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    FAO/PL:1968/M/9/1

    WHO/FOOD ADD./69.35

    1968 EVALUATIONS OF SOME PESTICIDE RESIDUES IN FOOD

    THE MONOGRAPHS

    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,
    1968.

    FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS

    WORLD HEALTH ORGANIZATION

    Geneva, 1969

    DICOFOL

    IDENTITY

    Chemical names

         1,1 bis (4-chlorophenyl) 2,2,2-trichloroethanol;
         2,2,2,-trichloro-1, 1-di (4-chlorophenyl) ethanol (IUPAC).

    Synonyms

         Kelthane(R)

    Formula

    CHEMICAL STRUCTURE 

    Other information on identity and properties

    Analysis of technical dicofol is not known. Purity of technical
    dicofol is 82-88 per cent. The United States Department of Agriculture
    (USDA, 1968a) places the total acaricide market for 1964 in the United
    States of America at about three million pounds active ingredients per
    year, dicofol being about half of that amount. Resistance is still
    today a cause for reduction of the use of dicofol, e.g. in Israel.

    EVALUATION FOR ACCEPTABLE DAILY INTAKE

    Biochemical aspects

    No specific identification of the metabolites of dicofol in animals
    has been made. However, on the basis of the known chemistry of the
    compound, 4,4'-dichlorobenzophenone is considered to be a probable
    metabolite. Thus, under alkaline conditions, dicofol is hydrolytically
    cleaved to 4,4'-dichlorobenzophenone and chloroform (Rohm and Haas,
    1968).

    Upon ingestion of dicofol by mammals, storage of the compound occurs
    in the adipose tissue. Rats were fed dicofol at a level of 32 ppm in
    their diet for 12 weeks. After eight weeks the level of the compound
    in the fat had reached equilibrium at concentrations of 25 ppm for the
    males and 70 ppm for the females, which amounts corresponded to 75 per
    cent and 200 per cent of the dietary levels. After 12 weeks, dicofol
    was withdrawn from the diet and the level of stored material declined.
    The rate of decline was greater for the male animals than for the
    females. By 14 weeks after withdrawal the level of dicofol in the fat
    was zero for the males but still remained at about 6 ppm for the
    females. Feeding with higher or lower dose levels also showed that
    dicofol was stored in the fat of the female rat to a greater degree
    than in the male (Smith et al., 1959).

    The effect of dicofol on plasma 17-hydroxy-corticosteroids in the dog
    was determined on two dogs which were fed 300 ppm and 900 ppm over two
    separate periods of one to two months' duration. The ability of the
    adrenal cortex to elaborate 17-hydroxy-corticosteroids in response to
    ACTH stimulation was slightly reduced at the 300 ppm level and
    markedly reduced at the 900 ppm level. The results also showed that
    following this treatment with dicofol, the ability of the adrenal
    gland to return to the pre-treatment level of response to ACTH
    proceeded slowly and, possibly, incompletely (Smith et al., 1959).

    Acute toxicity (80 per cent technical product)

                                                             
                           LD50 mg/kg
    Animal        Route    body-weight    Reference
                                                             

    Rat (M)       Oral         809        Smith et al., 1959
    Rat (F)       Oral         684        Smith et al., 1959
    Rabbit (M)    Oral        1810        Smith et al., 1959
    Dog (mixed)   Oral       >4000        Smith et al., 1959
                                                             


    Short-term studies

    Rat

    Dicofol was fed to groups, each containing 10 male and 10 female rats,
    for 90 days at dietary concentrations of 0, 20, 100, 500, 1250 and
    2500 ppm. Survival was adversely affected at 1250 ppm and above.
    Growth was inhibited at 100 ppm and higher levels in the females but
    only at 1250 ppm in the males. Increased liver to body weight ratios
    occurred in the survivors in both sexes. Liver lesions were the most
    consistent histopathological finding, but were only of scattered
    incidence at dose levels below 1250 ppm (Smith et al., 1959).

    Groups containing equal numbers of male and female rats were fed 0, 2,
    5, 10, 15 and 20 ppm in their diets for 55 weeks. Growth, survival and
    liver to body weight ratios were not affected at any dose level (Smith
    et al., 1959).

