IPCS INCHEM Home


    CHLOROTHALONIL        JMPR 1974

    IDENTITY

    Chemical name

         2,4,5,6-tetrachloro-1,3-benzenedicarbonitrile

    Synonyms

         2,4,5,6-tetrachloroisophthalonitrile, DAC-2787(R), Daconil
         2787(R).

    Structural Formula

    CHEMICAL STRUCTURE 2

     Other Information on Identity and Properties

         Molecular weight:        265.9

         State:                   White crystalline solid

         Melting point:           250-251C

         Boiling point:           350C at 760 mm Hg

         Vapour Pressures:

              Vapour Pressures        Temperatures
                  mm Hg                   C

                 < 0.1                     40
                   9.2                    170
                  17.4                    191
                  27.3                    212
                  43.3                    230

         Solubility:

         Solvent                          % by weight at 25C

         acetone                                   2
         AR-60                                     6
         AR-55                                     3
         cyclohexanone                             3
         dimethyl sulfoxide                        2
         dimethyl formamide                        3
         kerosene                                 <1
         mineral seal oil                         <1
         methyl ethyl ketone                       2
         xylene                                    8
         water                                     0.6 ppm

    Stability:    Stable under normal temperatures of storage. Chemically
                  stable in alkaline or acidic aqueous media. Stable to
                  ultraviolet radiation.

    Purity of technical material:

    Ingredient                              Range (%)      Average (%)

    2,4,5,6-tetrachloro                     95.6-98.5      97.6
    -1,3-benzenedicarbonitrile

    tetrachlorophthalonitrile                  -           <0.1

    tetrachloroterephtholonitrile           <0.1-1.6        0.5

    pentachlorobenzonitrile                  0.5-2.5        1.2

    partially chlorinated                    0.2-1.0        0.4
    dicyanobenzenes (all isomers)

    unchlorinated dicyanobenzenes           <0.1-1.6        0.3
    (all isomers)

    insolublein xylene                      <0.1-1.0        0.2

    EVALUATION FOR ACCEPTABLE DAILY INTAKE

    BIOCHEMICAL ASPECTS

    Biotransformation

         Following acute oral administration to dogs, chlorothalonil (500
    mg/kg) was rapidly excreted, mainly unchanged, in the faeces.
    Approximately 90% of the administered dose was found in faeces within
    72 hours. No chlorothalonil or metabolites were found in blood or
    urine when examined using methods having a sensitivity of 1 ppm for
    blood and 0.1 ppm for urine (Skinner and Stallard, 1967). Urine and
    faecal samples were collected from dogs and rats fed chlorothalonil in
    the diet for approximately ten months. In both species excretion of
    unchanged chlorothalonil in faeces was proportional to the
    concentration in the diet. Rats fed a dose of 0.15% excreted 21% in
    the faeces; those fed 1.5% excreted 67%; dogs fed 0.15% excreted
    9-15%; those fed 1.5% excreted 67-71%; and those fed 3% excreted
    86-86% unchanged chlorothalonil in the faeces. Assays based on total
    chlorine content established that recovery in faeces of chlorothalonil
    consumed in the diet was complete. The total chlorine assay and
    incomplete recovery of chlorothalonil or metabolites from faeces
    suggests a biotransformation product excreted with the faeces and not
    identified.

         Three male and three female weanling rats were fed for 22 days at
    5000 ppm in the diet. They were orally administered 14C
    chlorothalonil at a dose of 2.8  Ci/rat. The dose (1.5 mg) did not
    significantly increase the daily input of chlorothalonil. After 264
    hours, 95% of the material was recovered, predominantly in faeces
    (88%) and urine (5%) with none detected in tissues or as CO2.
    Chlorothalonil was not rapidly removed from the animals body (43% in
    24 hours; 64% in 48 hours, and 76% in 72 hours) (Ryer and Sullivan,
    1966).

         Studies on the transformation of chlorothalonil in soil (Stallard
    and Wolfe, 1967; Duane, 1970) have isolated and identified a
    metabolite of chlorothalonil as
    4-hydroxy-2,5,6-trichloroisophthalo-nitrile (DAC-3701).

    CHEMICAL STRUCTURE 3



    Residues and biotransformations of chlorothalonil in farm animals,
    plants and soil are discussed in the sections "Residues resulting from
    supervised trials" and "Fate of residues."

    Pharmacological effects

         Chlorothalonil has a cathartic effect which is apparently due to
    irritation of the gastro-intestinal tract. This was evidenced by a
    dose related decrease in urinary volume and increase in urine specific
    gravity. Studies using rats subjected to levels of 0, 1500, and 15,000
    ppm in the diet showed a dose related decrease in retention of an
    orally administered dye indicative of a potential laxative effect.
    Some experiments utilizing selected animals on feeding studies
    suggested an increase in water intake, a decrease in urine volume, and
    an increase in fecal moisture which was dose related especially at
    high concentrations in the diet (Paynter, 1967c; Skinner and Stallard,
    1967).

         Chlorothalonil administered orally at one gm/kg to mice increased
    intestinal mobility as measured by the percentage of the small
    intestine traversed by a charcoal marker within a selected time
    interval. The laxative action of chlorothalonil was significantly
    reduced by pre-treatment with corn oil but not with atropine or
    papaverine (Teeters, 1966).

         Residue analyses of tissues and organs of animals fed
    chlorothalonil in the diet indicated that there was no accumulation in
    any body organ. Small quantities of the 4-hydroxy metabolite were
    observed in liver and kidney with no parent compound noted (Wolfe and
    Stallard, 1968a).

    TOXICOLOGICAL STUDIES

    Special studies on mutagenicity

    Mouse

         The potential genetic hazard of chlorothalonil was evaluated in
    mice by the host mediated assay, in vivo cytogenic testing and the
    dominant lethal test. The compound did not produce any measurable
    mutagenic response when evaluated in vitro against eight indicator
    organisms of the Salmonella typhimurium, histidine auxotroph tester
    strains which can be reverted by both base substitution and frame
    shift mutagens. In these tester strains, both repair deficient and
    repair competent strains were used. When the tester strains were
    inoculated into animals treated with chlorothalonil daily for five
    days at an oral dose of 6.5 mg/kg (10 animals per treatment), no
    increase in the number of mutations over the control were found. The
    positive control, dimethylnitrosamine, increased mutation frequency in
    mice (ip, 4 mg/kg).

         Following oral administration of chlorothalonil daily for five
    days at 6.5 mg/kg, an examination of bone marrow for the presence of
    cells with micronuclei indicative of cytogenic abnormalities was
    negative.

         Treated orally for five days at 6.5 mg/kg, two male mice were
    mated sequentially with untreated females in a standard dominant
    lethal test. No adverse effect on fertility, implantation or foetal
    mortality was observed. A positive control (triethylene melamine),
    administered ip at 0.5 mg/kg, produced an increase in early death at
    the post meiotic period. At the concentration tested in the three
    procedures used, chlorothalonil did not produce mutagenic effects
    (Legator, 1974).

    Special studies on reproduction

    Rat

         Groups of rats (10 males and 20 females per group) were fed
    chlorothalonil in the diet at levels of 0, 0.15, 1.5, and 3.0% in a
    standard three generation, two litters per generation, reproduction
    study. Because of food refusal and poor weight gain, the test using
    the two higher levels was interrupted. After the first litter of pups
    (F1a), the high level of treatment which had been reduced to 2% was
    discontinued and a new dose level of 0.5% (with another control group)
    was substituted. The full three generation reproduction test was
    ultimately performed using dosage levels of 0, 0.15, 0.5 and 1.5% in
    the diet. At the high discontinued dose level there was a significant
    growth depression in nursing litters and an emaciated appearance in
    the pups at weaning. There was also a reduction of fertility and
    lactation at this maternally toxic level.

         Growth suppression in pups was noted at all test intervals
    through all three generations. It was considered that while smaller,
    pups were still within a normal weight range, no malformations were
    observed and reproduction indices were not affected. Necropsy
    examination performed on parents and on the terminal F3b generation
    revealed gross changes in the kidneys and in the G.I. tract. Gross
    changes included enlargement and distention of the caecum and colon,
    soft faecal matter, and occasional thickening of the stomach wall.
    Microscopic changes were also evident in stomach and kidney.
    Chlorothalonil examined at maternally toxic dietary levels did not
    have an effect on reproduction in the rat (Paynter, 1967a).

