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

    EVALUATION OF SOME PESTICIDE RESIDUES IN FOOD

    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

    gamma-BHC

    IDENTITY

    Synonyms

    gamma HCH, lindane; gammexane (R)

    Explanation

    Unless it is specifically stated to the contrary, the data here
    reviewed refer to lindane, which is defined by the International
    Standards Organization as a product of specified purity, not less than
    99 per cent gamma-BHC.

    Chemical name

    gamma-1,2,3,4,5,6-hexachlorocyclohexane

    Formula

    CHEMICAL STRUCTURE 

    BIOLOGICAL DATA AND TOXICOLOGICAL EVALUATION

    Biochemical aspects

    gamma-BHC is absorbed from the digestive tract, particularly in the
    presence of lipids. Once absorbed, gamma-BHC is distributed to various
    tissues or organs, accumulating above all in the fat depots (Van
    Asperen, 1957), liver and kidneys. The rate of accumulation of
    gamma-BHC in growing animals is, however, much lower than that of
    beta-BHC or of DDT. In rats ingesting repeated small doses of
    gamma-BHC, the concentration in the fat depots is in a state of
    equilibrium with the concentration of the diet (Lehman, 1953). The
    data on gamma-BHC metabolism are very incomplete. According to certain
    in vitro tests it would seem that part is broken down in the liver.
    The unchanged compound is eliminated in the faeces and urine and is
    found in the milk (Ely et al., 1953; Van Asperen, 1957; Ware &
    Gilmore, 1959). Very little information is available about its effects
    on basic enzyme systems. Growing animals are particularly susceptible
    to its toxic action (Kastli, 1955).

    A single dose of 60 mg/kg in rats has been shown to accelerate
    detoxication of several drugs processed by the liver microsomes,
    including paraoxon (Ghazal at al., 1964).

    The solubilities of the isomers of BBC in rat fat are: alpha, 4.05 per
    cent; beta, 0.66 per cent; gamma, 12-55 per cent; delta, 19.10 per
    cent. However, when each isomer is administered separately, the in
    vivo storage depends on the metabolism, the solubility being only a
    limiting factor (Sedlak, 1965).

    In an analysis of 282 samples of human fat obtained from the general
    population in the United States of America, an average content of 0.57
    ppm was found (Hoffmann at al., 1964). A study in the United Kingdom
    on 20 human fat samples showed a mean gamma-BHC concentration of 0.015
    ppm (Robinson et al., 1965). Single spraying of cattle with 0.03 per
    cent, or hogs with 0.06 per cent gamma-BHC and dipping of sheep and
    goats in a 0.025 per cent suspension, caused the appearance of
    gamma-BHC in the fat at levels ranging from 0.47 to 4.22 ppm (Claborn
    et al., 1960). gamma-BHC has been found in 30 samples of unprocessed
    cows' milk at a mean level of 0.01 ppm (Paccagnella et al., 1966).

    Acute toxicity

    From the viewpoint of acute toxicity, gamma-BHC is the most toxic of
    all the isomers present in the technical hexachlorocyclohexanes. It is
    a neurotropic poison causing excitation of the central nervous system
    with convulsions, followed - if the dose is sufficiently high - by
    depressive phenomena leading to death from respiratory collapse.

    The fatal dose for man is estimated to be 150 mg/kg body-weight, i.e.,
    of the order of 10 g for an adult weighing 70 kg. Children are
    particularly susceptible.

    Plasma taken from a three-year-old boy approximately 6 hours after he
    swallowed gamma-BHC, and 3 hours after the last convulsion, contained
    0.29 ppm gamma-BHC. Seven days later the concentration was 0.02 ppm
    and the patient was asymptomatic (Dale et al., 1966).