    Five groups, each of 10 male and 10 female rats were fed 0, 50, 200,
    1000 and 3000 ppm in their diet for 13 weeks. Body weight and food
    intake were reduced at the 200 ppm level and above, and at 3000 ppm
    there was 100 per cent mortality. Haematological criteria were
    comparable to the controls. Organ to body weight ratios were increased
    in the case of the liver at the 200 ppm level and above and in the
    case of the thyroid at the 1000 ppm level. Decreased uterus and
    prostrate to body weight ratios were observed at 1000 ppm. Liver
    glucose-6-phosphatase was depressed at 1000 ppm. while hexobarbital
    oxidase activity showed a dose-related stimulation in all treated

    groups. Histopathological examination revealed enlargement of
    centrilobar cells and nuclei at 200 ppm and above. Electron microscopy
    revealed smooth endoplasmic reticulum whorls to be present only at
    1000 ppm and above (Verschuuren et al., 1968).

    Dog

    Groups each containing three dogs were given levels of dicofol of 100,
    300 and 900 ppm for one year. Survival was affected only at 900 ppm.
    Body weight gain was normal and haematological and histological
    observations revealed no pathological effects (Smith et al., 1959).

    Long-term studies

    Rat

    Dicofol was fed to 60 groups, each containing 10 male and 10 female
    rats, at dietary levels of 0, 20, 100, 250, 500 and 1000 ppm for two
    years. Growth depression occurred in male rats at 500 and 1000 ppm,
    and in female rats progressively with increasing dietary concentration
    at 250, 500 and 1000 ppm. A growth depression after three months,
    recorded in female rats at 20 ppm (but not at 100 ppm) has not been
    observed again in later studies. Absolute organ weights showed no
    significant differences from the controls, with the exception of an
    increase in the case of the livers and kidneys of the female rats fed
    1000 ppm. Organ to body weight ratios were significantly increased for
    the liver at 250 ppm and for the liver, kidney and heart at 500 ppm in
    the females, but only for the liver at 500 ppm in the males.
    Histopathological findings were confined to hydropic changes in the
    liver which were regarded as reversible (Larson, 1957).

    Special studies

    (a) Reproduction

    Mouse. Groups of varying numbers of mice were maintained throughout
    five generations on dietary levels of 0, 7, 25, 100, 225 and 500 ppm
    of dicofol. At the 500 ppm level the litter sizes, average weight of
    the pups and also the values for fertility, viability and lactation
    indices were lower than for the control group. However, all these
    parameters were normal for the 225 ppm and lower levels (Brown,
    1967a).

    Rat. Four groups, each of 27 male and 27 female rats were fed
    dietary levels of 0, 100, 500 and 1000 ppm of dicofol in a
    two-generation reproduction study. There were no F1b pups surviving
    at 21 days when the original parents were fed 500 or 1000 ppm. Litter
    size from the 1000 ppm group was similar to the controls but over-all
    mortality in the pups was greater. Considerable reduction in fertility
    of the animals fed 500 and 1000 ppm was evident. No congenital defects
    were observed in any of the F2a or F2b animals (Brown, 1964-65).

    Groups of rats were maintained on diets containing 25 or 75 ppm of
    dicofol through a three-generation study. The average number of pups
    born per litter to parents receiving 75 ppm was slightly lower than
    for the controls. There was no compound related effects relative to
    body weight, fertility, gestation, viability or lactation indices at
    either level, nor were there any congenital abnormalities evident in
    either the viable or the still-born pups (Brown, 1967b).

    (b) Toxicity study of a possible metabolite

    The possible metabolite, 4,4'-dichlorobenzophenone was fed to groups
    each containing 15 male and 15 female rats, at dietary levels of 0,
    100 and 1250 ppm for three months. No effects were noted at either
    level except somewhat reduced heart to body weight ratios found in the
    males receiving 1250 ppm, but not in the females (Larson, 1965).

    Comments

    Short-term experiments on dogs and rats, reproduction studies on rats
    and mice and long-term experiments on rats are reported. From the
    results of the acute and short-term experiments a great species
    difference in susceptibility is evident between dogs and rats.

    No specific identification of possible metabolites has been made in
    animals but dichlorbenzophenone is a probable metabolite. No human
    studies have been reported.

    Comparative metabolic studies in animals and man, including adrenal
    function studies after oral administration are desirable.

    TOXICOLOGICAL EVALUATION

    Level causing no significant toxicological effect

         Rat: 50 ppm, equivalent to 2.5 mg/kg per day.

    Estimate of acceptable daily intake for man

         0.0-0.025 mg/kg body weight.

    RESIDUES IN FOOD AND THEIR EVALUATION

    Use pattern

    Pre-harvest treatments

    Kelthane is a miticide with systemic properties, used on a large
    number of crops. It has no insecticidal activity. The following table
    gives a review of application rates of dicofol and recommended
    pre-harvest intervals.

