WHO/FOOD ADD./70.38



    Issued jointly by FAO and WHO

    The content of this document is the result of the deliberations of the
    Joint Meeting of the FAO Working Party of Experts and the WHO Expert
    Group on Pesticide Residues, which met in Rome, 8 - 15 December 1969.



    Rome, 1970



    Chemical names

    2-phenylphenol; sodium 2-phenylphenate


    for the free phenol; o-hydroxydiphenyl

    Structural formulae


    Other relevant chemical properties

    The free phenol is a white, crystalline, free-flowing powder,
    molecular weight 170.2. Mild phenolic odour. Less than 0.1g is soluble
    in 1 ml of water. Freely soluble in ethanol, soluble in fats and oils.
    It is dissolved or dispersed in wax formulations.

    The sodium salt is a buff coloured solid. Molecular weight 264.3. Very
    soluble in water and ethanol; practically insoluble in oils. Used as
    water solution.


    Specifications for purity of both compounds have been published by the
    European Economic Community  (E.E.C., 1967):

    E231   2-phenylphenol

    melting point                56 - 58°C
    content                      not less than 99%
    biphenylether                not more than 0.3%
    p-phenylphenol               not more than 0.1%
    alpha-naphthol               not more than 0.01%
    sulphate after ashing        not more than 0.05%

    E232   sodium orthophenylphenate

    melting point of 2-phenylphenol precipitated by acidification of
    sodium salt, not recrystallized and dried over sulphuric acid 56
    - 58°C

    ph                2% water solution must be between pH 11.1 and 11.8
    content           not less than 95% C12H ONa.4H2.0
    biphenylether     not more than 0.3%
    p-phenylphenol    not more than 0.1%
    x-naphthol        not more than 0.01%


    The biological data available on this compound have been evaluated by
    the Joint FAO/WHO Expert Committee on Food Additives, and a monograph
    entitled "Sodium o-phenylphenol" is included in the Sixth Report of
    this Committee (FAO/WHO, 1962). A summary of the data then considered
    as well as some limited additional information which has recently
    become available is included below.


    Absorption, distribution and excretion

    Tissue examination of rats which had received 2-phenylphenol orally
    for two years revealed little tendency for storage of the compound.
    The kidney was the only organ containing detectable amounts of the
    compound; average values of 220 mg/kg tissue were found in the kidneys
    of rats fed 20,000 ppm in the diet, and approximately 10 mg/kg tissue
    in the kidneys of rats fed 2000 ppm (Hodge et al., 1952).

    After administration to rabbits, 2-phenylphenol is highly conjugated
    with glucuronic acid but it is not known whether it is converted to an
    ethereal sulphate in this species. The glucuronide has been isolated
    from rabbit urine and characterized by conversion to the
    triacetylmethyl ester (Williams, 1959; Dodgson et al., 1948; Kamil et
    al., 1951).

    When administered orally to rats, 2-phenylphenol is partly converted
    to 2,5-dihydroxybiphenyl which, like 2-phenylphenol, is excreted in
    the urine as a glucuronide and ethereal sulphate. The total output of
    2-phenylphenol within 48 hours amounted to about 70 percent as
    conjugates of 2-phenylphenol and 2,5-dihydroxyphenol (Ernst, 1965).


    Special studies on carcinogenicity

    Groups of 18 mice of each sex from two hybrid strains of mice were
    given 2-phenylphenol for 18 months. The dose of 100 mg/kg was given to
    the mice by gavage from the seventh day of age to the time of weaning
    at four weeks of age and thereafter the chemical was added to the diet
    in a corresponding amount of 280 ppm. There was no significant
    increase in the incidence of tumours (Innes et al., 1969).

