WHO/FOOD ADD./69.35



    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
    Committee on Pesticide Residues, which met in Geneva, 9-16 December,



    Geneva, 1969



    Chemical name

    Calcium arsenate and lead arsenate.


    (Lead salt) -diplumbic hydrogen arsenate, dilead arsenate, dilead
    orthoarsenate, dibasic lead arsenate, acid lead arsenate, Gypsine.


    (Lead salt)     -PbHAsO4
    (Calcium salt)  -3Ca3 (AsO4)2. Ca(OH)2

    Relevant physical and chemical properties

    Appearance:    (lead salt) white powder
                   (calcium salt) white flocculent powder.

    Solubility:    (both salts) practically insoluble in water.

    Stability:     (lead salt) stable to light, air and water and not
                   decomposed by carbon dioxide; decomposed by alkalies,
                   including calcium hydroxide;

                   (calcium salt) soluble in dilute mineral acids;
                   commercial products are decomposed by carbon dioxide
                   yielding calcium carbonate and dicalcium hydrogen
                   arsenate, the latter being appreciably soluble in

    Composition of technical product: As commercially prepared, the lead
    salt usually contains about 21 per cent As, the calcium sale about 26
    per cent As.


    Biochemical aspects

    The total daily intake of lead varies according to the environment,
    but it is generally agreed that the average person in a developed
    country ingests up to 0.4 mg of lead per day (Patterson, 1965; Kehoe,
    1966). Under normal circumstances the diet contributes 90 per cent of
    man's total intake of lead. The element enters the food-chain through
    many sources including aerial fall-out and the use of pesticides
    containing lead in agriculture. Lead can appear in canned foods
    because some of the metal is dissolved by food acids from the solder
    of the can (Lewis, 1966). Lead is also inhaled from the atmosphere,
    the most important source being the combustion of gasoline containing

    lead tetraethyl (McCaldin, 1966). Tobacco smoke also constitutes an
    inhalation source of lead (Patterson, 1965). Lead appears in drinking
    water, where it arises largely from the lead pipes through which it
    flows. The solubility of lead in water is increased by oxygen and
    nitrates and is decreased by carbon dioxide and carbonates (Sollmann,

    Of the lead ingested from the food less than 10 per cent is absorbed
    by the alimentary tract. It is excreted from the body largely in the
    faeces and to a lesser extent in the urine (Lewis, 1966). Lead is a
    cumulative poison, being stored in all tissues and organs and it is
    transmitted to the foetus (Calvery et al., 1938; Castellino and Aloj,
    1964). Evidence exists that children and pregnant women retain lead
    more readily than others owing to the presence of rapidly developing
    tissues with a high affinity for the metal (Anon., 1966).

    Arsenic is used in many forms as pesticides, the most widely used
    salts being lead and calcium arsenates.

    The metabolic pathways for different arsenical compounds vary. The
    level of arsenic deposited in the liver appears to reflect the
    toxicity of the different compounds (Frost et al., 1955). Naturally
    occurring organic arsenical compounds have been shown to accumulate to
    a much lower extent than inorganic arsenic compounds (Coulson et al.,
    1935). The arsenates are more toxic than the arsenites, which in turn
    are more toxic than the organic arsenical compounds (Sollmann, 1957b).

    Absorption of inorganic arsenical compounds occurs readily, to some
    extent even from the intact skin. After oral administration excretion
    is mainly in the faeces, in parental administration it is excreted
    almost completely in the urine. A considerable proportion of ingested
    arsenic is stored in all tissues (Sollmann, 1957b).

    Acute toxicity

    The oral fatal dose of arsenic trioxide in man is estimated to be
    between 15 and 50 mg/kg body weight. The effects of arsenic may be
    somewhat delayed; if the acute stage is survived, signs of hepatic and
    renal damage are seen after one to three days, with skin rash later
    on. Post-mortem appearances suggest haemorrhagic gastro-enteritis in
    acute cases and necrotic or degenerative changes in liver, kidney and
    bone marrow in delayed cases (Sollmann, 1957c).

