Sponsored jointly by FAO and WHO


    Food and Agriculture Organization of the United Nations


    pesticide residues in food:
    1981 evaluations

     the monographs

    data and recommendations
    of the joint meeting
    of the
    FAO panel of experts on pesticide residues
    in food and the environment
    and the
    WHO expert group on pesticide residues

    Geneva, 23 November-2 December 1981

    Rome 1982



         Tecnazene was reviewed at the 1974 Meeting and further studied
    at the 1978 Meeting when a temporary ADI was recommended and a few
    temporary MRLs were proposed. Further data on residue levels in
    potatoes have been received and are reviewed in this monograph
    addendum. No additional toxicological data has been received.



         The use pattern for tecnazene on stored potatoes was reviewed at
    the 1978 Meeting (FAO/WHO 1979)*. A 3% dust formulation is applied at
    the rate of 10 lb product per ton (4.5 g product/kg), to reduce
    sprouting during storage and to control dry rot. This recommendation
    produces a theoretical initial loading on the potatoes of 134 mg/kg.
    Tecnazene displays the additional merits of not inhibiting wound-
    healing in freshly-clamped potatoes and of controlling dry rot,
     Fusarium caeruleum. 


         Data reviewed by the 1978 Meeting showed that when potatoes were
    treated at 4.5 g/kg with 3% tecnazene dust and then stored for 4 to 5
    months, mean residues on the tubers were approximately 2 to 3 mg/kg.
    Increasing the storage period to six months caused a further reduction
    to approximately 1 mg/kg. The original concentration applied
    (134 mg/kg) was reduced mainly by handling, both before and after
    storage, but losses by evaporation were also shown to occur during
    storage. Washing reduced residues still further, to below 1 mg/kg
    (mean approximately 0.4 mg/kg) (FAO/WHO 1979).

         Residues resulting from different methods and rates of
    application have been examined. Potatoes were treated with a 3% dust
    formulation at 2.3 g/kg (50% of recommended rate) or 4.4 g/kg at the
    time of loading into store. The residue levels resulting from
    application by a vibrating device fixed over a loading elevator were
    compared with those resulting from the traditional method of
    application by shovel. Samples were removed for residue analysis after
    5 to 6 days, 1, 2, 3 and 4 months and were deep frozen, without
    airing, pending analysis. Results were as shown in Table 1.


    *  See Annex II for FAO and WHO documentation,

        TABLE 1.  Residues of tecnazene in potatoes treated with 3% 'Fusarex' dust

    Interval       Store       Rate of           Method                                    Residues (mg/kg) in potatoes
    between        number    application          of                                                                                    
    application              (kg dust/ten.    application            Unwashed                   Washed              Washed and peeled
    and                      potatoes)                                                                                                  
    sampling                                                  range           mean        range       mean        range            mean

                     1           2.265        Applicator          Not analysed            2.7-3.9     3.6              Not analysed
                     2           4.43                                                     3.9-5.1     4.3
    5-6 days         3           2.265        Standard            Not analysee            1.0-5.1     3.3              Not analysed
                     4           4.43         shovel                                      3.4-6.6     4.7

                     1           2.265        Applicator      6.0-16.4       11.9         1.7-2.5     2.0         0.25-0.39        0.32
                     2           4.43                         4.9-23.6       12.6         1.4-2.2     1.8         0.49-0.83        0.66
    1 month          3           2.265        Standard        2.3-16.1        6.3         1.6-2.8     2.4         0.53-0.67        0.55
                     4           4.43         shovel          2.6-30.8       14.4         1.5-2.2     1.8          

                     1           2.265                        5.1-16.5       10.5         1.5-2.3     2.0         0.17-0.23        0.21
                     2           4.43         Applicator     10.4-16.2       12.1         1.8-2.3     2.1         0.10-0.26        0.15
    2 months         3           2.265        Standard       10.7-34.9       18.3         1.7-3.4     2.7         0.15-0.30        0.22
                     4           4.43         shovel         13.9-38.2       26.1         2.7-3.2     2.9         0.16-0.27        0.19