                                                                               
                                  Rate of application (kg/ha)   Pre-harvest
                                                                 interval
             Crop                 Small plants   Large plants     (days)
                                                                           

    Apples, pears, crabapples,         2.20       4.41-5.30          7
    quince

    Cherries                           2.20       3.96               7

    Peaches, apricots,                 2.20       3.96              14
    nectarines

    Walnuts, filberts, pecans,
    chestnuts, hickory nuts            1.76       4.85              14
    and almonds, if hulls are
    not fed to livestock

    Almonds, if hulls are fed          1.76       3.09           Before nut
    to livestock                                                  formation

    Grapes, hops                        .66       1.60               7

    Strawberries                        .44       2.96               2

    Raspberries and other cane          .66       1.60               2
    berries

    Beans                               .44        .73               7

    Beans (dry)                         .44       1.00              45

    Beans (California)                  .66       1.32              45

    Cantaloupe, cucumbers,
    pumpkins, squash, melons,           .44        .73               2
    water melons

    Tomatoes, peppers                   .66       1.00               2

    Alfalfa, clover, other              .66       1.32
    legumes for seed only

    Corn (field)                        .88       1.76             Before
                                                                  ears form

    Plums, prunes, figs                1.76       2.50               7
                                                                           
    (Adapted from Rohm and Haas, Kelthane 35 label)
    
    Post-harvest treatments

    No post-harvest uses of dicofol are known.

    Other uses

    Dicofol is used for control of mites on lawns, ornamentals and shade
    trees, as well as against clover mites in buildings.

    Residues resulting from supervised trials

    Detailed residue data are available from United States trials with
    dicofol on important crops and have been deposited with FAO. Rates of
    application were similar to those given above. The typical data
    presented below are representative:

                                                                                
    Crop                Number of    Post-treatment      Residue (ppm)
                        treatments   interval (days)   Range           Average
                                                                            

    Almonds (whole)          1          129-157        3.11-0.18        1.60

    Apples                   1             7                            1.1

    Beans (whole)            1             6                            2.45

    Carrots (roots)        1-2             5           0.00-0.25        0.10

    Celery                   1             6           1.32-4.45        2.88

    Cherries                 1             7           1.2 -1.8         1.5

    Citrus (whole)         1-2             7           1.12-5.0         2.2

    Cottonseed               1           15-76         0.00-0.1         0.0

    Cucumbers                1             2           0.7 -2.3         1.6

    Figs                     1             7           1.86-5.32        3.92

    Grapes                   1             5           0.89-2.21        1.64

    Hops (green)             1             7           3.0 -7.9         5.4

    Lettuce                  2             2           1.10-9.87        5.59

    Mint (fresh hay)         1             7          35.8 -38.9       37.3

    Peaches                  1            14           4.9 -6.8         5.7

    (continued)
                                                                            
    Crop                Number of    Post-treatment      Residue (ppm)
                        treatments   interval (days)   Range           Average
                                                                            

    Pears                    2             7           1.1 -2.6         1.9

    Pineapples               4             5           0.0 -0.05       <0.05
    (pulp)

    Plums, prunes            1             9           0.06-0.16        0.11

    Raspberries              1             2                            2.7

    Spinach                  1             4           2.88-3.90        3.39

    Strawberries             1             3           0.13-0.90        0.37

    Tea, raw leaves          1             7          18.00-31.00      25.0
                             1             7           0.00-18.5        5.1

    Tomatoes                 1             1           0.5 -0.57        0.53

    Tropical fruits          5             4           0.0              0.0

    Walnuts                  1             7           0.57-0.92        0.86

    Water melons             1            20                            0.0
    (heart)
                                                                            
    
    Although dicofol is used for seed treatment no data on residues
    are available.
    
    Fate of residues

    In soils

    Dicofol is not used against pests in soil, but studies have been
    conducted to determine residues in soil resulting from spray
    application on crops. Dicofol residues in soil decrease rapidly at
    first, then more slowly. After three monthly applications of 2.56
    kg/ha, residues which had reached 1.13 ppm decreased to 0.25 ppm after
    636 days, (Rohm and Haas, 1967).

    In plants

    No information is available on metabolism in plants.

    In animals

    Cows fed 2 ppm dicofol for 71 days averaged from 0.23-0.40 ppm
    residues in their milk; when the same cows were fed 1.0 ppm, the level
    was not detectable. Two body fat samples taken at the end of the study
    contained 1.1 and 2.7 ppm (Zweig et al,, 1963).

