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



    The definitions hereunder were accepted by the meeting for use in the
    report and the associated monographs (FAO/WHO, 1970). They are as
    adopted at the 1967 Joint Meeting (FAO/WHO, 1968a), except "Regulatory
    Method of Analysis" and "Referee Method of Analysis" which were added
    at the 1968 Meeting (FAO/WHO, 1969b) and "Conditional Acceptable Daily
    Intake" and "Tentative Negligible Daily Intake" which were added at
    the 1969 Meeting.


    A pesticide residue is a residue in or on a food of any chemicals used
    for the control of pests and the term includes derivatives of such
    chemicals. The amounts are expressed in parts by weight of the
    chemical and/or derivative per million parts by weight of the food

    Explanatory note

    In interpreting this definition it is proposed to include the
    consideration of any substance which may, at a given time, be known to
    be derived from the product and which may be held to influence the
    toxicology of the residue. Residues from unknown sources (i.e.
    background residues) will be considered as well as those from known
    uses of the chemical in question. The term pesticide will be held to
    include any constituent of a pesticide used for the control of pests
    during the production, transport, marketing or processing of food or
    which may be administered to animals for the control of insects or
    arachnids in or on their bodies; it will not apply to antibiotics or
    other chemicals administered to animals for other purposes, such as to
    stimulate their growth or to modify their reproductive behaviour, or
    to fertilizers or, at least for the present, to other substances,
    other than herbicides, used to influence the rate of growth of plants.


    A negligible residue in an amount of a pesticide residue that is
    regarded as toxicologically insignificant.


    An unintentional residue is one which occurs in a food as a result of
    circumstances not designed to protect the food against pest attack.

    Explanatory note

    For this purpose the range of pesticide uses is as indicated under
    'pesticide residue'. The food should be specified in each case and the
    term includes products such as milk and meat from treated animals.

    Furthermore, the residue may be acquired at any stage in the growing,
    harvesting, distribution, marketing or processing of the food. The
    unintentional residue also includes a residue of a chemical which
    occurs in nature as part of the environment but which cannot be
    distinguished from residues due to the use of pesticides. Residues
    sometimes described as 'incidental', 'accidental' or 'background'
    residues are included within this term.


    The practical residue limit is the maximum unintentional residue (see
    definition) allowed in a specified food.

    Explanatory note

    A practical residue limit is the level of pesticide residue above
    which a regulatory action may be taken. It applies to a specific
    commodity and pesticide for which no tolerance has been established.
    Observation of a residue level above the 'limit' may be presumptive
    evidence of violation of good agricultural practice; values below the
    'limit' are presumed to result from incidental effects, including
    possibly isolated effects, from other approved use of the pesticide.


    The acceptable daily intake of a chemical is the daily intake which,
    during an entire lifetime, appears to be without appreciable risk on
    the basis of all the known facts at the time. It is expressed in
    milligrams of the chemical per kilogram of body weight (mg/kg).

    Explanatory note

    For this purpose 'without appreciable risk' is taken to mean the
    practical certainty that injury will not result even after a lifetime
    of exposure. Furthermore, for a pesticide residue, the acceptable
    daily intake is intended to give a guide to the maximum amount that
    can be taken daily in the food 'without appreciable risk' to the
    consumer. Accordingly, the figure is derived as far as possible from
    feeding studies in animals and/or in man. The studies are usually
    conducted with the pesticide chemical itself. However, if the residues
    of a pesticide are known to consist of more than one chemical which
    may influence the toxicology of the residue (see definition of
    'pesticide residue'), information on the toxicology of the respective
    residual chemicals and, where appropriate, their respective acceptable
    daily intakes has to be taken into account when assessing the risks.
    Acceptable daily intakes are always subject to revision at any time in
    the light of new information.


    A conditional acceptable daily intake is one which is established for
    a pesticide in order to limit its use to those situations where no
    satisfactory substitutes are available.


    A temporary acceptable daily intake is one which in recommended for a
    limited period.

    Explanatory note

    A specified period is provided to enable additional biochemical,
    toxicological or other data to be obtained, as may be required for
    establishing an ADI. (See 'Further Work Required'). In such cases any
    recommendation will normally involve the application of a safety
    factor, the size of which will be dependent upon the nature of the
    toxicity of the compound, but which will be larger than that normally
    used in estimating acceptable daily intakes. In all cases the position
    will be reviewed not later than the first meeting following the
    specified date.


    A tentative negligible daily intake is allocated to a pesticide when
    unintentional residues of it occur in food and for which at least a
    short-term toxicity study is available. The short-term study, however,
    will have yielded insufficient information to establish even a
    temporary acceptable daily intake.

    For discussion of a case in point see the monograph on


    A tolerance is the maximum concentration of pesticide residue that is
    permitted in or on food at a specified stage in the harvesting,
    storage, transport, marketing or preparation of the food, up to the
    final point of consumption, and the concentration in expressed in
    parts by weight of the pesticide residue per million parts by weight
    of the food (ppm).


    A temporary tolerance is one that is valid for a limited time which is
    specified in each case.

    Explanatory note

    Such tolerance recommendations are made under two conditions: (1) when
    they are derived from temporary Acceptable Daily Intakes, and (2) when
    they are derived from an Acceptable Daily Intake but the residue data
    is inadequate for firm tolerance recommendations.