                                                                                           
    Animal             Route               LD50             References
                                     mg/kg body-weight
                                                                                       

    Mouse              Oral                 86              Woodard & Hagan, 1947

    Rat                Oral               125-200           Dallemagne & Philippot, 1948
                                                            Lehman, 1948
                                                            Lehman, 1951

    Rat                Oral               177-230           Woodard & Hagan, 1947
                                                            Klosa, 1950

    Rat           Intraperitoneal          35-85            Coper et al., 1951

    Guinea-pig         Oral               100-127           Lehman, 1948
                                                            Lehman, 1951

    Rabbit             Oral               60-200            Cameron, 1945

    Dog                Oral             40 (lethal)         Barke, 1950
                                     100-200 (lethal)       Landle & Schneider, 1950

    Dog             Intravenous        7.5 (lethal)         Barke, 1950
                                                                                       
    

    Short-term studies

    Rat. When rats were fed a diet containing 400 ppm gamma-BHC for 4
    weeks, hepatic lesions appeared (Doisy & Bocklage, 1949).

    Forty-eight rats (24 male and 24 female) were given gamma-BHC by
    stomach tube in a daily dose of 32 mg/kg body-weight for 6 months.
    Nervous signs (trembling, spasms), fatty degeneration of the liver and
    of the epithelium of the renal tubules, vacuolization of the cerebral
    cells and a marked increase in mortality rate were observed. With 10
    mg/kg body-weight for 17 months no abnormalities were revealed
    (Klimmer, 1955). These findings of functional disturbances in the
    central nervous system were in accordance with previous results
    (Herken, 1950, 1951; Kewitz, 1952; Kewitz & Reinert, 1952),; when 60
    rats were fed for 12 months with a diet containing 2, 3, 4, 5 and 10
    ppm of gamma-BHC the general behaviour of the animals, their
    body-weight and post-mortem gross and histological examinations showed
    no abnormalities (Melis, 1955).

    Rabbit. Two rabbits were subjected to daily intramuscular
    administration at doses of 40 mg gamma-BHC for 19 days, 80 mg for 9
    days and 160 mg for three days. The animals died and showed among
    other things, hepatic degeneration (Dallemagne & Philippot, 1948).

    Dog. Dogs fed 10 mg/kg body-weight for 18 to 49 days showed hepatic
    lesions (Woodard & Hagan, 1947).

    Five dogs were given daily intramuscular injections of a 10 per cent
    solution of gamma-BHC in oil ranging from 20 to 390 mg/kg body-weight.
    This repeated administration of gamma-BHC brought about convulsions,
    paralysis and anorexia (Dallemagne & Philippot, 1948).

    Man. Of 148 spray operators who applied gamma-BHC during an
    antimalaria campaign, about 46 per cent became affected. The clinical
    examination showed digestive and respiratory disorders, cutaneous
    symptoms, and neurological effects (asthma, polyneuritis). There is a
    lack of precise information on the chemical composition of the
    hexachlorocyclohexane employed, on the conditions of application and
    on the amount absorbed (Wassermann et al., 1960; Wassermann et al.,
    1961).

    Long-term studies

    Mouse. Groups of 30 mice each were subjected to dermal applications
    of 0.5 per cent gamma-BHC in acetone. The applications were given
    twice weekly over a period of 15 months. Another group of animals
    received subcutaneous implantation of paraffin wax pellets containing
    3 per cent of gamma-BHC and were observed for 10 months. No
    abnormalities were found (Orr, 1948).

    Rat. Groups of 20 rats (10 males and 10 females) were given diets
    containing 5 to 1600 ppm of the alpha-, beta-, and gamma-isomers of
    BHC for two years. These experiments clearly showed that the
    gamma-isomer was the least toxic and the beta-isomer the most toxic.
    The organs injured were the liver and to a lesser extent the kidneys.
    In the case of gamma-BHC, the lowest concentration causing significant
    liver changes was 100 ppm. No significant effect was noted at
    concentrations of 50 ppm or lower (Fitzhugh et al., 1950).