         Groups of rats (10 males and 20 females per group) were fed the
    chlorothalonil metabolite, 4-hydroxy 2,5,6-trichloroisophthalonitrile,
    in the diet at levels of 0, 10, 50, 100 and 200 ppm for 70 days prior
    to mating in 3 generation, one litter per generation, reproduction
    study. Growth was reduced, clinical chemistry changes (increased SGPT)
    were noted and gross and microscopic changes observed at 200 mg/kg.
    Reproduction was affected at 100 mg/kg as evidenced by reduced litter

    size and weight as well as decreased survival. Milk analysis revealed
    the 4-hydroxy metabolite in the stomach curd of 7 day pups in a
    concentration comparable to that fed to the parents. No effects were
    noted at 50 mg/kg on the reproduction parameters recorded (Hastings
    and Jessup, 1974).

    Special studies on teratogenicity

    Rabbit

         Groups of 8 pregnant rabbits were administered chlorothalonil
    from day 8 to day 16 of gestation. The initial dose on days eight and
    nine (0, 180, and 375 ml/kg/day) was reduced because of decreased food
    consumption to 0, 62.5, and 31.25 mg/kg/day respectively for the
    remainder of the study. Deaths were noted in the treated groups and
    there was a severe weight loss with the treated dose. There was no
    apparent effect on the embryo and while there was a considerable
    effect on the adults, chlorothalonil is not considered to be a
    teratogen (Paynter, 1966).

    Acute toxicity

    TABLE 1.  Acute toxicity of chlorothalonil

                                                                            

    Species       Route          LD50 mg/kg        References
                                                                            

    Rat           Oral           10,000            Powers, 1965
                                                   Doyle and Elsea, 1963

                  Inhalation     4.7 mg/kg         Beasley and Leong, 1965

    Dog           Oral           > 5,000           Paynter, 1965a

    Rabbit        Dermal         10,000            Doyle and Elsea, 1963

                                                                            

         Signs of poisoning include depression, diarrhoea and an unkempt
    appearance. 3 mg crystalline technical product applied to the
    conjunctival sac produced a mild irritation which was probably
    mechanical (Doyle and Elsea, 1963).

         Acute studies of the 4-hydroxy metabolite showed an oral LD50 in
    male rats of 332 mg/kg. An LD50 could not be found in dogs because of
    emesis at all dose levels (Wazeter, 1971; Wazeter and Goldenthal,
    1972).

    Short term studies

    Rat (inhalation)

         Groups of rats (15 males and 15 females per group) were exposed
    to chlorothalonil by inhalation 6 hours/day, 5 days/week for three
    weeks. This exposure was at a mean concentration of 12.2 mg/l at a
    respirable particle size range of 1-5 microns (91%), 6-25 microns
    (9%), and 26-40 microns (<1%). There were no deaths or untoward
    behaviour among any of the animals. Growth was normal, and gross and
    histological examinations did not reveal any compound-related effects
    (Holliday et al., 1973).

    Rat (feeding)

         Groups of rats (10 males and 10 females per group) were fed diets
    containing 5000 ppm chlorothalonil for 4 weeks. In an attempt to
    determine the effect of chlorothalonil on absorption and utilization
    of protein, fat, and amino acids, 10 amino acids varying in
    concentration from 0.2 to 0.9% were added to the diet. On the basis of
    a ten week feeding of dietary levels containing chlorothalonil plus
    casein and corn oil or chlorothalonil plus amino acids, it was
    concluded that chlorothalonil did not interfere directly with the
    absorption and utilization of protein, fat, or amino acids. The
    reduction in weight gain predominantly noted at this high feeding
    level of chlorothalonil was presumably due to catharsis and not to
    absorption difficulties (Paynter, 1967b).

         Groups of rats (35 males and 35 females per group) were fed
    chlorothalonil in the diet at levels of O, 250, 500, 750 and 1500 ppm
    for 22 weeks. No mortality was observed and appearance and behaviour
    were normal. Growth was slightly reduced at all feeding levels in
    males and at 750 and 1500 ppm in the females. Food consumption was
    comparable in all groups.

         Haematological and urine analysis values were within normal
    limits. An increase in liver-kidney weight was noted especially in
    males at the two higher dosage levels. Kidney alterations,
    characterized by irregular swelling of the tubular epithelium,
    epithelial degeneration, and tubular dilation were seen in all test
    groups with the males affected to a greater degree than females
    (Blackmore and Shott, 1968).

         Groups of rats (10 males and 10 females per group) were
    administered chlorothalonil by oral gavage at dosage levels of 0, 0.5,
    1.0, 2.0, 4.0 and 8.0 gm/kg five days a week for 13 weeks.
    Administration of 4.0 gm/kg resulted in a slight, non-significant
    reduction of growth, poor general condition, and reduced white blood
    count. No significant findings were observed with regard to
    elucidating the potential renal toxicity problem observed in longer
    studies. Studies performed in this test indicated that chlorothalonil

    did not result in a specific abnormality. It was suggested there might
    be a decrease in resistance and defence mechanisms, making rats more
    susceptible to naturally occurring infections (Sterner and Loveless,
    1963).

    Rabbit (dermal)

         Groups of albino rabbits were daily administered a 75%
    formulation of chlorothalonil to either intact or abraded skin, 5 days
    per week, for three weeks. (Groups of two males and two females served
    as controls; 5 males and 5 females were treated groups.) Animals were
    administered chlorothalonil at dose levels of 0, 500, or 1000 mg/kg.

         Repeated application of chlorothalonil to the intact or abraded
    skin of rabbits resulted in dose-related dermal irritation consisting
    of erythema, atonia, and desquamation. The degree of irritation was
    more severe to the abraded skin. A number of animals at the high level
    showed atypical haematological values in conjunction with diarrhoea
    and/or dermal irritation as a result of application of chlorothalonil.
    As might be expected, histological examination of the skin revealed
    the presence of a moderate degree of acanthosis particularly in the
    abraded skin areas, hyperkeratosis, rarely focal parakeratosis, and
    slight to moderate leucocytic infiltration. No pathological
    abnormalities were noted in other tissues (Paynter, 1965b).

    Dog

         Groups of dogs (4 males and 4 females per group) were fed
    chlorothalonil in the diet at 0, 250, 500 and 750 ppm for sixteen
    weeks. There was no mortality and no apparent effect on behaviour or
    growth in any of the dogs tested. Haematological, clinical chemistry
    and urine analysis values were normal with the exception of slightly
    raised PBI values at high dose levels in females. Gross and
    microscopic examination of organs and tissues did not reveal any
    compound-related abnormalities (Paynter and Murphy, 1967).

         Groups of beagle dogs (8 males and 8 females per group) were fed
    chlorothalonil in the diet for two years at dosage levels of 0, 60 and
    120 ppm. There were no effects noted on behaviour and growth over the
    course of the study. Clinical chemistry values including haematology,
    biochemistry and urine analysis were comparable to the controls at all
    levels of feeding. Gross and microscopic examination of tissues and
    organs performed on animals sacrificed at 12 months indicated a
    compound-related change in the kidney. Further examination of tissues
    and organs at 24 months did not show chlorothalonil-related
    abnormalities. A slight degree renal tubule vacuolation in two of four
    animals at 120 ppm after two years in the absence of other changes
    (urinalyses values) was considered questionable especially as a slight
    degree of vacuolation was noted in control as well as other treated
    animals (Holsing and Voelker, 1970).

    Long term studies

    Rat

         Groups of rats (35 males and 35 females per group; 70 males and
    70 females were utilized for the control group) were fed
    chlorothalonil in the diet for two years at levels of 0, 1500, 15,000,
    and 30,000 ppm. Because of food refusal and poor weight gain at the
    two highest dose levels, the compound was discontinued within one
    week. The rats were fed basal diets for two weeks, after which
    chlorothalonil administration was resumed and dietary levels increased
    until the end of nine weeks when the intermediate group was fed 15,000
    ppm. This intermediate group was then continued for the remainder of
    the two year period. The high dose level was increased at biweekly
    intervals until the sixteenth week when the group treatment was
    terminated.

         Growth suppression was observed at all levels and was
    dose-related. This reduction in growth was reversible, as noted when
    the high dose group recovered after being removed from the diet
    containing chlorothalonil and fed a control diet. Haematological and
    urine analysis values were within the normal range. PBI values were
    generally reduced. Chlorothalonil had a cathartic action as evidenced
    by increased water consumption and increased weight of faeces. Organ
    weight and organ-to-body weight ratios increased for the liver and
    kidney at the higher levels. Microscopic examination of the thyroid,
    stomach, kidney, and liver revealed pathological changes.

