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    PESTICIDE RESIDUES IN FOOD - 1984


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    EVALUATIONS 1984




    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
    Rome, 24 September - 3 October 1984

    Food and Agriculture Organization of the United Nations
    Rome 1985

    DIPHENYLAMINE

    Explanation

         Diphenylamine (DPA) was evaluated in 1969, 1976, 1979 and 1982
    1/. The 1982 meeting noted that biphenyl-4-ylamine (identified in the
    1982 evaluation as p-biphenylamine), a known carcinogen, had been
    found in four of six samples of diphenylamine analysed for minor
    impurities. Information on the nature and level of the impurities in
    commercial DPA was therefore thought to be desirable.

         An extensive review of the uses, manufacture and properties of
    DPA was available to the present meeting. Information relevant to the
    uses of DPA in food production is evaluated in this monograph
    addendum.

    IDENTITY

    Purity of the commercial product

         Methods for the synthesis of DPA have been described by
    Kirk-Othmer (1968, 1978), Hoelscher and Chamberlain (1950, 1951) and
    Scott (1962).

         Diphenylamine of the quality used in early work on scald control
    in apples was produced by a chemical company in the USA. The standard
    they specified was 99.9% DPA minimum as a fine white powder of 52.9C
    minimum melting point; 10 mg/kg maximum primary amines expressed as
    aniline; 20 mg/kg maximum lead; volatiles by vapour phase
    chromatography 0.5% and ash 0.01%.

         The method of manufacture was by the reaction of aniline in the
    vapour phase at 480C and about seven atmospheres pressure over an
    activated alumina catalyst. The product vapours were cooled, condensed
    and subject to continuous distillation to remove most of the unreacted
    aniline and by-product ammonia. The crude DPA concentrate was then
    distilled batchwise to recover the remainder of the unreacted aniline
    and to separate DPA from the impurities. The cooled DPA in flake form
    was then dissolved in aqueous isopropanol and the solution purified
    with activated carbon. After filtration, the solution was cooled to
    cause the DPA to crystallise and the purified DPA was isolated by
    centrifugation.



              

    1/  See Annex 2 for FAO and WHO documentation

         It appears to have been material of this quality that was
    referred to in the 1969 evaluation. The samples analysed by Safe
    et al. (1977) (see 1982 evaluation) were from six different sources,
    but it was not disclosed what they were, nor who made the chemicals.
    It is therefore not possible to say whether any of the samples
    referred to the grades of purity in use for apple scald control.

    Commercial purification of DPA

         It appears from the literature that it is possible to recognise
    five stages in the purification of DPA produced by the above process.
    "Stage 1 DPA" comes into existence when the aniline has been partly
    converted to DPA but is still in the vapour stage at 480C. After
    cooling and release of ammonia gas the material is distilled to form
    "Stage 2 DPA". This would contain about 250 mg/kg or less of 
    biphenyl-4-ylamine, more frequently referred to as 4-aminobiphenyl 
    (4-ABP). This is again fractionally distilled to produce "stage 3 DPA"
    which is the "technical DPA" of general commerce.

         According to Kirby (Patent-date unknown) an orthophosphoric acid
    treatment of Stage 2 DPA would result in a twenty-fold reduction in
    impurity levels. If that factor is applied to the 250 mg/kg 4-ABP
    level of Stage 2 DPA, one could expect 12.5 mg/kg of 4-ABP in Stage 3
    DPA. In fact sales and technical literature for commercial DPA claim a
    maximum level of 4-ABP of 20 mg/kg. Material of this grade is used in
    industry as an antioxidant in explosives, plastics, oils and greases
    etc. This "Stage 3 DPA" when recrystallised from alcohol with a carbon
    treatment might be expected to have its 4-ABP level reduced from about
    20 to 2 mg/kg. Unpublished evidence to support this was seen in the
    late 1970s. This can be regarded as "Stage 4 DPA".

         In view of the publication by Safe et al. (1977), the
    Australian authorities obtained certificates of analysis of the DPA
    batches received from the manufacturer. The level of 4-ABP, confirmed
    by independent analysis, varied from about 0.8 mg/kg 4-ABP to just
    under 3 mg/kg. The DPA in all batches was from a supplier whose
    specification included one stage of recrystallization. It therefore
    appears that the original material of the 1960s could reasonably be
    expected to have contained about 2 mg/kg of 4-ABP if the means had
    been available then to determine it.