    With the aim of detecting any carcinogenic action, 3 groups of 20
    young rats (10 males and 10 females) were fed diets containing 25, 50
    and 100 ppm of gamma-BHC throughout their life-span. At the 2 highest
    concentrations, slight hypertrophy of the liver was observed, while
    with 100 ppm there was a slight tendency to fatty degeneration of this
    organ. At the lowest concentration, 25 ppm, there was no toxic effect,
    in particular, no histological lesions were detected in the liver or
    kidney. None of the concentrations used gave any significant increase
    in the percentage of tumours as compared with the control group
    (Truhaut, 1954).

    Groups of 12 rats (6 males and 6 females) were fed diets containing 50
    and 100 ppm of gamma-BHC; histological lesions were found in the liver
    parenchyma (Ortega et al., 1957).

    Twenty-five young rats were given gamma-BHC daily by stomach-tube at a
    dosage of 10 µg/kg body-weight (corresponding to about 0.1 and 0.15
    ppm) for 17 months. No abnormalities were found (Klimmer, 1955).

    Comments

    In all these animal species, gamma-BHC has proved to be a cumulative
    poison, causing hepatic and renal lesions and disturbances of the
    central nervous system. The dog seems particularly susceptible to
    neurological effects.

    Evidence of stimulatory activity on liver microsomal metabolism such
    as that observed for other chlorinated hydrocarbons has been presented
    for gamma-BHC, long-term studies have been performed only in rats and
    did not include reproductive aspects.

    TOXICOLOGICAL EVALUATION

    Level causing no toxicological effect in the rat

    25 ppm of gamma-BHC in the diet, equivalent to 1.25 mg/kg/day.

    Estimate of acceptable daily intake for man

    0-0.0125 mg/kg/body-weight.

    Further work required

    Elucidation of the significance of the finding that gamma-BHC is one
    of the compounds which affect liver cellular metabolism (p. 3).

    The chemical nature of the residue occurring in plants, which has not
    been fully investigated.

    This information should be provided not later than five years after
    the publication of this report, when a re-evaluation of this compound
    will be made.

    RESIDUES IN FOOD AND THEIR EVALUATION

    Use pattern

    (a) Pre-harvest treatments

    Soon after the introduction of gamma-BHC and prior to about 1950 its
    uses included applications to fruits, vegetables and other edible
    crops. These have almost ceased in Europe and N. America, but not in
    various other parts of the world, where it is known to be used for
    foliage application (e.g. to control cocoa insects). (However the
    meeting had very little information on the scale of use in different
    countries.)

    In the production of cereals, gamma-BHC is used either by application
    to plants, to the soil or to seeds. The dosage for foliar application
    usually is less than 2 kg of gamma-BHC per hectare possibly repeated
    two or three times: for soil insect control a dosage up to 1.8 kg per
    hectare may be used. In many countries the recommended interval
    between last application and harvest is 30 days.

    It was the opinion of the meeting that uses on stone, pome and citrus
    fruits and on berries have almost ceased. (Member countries having
    requirements for retaining these uses should supply supporting data.)

    Applications to soil used in the production of vegetables range from 4
    oz to 24 oz per acre: foliar applications from 1 to 16 oz.

    Aerosols, smokes and vapours of gamma-BHC are sometimes used on
    vegetable and fruit crops in glasshouses.

    Restrictions in various countries normally include measures against
    tainting and against excessive residues and minimum periods between
    treatments of soil (e.g. one to three years) and the planting of
    edible crops are specified.

    Gamma-BHC has had important uses against biting flies, lice, fleas,
    ticks and in the control of mange, scab or scabies caused by mites on
    livestock. Careful limitations in use are required, since in some
    instances repeated applications are required to obtain effective

    control. Use on meat animals is usually restricted (e.g. to 21 days
    before slaughter for cattle, sheep and goats, and seven days for
    hogs). Use on lactating animals or in milk rooms is not usually
    permitted.

    (b) Post-harvest uses

    Gamma-BHC has been widely used for protecting harvested cereals,
    pulses and nuts and for treating premises in which foods are stored.
    In one or two countries gamma-BHC is mixed at about 3 ppm with cereals
    in store. In some tropical countries (e.g. Ghana) maize, millets,
    guinea corn and rice paddy have been treated at doses up to 11 ppm.
    Gamma-BHC has also been used in holds of ships and has uses against
    some insects of public health importance.