                                         LD50 mg/kg
    Compound           Animal    Route   body-weight     References

    Calcium arsenate   Rat       Oral         20      Lehman, 1951

    Lead arsenate      Rat       Oral        825      Voigt et al., 1948

    Lead arsenate      Rat       Oral        100      Lehman, 1951

                                         LD50 mg/kg
    Compound           Animal    Route   body-weight     References
    Lead arsenate      Rabbit    Oral        125      Voigt et al., 1948

    Lead arsenate      Chicken   Oral        450      Voigt et al., 1948

    Short-term studies


    Groups of albino rats were employed in paired-feeding studies using
    500 g batches of feed containing 0 ppm and 215 ppm arsenic as calcium
    arsenate or arsenic trioxide. Consumption of a 500 g batch of feed by
    each rat required six to eight weeks. Greater arsenic absorption and
    storage occurred in the animals which consumed the calcium arsenate,
    the livers and kidneys retaining the heaviest concentrations. At the
    conclusion of the study, the animals fed calcium arsenate had 41 per
    cent larger livers and eight per cent smaller brains than the
    controls on a dry weight basis (Morris and Wallace, 1938).


    A total of 20 dogs were fed diets containing either 13, 38 or 64 ppm
    lead as the acetate, or 64 ppm lead as the arsenate. Fifteen animals
    succumbed with severe symptoms of lead intoxication and the remaining
    five were sacrificed having shown definite symptoms of poisoning at
    approximately one year after the beginning of the experiment. The
    shortest period of survival was 15 days, in which case the animal
    received 2.56 mg of lead per kg of body-weight per day. Two animals
    receiving the smallest amount of lead, namely 0.33 mg/kg, succumbed,
    one after 140 days and the other after 167 days on the diet.
    Differences in survival were explained partly by the ages of the
    animals when placed on the experimental diets. Young animals were more
    susceptible to lead intoxication than were older animals. The kidneys
    of all the dogs showed tubular degeneration. Hyperaemia and oedema of
    the brain were noted in all dogs which had convulsions. The bones of
    many of the dogs were hard, brittle and thickened and the marrow
    cavities of the long bones were narrowed. Compensatory formation of
    marrow was noted in the skull. Lead deposits were noted in the bones
    and stippled red cells were seen in the blood. The greatest amount of
    lead storage was found in the bone, with smaller concentrations in the
    kidneys, liver and brain. Lead was also found in the pups and milk of
    lead-fed dams (Finner and Calvery, 1939; Calvery et al., 1938).

    Long-term studies


    In a study to determine whether the lead or the arsenic element was
    principally responsible for the toxicity of lead arsenate, rats were
    fed lead arsenate, lead carbonate and calcium arsenate for two years.
    The lead and arsenic in the last two compounds were in amounts equal
    to that in the lead arsenate. At the end of the two-year period each
    rat that had received lead or calcium arsenate had consumed the
    equivalent of approximately 1.7 g of elemental arsenic; for a rat that
    eats an average of 15 g of food per day, this figure comprises a
    dietary level of 155 ppm of arsenic. It was concluded from the
    mortality rates that calcium arsenate was the most toxic. The
    histopathological findings in the rats fed calcium arsenate differed
    from the controls in showing excess haemosiderin in the spleen,
    swollen cells and granular pigment in the renal convoluted tubules and
    hyaline casts in the collecting tubules (Fairhall and Miller, 1941).

    Observations in man

    Liver and skin careers have been reported in vineyard workers exposed
    to arsenates in West Germany (Roth, 1956, 1957a, 1957b, 1958) and an
    unusual frequency of bronchial carcinoma was noted among vineyard
    workers of the French region "Beaujolais" associated with signs of
    chronic arsenical poisoning (Galy et al., 1963).


    Lead is a non-essential element with toxic properties caused by
    excessive cumulation. Although intake can not be avoided, it is
    clearly desirable to reduce the bodyload to a level where equilibrium
    between absorption and excretion can be maintained.

    The total literature on toxicological studies with arsenical compounds
    is voluminous and the available animal studies as well as human data
    indicate that inorganic arsenic compounds are cumulative poisons. Much
    controversy exists over the problem of whether or not inorganic
    arsenicals possess carcinogenic potentials. Some of the
    epidemiological studies raise possible suspicions of such activity,
    but no real scientific proof has yet been forthcoming. Because of
    these doubts and the inadequacy of the available long-term study in
    rats, it is not possible to evaluate these compounds until unequivocal
    evidence has been produced which will allow resolution of the problem.
    Satisfactory substitutes should be used wherever possible in an effort
    to decrease the dietary intake of these elements.