    A "Blue" cow fed 5 ppm dicofol for 17 days, excreted a maximum of
    0.022 ppm dicofol per se and a maximum of 0.55 ppm dicofol plus
    metabolites in the milk. Plateau values were obtained about six days
    after start of dicofol feedings, and initial decay was also rapid.
    From the fifth day after withdrawal of dicofol, the amounts of
    material excreted were small, and the rate of decrease became low.

    In a "White" cow fed 30 ppm dicofol for three days, 0.68 ppm dicofol
    were found in kidney fat. Dicofol metabolites were found in kidney
    fat, liver, udder, brain, kidney lungs, blood, heart, omentum, bone
    marrow and muscles (Rohm and Haas, 1968).

    The feeding of dicofol to steers produces no significant residues in
    body fat at a level of 0.75 and 1.5 ppm. A feeding level of 3.0 ppm
    produces a definite residue of 0.32 ppm (Peoples, 1967).

    In tissues, milk and urine of a cow fed dicofol two groups of
    metabolites were found, one more polar than dicofol and one less
    polar. The metabolites of the first group were not identified. In the
    second group, two substances were identified as 1,1 bis
    (4-chlorophenyl) 2-chloro-ethylene and as 1,1 bis
    (4-chlorophenyl)-2,2-dichloro-ethylene. Sixty per cent of total milk
    residues is due to the latter substance, but it is suggested that it
    may be present in technical dicofol rather than result from the
    metabolic reduction of dicofol itself (Rohm and Haas, 1958). The
    latter two compounds were also found as metabolites of DDT.

    In storage and processing

    Residues on fruits are reduced by washing. Wash-water of oranges
    contained up to 0.05 ppm dicofol; 0.12-0.57 ppm remained in the peel.
    Unwashed raspberries contained 0.7-2.9 ppm dicofol, residues which
    were reduced to 0.7-1.4 after washing.

    Peeling reduces residues to values below 1 ppm:

                                               
                           
    Fruit                  Residue (ppm)
                      Peel             Pulp
                                               

    Citrus fruit      0.29-12.0        0-0.27

    Almonds           0-12.2           0-0.03

    Cucumbers         0.09-0.4         0-0.17

    Pineapples        5.5 -24.2        0-0.05

    Tropical fruit    4.2 -9.7         0
                                               

    (Rohm and Haas, private communication)

    In canned or frozen fruits dicofol was found only in 1.3 per cent of
    domestic samples, with an average ppm of 0.01. No dicofol was found in
    samples imported into the United States of America (USDA, 1968b).

    Brewed tea contained residues up to 0.0085 ppm. Under rigorous
    treatment, such as preparing instant tea from tea leaves, or
    distilling oil from mint leaves, dicofol may be broken down to
    p,p'-dichlorobenzophenone and chloroform (Rohm and Haas, private
    communication).

    Evidence of residues in food in commerce or at consumption

    Examination of market samples of food in the United States of America
    showed that dicofol residues were found in 0.7 per cent of domestic
    samples and 1.8 per cent of imported samples (Duggan and Dawson,
    1967a). In fruit the following concentrations were found in the United
    States of America from 1964 to 1967 (USDA, 1968b).

                                                                              
                             Domestic samples         Imported samples

    Fruit                 Incidence     Average     Incidence     Average
                          per cent.     (ppm)       per cent.     (ppm)
                                                                          

    Small fruit
    (strawberries,
    cherries, plums,         5.1         0.03          2.1         0.02
    grapes, cranberries,
    etc.)

    (continued)
                                                                          
                             Domestic samples         Imported samples

    Fruit                 Incidence     Average     Incidence     Average
                          per cent.     (ppm)       per cent.     (ppm)
                                                                          

    Large fruit
    (apples,                 8.6         0.02          3.3         0.01
    oranges, pears,
    peaches, etc.)
                                                                          
    
    Total diet studies in the United States of America from 1964 to 1967
    showed the following results (Duggan and Weatherwax, 1967b; USDA,
    1968b)

                                                    
    Year        Positive per cent.   Daily average
                   composites        intake (mg)
                                                    

    1964-1965         0.5               0.003

    1965-1966         3.7               0.002

    1966-1967         5.6               0.012
                                                    

    In 41.9 per cent of fruit-composites (apples, oranges, pears,
    peaches, etc.) dicofol was found in an average concentration of 0.031
    ppm (USDA, 1968b). Dietary intake of dicofol in the United States of
    America was 0.00004 mg/kg body weight/day in 1965; 0.00015 in 1966 and
    0.00018 in 1967 with an average of 0.00013 for three years (USDA,
    1968b).