                     1           2.265                        4.8-23.6       10.8         3.2-4.6     4.0         0.27-0.54        0.45
                     2           4.43         Applicator     16.0-36.1       25.7         4.4-5.1     4.6         0.49-0.69        0.59
    3 months         3           2.265        Standard        5.9-34.2       18.6         4.5-5.5     5.0         0.44-0.90        0.64
                     4           4.43         shovel         11.6-50.9       24.6         2.6-6.4     5.3         0.49-0.89        0.73

                     1           2.265                        2.8-17.2        8.0         2.1-3.0     2.4
                     2           4.43         Applicator      9.2-22.8       17.4         3.4-4.3     3.8              Not analysed
    4 months         3           2.265        Standard        4.0-20.5       13.1         2.7-3.7     3.0
                     4           4.43         shovel         15.6-56.5       29.2         4.1-4.8     4.5              Not analysed
             The vibratory application device yielded a marginally more even
    distribution of residues than that provided by the traditional shovel
    technique. In unwashed potatoes the mean residues at the 2.3 g/kg
    treatment rate were consistently smaller than those obtained at the
    recommended rate, to a degree overall that might have been anticipated
    from a knowledge of the application rates. However, in potatoes washed
    before analysis the difference in residues between the two rates,
    although still present, was notably less marked (Table 1). In washed
    potatoes, mean residues were generally in the range of 2 to 5 mg/kg.
    These values are marginally higher than those reviewed at the 1978
    Meeting; however, they are also probably higher than those that would
    usually reach the consumer, as the potatoes were deep frozen on
    removal from the store without the airing that would normally occur
    during handling in commerce (Bullock and Cole 1980).

         Hamilton (1981) has commented that some of the available residues
    data was obtained during studies of the efficacy of tecnazene as a
    fungicide and sprout suppressant rather than to obtain data for safe
    use assessments. Hence, often no consideration was given to the amount
    of soil adhering to the tubers, which would provide a rough surface
    assisting the retention of the fungicidal dust. Some tubers have
    visible amounts of adhering dust, though sometimes unexpectedly low
    residues of tecnazene are observed from such samples, the tecnazene
    having already volatilized, leaving in place the filler which
    constitutes 97% of the formulation applied. The amount of adhering
    soil will be very variable and depend on many factors, such as soil
    type, wetness of soil and tubers at time of lifting, amount of
    subsequent handling and aeration, etc. after storage and before
    analysis. Washing the tubers certainly reduces this variability, as
    Table 1 shows.


         Data reviewed at the 1978 Meeting showed that washing, peeling
    and cooking potatoes all cause considerable reductions in tecnazene
    residue levels. When potatoes treated at 4.5 g/kg with 3% tecnazene
    dust were stored commercially for 4 to 5 months, mean tecnazene
    residues on tubers with adhering soil were approximately 3 mg/kg.
    Washing the potatoes reduced residues to below 1 mg/kg (mean
    approximately 0.4 mg/kg). After peeling, residues in uncooked edible
    flesh were normally below 0.1 mg/kg (mean approximately 0.04 mg/kg).  
    Boiling reduced the level of tecnazene in peeled edible flesh by 50%
    or more (FAO/WHO 1979).

         In the further studies referred to above, washed potatoes were
    also peeled using an abrasive peeler, which possibly removed less of
    the residue than would occur during domestic peeling. Under these
    circumstances, tecnazene levels in uncooked edible flesh were of the
    order of 0.5 mg/kg, i.e. approximately an order of magnitude smaller
    than levels in corresponding washed, but unpeeled, potatoes (Table 1).

    Residue levels in uncooked edible flesh were not affected by
    withdrawing the potatoes after an abnormally short storage period (one
    month) as compared with the more representative period of four months
    (Bullock and Cole 1980).

         Lindsay (1981) also studied losses of tecnazene residues on
    washing, peeling and cooking. Owing to the uneven distribution of
    residues of fungicides and sprout suppressants between tubers, and
    even between quarters of tubers, the following steps were taken to
    establish the amount of these materials removed by washing, peeling
    and cooking. To reduce the effects of this variation 12 tubers of a
    similar size were taken and were divided into two sets of six. The
    potatoes were then quartered and two quarters from different potatoes
    were used for each test as shown below.