    Residues resulting from supervised trials

    Fruit and vegetables

    Data on residues from supervised trials are not comprehensive. Many
    were obtained around 1950 and call for confirmation with the use of
    more modern analytical methods. The figures show rapid losses from
    leafy vegetables and a greater persistence on fruit; but after
    applications to soil significant residues remain for three years or
    more. Brett & Bowery (1958) reported residues below 0.1 ppm on
    tomatoes after three days, on snap beans after four days and on
    collards after about 13 days. To obtain data on the maximum possible
    residues, Lilly & Fahey (1956) used dosages as high as 50 times those
    required to produce effective insect control. The maximum residues
    found over a four-year period on soybeans were 0.74, 0.89, 0.27 and
    1.21 ppm (averages for each of the four years), on field corn over a
    three-year period they were up to 0.44 ppm. In the same series of
    trials sweet corn showed variations from 0.02 to 0.41 ppm, popcorn
    zero to 0.13 ppm. Other work reported by Lilly & Fahey (1956) on
    sunflowers, grain sorghums and a variety of garden beans over a
    four-year period showed no residues in excess of 0.6 ppm. Lichtenstein
    (1959) also cites residues in crops resulting from excessive
    applications of gamma-BHC to three soil types. Following normal
    agricultural practices San Antonio (1959) found that soil containing 5
    ppm resulted in 3 ppm in the edible parts of carrots, even though as
    high as 25 ppm was found in the fibrous root hairs. (He also found
    that the 3 ppm residue was greatly reduced by scraping the peel.) In
    more recent studies, using gas/liquid chromatographic analysis,
    Maier-Bode (1964) found not more than 0.5 ppm in beet treated 143 days
    previously at dosages of 1.5 to 3 kg/hectare. Other residues after
    treatments at the same dosage were 0.08 and 0.1 ppm in potatoes, and
    0.03, 0.06 ppm, 0.05 and 0.09 ppm in cabbages. Using twice the dosage
    employed in practice, Maier-Bode (1963) also found 0.5 to 1.0 ppm in
    beets. Beran (1961) reported 0.2 ppm in radishes and 0.11 ppm in
    beans.


        Tolerances

                                                                                          
    Country            Product                     Tolerance       Comments
                                                   ppm
                                                                                          

    Canada             Corn, beans and peas        10.0
                       Fruits                      10.0
                       Vegetables                  10.0
                       Fat of cattle, goats        7.0
                       and sheep
                       Fat of hogs                 4.0
                       Cereals                     No tolerance

    USA                Fruits                      10.0
                       Vegetables                  10.0
                       Fat of cattle, goats        7.0
                       and sheep
                       Fat of hogs                 4.0

    Netherlands        General                     2.0

    USSR               General                     2.0             Temporary

    Federal            Vegetables, pulses and      2.0             Proposed for 1968
    German             fruit
    Republic           Cereals                     0.1                "      "   "
                       Milling products from       0.03               "      "   "
                       Cereals

    Comecon            General                     5.0
    (Eastern
    Europe)

    Hungary            General                     2.5

    Brazil             General                     10.0            (Not specified)

    France             Wheat                       5.0             (On condition that
                                                                   flour does not contain
                                                                   more than 0.1 ppm)

    (continued)
                                                                                          
    Country            Product                     Tolerance       Comments
                                                   ppm
                                                                                          

    India              Wheat                       3.0             Under consideration

    Italy              Wheat                       2.5             Cleaning and washing
                                                                   required before milling

    Kenya              Wheat                       1.0

    Britain            Cereals                     2.5             Practical (not legal)
                                                                   limit
                                                                                          
    

    In largely unpublished compilations of information submitted to USFDA
    hearings in 1950, residues of less than 0.6 ppm were found on peaches,
    30 days after application of 6.0 per cent sprays and up to 5.1 ppm on
    apples after 21 days.

