FAO, PL:CP/15
    WHO/Food Add./67.32


    The content of this document is the result of the deliberations of the
    Joint Meeting of the FAO Working Party and the WHO Expert Committee on
    Pesticide Residues, which met in Geneva, 14-21 November 1966.1

    1 Report of a Joint Meeting of the FAO Working Party and the WHO
    Expert Committee on Pesticide Residues, FAO Agricultural Studies, in
    press; Wld Hlth Org. techn. Rep. Ser., 1967, in press




    biphenyl, phenylbenzene

    Chemical name





    Biochemical aspects

    Metabolic studies following oral administration of diphenyl have been
    performed in rats (West, 1940; West et al., 1956), rabbits (Deichmann
    et al., 1947; West et al., 1956; Block & Cornish, 1959) and dogs
    (Hazleton et al., 1956). In these species a variety of phenolic
    compounds were excreted in the urine, mostly as ethereal sulfates and
    glucuronides. The main metabolite appeared to be 4-hydroxydiphenyl.
    Unchanged diphenyl was excreted in the faeces only after the highest
    doses (Hazleton et al., 1956).

    In vitro 4-hydroxylation of diphenyl by liver microsomal enzymes has
    been demonstrated in several species, including man. In addition,
    2-hydroxylation was observed in adult cats, mice, hamsters, coypu and
    in young but not in adult rats. The extent of 2-hydroxylation in young
    rats is markedly increased in rats pre-treated in vivo with either
    3,4 benzpyrene or 20-methyl-cholanthrene and to a much lesser extent
    in rats pre-treated with phenobarbitone and nikethamide.
    4-hydroxylation was stimulated by pre-treatment with phenobarbitone or
    nikethamide but not by benzpyrene or methylcholanthrene (Creaven &
    Williams, 1965; Williams, 1965).

    Diphenyl was found to be less toxic when given with a diet containing
    a supplement of 1-cystine or d1-methionine, but diphenyl is not highly
    conjugated with cystine (West, 1940).

    Acute toxicity

    Animal      Route       LD50                   Reference
                            mg/kg body-weight

    Rat         Oral        3300-5000              Deichmann et al., 1947;
                                                   Pecchiai & Safflotti, 1957

    Rabbit      Oral        2400                   Deichmann et al., 1947

    Cat         Oral        >2600                  McEwen, 1958
    Short-term studies

    Mouse. Skin applications of a 23 per cent solution in oil were given
    twice weekly to a group of 140 mice for 7 months. Local inflammatory
    changes were commonly seen. No tumours developed (Selle, 1952; 1953;

    Rat. Groups of 11 young rats were fed for 32 days either a diet low
    in casein containing 10 000 ppm diphenyl or a normal diet containing
    3000 ppm diphenyl. Growth retardation was observed in both experiments
    (West, 1940; West & Jefferson, 1942). Daily oral doses of 0, 2, 20 and
    200 mg/kg for 4 weeks and 300 mg/kg for 12 days did not induce growth
    retardation (MacIntosh, 1945; Rogliani & Procaccini, 1956).

    In another study, groups of young rats were fed diets containing 0,
    100 and 1000 ppm diphenyl for 3 months. Growth rate, food efficiency,
    organ weights and histology were identical in all groups. At 1000 ppm
    only a slight polyuria was noted (Newell, 1953).

    A paired feeding test was performed for 89 days on male and female
    rats fed 5000 ppm and 10 000 ppm diphenyl in their diet. At both
    levels there was no difference in weight gain between the test animals
    and pair-fed controls, but the weight gain was slower than in controls
    receiving food ad lib. A study of food efficiency over 3 weeks in
    groups of 12 male and 12 female rats receiving 0 ppm, 100 ppm, 1000
    ppm and 10 000 ppm diphenyl in their diet revealed no significant
    differences between the groups (Ambrose et al., 1960).

    Small groups of rats were fed diets containing 0, 1000 or 5000 ppm
    diphenyl for 11 or 60 days before mating. No effect on reproduction
    was noted (Ambrose et al., 1960).