    Acute toxicity
                       LD50 mg/kg
    Animal    Route    body-weight            References
    Rat       oral     2700-3000 (approx.)    MacIntosh, 1945
                                              Hodge et al., 1952
    Cat       oral     500 (approx.)          MacIntosh, 1945

    Short-term studies


    A preliminary study demonstrated that when daily doses of 1,000 mg/kg
    body-weight of 2-phenylphenol were fed to two dogs, both died within a
    month. Groups of two dogs each were then fed 2-phenylphenol for a
    period of one year in daily amounts of 0, 20, 200, and 500 mg/kg body
    weight. No effect related to the administration of 2-phenylphenol was
    observed. Haematological values, urinary sugar and protein values,
    organ weights and histopathological examination of the various tissues
    did not differ from the normal range (Hodge et al., 1952).


    Groups, each comprising 15 male rats, were fed 2-phenylphenol in daily
    doses of 0, 2, 20, or 200 mg/kg body-weight for 32 days. There were no
    toxic symptoms attributable to feeding 2-phenylphenol. The mean
    growth-rate and the haemoglobin and white blood cell levels in all
    groups were comparable to the controls (MacIntosh, 1945).

    Five male and five female rats in each group were given by stomach
    tube doses of 0, 50, 100, 200, and 500 mg/kg body-weight for five days
    a week over a period of six months. The only abnormality observed was
    a slight increase in average liver and kidney weights in the animals
    fed the 500 mg/kg dose level (Hodge et al., 1952).

    When diets containing 0, 1,000, 3,000, 10,000, or 20,000 ppm of
    2-phenylphenol were fed for three months to groups of rats comprising
    12 males and 12 females, slight retardation of growth was observed in
    the 20,000 ppm group. There was no significant difference between the
    mortality of control and test animals. There were doubtful increases
    in weight of liver, kidney, and spleen of certain rats of the 10,000
    and 20,000 ppm groups. No tissue changes were observed (Hodge et al.,

    Long-term studies


    Male and female rats (25 of each sex per group) were maintained for
    two years on diets containing 0, 200, 2,000 and 20,000 ppm of
    2-phenylphenol. The animals fed 200 and 2000 ppm showed no adverse
    effects when compared with the controls, as judged by growth,
    mortality, gross appearance, haematology, urinary sugar and protein
    values, organ-weights, tissue content of 2-phenylphenol, and
    histopathological examination of various tissues. The group fed 20,000
    ppm of 2-phenylphenol differed from the controls by exhibiting slight
    retardation of growth, histological kidney changes (marked tubular
    dilation), and the presence of small amounts of 2-phenylphenol in the
    kidney tissues (Hodge et al., 1952).


    A 5.0 percent solution of 2-phenylphenol in sesame oil and a 0.1
    percent aqueous solution of the sodium salt tested on 200 subjects
    caused neither primary skin irritation nor skin sensitization. The
    sodium salt is slightly irritating in 0.5 percent aqueous solution and
    decidedly irritating in 1.0 percent and 5.0 percent solutions (Hodge
    et al., 1952).


    The short and long-term studies in rats are sufficient to be taken as
    a basis for the evaluation of 2-phenylphenol. The dog study was not
    considered adequate. In addition, the studies on metabolism are
    incomplete and there are no studies on reproduction. However, the
    Meeting considered that the toxicological studies were adequate to
    reaffirm the previous acceptable daily intake established by the Joint
    FAO/WHO Expert Committee on Food Additives in its Sixth Report
    (FAO/WHO, 1962).


    Level causing no significant toxicological effect

    Dog: 500 mg/kg body-weight/day

    Rat: 2000 ppm in the diet, equivalent to 100 mg/kg body-weight/day


    0 - 1.0 mg/kg body-weight (based upon the previous adi. - FAO/WHO,



    Pre-harvest treatments

    In Great Britain a dormant paint application to apple trees is
    approved for control of canker.

    Post-harvest treatments

    2-phenylphenol has been used broadly for over 40 years in many
    countries for its general antimicrobial properties. Due to its broad
    spectrum bactericidal and fungistatic effect, and commercial
    availability it is widely used. It is employed as a household
    disinfectant, preservative in oil-water emulsions used in the textile
    and metal industries, as well as a post-harvest treatment for fruits
    and vegetables to prevent losses due to rots and moulds in storage and
    transport of these foods. The sodium salt is used as a preservative
    for protein-based and other adhesives, as well as for the post-harvest
    use in fruits and vegetables.