    Animal feed

    Gamma-BHC has been used for both soil treatments and foliar
    applications on a variety of forage crops used as animal feed. To
    reduce sources of contamination of milk and meat it is necessary to
    examine these practices. Data on the occurrence of residues and on
    their fate during curing and storage of hay or silage, etc. are not
    extensive. On alfalfa, residues ranging from 0.05 ppm after 35 days
    (Penn. State, 1963) to 0.4 ppm (France et al., 1961) have been
    reported. Maier-Bode (1964) found 0.19 ppm in grass 28 days after
    application. Applications within 14 days of cutting resulted in up to
    1.1 ppm in hay baled and held up to eight months (Treece & Ware,
    1965); at 24 and 31 days before harvest, 0.7 and 0.1 ppm (Fahey et
    al., 1960). Hardee et al. (1963) demonstrated differences in the rate
    of disappearance from alfalfa, clover and trefoil; which indicates a
    need for caution in the extrapolation of results from one species to
    another.

    No substantial information seems to be available on residues in forage
    resulting from soil treatments. The current data suggest, however,
    that the residues resulting from direct foliar application on forage
    crops may not be acceptable on animal food crops. The FAO Working
    Party would therefore like to see more information of recent origin,
    before making specific recommendations on this aspect. Information
    from feeding trials with animals at the very low levels of residues
    that might be expected from soil or seed treatments would also be
    valuable.

    Use on animals

    Gamma-BHC has been popular for ectoparasite control in poultry houses,
    by direct application to hens and their roosts. Fairchild & Dahm
    (1955) applied one per cent dust to litter for lice control. Residues
    in successive fat and liver samples dissipated rapidly. Skin samples
    taken two weeks after dusting contained 0.44, 0.84 and 7.5 ppm from
    0.06, 0.25 and one per cent dusts. Ivey et al. (1961) confined
    chickens for 16 weeks in treated poultry houses. Residues in fat after
    four weeks were 27.7 to 58.8 ppm, in eggs 4 ppm. Even light treatments
    of similar poultry houses resulted in 6.6 ppm in fat after two weeks
    and 1.0 after 20 weeks. Eggs from these hens contained 0.81 ppm after

    two weeks and 0.08 ppm after 16 weeks. Lower concentrations were used
    by Ware & Naber (1961) to determine the effect of low level
    contamination of food. 0.01 ppm in feed resulted in detectable
    residues in eggs and chicken tissues. After 60 days' feeding, residues
    in egg yolks were 0.26, 0.46 and 4.96 ppm respectively from hens
    receiving 0.1, 1.0 and 10 ppm in their diets. After transfer to clean
    food, residues were down to a trace after eight days for the first
    group, to 0.09 ppm after 24 days for the second group and to 0.08
    after 53 days for the last group of birds.

    Ware & Naber (1962) also reported that direct application to poultry
    and to houses resulted in an initial residue of 5.57 ppm decreasing to
    1.03 ppm after 14 days. Treating roosts only, on dipping legs,
    resulted in lower residues. Deema, Naber & Ware (1965) evaluated
    residues resulting from confining hens above cartridges producing
    gamma-BHC vapour and found 0.13 ppm, 0.24 and 0.33 ppm after 80 days
    at three dosage rates. Harrison et al. (1963) after feeding poultry
    with 4, 16 and 64 ppm for 27 days found 19.1, 56.4 and 156.0 ppm in
    the body fat. Stadelman et al. (1964) after feeding hens at 0.15 for
    14 days, measured no detectable residues in eggs and less than 0.3 ppm
    in fat, 15 ppm for five days resulted in 0.7 ppm in fat. One week
    after discontinuing the pesticide, eggs contained 0.4 ppm and none was
    detected in fat or flesh 11 weeks later.