    A group of 13 rats was fed 0, 50 or 100 mg diphenyl per animal daily
    and killed 2-13 months after the beginning of the treatment.
    Regressive changes were noticed in the liver and kidney. Three animals

    observed after 7 weeks, 7 months and 1 year had, respectively,
    papillomatous hyperplasia of the forestomach, multiple papillomas of
    the stomach and a squamous cell carcinoma of the stomach. The
    incidence of lesions of the forestomach in untreated rats was not
    given (Pecchiai & Saffiotti, 1957).

    Rabbit. Five rabbits were given doses of 1000 mg/kg diphenyl by
    stomach tube as a 25 per cent solution in olive oil, 2-3 times weekly.
    All the animals lost weight and died within 5-20 weeks. Retention of
    urea was found in the terminal stages (Deichmann et al., 1947).

    Dog. Groups of 3 dogs received diphenyl in corn oil orally at doses
    of 0, 2.5 and 25 mg/kg 5 times weekly for 52 weeks. At 3-month
    intervals, blood and urine samples were normal. At the end of the
    experiment all the animals were killed and no pathological changes
    attributable to diphenyl were found (Hazleton et al., 1956).

    Monkey. Four groups of 2 female and 1 male rhesus monkeys were given
    diets containing 0, 100, 1000 and 10 000 ppm diphenyl for 1 year. No
    changes in the body-weight and blood were seen. At the 10 000 ppm
    level, a consistent increase of liver weight without histological
    change was noticed (Newell, 1953).

    Man. A human volunteer was given 35 mg diphenyl weekly per os for
    13 weeks without adverse effect (Farkas, 1939)

    Long-term studies

    Rat. Groups of rats were given diets containing 0, 100, 1000 and
    10 000 ppm diphenyl for 2 years. An intercurrent respiratory infection
    killed many animals in all groups. Tubular dilatation in the kidney
    was noticed at the two highest concentrations; however, 2 animals of
    24 of the control group showed similar changes (Newell, 1953).

    Eight groups of 15 weanling animals of each sex were given diets
    containing 0, 10, 50, 100, 500, 1000, 5000 and 10 000 ppm diphenyl. At
    5000 and 10 000 ppm there was growth inhibition, decrease in
    longevity, decreased haemoglobin and pathological changes in the
    kidneys at autopsy, including scarring, inflammation and tubular
    atrophy. These changes were not noticed at concentrations of 1000 ppm
    or less. The reversibility of the urinary changes induced by 5000 ppm
    diphenyl in the diet for 4 months has been demonstrated (Ambrose et
    al., 1960; Booth et al., 1961).

    A 4-generation reproduction study was carried out on rats given doses
    of 0, 100, 1000 and 10 000 ppm diphenyl. Only at 10 000 ppm fertility
    and litter size were affected. This has been attributed to a lowered
    food intake rather than to the direct effect of diphenyl (Newell,


    Diphenyl appears to have been studied mostly in dogs and rats, and
    special aspects have been investigated in other species. Long-term
    studies have been carried out only in rats. The suspicion of
    carcinogenicity raised by a study carried out under inadequate
    conditions was not confirmed in later reports. In vivo and in
    vitro studies in several species including man, reveal a common
    detoxification mechanism.

    Long-term feeding studies including recording or tumour incidence,
    information on possible chemical changes undergone by diphenyl on the
    fruit, and specifications of purity are desired.


    Level causing no toxicological effect

    Rat: 500 ppm in the diet, equivalent to 25 mg/kg/day

    Dog: 25 mg/kg/day

    Monkey: 50 mg/kg/day

    Estimate of acceptable daily intake for man

    Since children and ill people may consume a high amount of citrus
    fruit and diphenyl exerts a toxic effect on the kidney, a higher
    safety factor than usual has been used.

    0-0.125 mg/kg body-weight


    Use Pattern

    (a) Pre-harvest treatments

    The meeting was unaware of any pre-harvest uses of diphenyl.

    (b) Post-harvest treatments

    Diphenyl is used exclusively as a fungistatic agent on citrus fruits
    during transportation and storage. Its superiority for this purpose
    has displaced the use of other compounds in major citrus producing and
    exporting countries. These include Australia, Israel, South Africa and
    the United States of America. Recently, use in southern Italy has also
    been reported. Comprehensive bibliographies covering the history of
    development and use in those countries has been prepared by Resnick
    (1966) and Rajzman (1965). Treatment of the packaging materials for
    citrus is used rather than direct treatment of the fruit. Two methods
    are employed.

