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
    Committee on Pesticide Residues, which met in Rome, 4 - 11 December,
    1967. (FAO/WHO, 1968)

    Rome, 1968



    The definitions hereunder were adopted by the meeting for use in the
    report and the associated monographs (FAO/WHO, 1968).


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


    An unintentional residue in 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 temporary acceptable daily intake is one which is 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 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 is 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 when they are derived from
    Temporary Acceptable Daily Intakes or from figures for commodities at
    some stage prior to the point of consumption as food and when, in the
    absence of adequate information on losses of residue during storage,
    handling or preparation, calculations based on such figures using
    appropriate food consumption data reveal a theoretical possibility
    that the acceptable daily intake could be exceeded. In cases of this
    kind, to obtain assurance that acceptable daily intakes are not likely
    to be exceeded in practice, and before proceeding to recommend
    temporary tolerances, the meeting considers information on the actual
    occurrence of residues in food as offered to the consumer. This
    information includes the results from subjective sampling and/or from
    objective sampling, including total diet studies, in various countries
    and particularly in places 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 usually are
    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 come 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


    Further work required is work which must 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, and it has therefore been "required".
    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 in 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.

    Definitions of the terms FOOD FACTOR, PERMISSIBLE LEVEL and ACCEPTABLE
    CONSUMER LEVEL have not been included because they are regarded as

    See Also:
       Toxicological Abbreviations