    Studies in New Zealand, USA and Britain suggest that the condition of
    fleece is an important factor in determining the residues of gamma-BHC
    and their persistence in the fat and meat of sheep following dipping.
    Jackson et al. (1959), by biopsy two weeks after dipping in 0.025 per
    cent solution, found 4.22 ppm in sheep fat and 2.67 ppm in goats' fat.
    Twelve weeks were required for these residues to reduce to zero.
    Dipping shorn sheep at the same strength, Egan (1965) found 1.9 ppm
    and 0.2 ppm in kidney fat and meat respectively after one week and 0.1
    ppm in each after six weeks, in unshorn sheep however the residues
    were 8.9 and 1.0 ppm after one week, 3.8 and 0.4 ppm after six weeks,
    2.2 and 0.1 after 12 weeks, and 40 weeks passed before the levels were
    both down to 0.1 ppm.

    Collett & Harrison (1963) using a dip containing 0.0125 per cent
    emulsion also found higher residues in unshorn sheep. Fat of shorn
    sheep two weeks after dipping contained 2.5 ppm and unshorn sheep 5.0
    ppm (average figures) and residues; in fat of shorn sheep were
    negligible in eight weeks and in unshorn sheep in 12 weeks. From these
    results it seems that fleece is a reservoir for continued absorption.

    Swine appear to store gamma-BHC less than sheep. Fat of animals
    sprayed with normal dosages after one week contained 0.03 and 0.05
    ppm, and those after twice the dosage 0.5 and 0.06 ppm (USDA, 1965).
    Fat samples taken by biopsy showed 0.1 to 0.3 after 28 days (USDA,
    1965a).

    Gyrisko et al. (1959) reviewed the effects on flavour and residues in
    milk of feeding low residues on hay to dairy cattle. In agreement with
    earlier work they found that as much as 10 ppm in feed did not cause
    off-flavour in milk. Feed which contained 0.6 ppm at harvest had
    reduced to non-detectable levels when feeding was initiated.
    Unfortunately, no recent information is available on the feeding to
    lactating animals of the very low levels of residues which may be
    present on cull root crops, sugar beets and forage. Most countries do
    not register or recommend the use of gamma-BHC in buildings in which
    dairy animals or dairy products are kept and processed, or on
    lactating animals.

    Residues in food moving in commerce

    Few figures are available for individual food commodities. Total diet
    studies in the USA (Williams, 1964; Duggan et al., 1966; Cummings,
    1966) and Canadian restaurant meal surveys indicate very minor
    incidence in diets of these countries. The USA five-year survey using
    three different methods of analysis, rarely recorded residues in
    excess of 0.01 ppm.

    By contrast, British investigations of residues in home-killed mutton
    in 1962 (Egan, 1965) indicated a constant low level of residue in fat
    of meat in 61 samples. Thirty-seven samples contained not more than
    0.1 ppm, 48 not more than 0.3 ppm and three samples between 1.1 and
    2.0 ppm. The Reports of the Government Chemist (UK) for 1964 and 1965
    contain further useful information on the amount of total BHC isomers
    in food of origin from different countries:


                                                                                                                  
                                      1964                                     1965

    Food     Country      Number of   Range        Arithmetic    Number of     Range          Arithmetic
                          samples     ppm          mean ppm      samples       ppm            mean ppm
                                                                                                              

    Butter   Australian   45          0.0-0.40     0.02          45            0.0-0.11       0.02

             Danish       30          0.0-0.20     0.05          24            0.0-0.08       0.04

             New Zealand  45          0.0-0.02     <0.01         40            0.0-0.04       0.01

             UK           18          0.0-0.20     0.05          18            0.0-0.13       0.04

    Milk     UK           60          0.00-0.18    0.003         85            0.0-0.022      0.0045

    Mutton   Argentine    17          0.00-15.5    1.1           13            0.0-1.6        0.25

    Kidney   Australian   15          0.00-0.05    0.01          6             <0.05          -

    Fat      New Zealand  12          0.00-0.25    0.05          10            <0.05          -

             UK           107         0.00-5.1     0.43          128           0.0-10.6       0.46

    Beef     Argentine    13          0.0-1.1      0.15          22            0.0-0.80       0.13

    Kidney   UK           66          0.0-0.3      0.05          59            0.0-0.42       0.04

    Fat

    Corned
    beef     Argentine    20          0.0-0.1      0.03          26            0.0-0.1        0.02
                                                                                                              
    


    Hardon (1960) reported that beans sampled in commerce contained 0.1
    ppm gamma-BHC, and canned tomatoes 0.13 ppm (Alessandrini at al.,
    1959).