    (1) In Australia, Israel and South Africa, the fruit are wrapped
        individually with tissue paper impregnated with diphenyl at from 
        28 to 40 mg per 100 square inches.

    (2) In the USA a collective method is used: paper pads each of about
        28 × 44 cm and containing 2.35 gm of diphenyl are placed at the 
        rate of one pad on the bottom and one on top of a 40 pound 
        (18 kg) carton of fruit (i.e. about 47 mg diphenyl per individual
        180-200 gm fruit).

    The fungistatic action depends on providing diphenyl vapour around the
    fruit. It is not effective as a fungistat after being absorbed by the
    fruit. Hence, the necessity of maintaining a reservoir in packaging
    material throughout the period of transport and storage. The
    technology of use, in relation to conditions of transport and storage,
    distance of shipment and other parameters that control the treatment
    have been studied intensively in the USA (Rygg, Wilson & Garber, 1962;
    Klotz, L. J., 1957; and Rygg, Wells, Norman & Atrops, 1962), in
    Australia (Kiely & Long, 1960), in Israel (Farkas & Aman, 1940;
    Littauer & Mintz, 1945; Rajzman, 1961; Rajzman, 1961(a); and Rajzman,
    1961(b)) and in South Africa (Christ, 1962) (see also Rajzman, 1965).
    The current technology of use has evolved essentially from these

    (c) Other uses

    No other uses have been reported.

    National Tolerances


    Country                         Tolerance ppm    Comment

    USA                             110
    Canada                          110
    United Kingdom                  100
    Sweden                          100
    Belgium                         70)
    France                          70)              Subject to review
    Federal Republic of Germany     70)              in EEC countries
    The Netherlands                 30)

    Residues resulting from supervised trials

    The factors controlling the uptake and retention of diphenyl in fruit
    have been intensively studied and the literature is reviewed by
    Rajzman (1965) and by Resnick (1966). An earlier compilation of the

    results of several years of supervised trials was made by Hazleton
    (1956). These trials included fruit from the principal citrus
    producing areas of the USA, treated and analysed in accordance with
    the procedures at that time. Oranges, lemons and grapefruit had a
    maximum of 110 ppm, 70 ppm and 30 ppm respectively, but only 10 per
    cent of the samples contained more than 60 ppm, 40 ppm and 20 ppm
    respectively. In reviewing such data it should be borne in mind that
    in the light of later developments in analysis, it is probable that
    the residues then reported were probably below the amounts which
    actually were present when the analyses were carried out. Rajzman
    (1965) reviewed the data obtained between 1945 and 1961 and the
    residues found in whole fruit in various countries are summarized as

                        Number of      More than      More than      More than
                        samples        70 ppm         100 ppm        110 ppm
                                       Found  %       Found  %       Found   %

    Oranges             470            32     6.6     9      1.9     6       1.3

    Lemons              208            6      3.0     2      1.0     1       0.5

    Grapefruit          59             0      0       0      0       0       0
    Residues in food moving in commerce

    Although much information has been obtained on residues in citrus
    moving in commerce, in some cases information on the influence of the
    method of sampling or of analysis was lacking. Some of the earlier
    results are therefore due to unintentional variations in sampling and
    analytical procedures.

    Rajzman (1966) compiled a survey of diphenyl residues found in Israel
    fruit of different varieties from 1958 to 1965. The fruits were
    treated according to current commercial practice and stored under
    varying conditions simulating transport and storage of exported fruit.
    Residues were determined in the peel, pulp and whole fruit of 2093
    samples of oranges, grapefruit and lemons. Fruit variety had no effect
    on the quantity or distribution of the diphenyl absorbed. Peel content
    varied from 1.0 to 400 ppm. Pulp residues were very low, varying from
    0.1 to 0.91 ppm. Whole fruit residues varied from 0.9 ppm to 115.3 ppm
    as follows:

    More than 30 ppm - 28.77 per cent
    "     "   50 ppm - 8.0 per cent
    "     "   70 ppm - 2.01 per cent
    "     "  100 ppm - 0.10 per cent
    "     "  110 ppm - 0.05 per cent