         A distinct alteration was produced in the squamous epithelium of
    the cardiac portion of the stomach in most of the male and female
    rats. The squamous epithelium was rather consistently thickened and
    covered by a layer of keratin. In the kidneys of the higher dose
    animals, the epithelium of the proximal convoluted tubules was paler
    than usual and uniformly enlarged. At the termination of the study the
    thyroid glands of the 15,000 ppm animals exhibited an increase in
    epithelial pigmentation. Changes in the stomach at all levels included
    acanthosis and hyperkeratosis.

         At 13 weeks, the kidneys of both sexes fed 1500 ppm were similar
    to those of the control. Gross and microscopic pathological
    differences especially in males were, however, observed at the one and
    two year intervals at this dose level. Liver changes, predominantly in
    females, were characterized by an enlargement of the cells in the
    nuclei, particularly in the central lobular area, and the formation of
    large multinucleated cells in the pericentral area.

         No increase in tumor formation was evident. Alterations in the
    thyroid and the stomach appeared to be reversible; the alterations in
    the liver were slight and confined to the females; the alterations in
    the kidney were not reversible (Paynter, 1967c).

         When samples of urine and faeces were taken for metabolism
    studies (Skinner and Stallard, 1967) from rats from this long-term
    study, data were reported for the volume of urine collected from the
    rat over the period of sampling. The volume of urine was found to
    decrease proportionately as the dietary dose increased. Conversely,
    there appeared to be an increase in faecal excretion although the food
    consumption remained constant.

         Groups of rats (15 males and 15 females per group) were fed
    chlorothalonil in the diet at levels of 0, 500, 1000, and 5000 ppm for
    76 weeks. There were no apparent effects on behaviour and growth with
    the exception of animals at the high level where food refusal was
    noted. In a separate paired feeding study, there was no effect of
    chlorothalonil on growth or behaviour. Increased liver weight, kidney
    weight, and kidney to body weight ratio was apparent at the higher
    test intervals. Microscopic examination indicated chiefly tubular
    hypertrophy, epithelial irregularity and vacuolation. The degree of
    kidney damage was dose-related and appeared to increase in severity in
    males. No other adverse effects were noted in this study (Paynter and
    Busey, 1967).

         Groups of rats (35 males and 35 females per group) were fed
    chlorothalonil in the diet at levels of 0 and 5000 ppm for two years.
    Growth suppression in both males and females was evident throughout
    the two year period. Survival was not affected and haematological,
    biochemical and urine analysis values were within a normal range. A
    cathartic effect of chlorothalonil was suggested as evidenced by
    increased water consumption and increased weight of faecal excretion.
    Organ weight and organ-to-body weight ratios, were increased for the
    kidney and caecum. Histological examination of the kidneys at one year
    again showed evidence of tubular hypertrophy and epithelial
    alterations. No significant effects were noted with other tissues and
    organs (Paynter and Crews, 1967).

         Groups of rats (50 males and 50 females per group) were fed
    chlorothalonil in the diet at levels of 0, 4, 10, 20, 30, 40 and 60
    ppm for two years. No effects were seen on appearance, behaviour,
    growth, food consumption or mortality. Haematological, clinical
    chemistry and urine analysis values were normal. Animals sacrificed at
    13, 52 and 104 weeks were examined for gross and microscopic defects.
    A major lesion observed in studies at higher dose levels, necrosis of
    the epithelial lining of the proximal tubules in the deep portion of
    the cortex, was observed sporadically in this experiment at the one
    and two year intervals. Vacuolation observed at 13 weeks predominantly
    in females at 4 mg/kg and above, was not noted at later intervals.
    There was no dose-related histological effect noted. A no-effect level
    in this study would be 60 ppm (Holsing and Shott, 1970).

    COMMENT

         Chlorothalonil is rapidly excreted primarily unchanged. A
    metabolite in plants and animals, the 4-hydroxy compound, is more
    acutely toxic and more persistent than the parent molecule.

         Studies performed at maternally toxic levels showed no effects of
    chlorothalonil on reproduction. Growth retardation of pups was
    believed to be the result of ingestion of treated diet. The results of
    a reproduction study with the 4-hydroxy metabolite were negative at
    low levels although secretion into the milk was observed. The results
    of mutagenesis and teratogenesis tests were negative within the
    parameters of the defined studies. Results of long and short term
    chlorothalonil studies at high dietary levels to rats and dogs suggest
    a toxicological problem associated with the kidney. Kidney changes
    were characterized microscopically as hypertrophy, dilation,
    cytoplasmic vacuolation, and hyperplasia of the epithelial cells of
    proximal tubules and grossly as enlarged, greenish-brown granular
    kidneys. No clinical effects were noted although some renal pathology
    was suggested by a reduced urine volume. The significance of
    histological changes in the kidney at lower dose levels needs
    clarification.

         No direct observations in man were reported.

         Low-level feeding studies in rat and dog showed no effects in rat
    at 60 ppm and in dog at 120 ppm forming the basis for allocating a
    temporary ADI for man.

    TOXICOLOGICAL EVALUATION

    Levels causing no toxicological effect

         Rat: 60 ppm in the diet, equivalent to 3.0 mg/kg bw.

         Dog: 120 ppm in the diet, equivalent to 3.0 mg/kg bw.

    ESTIMATE OF TEMPORARY ACCEPTABLE DAILY INTAKE FOR MAN

         0 - 0.03 mg/kg bw.

    RESIDUES IN FOOD AND THEIR EVALUATION

    USE PATTERN

         Chlorothalonil is a fungicide with broad spectrum activity. It is
    effective against many fungus diseases which damage vegetables (rusts,
    anthracnose, downy mildews, leaf spots, soft rot, leaf blight, scab,
    early blight, late blight, pink rot, powdery mildew, etc.); agronomic
    crops (downy mildew, leaf spots, leaf rust, brown spot, blue mold,
    etc.), small fruits (anthracnose, gray mold powdery mildew, black rot,
    downy mildew, ripe rot, leaf scorch, leaf blight, etc.); tree fruits
    and nuts (scab, powdery mildew, black rot, white rot, fly speck, sooty
    blotch, bitter rot, fire blight, blossom blight, leaf spot, melanose,
    canker, greasy spot, leaf curl, etc.); tropical crops (signatoka,
    black pod, coffee berry disease, leaf disease); turf and ornamental
    crops. It has been tested on over 60 crops throughout the world and is

    non-phytotoxic to most of these crop plants (Diamond Shamrock, 1974).
    Literature available to the meeting further confirmed the fungicidal
    effectiveness of chlorothalonil in both field and glasshouse tests
    (DiDaris et al., 1965; Turner et al., 1964; Turner and Lamont, 1965).

         Chlorothalonil is available as a wettable powder, dust and in
    tablet form. The following formulations are produced.

         Daconil 2787 W-75, a 75% wettable powder designed to be mixed
         with water and applied as a spray. Registered for use in the
         U.S.A. for turf and ornamentals and in 20 other countries for use
         on a variety of crops (Diamond Shamrock, 1971).

         Bravo W-75, a 75% wettable powder formulation registered for use
         in the U.S.A. on agricultural crops.

         Termil tollets - a tollet containing 8 g active ingredient
         formulation to be vaporized by a suitable heat source at
         temperatures of 315-425C in a shallow pan.

         Exotherm Termil - a powder containing 20% active ingredients
         packaged in 100 g cans. Application is made by removing the lid
         from the can and igniting the powder to generate smoke.

         The recommended application rates for various crops using the
    wettable powder formulation Daconil 2787 W-75 are as follows:

                                                   Application
    Crop                                               rate

    Vegetable crops (asparagus, beans,             1000-3400 g/ha
    broccoli, Brussels sprouts, cabbage,
    cantaloupe, carrot, cauliflower, celery,
    chinese cabbage, corn (sweet), pumpkin,
    squash, tomato, turnip, watermelon)

    Agronomic crops (hop, peanut, spearmint,       1000-2300 g/ha
    sugar beet, tobacco)

    Small fruits (blackberry, blueberry,           120-480 g/100 litres
    currant, grape, raspberry, strawberry)

    Tree fruits and nuts (apple, cherry,           120-360 g/100 litres
    grapefruit, lemon, orange, peach,
    pecan, pear, tangerine)

    Tropical crops (banana, cacao, coffee,         240-480 g/100 litres
    rubber)

         Thermal dusting with Termil tollets or Exotherm Termil is used to
    control a variety of diseases of ornamentals and vegetable crops
    (asparagus, snap beans, cucumbers and tomatoes) grown in glasshouses,
    at an application rate of 7-7.5 g a.i./100 cu.m. of space.