    Use pattern

    Calcium and lead arsenate were extensively used as stomach poisons for
    insect control from 1900 to 1950. Since the advent of the new organic
    insecticides the use of calcium and lead arsenate has declined.

    However, there is still a substantial scale and pattern of use in
    several countries, particularly of lead arsenate. Calcium arsenate,
    due to its greater phytotoxicity, is used on crops less susceptible to
    damage, e.g. cotton and potatoes. In evaluating residues, only lead
    and arsenic are of toxicological significance.

    Pre-harvest treatments

    Calcium arsenate is applied to blueberries in eastern Canada and to
    vegetables in Japan and is present in some proprietary slug control

    Lead arsenate is used in Canada, Japan, Britain, Israel, United States
    of America and New Zealand for the control of insects such as apple
    maggots, codling moth, plum curculio, fruit flies, leafrollers and
    other chewing insects on fruit trees. It is also used to some extent
    for the control of chewing insects on vegetables (cucumbers and
    tomatoes in Japan) and ornamental crops.

    In the production of apples, cherries, grapes, pears and plums, the
    use of lead arsenate is economical and necessary, particularly on
    apples grown for export to countries in which plant quarantine
    regulations require freedom from certain important scheduled pests.
    These requirements could not be met without the use of currently
    recommended applications of lead arsenate (supplemented in some areas
    with other insecticides). Lead arsenate is also used in integrated
    control programmes to minimize the use of DDT.

    Post-harvest treatments

    None reported.

    Other uses

    Lead arsenate is also used for the control of earthworms and other
    soil-inhabiting insects on golf greens and lawns, and on airport turf
    adjoining runways to reduce bird hazard related to earthworm

    Residues resulting from supervised trials

    Extensive residue data, mainly from the use of lead arsenate, were
    collected for this review from several member countries of FAO and
    WHO. These data, which have been deposited with FAO, are summarized

    Extensive data from Canada and New Zealand on residues of lead and
    arsenic residues on apples range from less than 0.1 ppm to about 3 ppm
    for arsenic and 6 ppm for lead, depending on many variables.

    In the United Kingdom, field trials conducted for control of codling
    moths have produced data on the weathering of lead arsenate residues
    (Chiswell and Tew, 1965; Pocklington and Tatton, 1966; Tew et al.,
    1961; Tew and Sillibourne, 1964). The ratio of lead to arsenic
    remained close to the 3:1 ratio found in applied lead arsenate.
    Applications using hand lances led to greater residues at harvest than
    did reduced-volume machine applications.

    The rate of application and pre-harvest interval are of major
    importance on the amount of the final residue (Bishop et al., 1960).
    There is a marked and rapid decrease in arsenic deposits on foliage
    and fruit during the initial two to three weeks following the final
    application (Bishop et al., 1958). On apples, early in the season
    between "cover sprays" there is a loss in deposits on the apple
    surface which amounts to 3.6 per cent daily, mostly due to increase
    in size of apples. Later, the daily loss varies from 1.3 to 1.6 per
    cent and closer to harvest less than one percent (Webster and
    Marshall, 1934). A substantial portion of the residue is in the stem
    and calyx end which is not normally eaten (Canada, 1964; Tatton, 1965;
    Pocklington and Tatton, 1966; United Kingdom, 1964). When skin, stem
    and calyx are removed rarely more than 30 per cent of the residue is
    found in the edible pulp.

    The residue on apples at harvest from as few as two late season
    applications can, in the case of early varieties, be in excess of 2.0
    ppm, but this is reduced after harvest (see below). Data for pears and
    cherries are not as extensive but are similar to that for apples.

    No residue data were available for plums. Japanese data indicate
    residues no greater than 1.0 ppm arsenic and 1.0 ppm lead on grapes,
    cucumbers and tomatoes (Japan, 1968).

    Lead arsenate is quite stable and readily accumulates in soils either
    as a result of use in specific soil treatments or foliar application
    (Bishop and Chisholm, 1962; MacPhee et al., 1960). Crops grown in such
    soils will contain residues of arsenic (MacPhee et al., 1960). Arsenic
    can build up in soils to a level where it can reduce the yield of some
    sensitive crops such as peas and beans (Bishop and Chisholm, 1962;
    Chisholm et al., 1955; MacPhee et al., 1960). However, lead
    accumulation has not presented any problem to date as the result of
    agricultural use (Chisholm and Bishop, 1967).