    Souci & Maier-Haarlander (1961) reported on residues in nine samples
    of citrus fruit imported into Germany from USA, Italy and Cyprus in
    1961. Only one sample (Italian) contained residues in excess of 100
    ppm on a whole fruit basis (103 ppm). Rajzman (1965) gives figures for
    citrus imported into Germany in 1959-1965 as follows:

                    Number of samples                     % of samples protected
                                                        with diphenyl
    Year         Total     Without   With       30       70         100        >100
                           diphenyl  diphenyl   ppm      ppm        ppm        ppm

    1959-61      149       0         149        59       95         97         3

    1959-61      100       46        54         36       76         88         12

    1961-65      132       83        49         29       68         87         13

    1960-65      13        0         13         46       92         92         8

    1964-65      17        0         17         29       88         100        0

    1965         20        0         20         30       75         85         15

    Total        431       129       302        48       88         94         6
    The meeting was aware that work, on which they have not received
    detailed results, had been completed or was in progress in various
    countries on the residues which are occurring in fruits received in
    the course of commercial practice. From the published information,
    however, it was concluded that the majority of samples of citrus fruit
    moving in commerce in recent years have contained below 100 ppm; but
    in a small per cent of cases residues up to 110 ppm have been

    Residues at consumption (Effects of processing, cooking, etc.)

    (a) Pulp and peel

    Residues are mainly localised in the oil glands of citrus immediately
    beneath the fruit surface. The peel itself may contain up to several
    hundred ppm but the pulp contains amounts up to about 1.0 ppm. In
    relation to the original amount of residue present in peel, lemons
    contain more residue in pulp than oranges or grapefruit. Even in the
    case of lemons, the residue in the pulp does not exceed 2.1 per cent
    of the original residue in whole fruit (0.50 ppm). In oranges
    containing as high as 400 ppm in the peel only, the pulp content never
    exceeded 0.91 ppm (Rajzman, 1966).

    (b) Juice

    Hazleton (1956) compared residues resulting from extraction of citrus
    juice by hand and by mechanical means. (A digest of these data are
    also contained in Resnick, 1966). Mechanical extraction of juice
    resulted in higher residues, but these did not exceed 4.3 ppm in
    orange juice in two samples out of 284 for which the average was 1.15
    ppm. This compares with a maximum of 2.5 ppm in one sample of orange
    juice pressed by hand, and an average of 0.54 ppm for the 221 samples.
    Grapefruit juice contained 0.26 ppm and 0.66 ppm by hand and
    mechanical extraction respectively. Mechanically extracted lemon juice
    contained the highest residues, ranging from 1.0 to 11.2 ppm,
    averaging 3.3 ppm for 71 samples. Newell (1953) sealed diphenyl
    protected fruit in wooden boxes for a period of eight weeks to attempt
    to produce maximum absorption into fruit. The residues resulting in
    orange, grapefruit and lemon juice were 1.3 ppm, 1.1 ppm and 0.4 ppm
    respectively. Canadian Food and Drug Directorate (1965) examined
    residues in juice from 284 samples of oranges. Forty-five per cent
    showed less than 1.0 ppm in the juice, while for the balance only
    eight were in excess of 2.5 ppm, with two values grouped at
    approximately 4.4 ppm.

    (c) Marmalades and jams

    Diphenyl residues in citrus peel that may be used for the manufacture
    of marmalades and jams are substantially reduced during the mincing of
    peel and fruit and the cooking process. Losses of residue by these
    processes has been reported by Tomkins & Isherwood (1945), Dickey
    (1956), Rajzman (1962) and Souci & Maier-Haarlander (1963). The
    elimination of residue is directly related to the degree of chopping
    before cooking and whether whole fruit or peel only is used.
    Elimination during these processes ranged from 18.6 per cent to 100
    per cent depending on the method of preparation. In one case 23.1 ppm
    remained in marmalade after cooking, while in most other cases the
    remaining residues ranged between 0.0 and 16.8 ppm, with the majority
    between 0 and 12 ppm.