    RESIDUES RESULTING FROM SUPERVISED TRIALS

         Residue data are available from supervised trials on a variety of
    fruits and vegetables (Diamond Shamrock, 1974). A summary of much of
    this information appears in Table 2 together with details of rates and
    number of applications and pre-harvest intervals used. The majority of
    these data are from trials in the U.S.A. with a few trials from
    Canadian locations.

         Chlorothalonil residues were detected on most aboveground crops
    at the time of harvest. The higher residues occurred on leafy
    vegetables, e.g. lettuce, escarole, chicory, spinach, celery and
    crucifers including collards and kale, with generally lower levels on
    melons, fruits and root crops. High residues were detected also in
    lima bean plants, sugar beet tops and peanut hay which may be used for
    animal feeds. The amount of fungicide applied, time interval between
    last application and harvest, surface area, weight and surface
    structure of the crop are factors that affect the level of the
    residue. The residue level diminishes with time after application.

         Glasshouse trials of thermal dusting were carried out on
    cucumbers, leaf lettuce and tomatoes. The residue data are summarized
    in Table 3. In general, the residue levels were low, <4 mg/kg,
    following a pre-harvest interval of 1 day.

         Only negligible residues of the metabolite
    4-hydroxy-2,5,6-trichloro-1,3-benzenedicarbonitrile, DAC 3701 (see
    "Biotransformation" and "Fate of Residues"), were detected in most
    commodities. Only in the case of peaches were significant residues
    (up to 0.5 mg/kg) detected routinely. Peanut hay and lima beans
    (including pods) also sometimes showed residues of 0.5-1 mg/kg.

         A series of experiments were performed to see if chlorothalonil
    or the 4-hydroxy metabolite could be a residue in meat or milk from
    feeding these products to cows. Groups of cows (4 cows/group) were fed
    chlorothalonil plus the 4-hydroxy metabolite at dosage levels of 0, 25
    ppm chlorothalonil plus 0.2 ppm metabolite, 75 ppm chlorothalonil plus
    0.6 ppm metabolite, and 250 ppm chlorothalonil plus 2.0 ppm metabolite
    for 30 days. Half the animals were sacrificed at the end of the test
    and half after a 32 day recovery period. At a sensitivity of 0.02 ppm,
    no chlorothalonil was found in milk (Wolfe and Stallard, 1969). A
    small quantity of the metabolite was noted in milk: details are given
    in Table 4. Residues in the milk reached maxima of 0.20, 0.26 and 0.78
    respectively at the 3 feeding levels after about 18 days (Wolfe and
    Stallard, 1970a). At the 30-day interval small residues of
    chlorothalonil and the metabolite were seen in muscle, fat, liver and
    kidney. Residues of the metabolite were respectively 0.51, 2.1, 0.93
    and 3.7 mg/kg at the highest feeding level. No residues were seen
    after the 32 days recovery period (Wolfe and Stallard, 1970b).



    
    TABLE 2a.  Residues of chlorothalonil from supervised trials.

                                                                                                                                  

                             Application                                                              Residues. mg/kg
                             Rate,                  Pre-harvest      No.                                             Range
                             a.i.,                  interval         of          Determinations       Total          (means
    Crop                     kg/ha       No.        (days)           trials      per trial            range          per trial)
                                                                                                                                  

    Carrots                  1.3         12         13               1           9                    0-0.7          0.15
      (tops removed)         1.7         9          0-7              3           8-9                  0.1-3.6        0.3-2.8
                             1.9         9          2                1           6                    1-8-5.8        4.4
                             2.5         7-10       0-7              4           6-8                  0-8.7          0.02-7.3

    Broccoli                 1.3         9          1-15             3           9                    0.01-9.0       0.01-6.0
                             2.5         6-8        0-12             4           5-9                  0-2.6          0-1.4

    Brussels
    sprouts                  1.3         4-5        0-21             4           9-18                 0.7-3.5        1.7-2.5
                             1.7         5          8                1           3                    4.6-5.3        5.0
                             2.5         4-8        0-18             2           3,5                  0.9-4.3        1.0-3.5
                             3.4         5          0-14             4           2-5                  2.0-11         3.2-11

    Cabbage                  1.7         5-9        0                2           3,7                  0.8-2.7        1.5-1.6
                             2.5         7-9        0-7              5           5-9                  0-0.2          <0.01-0.4

    Cauliflower              0.8         2          33               1           9                    0.03-0.09      0.06
                             2.5         2-10       0-33             5           7-9                  0-1.9          0.02-1.2

    Cucumber                 0.8         4-9        0-6              5           6-9                  0-1.1          0.05-0.9
                             1.3         4-9        0-6              4           6-18                 0-1.2          0.1-0.8
                             1.7         1-12       0-7              12          3-23                 0-2.5          0.2-2.4
                             2.5         4-13       0-14             12          6-9                  0-2.8          0.01-1.8

    Summer squash            0.8         6-9        0-3              2           5,6                  0.07-0.9       0-2-0.3
                             1.3         6-9        0-3              2           6                    0.2-1.2        0.45-0.9
                             1.7         1-9        0-9              9           3-25                 0-2.0          0-1-1.3
                             2.5         5          0-14             3           3                    0.06-0.25      0.07-0.2

    TABLE 2a.  (Cont'd.)

                                                                                                                                  

                             Application                                                              Residues. mg/kg
                             Rate,                  Pre-harvest      No.                                             Range
                             a.i.,                  interval         of          Determinations       Total          (means
    Crop                     kg/ha       No.        (days)           trials      per trial            range          per trial)
                                                                                                                                  

    Cantaloupe
    (whole melons)           1.7         7-11       0-14             4           5-17                 0-1.1          0.02-0.6
                             2.5         7          4                1           12                   0.7-1.8        1.1

    (pulp)                   2.5         7          0                1           5                    0.05-0.1       0.07

    Muskmelon
      (pulp)                 1.3         11         0                1           3                    0              0

      (rind)                 1.3         11         0                1           3                    0.03-0.2       0.1

      (pulp)                 2.5         11         0                1           3                    0              0

      (rind)                 2.5         11         0                1           3                    1.4-1.7        1.5

    Honeydew melon           1.7         10         0-14             3           5-8                  0-1.6          0.03-0.7
                             2.5         7          0-14             3           6                    0.07-0.4       0.1-0.25

    Winter squash
      (whole)                1.7         5-10       0                2           3                    0.04-1.7       0.05-1.4

      (pulp)                 1.7         5-10       0                2           3,8                  0              0

      (whole)                2.5         7          7                1           3                    0.8-2.3        1.4

    Watermelon
      (whole)                0.8         8-10       0-14             4           3                    0-0.6          0.02-0.35

      (rind)                 1.3         7          14               1           3                    0.2-0.4        0.3

      (whole)                1.7         8-10       0-14             4           3                    0.03-1.0       0.08-0.5

    TABLE 2a.  (Cont'd.)

                                                                                                                                  

                             Application                                                              Residues. mg/kg
                             Rate,                  Pre-harvest      No.                                             Range
                             a.i.,                  interval         of          Determinations       Total          (means
    Crop                     kg/ha       No.        (days)           trials      per trial            range          per trial)
                                                                                                                                  

      (whole)                2.5         8-10       0-14             4                                0.05-1.0       0.05-0.8

    Pumpkin (whole)          1.7         10         0-7              3           3                    0.8-1.8        0.8-1.4

      (pulp)                 1.7         10         0                1           2                    0              0

    Tomato                   0.6         18         3                1           9                    0-0.1          0.05
                             1.3         6-18       0-14             5           6-18                 0.03-5.5       0.05-4.4
                             1.7         4-10       0-15             17          3-27                 0.01-5.5       0.09-3.4
                             2.5         5-18       0-14             12          3-32                 0.2-4.5        0.2-4.5

    Peanuts (nuts)           0.8         6          78               1           3                    0.03           0.3
                             1.3         4-12       4-78             11          4-24                 0-0.3          0-0.09
      (hulls)                1.3         4-12       4-55             9           3-12                 0-0.8          0.09-0.5

      (hay)                  1.3         4-11       4-68             11          2-30                 0.96           0.3-89

      (nuts)                 1.7         6          78               1           3                    0.02-0.04      0.03

    Potatoes
      (whole)                0.8         10         12               2           9                    0              0

      (peeled)               0.8         13         15               1           6                    0              0

      (peelings)             0.8         13         15               1           3                    0-0.01         0

    Potatoes
      (whole)                1.3         3-13       12-23            16          35-48                0-0.07         0-0.02

      (peeled)               1.3         10-13      0-15             4           33                   0-0.02         0.01

    TABLE 2a.  (Cont'd.)