    The second class includes cases where information on losses of residue
    during storage, handling and preparation is inadequate and where
    calculations based on such inadequate figures and on appropriate food
    consumption data reveal a theoretical possibility that acceptable

    daily intakes could be exceeded. In cases of this kind, temporary
    tolerances are recommended only after information on the actual
    occurrence of residues in food, obtained from total diet and similar
    studies, has been considered and after assurance has been obtained
    that acceptable daily intakes are not likely to be exceeded. The
    information considered includes the results from subjective sampling
    and/or from objective sampling, including total diet studies, in
    various countries and particularly in where pesticides are most widely
    used. In all cases the position will be reviewed not later than the
    first meeting following the specified date.


    Good agricultural practice is the recommended usage of a pesticide
    which is necessary and essential for the control of a pest under all
    practical conditions bearing in mind any toxicological hazards

    Explanatory note

    The 'recommended usage' complies with the procedures, including the
    formulation, dosage rates, frequency of application and pre-harvest
    intervals recommended by appropriately trained specialists; it is the
    usage that has been registered, approved or otherwise accepted for the
    purpose by the relevant official department and which is normally
    included on the label. Such recommended methods of application should
    be based on supervised trials and other experimental work and should
    take into account such variations in climate, in crop husbandry and in
    incidence of pests as may occur under practical conditions from time
    to time in the various places in which the pesticide may be used. For
    this purpose good agricultural practice shall be held to include
    practice in the control of pests during the storage, transport,
    marketing and processing of foods.


    A total diet study is one designed to show the pattern of pesticide
    residue intake by a person consuming a typical diet.

    Explanatory note

    To make total diet studies, random samples of food are usually
    purchased in representative population centres in the country, or
    district, concerned and weighed out in the proportions in which they
    are consumed in the total diet. The weighed portions are then washed,
    cooked or otherwise prepared in the normal way for table presentation
    and then mixed to give a number of predetermined food group samples
    comprising, for example, cereals, green vegetables, root crops, fruits
    and preserves, fats, meats and milk. These groups are chosen with the
    intention of minimizing the subsequent analytical problems; they also
    serve to identify the areas of the diet which contribute most to total
    residue present. The foods are purchased and prepared under expert 

    supervision with the requirements of the studies in mind; but
    otherwise they resemble as far as possible the normal character of
    the total diet: Water and beverages are included.

    Each food group sample, prepared as above, is analysed for various
    residues. This may involve several different analyses for each group.
    The exact analytical procedure may vary from group to group. In
    addition, from experience, it may become possible to omit certain
    analyses for some groups. Thus, the different groups will not
    necessarily be subject to exactly the same analytical procedure.
    Similar studies have also been described as 'market basket studies'.


    A subjective sample is one taken after a known, or a suspected, use of
    a pesticide on a crop.

    Explanatory note

    Subjective samples include those taken during the early stages of the
    introduction of a pesticide into practical application when it is
    desirable to ascertain the residues occurring after known methods of
    application in the field, as well as those taken in circumstances
    where there are reasons to suspect that good agricultural practices
    have not been properly followed. Such samples may relate to crops from
    specific sites or from districts, or from countries where particular
    pesticides are known, or suspected, to have been used. Subjective
    sampling, rather than total diet studies, is sometimes used to assess
    the actual dangers to consumers, particularly where the sampling and
    analytical facilities are limited: it enables the facilities to be
    concentrated on those categories of food intake considered to offer
    the greatest risks. Subjective sampling also enables certain of the
    analytical difficulties encountered in total diet studies to be


    An objective sample is a random or impartial sample.

    Explanatory note

    The samples taken during total diet intake studies fall into this


    A regulatory method is one used for the determination of residues in
    the course of the administration of legislation relating to the

    Explanatory note

    For this purpose, it in often necessary to identify the nature of the
    residue as well as to determine its level. Subject to any expression
    of requirements in the particular law, the accuracy, precision and
    sensitivity of a regulatory method need be sufficient only to
    demonstrate clearly whether a tolerance level has been exceeded.
    Usually regulatory methods are not specified in pesticides legislation
    and at any given time there may be a number of methods available for a
    particular purpose.


    A referee method is one that has been specified, or agreed upon, for
    use in the event of a dispute.

    Explanatory note

    Referee methods are mainly required to settle disputes concerning the
    level of a residue but procedures for identification of a residue may
    sometimes have to be included in such methods. Referee methods lay
    special emphasis on accuracy and precision, even if this may involve
    equipment and experience not normally available in laboratories
    undertaking regulatory work. Nevertheless some regulatory methods are
    suitable for use as referee methods, although their evaluation by
    inter-laboratory comparisons is desirable before they are adopted as


    Further work required is work which met be done and properly reported
    before acceptable daily intakes and/or tolerances can be recommended
    or confirmed.

    Explanatory note

    In certain instances although acceptable daily intakes have been
    established, further work has been considered to be essential to
    remove doubts about the toxicological significance of some
    experimental observations. Results of the further work required should
    be made available not later than the specific date mentioned, after
    which the compound will be re-evaluated. The re-evaluation may be done
    at an earlier meeting, should relevant information become available.


    Further work desirable is work which, when properly reported, would be
    expected to provide additional assurance that recommended acceptable
    daily intakes and/or tolerances are adequate for the protection of the
    health of the consumer.

    See Also:
       Toxicological Abbreviations