         In relation to the impurities in the diphenylamine on which
    previous JMPR evaluations were based, it became possible to establish
    the source of the material used by Coulston et al. (1971) in work
    cited by the 1976 JMPR. Subsequent analysis of DPA from the same
    source and with the same reference number showed a 4-ABP content of
    0.4 mg/kg. The DPA was marketed as "American Chemical Society (ACS)
    Grade". In reply to enquiries, the manufacturers stated that they had
    had two suppliers of ACS DPA and that two stages of recrystallization
    were made routinely. The specification received did not include a
    statement of the 4-ABP content.

         The DPA with 2 recrystallizations may be called "Stage 5
    material", and is believed to be the purest DPA available
    commercially; it would contain about 0.4 mg/kg 4-ABP and is likely to
    be similar to the material used in 1971 by Coulston et al.

         The characteristics of DPA corresponding to the five stages
    described above are summarized in Table 1.

        Table 1.  Characteristics of DPA at various stages of purification

                                                                                              

    Process       Physical       Colour         Analysis
                                                                                              

    1st           Vapour         -              DPA with gross amounts of 4-ABP, anilene
                                                and co-products.

    2nd           Flake or       Yellow         DPA with 250 mg/kg or less of 4-ABP,
                  solid          to brown       aniline and co-products.

    3rd           Flake or                      DPA with 20 mg/kg or less of 4-ABP, and
                  solid or       White          less than 1000 mg/kg of primary amines.
                  crystals

    4th           Crystals       Colourless     DPA with about 2 mg/kg of 4-ABP and less
                                 to white       than 10 mg/kg of primary amines.

    5th           Crystals       Colourless     DPA analytical standard containing
                                 to white       about 0.4 mg/kg of 4-ABP
                                                                                              
    
    1st and 2nd Stage DPA is not normally encountered in commerce.

    3rd Stage      DPA is used as an intermediate for the synthesis of
                   other chemicals. It is also an antioxidant used in the
                   formulation of such products as oils, greases,
                   plastics, explosives.

    4th Stage      DPA is the present standard of DPA used for apple
                   scald control; some may be used in fragrances and
                   cosmetics.

    5th Stage      DPA is used as an indicator and as a reagent in
                   analysis. It is the grade marketed for analytical work.
                   Similar to the grade used by Coulston et al. (1971).

         The nature and content of impurities other than 4-ABP in DPA are
    uncertain. Acridine, quinoline and indole are implicated in published
    literature. Safe et al. found cyclohexyl-anilines, as well as 2- and
    4-aminobiphenyls. In the present context, it is the 4-ABP content that
    is of most concern.

         In the present circumstances, it seems possible to propose the
    following partial specification for diphenylamine (food grade):

    Appearance:    white crystalline powder

    Purity:        99% minimum

    Impurities:    aniline   5 mg/kg maximum
                   biphenyl-2-ylamine20 mg/kg maximum
                   (2-aminobiphenyl)
                   biphenyl-4-ylamine1 mg/kg maximum
                   (e-aminobiphenyl)

    Melting point: 52.5C

         Manufacturers with whom this specification has been discussed
    believe that it would be possible and economically practical to comply
    with it.

    RESIDUES IN FOOD AND THEIR EVALUATION

    USE PATTERN

         Diphenylamine as an industrial chemical is used widely because of
    its antioxidant properties. Its main and almost only significant
    agricultural use is to control superficial scald in apples (see 1969
    evaluation). Information provided by one of the major companies
    supplying DPA formulations for scald control indicates that the annual
    world-wide use for this purpose is about 85 tonnes.

    Application

         Both pre- and post-harvest treatments have been used, but the
    latter have been found more effective. In current practice (see also
    1969 evaluation), harvested fruit are (a) dipped in aqueous suspension
    (500 to 3000 mg/l,) (b) sprayed in boxes, pallet loads, bins or
    conveyors (1000 to 2000 mg/l) boxes immersed in suspensions or
    emulsions, or (c) individual apples wrapped in impregnated paper (1 to
    2 mg/wrap).