    Methods of residue analysis

    (a) Analysis

    Rajzman (1965) reviewed the methods of analysis up until that time.
    The two most promising new methods that offered reliability,
    reproducibility and speed are: (1) thin layer chromatography followed
    by spectrophotometric determination of the TLC spots at 248 mµ
    (Norman, Rygg & Wells, 1966) and (2) a gas-liquid chromatography
    method based on the methods of Vogel & Deshusses (1964, 1965).
    Both methods are currently under study. A collaborative study has been
    conducted by five government laboratories in the member countries of
    E.E.C. A comparative study of both methods is also in progress at the
    Centraal Instituut voor Voedingsonderzoek, TNO, Zeist, the
    Netherlands. A progress report from this institute by Vos (1966) was
    available to the FAO Working Party on Pesticide Residues. The
    conclusion drawn by Vos is as follows:

    "The gas chromatographic method is the fastest and most accurate one.
    The average value found agrees with that obtained from the thin layer
    method. The values of the latter show a larger spreading. It is
    possible that the biphenyl zone on the plates still contains some
    interfering substances.

    Although many other methods for the determination of biphenyl in
    citrus fruit have been described in the literature, the G.L.C. - and
    thin layer method were selected to be tested in practice. They seemed
    to be most suitable for our purposes, viz. routine determination in
    large number of samples.

    We certainly can recommend the gas chromatographic determination for
    this purpose.

    If the relatively expensive equipment for gas chromatography should be
    a serious objection, we recommend the thin-layer method. Although it
    is slightly less accurate, it is also suitable for routine

    One further refinement is now available in the development of a
    totally automated analytical procedure by Gunther & Ott (1966) for
    citrus fruit rind employing a continuous flow recording

    The F.A.O. Working Party considered that, at the level of the
    suggested tolerance, both the thin layer and the gas-liquid
    chromatographic methods would be suitable for residue analysis.
    Nevertheless it was decided to delay making a firm recommendation
    until full reports were available on the investigations currently in
    progress in the E.E.C. and T.N.O./Zeist.

    (b) Sampling

    It is understood that work is also in progress at the TNO, C.I.V.O.
    Institute, Zeist, to explore the subject of sampling. In the meantime,
    attention is drawn to the ISO Fifth Draft Proposal: Sampling of fresh
    fruits and vegetables. ISO/TC 34-Agric. Food Products, Subcommittee 3
    - Fruits, Vegetables and Their Derived Products, Working Group 2
    - Sampling, October, 1965.


    As diphenyl is not used on other foods the entire acceptable daily
    intake could be assigned to citrus or citrus products. Although no
    international agreement has been reached on the amount of citrus and
    citrus products in the "high consumption diet", a combined figure of
    230 grams per day for fresh citrus plus 60 grams per day for canned
    citrus (i.e. a maximum of 290 grams per day) has been suggested. (In
    Canada the suggested level of food consumption for these products for
    tolerance purposes is 190 grams.)

    If the acceptable daily intake level were 0.125 mg/kg for a 60 kg
    person the permissible level from all sources becomes 7.5 mg per day.

    Evidence has been received to demonstrate the need for the use of
    diphenyl in the storage and transport of citrus over long distances.
    The residues resulting in the whole fruit only rarely exceed 110 ppm.
    In fresh fruit, pulp as eaten by the consumer rarely exceed 1.0 ppm.
    Juices in extreme cases may contain residues as high as 4.4 ppm, but
    most cases will contain less than 2.0 ppm. Marmalade and jam may also
    contain some residues, but these may become insignificant in most
    diets. Even in the cases of small children consuming large amounts of
    orange juice, the amounts of diphenyl taken would be well below
    acceptable daily intake.

    Therefore, a tolerance of 110 ppm is recommended to be applied at the
    point of entry of the citrus into the country.

    Further information

    (1) Data are desired on the residues that may result from methods of
    preparation of fruit juice which employ the whole of the fruit
    including the peel.

    (2) A specification for diphenyl for use as a fungistatic agent on
    citrus seems desirable. The Working Party would like to receive
    further information on the likely impurities in commercial diphenyl.


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    See Also:
       Toxicological Abbreviations
       Diphenyl (FAO Nutrition Meetings Report Series 38a)
       DIPHENYL (JECFA Evaluation)
       Diphenyl (FAO/PL:1967/M/11/1)