                                                                                                                                  

                             Application                                                              Residues. mg/kg
                             Rate,                  Pre-harvest      No.                                             Range
                             a.i.,                  interval         of          Determinations       Total          (means
    Crop                     kg/ha       No.        (days)           trials      per trial            range          per trial)
                                                                                                                                  

      (peelings)             1.3         13         15               1           4                    0-0.05         0.01

      (whole)                1.7         5-12       0-23             11          19-44                0-0.06         0-0.01

      (peeled)               1.7         5-12       0-13             3           21                   0              0

      (peelings)             1.7         5-12       0-14             6           14                   0-0.15         0.06

      (whole)                2.5         10         14               1           9                    0-0.01         0

    Sugar beets
      (roots)                1.3         4          61               1           10                   0-0.02         0.01
                             1.7         4-6        14-41            9           9-27                 0-0.5          0-0.3

      (tops)                 1.7         4-6        14-41            3           9                    0-5-17         0.9-11

      (roots)                2.5         3-6        14-59            5           5-12                 0-1.2          0.02-0.5

      (tops)                 2.5         3-5        14-59            3           6-17                 0.2-32         1.2-16

      (roots)                3.4         5          23               1           6                    0.03-0.09      0.05

    Sweet corn
      (kernels
       and cob)              1.3         14         14               2           17                   0              0
                             1.7         10         0                1           9                    0-0.03         0
                             2.5         11         0-7              3           5-9                  0.01-0.1       0.04

    Snap beans               1.7         5-8        0-7              5           5-17                 0.04-14        0.1-11
                             2.5         8          0-7              3           9                    0.8-10         2-3-5.4

    TABLE 2a.  (Cont'd.)

                                                                                                                                  

                             Application                                                              Residues. mg/kg
                             Rate,                  Pre-harvest      No.                                             Range
                             a.i.,                  interval         of          Determinations       Total          (means
    Crop                     kg/ha       No.        (days)           trials      per trial            range          per trial)
                                                                                                                                  

    Lima beans
      (beans)                1.3         10         0                1           3                    0-2-0.4        0.3

      (plants)               1.3         10         0                1           9                    220-535        400

      (beans)                1.7         7          0-15             2           5-9                  0-0.1          0-0.7

      (pod + bean)           1.7         13         0                1           3                    10-13          12

      (plants)               1.7         4-13       0-15             3           2-9                  22-310         47-117

    Celery                   0.8         5-24       0-14             6           8-9                  0.2-21         0.4-18
                             1.3         9-24       0-14             5           6-9                  0.1-52         0.4-29
                             1.4         8          7-14             2           6-8                  0.06-1.7       0.1-1
                             1.7         9-24       0-14             7           6-9                  0.1-53         0.7-34
                             1.8         8          7-14             2           6                    0.1-5.4        0.3-3.4
                             1.9         26         7-14             2           6-8                  0.2-17         0.6-12
                             2.5         5-14       0-14             5           8-9                  0.6-17         1.4-10
                             3.4         10-18      1-14             4           6-9                  2.8-26         4.5-18

    Oranges (whole)          1.3         1-14       0-14             3           6                    1.8-5.1        2.7-4.3
      (peel)                 1.3         1          173-397          5           20                   0-0.7          0.1

    Grapefruit
      (whole)                0.4-0.8     1          309              2           6                    0.01-0.02      0.01
                             1.3         1          200-309          3           11                   0-0.05         0.02
      (peel)                 1.3         1-2        22-309           6           6-17                 0-0.2          0.06-0.09

    Limes (whole)            1.3         1          119-280          2           12                   0-0.01         0

    Lemons (whole)           1.3         1          280              1           4                    0.01-0.02      0.01

    TABLE 2a.  (Cont'd.)

                                                                                                                                  

                             Application                                                              Residues. mg/kg
                             Rate,                  Pre-harvest      No.                                             Range
                             a.i.,                  interval         of          Determinations       Total          (means
    Crop                     kg/ha       No.        (days)           trials      per trial            range          per trial)
                                                                                                                                  

    Tangerines
      (whole)                1.3         1          280              1           6                    0.01           0.01

    Cherries                 0.4         1-4        3-10             2           4-12                 0-0.2          0.04-0.2
                             0.6         4          0-24             5           2-13                 0.1-11         0.1-9.3
                             1.0         4          20               1           6                    0.1-0.2        0.2
                             1.3         3-5        2-24             5           5-14                 0.7-7.8        1.4-5.7
                             1.5         4-5        20-24            3           18                   1-10           3.1-4.2

    Peaches                  0.6         4          8                1           3                    6-8            6.7
                             0.8         4          8                1           6                    3.3-6.3        5.0
                             1.0         7          0-14             3           3                    6.4-19         8-15
                             1.3         4-11       6-14             3           3-12                 2.8-20         4-16
                             1.5         6-7        0-25             11          3-18                 1.3-45         4-31
                             1.7         4          8                1           3                    27-28          28
                             2.5         4          8                1           3                    32-54          45

    Currants                 1.0         4          3                1           6                    16-20          18
                             1.3         4          3                1           6                    16-20          18
                             1.5         4          3                1           6                    20-23          23

    Blackberries             1.3         2          4                1           12                   4-11           7.3
                             1.7         2          23-48            2           12                   0.5-2          1.2
                             1.9         2          4                1           12                   3-16           9.6
                             2.5         2          0-16             3           9                    0.3-8          2-4
                             3.0         2          0-16             4           7-12                 0.5-43         1.6-21
                             3.4         2          0-16             3           9                    1.3-9.3        2.5-4

    Raspberries              0.4         2          4                1           6                    0.05-1         0.3
                             0.8         2          4                1           6                    0.2-2.4        1.2
                             1.3         2-3        0-8              3           6-12                 0.4-6.5        0.7-4.1

    TABLE 2a.  (Cont'd.)

                                                                                                                                  

                             Application                                                              Residues. mg/kg
                             Rate,                  Pre-harvest      No.                                             Range
                             a.i.,                  interval         of          Determinations       Total          (means
    Crop                     kg/ha       No.        (days)           trials      per trial            range          per trial)
                                                                                                                                  

                             1.5         2          0-8              2           6                    0.6-2.7        0.7-1.7
                             1.7         3          0-7              3           3                    5.6-20         5-7-15

    Collards                 2.5         3          0-14             4           9                    3.3-88         5.7-69

    Kale                     2.5         3          0-14             4           6                    1.5-71         2.8-62

    Escarole                 1.7         8          0-7              3           4-6                  0.4-24         1.3-15

    Endive                   0.4         5          1                1           2                    24-28          26
                             0.8         5          1                1           3                    22-44          31

    Chicory                  1.7         8          0-7              3           3-5                  0.04-30        0.3-24

    Lettuce leaf             1.3         3          0                1           8                    13-43          24
                             2.5         3-4        0-7              3           8-9                  5-89           13-68

    Lettuce head             1.7         4-7        0-14             5           2-12                 0.1-100        1.3-86

    Spinach                  1.3         5          3-8              2           6                    4-48           14-29

    Turnip greens            1.7         2          2                1           7                    5-10           7.2

    Onions, green            1.7         3-4        0-7              3           6-8                  0.6-11         1.1-7.6
                             2.5         3-4        0-7              3           6-7                  1.3-24         2.0-18

    Onions, mature           0.8-1.3     8-9        12-14            2           30                   0-0.1          0-0.05
      dry                    1.7-2.5     5-9        7-9              2           105                  0-0.3          0-0.1

    Peppers                  1.7         9-13       0-7              2           3-9                  0.4-9.4        1.2-8.4
                             2.5         7          0-7              3           9                    0.1-3.3        0.5-1.9
                                                                                                                                  

    TABLE 2b.  Residues of hydroxy-metabolite (DAC-3701) from supervised trials

                                                                                                                                  
                             Application                                                              Residues. mg/kg
                             Rate,                  Pre-harvest      No.                                             Range
                             a.i.,                  interval         of          Determinations       Total          (means
    Crop                     kg/ha       No.        (days)           trials      per trial            range          per trial)
                                                                                                                                  

    Carrots                  1.3         8          0-7              2           3,5                  0.01-0.06      0.01-0.04
    (tops removed)           2.5         7          0                1           6                    0.04           0.04

    Broccoli                 1.3         9          1-15             3           9                    0              0
                             2.5         8          0                1           7                    0-0.06         0.01

    Brussels sprouts         2.5         8          0                1           5                    0.01-0.02      0.02

    Cabbage                  2.5         9          0                1           6                    0              0

    Cucumber                 0.8         7          0                1           6                    0-0.03         < 0.01
                             1.7         7          0                1           6                    0-0.03         < 0.01
                             2.5         6          0                1           3                    0              0

    Cantaloupe
    (whole melons)           1.7         7          4                1           13                   0.02-0.04      0.03
                             2.5         7          4                1           8                    0.02-0.08      0.05

    (pulp)                   2.5         5          1                1           5                    0.08-0.14      0.1

    Watermelon
    (rind)                   1.3         7          14               1           3                    0              0

    Tomato                   1.3         6          0                1           6                    0-0.2          0.01
                             1.7         5          1                1           3                    0.06-0.1       0.08
                             2.5         5-8        0-1              3           11                   0.01-0.1       0.02-0.09

    Peanuts (nuts)           1.3         4-12       4-55             6           10-20                0              0
      (hulls)                1.3         4-12       6-55             5           3-9                  0-0.05         0-0.02

    TABLE 2b.  (Cont'd.)