    In Canada 60 restaurant meals were examined. Dicofol was found in an
    average concentration of 0.07 ppm in fruit and fruit salads, in
    legumes, 0.08 ppm whereas only traces were found in milk (Swackhamer,
    1965).

    Methods of residue analysis

    The methods are adequate for present purposes. Methods for
    colorimetric determination of dicofol are based on the method of
    Rosenthal, 1957. Dicofol is converted to chloroform with alkali.
    Chloroform is separated from extraneous materials and produces, with a
    water-pyridine-sodium-hydroxide mixture, a Fujiwara-type red dye,
    which is read at 535mµ against a pyridine blank. This method may be
    used for residue determination in plants, fruit and vegetables and has
    been simplified for analysis of milk (Gordon, 1963). Residues in crops

    and soil may also be determined, after chromatographical clean-up, by
    GLC using an electron capture detector (Morgan, 1967). An ultra-violet
    spectrophotometric method involves hydrolysing the dicofol to
    4,4'-dichlorobenzophenone (Gunther and Blinn, 1957). A method omitting
    the hydrolysis step and allowing the dicofol to be oxidized to
    non-interfering compounds permits the measurement of
    4,4'-dichlorobenzophenone present in mint-oil and mint-hay (Rohm and
    Haas, private communication).

    The sensitivity of the analytical procedures is 0.01 ppm.

    National tolerances

                                                                         
                                         Tolerance     Pre-harvest
         Country         Crop               (ppm)     interval (days)
                                                                     

    United States     Berries                5
    of America

    German Federal    Fruit, including
    Republic          grapes and hops        0.5          14

                      Vegetables             0.5

                      Beans                               14

                      Cucumbers                            4
                                                                     
    
    RECOMMENDATIONS FOR TOLERANCES AND PRACTICAL RESIDUE LIMITS

    Appraisal

    Dicofol is used exclusively to control phytophagous mites and although
    closely related to DDT has virtually no insecticidal activity. Its
    principal use is on apples, grapes and hops in Europe and North
    America, and tea (spot treatments only) in the Far East, with some
    minor use on citrus in these same areas. In North America, the rates
    and frequencies of application are generally greater than in other
    countries because of more serious mite problems. It is not used on
    animals. Dicofol is a technical product containing 82-88 per cent of
    the pure (active) compound. The impurities are known and their
    relative concentration are constant.

    The data available to the meeting were obtained solely in the United
    States of America and did not include information about uses elsewhere
    or figures for residues after such use, although figures were
    available for some imports into the United States of America.

    Very little is known about the metabolism of dicofol in plants and
    animals. In animals, dicofol can be found as such together with
    various metabolites. Precise figures for the amounts of these
    compounds in experimental plants or animals, either from a single or
    from repeated applications, have not been published.

    1,1 bis (4-chlorophenyl) 2-chloro-ethylene and 1,1 bis
    (4-chlorophenyl-2,-2-dichloro-ethylene) have been identified as
    metabolites in animals. However, the latter may be present in the
    technical product used. In mint oil and tea, 4,4-dichlorobenzophenone
    has been identified.

    The literature includes methods of residue analysis which measure
    dicofol alone or together with some breakdown products. For the
    determination of dicofol alone the sensitivity is 0.01 ppm. However,
    no referee method of analysis has been evaluated.

    Recommendations

    Temporary tolerances

    The following temporary tolerances (to be in effect until 1972) are to
    apply to raw agricultural products moving in commerce unless otherwise
    indicated. In the case of fruit and vegetables the tolerances should
    be applied as soon as practicable after harvest and in any event prior
    to actual retail to the public. In the case of commodities entering
    international trade, the tolerances should be applied by the importing
    country at the point of entry or as soon as practicable thereafter.

         Fruit, vegetables, hops, tea (from a
         particular estate, for blending only)      5 ppm

         Tea (blended)                              1 ppm

    Further work or information

    Required before 30 June 1972:

    1. Data from countries other than the United States of America on the
       required rates and frequencies of application, pre-harvest 
       intervals, and the resultant residues.

    2. Information on the nature of the terminal residues in plants,
       animals, and their products.

    Desirable:

    1. Collaborative studies to establish a referee method.

    2. Comparative metabolic studies in animals and man, including adrenal
       function studies after oral administration.

