed for residues of maleic hydrazide (Uniroyal Chemical, 1977a).
    The potatoes were divided into two parts longitudinally, one half
    being analysed raw and the other after boiling in water, discarding
    the liquor and mashing the cooked potato. Table 1 compares the residue
    of maleic hydrazide found in the raw and cooked potatoes; no
    significant difference in levels was observed.

    TABLE 1. Residues of maleic hydrazide in potatoes before and after

    Sample         Treatment to harvest     Maleic hydrazide found, mg/kg
                   interval (days)          Raw       cooked

    A              65                       10        10

    B              50                       22        20

    Recovery of maleic hydrazide added at 20 mg/kg to untreated potatoes
    was 95%. Samples were analysed by the method of Lane (1963).

    These findings illustrate the inherent stability of residues of maleic
    hydrazide to cooking processes. Additionally it has been observed that
    crops containing maleic hydrazide can be boiled in strong caustic
    solutions without loss of the residues or its hydrolysis. Under these
    conditions the addition of zinc is necessary to act as a reducing
    agent to liberate the hydrazine.

    No data were available to the Panel concerning the effect on maleic
    hydrazide residues of different methods of industrial processing in
    the manufacture of various potato products; the requirement for this
    information remains. Limited data from treated potatoes showed that
    free hydrazine did not occur as a residue (Uniroyal Chemical, 1977a).


    Residues of maleic hydrazide in harvested potatoes are not diminished
    on cooking by boiling in water. No information was available regarding
    other means of cooking or processing.

    Tobacco treated with maleic hydrazide can contain up to a maximum of
    500 mg/kg at harvest and thereafter, no loss occurring during curing
    or storage; however, 90% of samples will be below 100 mg/kg. Blending
    and manufacture of tobacco products, eg. cigarettes, cigars, snuff,
    can reduce observed residues to below about 50 mg/kg. Generally, only
    5-10% of the maleic hydrazide in tobacco transfers to the smoke.


    The following guideline levels can be recorded for tobacco and tobacco
    products. The guideline level for potatoes is confirmed at 50 mg/kg.
    Guideline levels are for the sum of free and bound unchanged maleic
    hydrazide and its B-D-glucoside.

                   Commodity      Guideline level, mg/kg

              Tobacco leaf             100

              Tobacco products          50
              cigars, smoking
              tobacco, chewing
              tobacco, snuff)          


    See Report of 1976 Meeting (FAO/WHO, 1977a, Annex 2). Data on the
    effect of cooking on residues in potatoes and on the carry-over of
    maleic hydrazide from raw into cured tobacco and into cigarette smoke
    are no longer required. The other requirements remain.


    Anonymous. (1976a) Pesticide residues in tobacco and tobacco products.
    Volume 1. Information on Agriculture, No. 14. Comm. Europ. Commun.,

    Anonymous. (1976b) Pesticide residues in tobacco and tobacco products.
    Volume II. Information on Agriculture, No. 23. Comm. Europ. Commun.,

    Anonymous, (1976c) Pesticide residues in tobacco and tobacco products.
    Volume III. Information on Agriculture, No. 26. Comm. Europ. Commu.,

    FAO/WHO (1977a) Pesticide residues in food. Report of the 1976 Joint
    FAO/WHO Meeting. FAO Food and Nut. Ser., No. 9; FAO Plant Prod. and
    Prot. Ser., No. 8; Wld. Hlth. Org. techn. Rep. Ser., No. 612.

    FAO/WHO. (1977b) 1976 Evaluations of some pesticide residues in food.

    Lane, J.R. (1963) Collaborative study of maleic hydrazide residue
    analysis. J. Ass. Off. Agr. Chem 46(2): 261-268.

    Liu, Y-Y. and Hoffmann, D. (1973) Quantitative chromatographic
    determination of maleic hydrazide in cigarette smoke. Anal. Chem. 45:

    Nesemann, E., Rabitz, H. and Seehofer, F. (1974) Methoden zur
    quantitativen Bestimmug von Boiziden in Tabak. IV Eine Methoden zur
    Bestimmug von Maleinsäure hydrazide. Beitr. Tabakforsch. 7: 240-243.

    Uniroyal Chemical.  (1977a) Persistence of maleic hydrazide in
    potatoes. (Unpublished)

    Uniroyal Chemical. (1977b) Maleic hydrazide residues found in U.S.
    tobacco. (Unpublished report and review).

    See Also:
       Toxicological Abbreviations
       Maleic hydrazide (Pesticide residues in food: 1976 evaluations)
       Maleic hydrazide (Pesticide residues in food: 1980 evaluations)
       Maleic hydrazide (Pesticide residues in food: 1984 evaluations)
       Maleic hydrazide (Pesticide residues in food: 1984 evaluations)
       Maleic hydrazide (Pesticide residues in food: 1996 evaluations Part II Toxicological)
       Maleic Hydrazide (IARC Summary & Evaluation, Volume 4, 1974)