                                                                                                                                  
                             Application                                                              Residues. mg/kg
                             Rate,                  Pre-harvest      No.                                             Range
                             a.i.,                  interval         of          Determinations       Total          (means
    Crop                     kg/ha       No.        (days)           trials      per trial            range          per trial)
                                                                                                                                  

    Peanuts
      (hay)                  1.3         4-11       4-55             6           9-33                 0-0.6          0.03-0.4

    Sugar beets
      (roots)                2.5         3          25               2           9                    0-0.01         0.01

      (tops)                 2.5         3          23               1           6                    0              0

      (roots)                3.4         5          23               1           6                    0-0.01         0.01

    Lima beans
      (pod + bean)           1.7         4          3                1           3                    0.8-1.1        1.0

    Celery                   0.8         20         0                1           4                    0.05-0.1       0.05
                             1.4         8          7-14             2           2-5                  0.05-0.2       0.09-0.15

    Peaches                  0.6         3          0-10             2           3                    0.1-0.3        0.2
                             0.8         2-10       0-10             4           2-5                  0-1-0.4        0.2-0.3
                             1.3         2-4        0-12             4           2-3                  0.01-0.5       0.01-0.3

    Lettuce head             1.3         4          1-7              2           4                    0-0.04         0.01
                             1.7         4          21               1           6                    0-0.04         0.02

    Spinach                  1.3         5          3                1           8                    0.04-0.3       0.1

    Turnip greens            1.7         2          2                1           5                    0-0.02         0

    Onions, mature           0.8-1.3     5-8        14               3-8         3-8                  0.0.02         0-0.01

      dry                    1.7-2.5     8          -                3-5         3-5                  0-0.2          0.1-0.2
                                                                                                                                  

    TABLE 3.  Chlorothalonil and DAC-3701 residues in glasshouse crops from supervised trials

                                                                                                                                        
                                                                                                            Residues (ppm)
                                                          Days from                  No. of            Range               Means or
    Crop and               Rate           No. of          application     No. of     determinations    individual          range of
    residue                g/1000 ft3     applications    to harvest      trials     per trial         determinations)     means/trial
                                                                                                                                        

    Cucumbers
      chlorothalonil       2              12-15           1               4          3                 0.01-0.09           0.03-0.06

      DAC-3701             2              12-15           1               4          3                 0                   0

    Lettuce, leaf
      chlorothalonil       2              5-12            1               7          3                 0.05-3.6            0.05-3.0

    Tomatoes
      chlorothalonil       2              1-8             1               8          2-3               0.02-0.4            0.03-0.3
                           1.8            3-8             1               6          4                 0.1-3.7             0.2-3.0
                           2              12-18           1               5          3                 0.5-1.4             0.7-1.4
                           2              1-9             1               9          3                 0-0.8               0-0.6
                           2              8-16            0.5             9          3                 0.04-0.7            0.08-0.6

      DAC-3701             2              1-8             1               8          2-3               0                   0
                                                                                                                                        
    

    TABLE 4.  DAC-3701 residues (mg/kg) in cows milk during
              feeding trial
                                                                       
                     Residue (mg/kg at 0.2*, 0.6** and 2.0*** ppm
                     DAC-3071 in diet
                                                                       
    Days      0              0.2            0.6            2.0

    0         < 0.03         < 0.03         < 0.03         < 0.03

    2         < 0.03         < 0.03         < 0.03         0.06

    4           0.04         0.04           0.06           0.16

    8           0.04         0.08           0.10           0.51

    14        < 0.03         0.13           0.16           0.57

    18        < 0.03         0.20           0.26           0.74

    22        < 0.03         0.11           0.17           0.78

    26        < 0.03         0.11           0.13           0.59

    30        < 0.03         0.16           0.26           0.74

    37        < 0.03         0.06           0.12           0.55

    44        < 0.03         0.04           0.16           0.16

    51        < 0.03         < 0.03         < 0.03         0.06

    60        < 0.03         < 0.03         < 0.03         < 0.03
                                                                       

    *    +25 ppm chlorothalonil

    **   +75 ppm chlorothalonil

    ***  +250 ppm chlorothalonil

         Residues of chlorothalonil were not detected in the tissues of
    dogs and rats fed levels in the diet of up to 30 000 mg/kg (Wolfe and
    Stallard, 1968a) although small quantities of the hydroxy metabolite
    were found in the liver and kidney.

         No residues of chlorothalonil were detected in milk from a
    Holstein cow fed the compound at the 5 ppm level in the ration for
    four days (Gutenmann and Lisk, 1966). The method was sensitive to
    about 0.03 ppm.

    FATE OF RESIDUES

    General comments

         The disappearance and fate of chlorothalonil residues is
    reasonably well documented. The only identified metabolite is the
    4-hydroxy compound, DAC-3701, mentioned previously. Although
    chlorothalonil residues decrease quite rapidly on plants, the actual
    fate is unknown.

    In animals

         In the experiment by Gutenmann and Lisk (1966) mentioned above,
    samples of milk, urine and faeces were collected throughout the
    feeding period and for five days thereafter. No residues of
    chlorothalonil, acid products of nitrile hydrolysis or conjugates of
    acidic or phenolic derivatives were detected. In the same series of
    experiments, chlorothalonil disappeared rapidly when incubated with
    rumen juice at the 1 ppm level. Two unidentified metabolites were
    formed. Feeding studies with dogs and rats showed that chlorothalonil
    was rapidly eliminated in the faeces with negligible amounts in the
    urine (Skinner and Stallard, 1967). The eliminated material was mostly
    unchanged chlorothalonil. Analysis of tissue samples from rats and
    dogs from chronic feeding studies of one and two years indicated no
    detectable storage of chlorothalonil. A radio-tracer study with rats
    confirmed that elimination of chlorothalonil was complete and there
    was no significant tissue storage (Ryer and Sullivan, 1966; Skinner
    and Stallard, 1967).

         Dogs and rats were fed for 2 years on diets containing 1500,
    15 000 and 30 000 mg/kg of chlorothalonil (Wolfe and Stallard, 1968a).
    Residues were not detected in muscle tissue. Residues of
    4-hydroxy-2,5,6-1,3-benzene-dicarbonitrile (DAC-3701) in kidney
    tissues of dogs were <1.5 mg/kg and <3.5 mg/kg in the livers of
    dogs and rats. Residue levels of the hydroxy metabolite were <0.25
    mg/kg in the urine of the dogs and rats.

         In the feeding experiment involving both chlorothalonil and
    DAC-3701 (Wolfe and Stallard, 1969, 1970a, 1970b; see preceding
    section and Table 4), the DAC-3701 residues in the milk accounted for
    10-16% of the administered metabolite, but it was not possible to
    determine whether part of the milk residue derived from the
    chlorothalonil in the diet.