    Principal formulations in the U.S.A. are:

    2-phenylphenol:   5% liquid;   98% wettable powder;   2% in wax.

    Wax formulations are applied by commercial application equipment in
    tandem with sorting and washing facilities. These are specifically
    designed for the crop concerned as to technology of use, formulation
    strength, time of immersion in the bath and monitoring of the process
    to ensure maintenance of treatment criteria for effectiveness without
    damage to the crop. Wax strength formulations vary, e.g. carrots 0.5%,
    citrus 0.8%, cucumbers 2.5%, nectarines 0.2%, peaches 0.2%; peppers
    2.5%, plums 2%, tomatoes 2.5%. A 5% liquid dip is used for crates,
    field boxes, hampers, lugs and wood containers for fruits and
    vegetables (U.S.D.A., 1967).

    sodium o-phenyl phenate:  97% wettable powder, solutions ranging from
    1.5% to 40%, wax emulsion from 0.7% to 2.0%.

    The strength of solution used varies with the crop concerned and the
    time of immersion to obtain protection and avoid phytotoxic reactions
    in fruits or vegetables. The times of immersion will vary from a few
    seconds to several minutes, but are precisely prescribed and
    monitoring is required for each formulation and crop. Examples
    includes apples 0.45% - 1.4% solution, bananas 2% applied to cut stem
    area of crown of head area (no residue in fruit or skin), cantaloups
    1.5%, carrots 0.1%, cherries 1.0% with wetting agent, citrus 0.5% wax
    emulsion to 3% in water (plus caustic and hexamine), cucumbers 1%
    - 2%, nectarines 1%, peaches 0.05 - 0.6%, pears 0.23% to 1.45%,

    peppers 1%, pineapple 1.25% (1% in wax), plums 0.1%, sweet potatoes
    0.37% - 0.5% solution or 0.7% wax emulsion, tomatoes 1% (U.S.D.A.,

    These use patterns were available from the U.S.A. only.


    As mentioned above, the technology for use of these compounds has been
    developed under commercial conditions requiring accurate control of
    time of treatment which may be from as brief as 10 seconds (apples and
    pears) to 15-18 minutes (peaches), at specified temperatures, pH etc.
    The data pertaining to the conditions of these trials were collected
    from several locations in the U.S.A. They are unpublished. They have
    been collated and submitted with full details to FAO by the Dow
    Chemical Company (Dow, 1969).

    A review of several abstract journals revealed no published literature
    bearing on this subject from other countries. It is known that both
    compounds are used by several citrus exporting countries, but these
    have not been identified, nor were use patterns, technology of use or
    data on residues resulting from supervised trials supplied for
    evaluation from other than the U.S.A.

    The results of U.S.A. trials are summarized in Tables 1 and 2 (Dow,
        TABLE I

    Residues resulting from supervised trials with 2-phenylphenol

                            Percent 2-phenylphenol     Range of residues as
    Fruit or vegetable            in wax*               ppm o-phenylphenol

                                                                    Not rinsed

    Carrots                        0.5                              17.0

    Cucumbers                      0.5-2                            4.2-5.6

    Peppers                        2                                0.1-1.0

    Plums                          2                                2.5-12.8

    Sweet potatoes                 1                                4.0-5.7

    Tomatoes                       2-3                              0.1-7.7
    *Concentration varies according to crop and/or contact time

    TABLE 2

    Residues resulting from supervised trials with Sodium o-phenylphenate

                         Percent sodium o-phenylphenate   Range of residues as
    Fruit or vegetable            in water*               ppm o-phenylphenol

                                                         Rinsed     Not rinsed

    Apples                     0.42-0.77                 0.2-14.0

    Cantaloups                 1.5
      edible portion                                                1.0-6.0
      whole fruit                                                   42.0-117.0