    Calcium arsenate residues in soil after use on cotton have been
    included in the USDA monitoring programme. In one report, the average
    arsenic content of cultivated fields ranged from 2.8 to 12.8 ppm,
    while in uncultivated areas the range was 1.2 to 5.9 ppm NRC, 1966).

    Fate of residues

    In storage and processing

    Substantial reductions of both arsenic and lead residues result from
    mechanic removal during sorting, grading, movement on belts and
    brushing operations in most commercial packing operations. Residues
    followed through from practical rates of application to apples to
    sampling this fruit after packaging for export and transported
    indicated that in most instances the residues were reduced by a factor
    of 50 per cent or more (Canada, 1964).

    There is an increasing tendency to wash and wax apples prior to
    export, procedures which further reduce residues. Most consumers wash
    and wipe apples and pears if the peel is consumed. In many countries,
    the peel is removed before consumption. After processing, apple
    products contain small amounts of arsenic, ranging from 0 to 0.27 ppm.
    with an average of 0.11 ppm. Apple pomace, used as cattle food, can
    contain substantial amounts of residue. When made from whole fruit,
    these levels can go as high as 16 ppm, and if skins and cores only are
    used, as high as 16 ppm.

    Evidence of residues in food in commerce or at consumption

    The Public Analysts' reports for 1963, 1964 and 1965 (Hamence, 1965a
    and 1965b; Rymer and Hamence, 1967) indicated that about one per cent
    or less of the two to three hundred samples of fruit or apples
    examined in the United Kingdom failed to meet the statutory limits for
    arsenic and lead. In Canada various crops which may be treated with
    arsenates, such as apples and blueberries, have been examined over the
    last 10 years. In over 500 commercial samples of apples, less than one
    per cent contained more than 1 ppm arsenic. Blueberries presented no

    Methods of residue analysis

    The AOAC (1965) method for arsenic can serve as a referee method.

    Various modifications of the Gutzeit Test were used in earlier work
    for the determination of arsenic residues. While a fair degree of
    reliance can be placed on data obtained through this method,
    especially if the analysts were experienced in its use, the newer
    methods (AOAC, 1965) have been demonstrated to be superior (Hoffman
    and Morse, 1961; Hoffman and Gordon, 1963).

    There is still a requirement for a simple method of analysis to
    distinguish between the trivalent and pentavalent forms of arsenic.

    The dithiazone extraction methods of analysis for lead are not
    satisfactory. A co-precipitation technique with strontium sulfate
    (Flann and Bartlett, 1968) and atomic absorption methods are presently
    being considered by AOAC.

    National tolerances

    There are wide differences in the approach various countries take to
    regulating the amounts of arsenic or lead allowed to remain in food or
    in ingredients used in food manufacture and preservation. Most
    countries rely on a general clause in their pure food law which
    prohibits harmful or poisonous substances in foods. In addition, some
    countries also have extensive lists of legally permitted amounts which
    may be present in food. In addition, some countries (e.g. United
    States of America) have recently established tolerances for arsenic in
    meat, edible byproducts and eggs to accommodate the use of arsenic
    compounds in animal feed. A comprehensive survey of the regulations
    pertaining to products ranging from fish, cocoa, fruits, vegetables,
    chemicals used in food manufacture, beer, wine, etc., has been
    deposited with FAO and WHO. Some countries list the tolerances for
    arsenic as "arsenious oxide", As2O3, while others express the
    tolerance in terms of As only. Lead is expressed only as Pb. Some
    examples appear in the following table. In addition, some countries
    (e.g. Britain) have a general clause covering foods other than those
    specifically scheduled which limit their arsenic content to 1 ppm and
    the lead content to 2 ppm.