    In plants

         In studies with ring labelled 14C-chlorothalonil, Kunkel (1967a)
    found no evidence of translocation from topical applications on
    cucumber cotyledons, cucumber leaves, cucumber hypocotyls, bean
    unifolilate leaves or tomato leaves. He also demonstrated that the
    labelled compound was not translocated into the aerial parts of corn
    or tomato plants when they were cultivated for 23 days in soil treated

    with 14C-chlorothalonil. In another study, Kunkel (1967b) showed that
    autoradiographic techniques did not demonstrate 14C-movement or
    translocation within root systems of sweet corn, cucumber or tomato
    grown in soil treated with ring-labelled chlorothalonil. Since
    DAC-3701 is a soil metabolite of chlorothalonil and 14C activity was
    not translocated from the soil, the experiments also showed that the
    4-hydroxy metabolite is not translocated into the root system or
    aerial parts of these plants. The residue data from supervised trials
    (Table 2) showed that DAC-3701 is a residue following chlorothalonil
    treatment. Of the crops tested for DAC-3701 residues, peaches
    contained up to 0.5 mg/kg, spinach up to 0.3 mg/kg, onions up to 0.2
    mg/kg, celery up to 0.2 mg/kg, cantaloupe up to 0.1 mg/kg and lima
    bean plants up to 1 mg/kg. Negligible residues of DAC-3701 (<0.1 ppm)
    were reported for carrots, tomatoes, peanuts (except peanut hay),
    sugar beets, turnip greens, broccoli, Brussels sprouts, cabbage,
    cucumber, watermelon and lettuce.

    In soil

         Tests conducted under both laboratory and field conditions
    demonstrated that chlorothalonil is rapidly degraded in soil (Stallard
    and Wolfe, 1967). In the laboratory experiments its half-life in the
    types of soils tested ranged from 4 to over 40 days. The degradation
    rate increased with increasing organic matter content, moisture
    content and temperature but appeared to be independent of pH within
    the range 6-8. Chlorothalonil was evidently not lost by
    volatilization, since it disappeared rapidly from treated soil
    incubated in tightly closed jars.

         In the field trials, turf plots in 3 locations in the U.S.A. were
    treated with chlorothalonil and the half-life of the chlorothalonil
    residues ranged from 26-45 days. The data indicated a decreased
    degradation rate during the winter months.

         4-Hydroxy-2,5,6-trichloro-1,3-benzenecarbonitrile (DAC-3701) was
    the major soil degradation product following treatment with 14C-ring
    labelled chlorothalonil and incubation (Duane, 1970). This compound
    accounted for over 80% of the radioactivity extracted from the soil.
    (Approximately 20% of the radioactivity was not extracted.) A second
    degradation product, more polar than DAC-3701 and without a hydroxyl
    group, was detected but not identified. During these experiments it
    was shown that 14C-chlorothalonil was not volatilized from the soil
    and no volatile degradation products were formed.

         Laboratory experiments with 5 representative soil types
    demonstrated that the half-life values for DAC-3701 ranged from 36
    days in a sandy loam type soil to 220 days in clay type soil (Wolfe
    and Stallard, 1968b).

         Duane (1970) demonstrated that bacteria isolated from soil were
    capable of metabolizing chlorothalonil in culture media. Thus it may
    be assumed that naturally occurring soil microorganisms are in part
    responsible for the rapid loss of chlorothalonil under field
    conditions.

    In storage and processing

         Some data are available on the effect of washing, field trimming
    and peeling on the residue levels of chlorothalonil in some
    commodities (Diamond Shamrock, 1974). Table 5 summarizes the data on
    the effect of washing with water. Residues on carrots, cucumbers,
    summer squash, tomatoes, currants and cranberries were reduced by
    more than 50%. Washing was least effective with the leafy vegetables.
    Significant reduction in chlorothalonil residues results from trimming
    cabbage and head lettuce (Table 6). Chlorothalonil residue are
    concentrated on the surface and as a result peeling removes 
    almost all the residues leaving the pulp of many fruits and 
    vegetables almost residue-free (Table 7). Following processing,
    residues of chlorothalonil were not detected ( <0.1 mg/kg) in canned
    spinach (Table 8). The fate of any DAC-3701 residues was not
    determined.


    TABLE 5.  Effect of washing with water on residues of
              chlorothalonil

                                                                   

                             Residue (mg/kg)              Reduction
    Crop                Unwashed       Washed                %
                                                                   

    Carrots             4.39-7.34      1.05-3.53          52-76

    Cucumbers           0.08-0.45      0.01-0.03          87-95

    Squash, summer      0.21-1.33      0.01-0.12          76-97

    Tomatoes            0.21-0.82      0.02-0.08          90

    Celery              1.04-20.0      0.76-8.18          0-59

    Peaches             7.6-15.0       4.9-8.6            35-45

    Currants            18.3           2.6                86

    Cranberries         0.91           0.25               73

    TABLE 5.  (Cont'd.)

                                                                   

                             Residue (mg/kg)              Reduction
    Crop                Unwashed       Washed                %
                                                                   

    Collards            5.73-69.0      1.7-31.3           31-70

    Kale                2.8-62.0       1.6-20.0           43-74

    Escarole            1.32-4.1       0.63-2.6           36-44

    Chicory             0.31-4.0       0.23-1.5           26-62

    Lettuce             23.7-67.6      8.9-37.1           45-70

    Cauliflower         1.23           0.85               30

                                                                   


    RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION

         Data were not available to the Meeting to indicate the level and
    incidence of chlorothalonil residues in food moving in commerce or in
    food at the time of consumption. Chlorothalonil residues were not
    determined in the U.S.A. national food and feed monitoring program
    (Duggan and Cook, 1971).

    METHODS OF RESIDUE ANALYSIS

         Residues of chlorothalonil and its metabolite
    4-hydroxy-2,5,6-trichloro-1,3-benzenedicarbonitrile DAC-3701), can be
    determined by gas-liquid chromotography (GLC) with either electron
    capture or microcoulometric (halide) detectors (Wolfe and Stallard,
    1970). The parent compound is chromatographed directly but the
    metabolite is converted to the methyl ether by reacting with
    diazomethane prior to chromatography.

         Crop and soil samples are extracted with acidified acetone. The
    acetone is removed by distillation and the residues are partitioned
    into diethyl ether. The ether extract is cleaned-up on a Florisil
    chromatographic column. Chlorothalonil is eluted with 5%
    acetone-dichloromethane and DAC-3701 with 50% acetone-dichloromethane.
    Following reaction with diazomethane, the methyl ether of DAC-3701 and
    chlorothalonil are determined by GLC either by electron capture or
    microcoulometric detection. The sensitivity of the method is


    
    TABLE 6.  Effect of trimming on residues of chlorothalonil in cabbage and lettuce

                                                                                                                                     

                                Rate,                         Days from                             Residue            Mean
                                a.i.,        No. of           application      No. of               range              residue
    Crop                        kg/ha        applications     to harvest       determinations       (mg/kg)            (mg/kg)
                                                                                                                                     

    Cabbage
      (field trimmed)           1.7          9                0                7                    0.77-2.67          1.60
                                1.7          5                0                3                    1.25-1.72          1.47

      (market trimmed)          2.5          7-8              0-7              7-9                  0.00-0.18          <0.01-0.03

    Lettuce
      (whole untrimmed
      heads)                    1.7          4-7              0-7              2-12                 11.5-100           33.7-85.5
                                1.7          4                14               11                   0.10-3.0           1.33

      (trimmed heads)           1.3          5                1-7              4                    0.15-1.98          0.53-0.95
                                1.7          4                2-14             6                    0.07-2.9           0.80-0.90

                                                                                                                                     
    

    TABLE 7.  Effect of peeling on chlorothalonil residues

                                                                       

    Crop                  Residues (mg/kg)
                                                                       

    Cucumbers             Peelings - 1.26; Pulp - <0.01

    Muskmelon             Rind - 0.11-1.50; Pulp - 0.00

    Winter squash         Whole - 0.05-1.42; Pulp - 0.00

    Pumpkin               Whole - 1.42; Pulp - 0.00

    Cantaloupe            Whole - 1.09; Edible portion - 0.07

    Peanut                Hulls - 0.13-0.51; Meat - 0.00

    Potatoes              Peelings - 0.00-0.06; Pulp - 0.00

    Lima beans            Pod and beans - 11.9; Beans - 0.00

    Grapefruit            Peel - 0.09; Whole - 0.02

    Oranges               Whole - 2.70-4.29; Pulp - <0.01-0.08;
                          Juice - 0.00
                                                                       

        TABLE 8.  Effect of canning on chlorothalonil residues in spinach

                                                                                              

                      Rate,                   Days from                Residue      Mean
                      a.i.,     No. of        application   No. of     range        residue
    Crop               %        applications  to harvest    analysis   (ppm)        (ppm)
                                                                                              

    Spinach
      (raw)           control       0             -            6       <0.1         <0.1
                      0.11          5             3            6       16.1-47.8    29.1
                      0.11          5             8            6       3.7-30.9     13.6

      (processed,
       canned)        control       0             -            3       <0.1         <0.1
                      0.11          4             16           3       <0.1         <0.1

                                                                                              
    
    0.02 mg/kg. Recovery values obtained from fortified crops were greater
    than 72 and 76% for chlorothalonil and DAC-3701 respectively. Some
    modifications to the method described above are required for animal
    tissue (Wolfe and Stallard, 1970b) and milk samples (Wolfe and   
    Stallard, 1969, 1970c). Average, recoveries for chlorothalonil and
    DAC-3701 respectively were:

         muscle  - 81, 91%
         fat     - 76, 91%
         kidney  - 82, 84%
         liver   - 93 83%
         milk    - 88, 83%

    The sensitivity of the method for milk is 0.02 mg/kg for
    chlorothalonil and 0.03 mg/kg for DAC 3701. Chlorothalonil is not
    recovered by the Mills Florisil multi-residue procedure but is
    recovered (McMahon et al., 1973) in the alternative Florisil elution
    system (Mills et al., 1972). Recovery from deactivated Florisil
    (Osadchuk et al., 1971) is achieved by elution with 10% ethyl acetate
    in hexane (McLeod and Ritcey, 1973).