         During the 1970s the techniques of spraying (rain) or drenching
    (waterfall) treatments together with 20-bushel bin dunking have been
    accepted as the most cost-efficient. Particular attention is now paid
    to time of exposure to the chemical suspension, to the temperature of
    the fruit and to the subsequent drying of the chemical film as these
    all determine the peak value of chemical residues.

         Most treated fruit are held in storage for 80 to 200 days or more
    before marketing.

         Early harvesting and longer storage periods are conducive to
    scald. Holmes et al.(1981) determined the lowest effective DPA
    concentrations as influenced by harvest date and storage time on
    Granny Smith apples in southern Victoria (Table 2).

    Table 2.   Lowest Effective DPA Concentration in relation to
               harvest date and storage time

                                                                   

    Harvest Date              Removal Date from Store
                                                                   
                    September 2     October 12        November 22
                                                                   
                    Lowest effective dip concentration, mg/l
                                                                   

    April 7            2400            2400              2400
    April 14            600            2400              2400
    April 21            600             600              2400
    April 28            600             600              2400
    May 5                 0             600               600
                                                                   

         If dipping was delayed on early-picked fruit it was found that
    not even 2000 mg/l was effective. Present recommendations are
    therefore not to delay dipping by more than four weeks if Granny Smith
    are harvested early (mid-April).

         Diphenylamine may be used in conjunction with cooled storage in
    atmospheres where the carbon dioxide concentration is controlled.
    Scott et al. (1962) showed that under such conditions Granny Smith
    apples could be stored for at least seven months. There was better
    retention of green colour, reduced rots and senescent blotch, freedom
    from core flush, firmer fruit as measured by penetrometer tests, and
    better customer acceptance as judged by organoleptic panels. The
    highest quality was evident when 5% carbon dioxide and 2.5% oxygen
    were combined with the DPA.

         Diphenylamine may be used in conjunction with calcium salts,
    added to control bitter pit of apples. Ginsberg et al. (1976) in
    South Africa have reviewed the data available to 1976 on the combined
    use of DPA and either calcium chloride or calcium nitrate.

         Lee et al (1984)showed that the addition of 3% calcium
    chloride to the DPA dip bath did not influence the level of DPA
    deposited on apples, nor did the addition of surfactant spreaders.
    This is no doubt true of current commercial formulations but it is
    certainly not true for formulations used in the 1960s and early 1970s.

         Diphenylamine is also used in combination with fungicides to
    control fungal rots, and in multi-formulation dips containing DPA,
    calcium salts, fungicides and waxes. Factors affecting the use and
    efficacy of the latter have been discussed by Little et al.
    (Little, 1977a,b; 1984. Little et al., 1980a,b; 1981a,b; 1984.
    Little and Peggie,(1984).

    Recommendations and registrations

         Recommendations are noted in Table 3. Some of them may no longer
    be current practice.

    Formulations

         Currently available formulations for use world-wide consist of
    7 xylene-based emulsifiable concentrates, 1 wettable powder, 1 wax
    coating, 1 soluble concentrate and 3 sources of impregnated paper
    wraps.

         It is now common practice to use DPA, calcium and fungicides as a
    single post-harvest treatment, but each is presented as a separate
    formulation and the grower combines them as a tank-mix. Since the
    N-hydrogen of DPA is easily replaced and any nitrous acid present will
    form N-nitrosodiphenylamine, calcium nitrate salts are not advisable
    in the tank mix in case nitrite might be a contaminant.

    Other agricultural uses of diphenylamine

         Stem cavity browning and brown core of McIntosh apples were
    controlled by DPA, but only in conjunction with controlled atmosphere
    storage (Lougheed et al.(1978).

         Wills and Scott (1982) controlled soft scald on Jonathan apples
    with a mixture of DPA, a vegetable oil and "Tween 80".