    Carrots                    0.1                                  2.8-11.0

    Cherries                   0.65-1.08                 0.3-2

    Citrus                     2.0                       5.5-9.3

    Cucumbers                  1.0                       1.3-7.7

    Nectarines                 0.75-1.2                  0.4-1.4

    Peaches                    0.1-0.12                             9.0-15.0

    Pears                      0.4-0.99                  1.0-25.0   1.0-22.0

    Peppers                    1.0                       4.2-7.1

    Pineapples                 1.25                      3.8-7.1

    Plums                      0.4                       0.8-1.3

    Sweet potatoes             0.5-1.0                   0.5-11.0   1.7-3.4

    Tomatoes                   0.9                       0.5-1.4

    *Concentration varies according to crop and/or contact time

    Carrots treated with 0.1% sodium o-phenylphenate, stored and steam or
    abrasion peeled prior to canning in a commercial manner contained no
    residues in the canned product. In cantaloups the residue is mostly in
    the unedible portion (42.0-117 ppm in whole fruit, 2.8-11.0 ppm in

    edible portion) (Dow, 1969). The value of OPP residues found in peel
    of oranges varies slightly with variety. Shamoute oranges peel varied
    between 5.9-23 ppm; Valencias between 8.8 and 21.3 ppm; grapefruit
    peel 7.0-26.1 ppm; lemons 5.4-15.6 ppm in peel. The quantities of OPP
    in pulp of citrus is very low. In many cases none could be detected,
    but when peel contained the higher levels, OPP residues from trace to
    0.4 ppm were found in pulp (Rajzman and Apfelbaum, 1968).

    There is no information available on possible chemical alteration of
    the nature of the residue. All residue analysis methods to date rely
    on expressing the residue as 2-phenylphenol.

    Evidence of residues in food in commerce or at consumption

    Information on the residue content of food in commerce is rare. Only
    one published paper has a bearing on this subject (Rajzman and
    Apfelbaum, 1968). Citrus fruit treated in 22 packing houses in Israel
    were collected, sampled and analysed. The residues in whole fruit
    range from 1.8 to 8.3 ppm with 80% of the samples containing less than
    5 ppm. The authors conclude that in view of the small number of
    samples used, their finding of a maximum of 8.3 ppm should not be
    considered as the maximum quantity which can occur in citrus treated
    in the manner described.

    There is no information available with regard to residues in food at
    the time of consumption. It can be assumed there will be little loss
    of residue in wax-treated fruits and vegetables. Since the treatment
    is by post-harvest application, the amounts in wax-treated food
    reaching the consumer can be considered as those reported as resulting
    from supervised trials. Possibly slightly lower levels will remain in
    food treated with water formulations.


    Colorimetric procedures have most often been proposed for the
    determination of residues of 2-phenylphenol. Tomkins and Isherwood
    (1945) used coupling with diazotized sulphanilic acid in determining
    residues in oranges and marmalade after a steam-distillation
    extraction, with acid-alkali treatment clean-up stages. Gottleib and
    Marsh (1946) suggested an aminophenazone procedure for the
    determination of several phenolic fungicides. The results of a
    collaborative study of this method as applied to the determination of
    residues of 2-phenylphenol in apples, pears and citrus fruit have been
    reported by Schiffman (1957); Hayward and Grierson (1960) used this
    method on oranges. A similar procedure has been officially recommended
    by the Communauté Economique Européene (van Elslande, 1967) for
    residues in fruits and this should be suitable for regulatory purposes
    at the present time. A modified steam-distillation extraction
    apparatus has been described by Leinbach and Brekke (1961) who used an
    indophenol colorimetric method for residues in purees of raspberry,

    strawberry, prunes, loganberry and fig and in orange juice. The
    coloration given by reacting 2-phenylphenol with titanium sulphate
    (Caulfield and Robinson, 1953) is not sufficiently sensitive for
    residue analysis. A spectrofluorometric procedure for the examination
    of single fruits was proposed by the Cotta-Ramusino and Stacchini
    (1966) which is sensitive to <0.1 mg of 2-phenylphenol for fruit,
    Gunther et al. (1963) reported a procedure for the routine examination
    of citrus fruits for biphenyl and 2-phenylphenol, determining the
    latter colorimetrically after coupling with p-nitrofluoroborate, and
    obtained recoveries ranging from 89 to 100 percent at the 0.5 to 10
    ppm level.