    FIGURE 1

         The trial thus covered washing, peeling and a range of types of
    cooking. Each analysis was done in duplicate by GLC with EC detection
    after appropriate clean-up of a hexane extract of dried macerated
    sample. The results in Table 2 show that washing removed most of the
    tecnazene and peeling removed most of the remainder. Residues were low
    in cooked potatoes.

         Hamilton (1981) has reviewed and collected some data on residues
    of tecnazene on potatoes, 'as received' and after washing, from
    various sources, including known treated material from farms and
    retail purchases. Tables 3 and 4 show the results reported, which
    illustrate the variability of removal efficiency.

        TABLE 2.  Tecnazene residues (mg/kg) - cv. Maris Piper

    Samples analysed                   1                         2                        3

    As received                  24.0      23.0           13.3       3.2            18.1      24.2
    Washed                        5.3       1.8            1.9       2.2            -         -
    Peeled                        0.8       1.0            1.3       0.3            0.8       0.8
    Boiled unpeeled (washed)      0.06     trace           nd         nd            1.5       0.7

    As received                  17.0      26.0            3.9      12.0            36.1      19.8
    Boiled peeled                 0.04      0.4            0.04      0.09           0.14      0.05
    Chipped                       0.15      0.4            0.1       0.7            0.04      nd
    Crisped                       0.23      0.15           0.1       0.9            trace1    trace

    Percentage removed (mean of two analyses)

    Washing                      85                       75                        -
    Peeling                      96                       90                        97
    Boiling unpeeled            >99                      100                        95
    Boiling peeled               99                       99                        99
    Chipping                     99                       96                        99
    Crisping                     99                       95                        99

    1  trace = < 0.005 mg/kg)
    TABLE 3.  Residues of tecnazene in unwashed potatoes from various

                        No. of             Tecnazene (mg/kg)
    Source              samples        Range               Mean

    Market                61           0.1 - 19.3          3.6

    Various               26           0.1 - 20.5          5.4

    Various                5           2.0 - 7.7           4.0

    Farms                  6           2.8 - 33.7         10.1

    Market                 5           0 - 5.1             1.5

    Farms                 16           0.1 - 23.7          5.8

    TABLE 4.  Residues of tecnazene in potatoes before and after washing

    Source    Cultivar       Tecnazene (mg/kg)        % Removed
                               As received         Washed   by washing

    Farm 1    Record              9.5             6.4         33

    Farm 1    Maris Piper         7.1             6.8          4

    Farm 2    Maris Piper         3.6             3.8          -

    Farm 2    Maris Piper        33.7             5.8         83

    Farm 3    Pentland Hawk       3.6             3.6          0

    Farm 4    Croft               2.8             2.6          7

    Shop 1    -                   2.3             2.0         13

    Shop 2    -                   0.02            0.01        50

    Shop 3    -                   0.05            0.02        60

    Shop 4    -                  <0.01            0.02         -

    Shop 5    -                   5.1             3.7         28

         Very variable levels of tecnazene have been found at every point
    of analysis of treated potatoes. The reasons for the wide variation of
    residues in potato flesh after washing and peeling are not known. The
    condition of the skin due to maturity of the potato and choice of
    cultivar may well be factors affecting penetration into the flesh. The
    time of application after lifting and the temperature of storage, both
    during the short curing period and the lengthy storage period, may
    also be contributory factors. There appears to be an increase in the
    residue levels in flesh related to the length of storage time, but
    again this finding is not always consistent. The residues found in the
    flesh of peeled potatoes are all below 1 mg/kg, but there are reports
    of levels of over 1 mg/kg being found in boiled (after peeling)
    potatoes, although it is unlikely that any allowance had been made for
    loss of water in cooked potatoes.

         Washing potatoes removed adhering soil and tecnazene dust, but
    the percentage removed is very variable and can be small, as shown by
    Bullock and Cole (1980) and Hamilton (1981).