         The use of DPA as a pre-treatment to prevent phytotoxicity to
    apples from methyl bromide fumigation (Sproul et al.1976) is the
    subject of a patent application (McLachlan et al.1983). Rahman
    (1980) has suggested the use of DPA on pineapples to extend the time
    of marketing of the fruit. Dalton & Nel (1982) have treated sunburn on
    South African Granny Smith apples. There seems the possibility that
    soft scald may also be controlled on the Jonathan variety (Wills et
    al. 1981), but may cause damage by initiating low-temperature
    breakdown in the core of the apples (Wills & Scott, 1973).

         DPA has been used in photodegradable formulations of DDT (Parmar,
    1976), and to degrade DDT deposits in sunlight (Ivie & Casida, 1971).
    It can stabilize ethylene thiuram monosulphide fungicide formulations,
    (Yamaguchi, 1972). It has also been suggested for use to protect rice
    against thiocarbamate herbicides but this use has not been developed
    yet (Takematzu, 1976).

        Table 3.  Recommended applications of diphenylamine to apples

                                                                                              

    Method of Application     Diphenylamine            Ethoxyquin               Ref.
                                                                                              

    Australia

    Tree spray                300 to 400 g/100 l       --                       Hall 1972
                              3000 to 4000 ppm

    Dip or spray              100 to 250 g/100 l       200 to 500 g/100 l
    after harvest             1000 to 2500 ppm         2000 to 5000ppm

    Wrap, plain               31 mg/m2                 76 mg/m2

    Wrap, oiled               23 mg/m2                 54.62 mg/m2

    Tray packs                300 mg per tray          1500 mg per tray

    In cell-packs             50-80 mg/kg in cell      4000 mg per carton
                              dividers and layer       of 20 kg fruit
                              pads

    South Africa

    Dip or drench             2000-2500 mg/l           --                       Eksteen, 1980

    USA
                                                       Precautions
    Pre-harvest spray         22 kg a.i./ha            Spray once only,         Thomson,1981
    to run-off                                         not above 27C
                                                       Harvest within
                                                       36h

    Post-harvest dip          2000 mg a.i./l           Dip only between
    or spray (30 sec.)                                 10 and 32C,
                                                       preferably between
                                                       15 and 27C
                                                       Treat fruit once
                                                       only

    Wax emulsion              5000 mg a.i./l
    spray or roller
    treatment
                                                                                              
    
         The use of DPA as a bird repellant is recorded (Thomson, 1981),
    and it has been used to stabilize carotene in alfalfa meal (Thompson,
    1950). It has been superseded in a number of minor pesticidal
    applications by other compounds.

    RESIDUES RESULTING FROM SUPERVISED TRIALS

         A wide range of residue levels has been reported during the last
    25 years. There are reports showing up to 19 mg/kg on whole fruit or
    about 50 to 150 mg/kg on the peel just after dipping in 1000 to
    1500 mg/l DPA (Hall and Scott, 1961), whilst others show maxima of
    about 0.2 mg/kg in the flesh and 5 mg/kg on the skin (Huelin, 1968).
    At least two factors contributing to the wide range can be identified:
    (1) it is not always clear whether skin, flesh, or whole apple was
    analysed; (2) methods of analysis have changed, and it must be
    accepted that later work is likely to be more reliable.

         Residues resulting from supervised trials were reviewed in the
    1969, 1976 and 1979 evaluations, the latter including extensive
    information on the effects of a variety of factors on residues
    resulting from post-harvest treatments.

         In trials since 1979 Lee et al.(1984) showed that the nature
    and quality of the commercial formulation influenced the magnitude of
    the deposit of DPA on the fruit. In one trial with three commercial
    formulations from different sources the deposit on identical Granny
    Smith apples dipped for 60 sec. in a bath containing 2000 mg/l DPA
    ranged from 1.5 to 3.0 mg/kg. (two formulations deposited 1.5 mg/kg)
    when the temperature of the bath and fruit was 13C.

         Lee et al.(1980) also reported that when the DPA bath was at
    35C, DPA residues on apples were higher than when bath temperatures
    were between 5C and 21C. No significant differences were found
    between 13 and 22C, but residues were significantly lower at 4C.