    Chromatographic methods available include a gas chromatographic
    examination of concentrated orange juice (Thomas, 1960), applicable
    over the range 1 to 10 ppm on 1 ml of sample and a thin-layer
    chromatographic procedure for the detection of residues of biphenyl
    and 2-phenylphenol in lemons (Chioffi, 1965). Mestres and Chave,
    (1965) used extraction with cyclohexane in a Dean and Stark apparatus
    before separating and determining biphenyl and 2-phenylphenol by gas
    chromatography with flame-ionisation detection. These chromatographic
    techniques should be developed and evaluated for application as
    regulatory procedures.


                                                         Tolerance (ppm)
        Country             Crop                         as 2-phenylphenol

    Canada            Cherries, nectarines                      5
                      Citrus fruits, cucumbers,
                       pepper (bell), pineapple,
                       tomatoes                                10
                      Sweet potatoes                           15
                      Carrots, peaches, plums                  20
                      Apples, pears                            25
                      Cantaloups                              125

    E.E.C.            Citrus fruits                            12

    Netherlands       Citrus fruits                            10

    United Kingdom    Citrus fruit                             70
                      Apples, pears, pineapples                10
                      Melons                                  125

                                                         Tolerance (ppm)
        Country             Crop                         as 2-phenylphenol

    United States     Cherries, nectarines                      5
     of America       Citrus, citron, cucumbers, grapefruit,   10
                       kumquats, lemons, limes oranges,
                       peppers (bell), pineapple, tangelos,
                       tangerines, tomatoes
                      Sweet potatoes                           15
                      Carrots, peaches, plums (fresh prunes)   20
                      Apples, pears                            25
                      Cantaloups, of which not more than      125
                       10 ppm shall be in the edible portion.


    The antimicrobial properties of 2-phenylphenol have been utilized in
    many countries for over 40 years. Due to its broad spectrum fungicidal
    and bactericidal properties and commercial availability it has been
    used widely as a germicide. In addition to its current use as a
    post-harvest pesticide it has been used in household disinfectants,
    preservatives for water-oil emulsions in textile and metal industries.
    The sodium salt is also used as a preservative in water base paints
    and adhesives. The free phenol is used in the post-harvest treatment
    of fruits and vegetables in wax formulations as a protectant in
    shipment and storage. The sodium salt is dissolved in water and used
    as a post-harvest rinse for fruit and vegetables. The tree phenol is
    also used to treat harvesting containers, shipping and storage
    facilities, fruit handling machinery and shipping containers.

    The data on residues from supervised trials are based only on U.S.A.
    technology of use and on the two products as manufactured by Dow
    Chemical Company. These are proprietary compounds, manufactured by
    several companies in many countries. No information was provided on
    the use pattern or technology of use in other countries.

    The residues from both compounds are expressed as 2-phenylphenol.
    Highly specific methods of dipping and washing individual species of
    fruits and vegetables in the protective baths have been developed,
    with carefully prescribed times of immersion varying from as little as
    10 seconds (apples and pears) to e.g. 6 minutes for citrus. A skilled
    technology and monitoring of wash solutions is required to maintain
    correct conditions for treatment. Consequently, amounts of residues
    vary depending upon the type of formulation used, the technology of
    treatment and the fruit or vegetable itself. Supervised trials in the
    U.S.A. carried out in several types of commercial scale fruit and

    vegetable handling facilities resulted in residues of (ppm) apples
    0.2-14, cantaloups (whole fruit) 42-117, carrots 2.8-17 (removed by
    processing), cherries 0.3-2, citrus 5.5-9.3, cucumbers 1.3-7.7,
    nectarines 0.4-1.4, peaches 9-15, pears 1-22, peppers 4.2-7.1,
    pineapples 3.8-7.1, plums 0.8-12.8, sweet potatoes 0.5-5.7, tomatoes
    0.5-7.7. Variations of conditions of treatment and contact time could
    presumably result in slightly higher residues.