    Calcium and lead arsenate are not used in combination, but they can be
    considered together for the purposes of recommending tolerances since
    only residues of arsenic and lead have to be considered. Although
    these two compounds were used extensively in the past, their
    modern-day use is restricted to specific pest control problems which
    cannot be satisfactorily controlled with the modern organic
    insecticides. While calcium arsenate is still extensively used on
    cotton and potatoes with minor risks of residues resulting in human
    food, lead arsenate is now used mostly in the production of apples,
    with some small scale use on pears, cherries, grapes and plums and a
    limited number of vegetables. Its use is particularly important in the
    commercial production of apples in some regions in meeting
    requirements prior to phytosanitary certification for apple maggot
    control and in integrated control programmes for apple insects. It is
    most economical and practical to use and where its use is permitted,
    there is a much lower scale of use of DDT and other organochlorine

    Although residues of both lead and arsenic are persistent, data are
    available which indicate that approximately 50 per cent of these
    residues are removed during the commercial handling and packing of
    apples and further losses occur during the processing of apples to
    such products as apple sauce. Under conditions of good agricultural
    practice residues at harvest on apples average about 2 ppm. Most of
    this residue is on the surface, with rarely more than 30 per cent in


                              Canada           New Zealand          Britain*             France**            States              Japan
         Food                                                                                                of

                           As       Pb        As        Pb        As        Pb        As        Pb        As        Pb        As       Pb

    Apples, pears           2        7        1.1       nil        1         3        1.0                   combined          2.7      5.0

    Grapes                  2        7                                                1.0                   combined
                                                                                                               7.0            0.76     1.0

    Fresh vegetables        1        2                                                1.0                   combined
                                                                                                               7.0            0.76     1.0

    Fruit and fruit                           1.0       nil
    products, canned

    Marine and fresh                        canned                        canned
    water animal            5       10        nil       nil                  5

    Dried vegetables                                               2
                                                             (dry onions)    5        1.0

    Fruit juices         0.1-0.2  0.2-0.5                       0.1-0.5   0.2-2.0   0.2-0.3

                                                                                                           0.5 muscle
    Meat and/or meat        1                                                                               meat 
    products (not all     liver      2        nil       nil               canned      1.0                  1-2 by-products
    included)             only                                              5.0                             0.5 eggs

    Tea                     1       10                                      5.0
    (fat free, dry)                                                          5


                              Canada           New Zealand          Britain*             France**            States              Japan
         Food                                                                                                of

                           As       Pb        As        Pb        As        Pb        As        Pb        As        Pb        As       Pb

    Wine                   0.2      0.5                           0.2       1.0       0.2
    Ale, beer, stout       0.2      0.5      0.15        2      0.2-0.5               0.2

    *  When not scheduled limit is 1 ppm As and 2 ppm Pb.
    ** Suggested levels, 1950.

    the edible pulp. However, after packaging this fruit for export, less
    than one per cent of 500 commercial lots of samples contained
    residues over 1 ppm, the average being between 0.2 and 0.5 ppm.

    Total environmental and food monitoring surveys in North America and
    information from other sources indicate that less than one per cent
    of the arsenic and less than 10 per cent of lead ingested daily
    results from the agricultural use of lead arsenate. The balance of the
    load results from the use of arsenicals and lead for other purposes or
    the presence of these elements in the environment. Thus, the amount of
    arsenic in the total diet is not likely to be greater than 0.1 ppm or
    a maximum of about 0.2 mg per day, while the total daily intake of
    lead from all sources in food has been estimated at 0.2 to 0.4 mg per
    day in the United States of America and 0.4 to 0.6 mg per day in a
    major western European country. The former levels include the residues
    resulting from currently approved agricultural uses of calcium and
    lead arsenate in the United States of America, Canada, New Zealand and
    other countries.

    The attention of Member governments, however, should be drawn to this
    situation so that they may take appropriate steps to reduce the intake
    of lead and arsenic from other sources, should they so desire, bearing
    in mind that the agricultural use of these compounds combined is
    contributing much less than 15 per cent of the total lead currently
    being ingested by man. In this connexion, it should be pointed out
    that in several countries residues of arsenic and lead, resulting from
    incidental contamination in the production of several foods, e.g.
    grapes (i.e. residues in wine) have already been approved as "food


    Since no acceptable daily intake has been recommended for either
    arsenic or lead, no recommendation for tolerances can be made at this


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    See Also:
       Toxicological Abbreviations
       Lead arsenate (ICSC)
       Lead arsenate (FAO Meeting Report PL/1965/10/1)