         Odental et al.(1981) tested residue levels after using the
    waterfall and rain systems of applying DPA to Granny Smith apples.
    Fruit picked at optimum harvest time were treated at 2500 mg/l at a
    rate of 3000 and 2000 litres per minute for 25 and 60 seconds
    respectively in 20-bushel bins. The fruit were stored at 0.5C and
    sampled after 30 days from the top, middle and bottom layers. The
    residues in the three layers were 4.5, 5.2 and 5.3 mg/kg (waterfall)
    and 3.6, 5.7 and 5.9 mg/kg (rain system) respectively. DPA uptake
    differed little between powder and emulsion formulations and the
    addition of 1000 mg/l thiabendazole or benomyl made little difference.
    These levels compare well with the immersing of bins in dip reported
    earlier (Hanekom et al. 1976).

         Little and his colleagues at Knoxfield, Australia, between 1979
    and 1984, examined the effect on the DPA residue of including calcium
    and fungicides in the treatments. They also examined dip time and
    temperature effects on residues. The DPA was applied 'on line' ("rain"

    in South Africa) and by drench ("waterfall" in South Africa). A
    xylene-based emulsifiable concentrate and a non-hydrocarbon-solvent-
    based preparation were compared.

         There were direct relationships between DPA residues and time in
    the dip, temperature of the fruit and dip, and concentration of the
    DPA. There were indications that stickers used with the calcium and
    possibly the added calcium itself and fungicides also affected residue
    levels. The residues recorded in the reports are expressed as mg/kg in
    the skin. If reduced by a factor of 8 to convert to mg/kg whole fruit,
    it can be seen that residues equivalent to about 11 mg/kg on the whole
    fruit were found only at the highest fruit temperature (40C), longest
    dip time (100 secs), in a xylene-based formulation (at 4000 mg/l),
    with sampling shortly after dipping and with calcium and stickers.

         With the current standard recommendations for dipping (see "Use
    pattern" above), the MRL of 5 mg/kg would not be exceeded. An
    examination of the ongoing records of the monitoring of DPA residue
    levels on export fruit from Australia for 1983 shows no cause for
    concern in that respect (Little, 1979; Little et al. 1984;
    Snelson, 1984).

    FATE OF RESIDUES

         Information on the fate of residues in storage was reviewed in
    1969, 1976 and 1979. Losses on peeling are indicated in the 1976 and
    1979 evaluations. The following additional information has been
    received.

    In Cooking

         Pennwalt (1982) in two series of trials in France and the USA,
    showed that 70-95 percent of the residue present in whole raw apples
    was lost when the apples were baked for 30 minutes at 180C. Cored
    apples had a lower residue after baking than fruit with the core
    intact. The loss during baking was greatest in apples that were in
    store at 0C for 2 weeks prior to baking, but the reason for this was
    not determined.

    RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION

         Data from the USA (Pennwalt, 1984) provided evidence that the
    application of DPA to apples in commercial packing houses results in
    residues, at the time of treatment, which are within the MRL
    recommended by the JMPR (5 mg/kg). During 1983, 87 samples of apples
    were received from more than 40 packing houses through the USA. These
    represented 5 varieties treated over a period of 5 months. Analyses
    were performed with 3-8 days of treatment. The results are shown in
    Table 4.

    Table 4.  Residues of diphenylamine in apples in packing
              houses in the USA (Pennwalt 1984)

    High                   6.60 mg/kg
    Low                    0.10 mg/kg
    Average                1.62 mg/kg
    Standard duration      1.01 mg/kg

    Range, mg/kg           Number                %
                                                      

     >5                     1                   1.1
      4-5                   2                   2.3
      3-4                   6                   6.9
      2-3                  11                  12.6
      1-2                  49                  56.3
      0.5-1                14                  16.1
     >0.5                   4                   4.6
                                                      
                           87                 100.0
                                                      

    METHODS OF RESIDUE ANALYSIS

         Several analytical methods have been published since the 1979
    evaluation.

         Waefler et al. (1972) described a rapid method sensitive to
    0.05 mg/kg. Samples are extracted under alkaline conditions with ethyl
    acetate and analysed by capillary gas chromatography on a persilylated
    OV-73 column with flame ionization detection.