    Methods of analysis for residues are available and they should be
    evaluated by collaborative studies. (This in not considered critical).
    In general all methods are based on determining the 2-phenylphenol
    content of an aqueous solution residue extract by colometric
    measurement after coupling with 4-aminoantipyrine.

    No data are available on residues on fruits and vegetables as
    consumed, but since these are post-harvest uses it would be a fair
    speculation to assume that the residues would be the average of the
    ranges outlined above.

    Since the technology of treatment is so critical, in approaching the
    recommendation of tolerances, some leeway should be provided for error
    in time of immersion, pH of bath and other factors in this technology.


    Cherries, nectarines                      3 )
    Citrus, cucumbers, peppers (bell),          )
     pineapples and tomatoes                 10 )
    Sweet potatoes                           15 )
    Apples, plums, (fresh prunes)            15 )  ppm as 2-phenylphenol
    Carrots, peaches                         20 )
    Pears                                    25 )
    Cantaloups (whole fruit)                120 )
    Cantaloups (edible portion)              10 )



    1. A reproduction study in experimental animals.

    2. Metabolic studies in experimental animals and man.

    3. Long-term studies using a larger number of animals.

    4. Data on residue levels in raw agricultural commodities moving in

    5. Data on residues in food at the time of consumption.

    6. Results of collaborative studies of chromatographic methods of


    Benger, H. (1968) Fluorimetsche bestimmung von o-phenyl-phenol in
    citrusfrüchten. Arch. Hyg. 152(3):225-30

    Caulfield, P.H. and Robinson, R.J. (1953) Spectrophotometric 
    determination of o-phenylphenol with titanium sulphate. Analyt.
    Chem. 25:982-3

    Chioffi, V. (1965) Investigation of diphenyl and o-phenylphenol in
    lemons by thin-layer chromatography. Boll. Lab. Chim. Provinciali
    (Bologna), 16:366-76 Chem. Abs., 1966, 64:1254d.

    Cotta-Ramusino, F. and Stacchini, A. (1966) Spectrofluorometric 
    determination of o-phenylphenol in citrus fruits. Fruits (Paris), 
    21:37-9; Chem. Abs., 64:14858h.

    Dodgson, K.S., Garton, G.A., Stubbs, A.L. and Williams, R.T. (1948)
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    Chemical Co., Midland, Mich., U.S.A. to FAO

    E.E.C. (1967) Amtsblatt der Europaischen Gemeinschaften, No. G1203B, 
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    Elslande van, R. (1967) Dosage des résidues d'orthophénylphénol et
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    bei der Ratte. Arzneimittel. - Forsch., 15:632-6

    FAO/WHO (1962) Evaluation of the toxicity of a number of 
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    Gunther, F.A., Blinn, R.C. and Barkley, J.H. (1963) Procedure for 
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    citrus fruit. Analyst, 88:36-42

    Hayward, F.W. and Grierson, W. (1960) Effects of treatment conditions 
    on o-phenylphenol residues in oranges. J. Agr. Fd. Chem. 8.308-10

    Hodge,  H.C., Maynard, E.A., Blanchet, H.J. Jr., Spencer, H.C. and
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    Rajzman, A. and Apfelbaum, A. (1968) Survey of o-phenylphenol 
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    See Also:
       Toxicological Abbreviations
       Phenylphenol, 2- (WHO Pesticide Residues Series 5)
       Phenylphenol, 2- (Pesticide residues in food: 1990 evaluations Toxicology)