    Fate of residues

    (a) In soil

    Gamma-BHC is relatively volatile and moderately soluble in water, for
    which reasons it is one of the less persistent organochlorine
    pesticides. It is generally considered that three years should elapse
    after heavy applications and before root crops are planted in treated
    soils; but soil type has an important influence on the rate of
    disappearance from soil (Harris, 1966; Duffy, 1966; Lichtenstein &
    Schulz, 1965; Lichtenstein et al., 1963, 1964; Harris & Lichtenstein,
    1961, etc.). Some of the early work may have been misleading due to
    inadequacies in the analytical method and this has been recently
    reviewed (Yule, Chiba & Morley, 1967). Enzymatic processes have been
    responsible for the detoxification of insects (e.g. Bradbury, 1957;
    Clark et al., 1966; Ishida & Dahm, 1965) and in the rat (Grover &
    Sims, 1965). Gamma-pentachlorocyclohexane has been identified as a
    decomposition product in soil. It is 103 less toxic to insects than
    gamma-BHC. Soil microorganisms and alkaline soils are involved in this
    degradation process (Yule, Chiba & Morley, 1967). Further work is
    required to determine whether the disappearance of gamma-BHC from soil
    can be achieved in a reasonable period by land and crop management
    practices.

    (b) In plants

    It has been demonstrated that gamma-BHC can be absorbed by roots and
    translocated to leaves (Bradbury & Whitaker, 1956) where it can kill
    insects (Howe, 1950; Starnes, 1950; Shapiro, 1951; Ehrenhardt, 1954).
    Jameson (1959) concluded that (when used as a dressing) the
    insecticide penetrates into seeds and is absorbed by the cotyledons.
    Way (1959) compared the action of gamma-BHC with other organochlorine
    seed dressings and Bradbury (1963) the action on cabbage and wheat, in
    both of which the gamma-BHC fell off rapidly.

    There appears to be very little information on metabolism and
    degradation in plants. Such information is necessary because
    toxicological evaluation has been based solely on feeding the parent
    compound.

    (c) In storage and processing

    Because of the volatility and solubility of gamma-BHC, storage and
    processing, including cooking, would be expected to result in losses.
    The literature contains divergencies on this subject probably due to
    the use of non-specific analytical methods in the early work and

    because the losses were closely dependent upon the temperatures,
    degrees of exposure to free air and other conditions pertaining in the
    particular test.

    From his own studies Van den Driessche (1958) suggests that in the
    canning and cooking process 23 per cent of residues of BHC (presumably
    13 per cent gamma) in treated vegetables would be lost in cooking
    water, and in the canning of beans and peas 63 per cent of the residue
    might be dissipated.

    Information on losses of gamma-BHC during the storage of cereals and
    on its carry over into flour and bread were reviewed in some detail at
    the second session of the FAO Working Party on Pesticide Residues
    (PL/1965/12). Losses during storage depend upon the physical
    conditions (e.g. Bridges, 1958) being high in the tropics and in well
    ventilated stores (e.g. Giles, 1964) and low under cooler closed
    conditions (e.g. Gunther, Lindgren & Blinn, 1958; Schesser, Priddle &
    Farrell, 1958). During the milling of flour, the losses depend on the
    particular processes used. Preliminary cleaning, brushing and washing
    have been shown to remove insecticide and several workers have found
    appreciably lower ppm residues in the flour (i.e. up to 50 per cent)
    than in the original grain, although the residues in certain
    by-products (e.g. bran for feeding to animals) may contain a higher
    ppm (Bridges, 1958; Feuersinger, 1960, 1962; Schesser et al., 1958;
    Sellke, 1952; Zeumer & Neuhaus, 1953). There are few data on losses of
    residues during bread making. Bridges (1958a) found that flour
    containing 2.5 ppm contained 40 per cent of this as unchanged residue
    in the bread with the remainder probably as tri-, di-, and mono-
    chlorbenzenes.