         In Australia, Luke and Cossens (1980) extracted apple peel with
    acetonitrile and cleaned up the extract by hydrochloride formation.
    Determination was by GLC with a Hall electroconductivity detector.
    Using 12.5g peel, a limit of determination of 0.05 mg/kg was reached.
    The detector in use now is modified. The method is rapid and
    consequently suitable for the large-scale monitoring of Australian
    export apples.

         In England, Allen and Hall published two methods: the first
    involved formation of the fluorobutryl derivative of DPA after 
    clean-up and the second steam distillation of the DPA and direct
    determination. The former method used electron-capture GLC and the
    latter a nitrogen-sensitive termionic detector. The latter method
    after correction for recovery losses gave residue levels about one
    third higher (Allen & Hall, 1980).

         Results obtained by both methods have been reported (Johnson et
    al. 1980). Allen and Hall speak of a possible binding of the DPA to
    the apple during the storage period and suggest that possibly one
    method released the DPA and the other did not. They recommend the use
    of Veith and Kiwis steam-distillation and solvent-extraction apparatus

    with the direct method of determination because of the higher results.
    Little and his colleagues have also used the latter method in
    experiments described in an unpublished paper (Little et al.
    1984).

         A development of an earlier dip-side test originated by J.B.
    Watkins of the Trout Food Preservation Research Laboratories,
    Brisbane, is described by Little et al. (1981). It is a rapid and
    reliable method based on the formation of a blue oxidation product of
    diphenylbenzidine. This can be compared with standard preparations at
    a wavelength of 650 nm.

         Diachenko (1979) described a procedure sensitive to 20 g/kg
    (ppb) to determine industrial amines in fish. The tissue is digested
    in aqueous sodium hydroxide and extracted with benzene. After washing
    in acid, the extract is cleaned by gel-permeation chromatography and
    quantitated using nitrogen-selective GLC. This method can separate DPA
    from other diarylamines.

         Laub and Woller (1976) described a method of volatilizing
    material by heating in a micro-oven and passing the volatiles on to a
    thin-layer plate via a nitrogen stream, where they are adsorbed and
    separated by TLC. DPA, biphenyl and e-phenylphenol were shown to be
    detected in citrus and banana peels.

    NATIONAL MAXIMUM RESIDUE LIMITS

         The following national MRLs have been reported. It should be
    noted that not all countries publish MRLs routinely and the absence of
    an MRL does not necessarily mean that DPA-treated fruit would be
    barred entry to the country concerned.

    Table 5.  National MRLs effective March 1984

                                                                

    Country                              MRL, mg/kg
                                  Apples             Pears
                                                                

    UK                              10                10
    USA                             10                 -
    Canada                          10                 -
    Fed. Rep. Germany                3                 -
    Denmark                          -                 -
    Finland                          5                 -
    Hungary                         10                 -
    Israel                          10                 -
    Kenya                           10                 -
    Norway                          10                 -
    Sweden                           3                 -
                                                                

    Table 5 (continued)

                                                                

    Country                 MRL, mg/kg
                                Apples             Pears
                                                                

    Belgium                          3                 3
    Eire                             3                 3
    France                           3                 -
    South Africa                    10                 -
    Netherlands                      3                 3
    Australia                       10*                7
    New Zealand                     10                 -
    Hong Kong                             Permitted
    Philippines                           Permitted
    Iran                                  Permitted
    Malaysia                              Permitted
    Brazil                           Approval anticipated
    Italy                            Approval anticipated
                                                                

    * Proposal to lower to 5 mg/kg.

         In some countries a zero MRL exists for milk and meat.

         The first country to register the use of DPA was the USA which in
    1962 allowed its use on apples with a tolerance of 10 mg/kg. There is
    a zero tolerance for milk and meat.

         The Codex Alimentarius MRL is 5 mg/kg.

    OCCURRENCE OF DPA IN UNTREATED FOOD AND THE ENVIRONMENT

         DPA has been identified in baked potato, buckwheat flour, tomato,
    green tea, salted fish and dried plums. (Coleman et al. 1981);
    Yajima et al. 1983; Chung et al. 1983; Nose et al. 1971;
    Fahmy et al. 1983; Moutounet et al. 1975. So far as can be
    ascertained from the literature it has not been found in apple
    volatile compounds. Although early work showed blank control apple
    levels as high as 0.9 mg/kg apparent DPA (USDA, 1961), more recent
    analyses with specific detectors have not detected DPA in control
    samples. (Allen & Hall et al. 1980; Luke & Cossens, 1980).