    REFERENCES

    Brown, J. R. (1964-65) Toxicologic studies on the effects of kelthane
    in the diet of albino rats on reproduction (first interim, second
    interim and final reports). Departments of Physiological Hygiene,
    University of Toronto. Unpublished reports

    Brown, J. R. (1967a) Toxicological studies on
    2,2-bis-chlorophenyl-2,2,2-trichloroethanol, kelthane. Brown
    Biological Laboratories Ltd. Unpublished report

    Brown, J. R. (1967b) Three-generation reproduction study on rats
    receiving technical kelthane in their diet. Department of
    Physiological Hygiene, University of Toronto. Unpublished report

    Duggan, R. E. and Dawson, K. (1967a) Pesticides: A report on residues 
    in food. FDA Papers, 1: 2-5

    Duggan, R. E. and Weatherwax, J. R. (1967b) Dietary intake of
    pesticide chemicals. Science, 157: 1006-1010

    Gordon, C. F., Haines, L. D. and Martin, J. J. (1963) Acaricide
    residues: An improved method for kelthane residue analysis with
    applications for determination of residues in milk. J. Agr. Food
    Chem., 11: 84-86

    Gunther, F. A. and Blinn, R. C. (1957) Ultraviolet spectrophotometric
    microdetection of the acaricide 4,4'-dichloro-alpha-(trichlormethyl)
    benzhydrol (SW 293). J.Agr. Food Chem., 5: 517-519

    Larson, P. S. (1957) Two-year study on the effect of adding kelthane
    to the diet of rats. Medical College of Virginia. Unpublished report

    Larson, P. S. (1965) Toxicologic study on the effect of adding
    dichlorobenzophenone to the diet of rats for a period of three months.
    Department of Pharmacology. Medical College of Virginia. Unpublished
    report

    Morgan, N. L. (1967) The identification and relative retention times
    of p,p'-kelthane and its breakdown product p,p'-dichlorobenzophenone
    using GLC. Bull. environ. Contam. Toxicol., 2: 306-312

    Peoples, S. A. (1967) Residues in the body fat of steers fed kelthane
    in their ration. Dept. of Physiol. Sci. School of Veterinary Medicine,
    University of California, Davis. Unpublished report

    Rohm and Haas. (1958) Research Reports 13-27 and 11.141. Robin and
    Haas Co.

    Rohm and Haas. (1967) RAR Memorandum 521. Rohm and Hass Co.

    Rohm and Haas Co. (1968) Kelthane. Unpublished report

    Rosenthal, J., Frisone, G. J. and Gunther, F. A. (1957) Colorimetric
    microdetermination of the acaricide
    4,4'-dichloro-alpha-(trichloromethyl) benzhydrol (FW-293).J. Agr. Food
    Chem., 5: 514-517

    Smith, R. B. Jr, Larson, P. S., Finnegan, J. K., Haag, H. B., 
    Hennigar, G. R, and Cobey, F. (1959) Toxicologic studies on 2,2
    bis-(chlorophenyl)-2,2,2-trichloroethanol (kelthane). Toxicol. appl.
    Pharmacol., 1: 119-134

    Swackhamer, A. B. (1965) Report on pesticide residues in restaurant 
    meals in Canada. Food and Drug Directorate, Department of National
    Health and Welfare, Ottawa, Canada. Pesticide Progress, 3: 108-114

    USDA. (1968a) Agricultural Economic Report 131

    USDA. (1968b) United States Department of Health, Education and
    Welfare. The regulation of pesticides in the United States

    Verschuuren, H. G., Kroes, R. and den Tonkelaar, E. M. (1968)
    Toxiciteitsonderzoek met kelthaan bij ratten gedurende 90 dagen
    (Toxicity experiment with kelthane in rats of 90 day duration).
    National Institute of Public Health, Utrecht. Unpublished report

    Zweig, G., Pye, E. L. and Peoples, S. A. (1963) Residues in butter fat
    and body fat of dairy cows fed at two levels of kelthane (1.0 and 2.0
    ppm). J. Agr. Food Chem., 11: 72-79
    


    See Also:
       Toxicological Abbreviations
       Dicofol (ICSC)
       Dicofol (AGP:1970/M/12/1)
       Dicofol (WHO Pesticide Residues Series 4)
       Dicofol (Pesticide residues in food: 1992 evaluations Part II Toxicology)
       Dicofol (IARC Summary & Evaluation, Volume 30, 1983)