         Residues in excess of 1 mg/kg were found on all of the 6 samples
    taken from farm stores after 6 months storage (Table 4) and on 2 out
    of 5 shop samples (Table 2), which were analysed about 6 months after
    harvest. The samples, ex farm, were analysed within 3 days after
    removal from store, but it is unlikely that the two shop samples were
    analysed that soon.



         Tecnazene is used on potatoes as a post-harvest sprout
    suppressant and to control dry rot. The further residues data that are
    now available on potatoes broadly confirm the data reviewed by the
    1978 Meeting. The new data from Bullock and Cole (1980) involved
    alternative means of application and also incorporated a 'Worst case'
    evaluation, as the potatoes were deep frozen immediately on removal
    from the store. Thus the potatoes did not receive the handling and
    airing at ambient temperature that is known to reduce residue levels
    by evaporation once the tubers are removed from storage. In addition,
    peeling was by abrasive peeler, which can be expected to remove less
    residue than normal domestic peeling. In these extreme circumstances,
    tecnazene levels in uncooked, peeled edible flesh were of the order of
    0.5 mg/kg, which is somewhat higher than the levels reported to the
    1978 Meeting. However, when due account is taken of (i) the reduction
    of residue levels which can be expected to occur during cooking and
    (ii) the extreme circumstances in which the residue data were
    generated, this information is reassuring. The data confirms that
    residue levels in washed potatoes are reduced by approximately an
    order of magnitude by peeling.

         The data reviewed at the 1978 Meeting indicated that in washed
    and peeled potatoes residues will normally be below 0.1 mg/kg (mean
    0.04 mg/kg) and that this residue is reduced by 50% or more on
    cooking. On this basis, residues in boiled potatoes would rarely be
    likely to exceed 0.05 mg/kg. However, the work of Lindsay (1981) shows
    that these figures may be low in some circumstances, although the
    reduction due to washing and cooking is confirmed.


         None of the required or desirable data specified by the 1978 JMPR
    (FAO/WHO, 1979a) were available, However, the present Meeting again
    discussed the relevance of the tumour-initiating activity observed in
    a study where tecnazene was painted on the skin of mice. It was agreed
    that this had little relevance to the evaluation of pesticides
    residues in food especially when acceptable oral carcinogenicity
    studies in rats and mice were taken into account. Because of this
    reduced concern regarding the mouse skin painting study, the Meeting
    agreed that the temporary ADI allocated previously (FAO/WHO, 1979) be
    extended for 2 years.

         The Meeting confirmed the necessity for an adequate reproduction
    study on tecnazene.

    Level causing no toxicological effect

         Rat : 750 ppm in the diet equivalent to 38 mg/kg bw/day
         Mouse : 1500 ppm in the diet equivalent to 200 mg/kg bw/day
         Dog :  15 mg/kg bw/day

    Estimate of temporary acceptable daily intake for man

         0 - 0.01 mg/kw bw


         Although there are indications that the temporary MRL of 1 mg/kg
    on potatoes (washed before analysis) proposed in 1978 may be too low,
    available relevant data are insufficient to recommend any replacement
    figure. The future data on losses due to washing, peeling and cooking
    are reassuring.


    Required (by 1983)

         An adequate study on reproduction.


    1.   Clarification of the tumour-initiating activity observed in a
         skin painting experiment on mice.

    2.   Short-term tests on mutagenicity.

    3.   Metabolism studies in different mammalian species.


    Bullock, D.J.W. and Cole, M.C. "Tecnazene"; Residues in potatoes
    1980      following application of 'Fusarex' by shovel and by
              applicator methods" ICI Plant Protection Division Report No.
              TMJ 1794A. (Unpublished)

    Hamilton, G.A. Information on tecnazene from the United Kingdom.
    1981      (Unpublished)

    Lindsay, D.A. Information on tecnazene from the United Kingdom.
    1981      (Unpublished)

    See Also:
       Toxicological Abbreviations
       Tecnazene (EHC 42, 1984)
       Tecnazene (HSG 12, 1988)
       Tecnazene (WHO Pesticide Residues Series 4)
       Tecnazene (Pesticide residues in food: 1978 evaluations)
       Tecnazene (Pesticide residues in food: 1994 evaluations Part II Toxicology)