         Both in Austria and in Sweden, DPA has been recorded as a
    component of the smoke of tobacco (Klus & Kohn, 1977; Peterson et
    al. 1980). It was discovered in the volatiles of exogenous origin
    from the human oral cavity (Kostelc et al. 1981). The sources were
    stated to be water and cosmetics.

         Veith et al. (1979) have measured the uptake and
    bioconcentration factor of DPA in fish. This is of concern if river
    pollution occurs where DPA is manufactured. DPA has a bioconcentration
    factor of 30 (cf DDT, 29400) and potentiation 0.1 (cf DDT, 580).
    Schafer et al. (1983) have reported on the acute oral toxicity,
    repellency and hazard potential of DPA amongst 197 other chemicals to
    one or more species of wild and domestic birds. The LD 50 was found to
    be greater than 101 mg/kg.

         Briggs included DPA in a study of factors which determine
    transport of a pollutant by water and its possible bioconcentration
    factor. (Briggs, 1981).

    APPRAISAL

         An extensive review of all aspects of the use of diphenylamine in
    agriculture was available to the meeting.

         In view of certain toxicological issues, attention was given to
    the various methods of synthesising and purifying diphenylamine to
    produce a quality which is suitable and acceptable for the treatment
    of apples and pears as a means of preventing the development of
    superficial scald. A proposal is made for a specification for such a
    pure (food grade) diphenylamine. This specification has been discussed
    with the several manufacturers concerned with the production of
    diphenylamine formulations for treating apples and pears, who believe
    it would be possible and economically practical to comply with such a
    specification and thereby ensure that there were no grounds for
    concern over the safety of such treatments to consumers of treated
    fruit.

         The importance of diphenylamine in preventing superficial scald
    of pome fruit, which has serious economic and logistical effects on
    the storage, marketing and distribution of high quality fruit, is
    noted. The importance of harvest date and fruit maturity in relation
    to the effectiveness of diphenylamine is confirmed. Recent
    developments have provided practical means of simultaneously
    controlling other fruit storage diseases. These demand the
    availability of high quality diphenylamine formulations.

         A study of the extensive data on residues of diphenylamine in
    fruit confirms that the MRL recommended by the 1979 meeting (5 mg/kg)
    is adequate to cover the residues resulting from the effective use of
    modern commercial diphenylamine formulations. This is further
    confirmed by monitoring studies in Australia and the USA.

         A number of developments in analytical techniques in recent years
    have improved the simplicity, accuracy and versatility of methods
    which are suitable for regulatory purposes. The advantage of analysing
    only the peel is confirmed but it is stressed that the results must be
    expressed on the basis of the whole fruit.

         It appears that if diphenylamine occurs naturally in apples, the
    level is too low to present any practical problems in enforcing the
    recommended MRL.

         Some observations are made about the occurrence of diphenylamine
    in untreated food and the environment.

         The meeting confirms that the MRL previously proposed is
    appropriate. It recommends that only purified grade diphenylamine be
    used in the formulation of preparations for the treatment of apples
    and pears. This grade should meet the following specification.

    Appearance:                             white crystalline powder
    Purity:                                           99.9% minimum
    Impurities:
         aniline                                      5 mg/kg max.
         biphenyl-2-ylamine (2-aminobiphenyl)         20 mg/kg max.
         biphenyl-4-ylamine (4-aminobiphenyl)         1 mg/kg max.
    Melting point:                                         52.5C

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    See Also:
       Toxicological Abbreviations
       Diphenylamine (ICSC)
       Diphenylamine (FAO/PL:1969/M/17/1)
       Diphenylamine (Pesticide residues in food: 1976 evaluations)
       Diphenylamine (Pesticide residues in food: 1979 evaluations)
       Diphenylamine (Pesticide residues in food: 1982 evaluations)
       Diphenylamine (Pesticide residues in food: 1984 evaluations)