    Loss from Cheddar and Stilton cheese was slow (Bridges, 1958), about
    40 per cent remaining after 44 weeks. Penetration into both types was
    slow but no chemical changes were found in either raw or cooked
    cheese. Johnson (1958) reported the results of processing on residues
    in cucumbers used for pickles. It was concluded that final residues in
    pickles would be less than 0.5 ppm from field treated cucumbers, but a
    concentration of 10 ppm could result if harvested cucumbers were
    sprayed directly.

    Method of residue analysis

    A number of multidetection systems are available for the detection and
    determination of residues of gamma-BHC, together with residues of a
    number of other compounds, including other BHC isomers. An example is
    the AOAC system (1966) in which acetonitrile partition and Florisil
    column clean-up are identified and measured by gas chromatography
    coupled with thin layer or paper chromatography. Alternative clean-up
    systems; e.g that of de Faubert Maunder et al. (1964) using
    dimethylformamide, and other methods of confirmation of identity,

    e.g., using infra-red spectrophotometry, are also available. The
    methods are in general sensitive to 0.002 ppm of gamma-BHC in milk and
    0.02 ppm of gamma-BHC in most other foods, though under favourable
    conditions greater sensitivity can, if appropriate, be obtained.

    RECOMMENDATIONS FOR TOLERANCES

    The residue data reviewed at the meeting, for the most part, were
    produced between 1948 and 1959 before improved specific methods of
    analysis were available. These results can only be used as a guide,
    subject to review, when better data are available. When considering
    information on residues of this pesticide, the meeting found it
    necessary to rely on the expert opinion of its members, rather than
    conclusions that could be derived exclusively from obsolete or
    incomplete data.

    The properties of this pesticide are such that it was assumed that
    substantial losses of residue would occur in storage, processing and
    cooking of foods such as some vegetables, meat and cereals, but only
    minor losses in the case of small fruits and milk products.

    Tolerances recommended for residues of gamma-BHC based on these guide
    lines are:

                                                                  
    Small fruits        3.0 ppm             )
                                            )
    Vegetables          3.0 ppm             )
                                            )   Temporary tolerance
    Cereals             0.5 ppm             )
                                            )
    Milk products       0.1 ppm (fat basis) )
                                                                  

    Meat and poultry    0.7 ppm (fat basis) )   Practical
                                            )   residue
    Fluid milk          0.004 ppm           )   level
                                                                  
    These should be reviewed in the light of additional data, but in
    any event not later than within three years.

    Further work

    1.   Guidance is required from countries on uses still of value in
         food production or protection in storage and transit.

    2.   Data are needed on the disappearance of residues during storage
         and processing of food, and information on the chemical nature of
         terminal residues on food as consumed.

    3.   Residue data, using specific methods of analysis which will
         identify metabolites and gamma-BHC, after supervised trials and
         on residues in food moving in commerce.

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    H. (1953) J. Amer. vet. med. Ass., 123, 448

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    (1964) Arch. exp. path. Pharmakol., 249, 1

    Herken, H. (1950) Arztl. Wschr., 5, 193

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    Robinson, J., Richardson, A., Hunter, C. G., Crabtree, A. N. & Rees,
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    Truhaut, R. (1954) Communication au symposium intern. de la prévention
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    Wasserman, M., Sandulescu, G., Iliescu, S. & Mandric, G. (1960)
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    residues in samples of peeled, canned tomatoes coming from experiments
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    products VI.  Retention of gamma-Benzene hexachloride by wheat and
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    Deema, P., Naber, E. D. & Ware, G. W. (1965) Residues in hen eggs from
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    Jackson, J. B., Ivey, M. C., Roberts, R. H. & Radeleff, R. D. (1959)
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    Wochenschrift Die Muhle, Detmold
    


    See Also:
       Toxicological Abbreviations