         Chlorothalonil can be recovered through the carbon-cellulose
    cleanup procedure of McLeod et al. (1967). Gutenmann and Lisk (1966)
    determined chlorothalonil by electron capture GLC in milk, urine and
    faeces after extracting with acetone-phosphoric acid and partitioning
    into hexane. Possible acid metabolites were determined after
    diazomethane esterification of the evaporated acetone extract.

         With the exception of the Mills Florisil multiresidue procedure,
    the multiresidue procedures discussed above appear to be suitable for
    regulatory determination of the parent compound. When the total
    residue, chlorothalonil and DAC-3701, is required the GLC method
    proposed by Wolfe and Stallard (1970c) can be recommended for
    regulatory purposes.

    NATIONAL TOLERANCES REPORTED TO THE MEETING

         Some examples of national tolerances were reported to the Meeting
    and are listed in Table 9.

    TABLE 9.  Examples of national tolerances as reported to the Meeting

                                                                          

                                                               Tolerance
    Count            Commodity                                 (mg/kg)
                                                                          

    Australia        Beets, carrots, corn, cucumbers,
                     onions, peppers, potatoes,
                     tomatoes                                      7

                     Peanuts                                       0.2

    TABLE 9.  (cont'd)

                                                                          

                                                               Tolerance
    Count            Commodity                                 (mg/kg)
                                                                          

    Canada           Celery                                        15

                     Broccoli, Brussels sprouts,
                     cabbage, cauliflower, cucumbers,
                     melons, pumpkins, snap beans,
                     squash, tomatoes                              5

                     Carrots                                       1

                     Peanuts                                       0.3

    Netherlands      Potatoes                                      0.05

                     Apples, apricots, beets, carrots,
                     citrus, corn, cucumbers, grapes,
                     melons, onions, peaches, pears,
                     peppers, plums, tomatoes                      0.01

    Switzerland      Potatoes                                      0.05

    U.S.A.           Celery                                        15*

                     Broccoli, Brussels sprouts, cabbage,
                     cauliflower, cucumbers, melons,
                     pumpkins, snap beans, squash
                     (summer and winter), tomatoes                 5*

                     Carrots, sweet corn (kernels plus
                     cob with husks removed)                       1*

                     Peanuts                                       0.3*

                     Potatoes                                      0.1*
                                                                          

    *  Including metabolite
       4-hydroxy-2,5,6-trichloro-1,3-benzen-edicarbonitrile.

    APPRAISAL

         Chlorothalonil is a broad-spectrum fungicide with effective
    action against many fungus diseases which damage vegetable, tree,
    small fruit and other agricultural crops, turf and ornamentals. The
    use pattern of chlorothalonil is such that residues remain on most
    above-ground crops at the time of harvest. It is desirable to have
    some residue of the fungicide on the mature crop to protect it from
    disease organisms during shipment.

         4-Hydroxy-2,5,6-trichloro-1,3-benzenedicarbonitrile is a major
    metabolite of chlorothalonil in soil and a metabolite in plants, but
    only negligible residues were found on most crops investigated.
    Chlorothalonil does not translocate into plants from the soil or from
    topical application.

         Extensive crop residue data indicated that chlorothalonil is a
    relatively persistent fungicide. The level of the residue depends on
    such factors as rate of the fungicide applied, time interval between
    last application and harvest and the surface area, weight and surface
    structure of the crop. The residue level diminishes with time after
    application, and pre-harvest intervals are therefore recommended for
    some crops. Some data are available on the effects of washing,
    trimming and peeling on chlorothalonil residues.

         Chlorothalonil residues do not occur in the tissues or milk of
    cows, but residues of the 4-hydroxy metabolite are found when cows are
    fed chlorothalonil and the 4-hydroxy compound together in their
    ration. The residue levels depend on the levels fed and reach a steady
    value in the milk after 18 days. Residues in milk declined to below
    detection level within 21 days after withdrawal. It was not determined
    whether residues of the 4-hydroxy metabolite would occur in the milk
    and tissues of cows if only chlorothalonil were ingested.

         Since no data were provided on residues in crops that may be fed
    to animals, it was not possible to recommend maximum residue limits
    for milk and meat.

         Most available multi-residue GLC methods appear to be suitable
    for the determination of the parent compound, but chlorothalonil is
    not recovered by the original Mills Florisil multi-residue cleanup
    procedure (McMahon et al., 1973). The GLC method proposed by Wolfe
    and Stallard (1970) for chlorothalonil and the metabolite
    4-hydroxy-2,5,6-trichloro-1,3-benzenedicarbonitrile appears to be
    suitable for regulatory purposes when the total residue is required.
    National tolerances are in effect in a number of countries.

    RECOMMENDATIONS

         The following maximum residue limits are recommended for
    chlorothalonil and the metabolite
    4-hydroxy-2,5,6-trichloro-1,3-benzenedicarbonitrile, expressed as
    chlorothalonil.

    TEMPORARY TOLERANCES

                                                                        

                                                    Pre-harvest
                                                    interval on which
                                       Limit        recommendations
    Commodity                          (mg/kg)      are based (days)
                                                                        

    Peaches                              30                7

    Currants (black, red and white)      25                3

    Celery                               15                7

    Peppers                              10                1

    Blackberries, raspberries,           10                7
    cherries, chicory sprouts

    Collards, kale, endive,              10                14
    lettuce (head)

    Broccoli, Brussels sprouts,          5                 7
    cabbage, cauliflower, beans
    (green including pod), oranges,
    onions, cranberries

    Cucumbers, melons, pumpkins,         5                 1
    squash, tomatoes

    Carrots, sweet corn, sugar           1                 1
    beets

    Lima beans, peanuts (whole)          0.5               0

    Peanuts (kernel), potatoes           0.1               0
                                                                        

    FURTHER WORK OR INFORMATION

    REQUIRED (by 1977)

    1.   Additional study to resolve lower limit of kidney effects in rat.

    2.   Define growth reduction in pups relative to dietary ingestion or
         secretion into milk.

    3.   Data on residues of chlorothalonil and the 4-hydroxy metabolite
         in crops that may be fed to animals.

    4.   The results of feeding studies on dairy cattle understood to be
         in progress to determine the level and nature of residues in milk
         and tissues.

    DESIRABLE

    1.   Observations in man.

    2.   Residue data for food moving in commerce.

    3.   Further information on effects of processing, including household
         cooking, on residues.

    REFERENCES

    Beasley, A. and Leong, K. (1965). Acute inhalation exposure - rats.
    Report from Hazelton Laboratories Inc., submitted by The Diamond
    Shamrock Chemical Co. (Unpublished)

    Blackmore, R. and Shott, L. (1968). Final report four month feeding
    study - rats. Report from Hazelton Laboratories, Inc. (Unpublished)

    Diamond Shamrock (1971). Documentation on the pesticide,
    chlorothalonil. Diamond Shamrock Chemical Co. (Unpublished)

    Diamond Shamrock (1974). Documentation concerning the pesticide,
    chlorothalonil. Diamond Shamrock Chemical Co. (Unpublished)

    Di Dario, A., Curry, T.L., Thayer, P. and Turner, J.J. (1965). The
    biological performance of tetrachloroisophthalonitrile as influenced
    by particle size and crystalline form. Phytopathology, 55:1055.

    Doyle, R. and Elsea, J. (1963). Acute oral, dermal and eye toxicity
    and irritation studies on DAC-2787. Report from Hill Top Research
    Institute Inc., submitted by Diamond Shamrock Chemical Co.
    (Unpublished)

    Duane, W.C. (1970). Biodegradation of Daconil 2787(R). Report
    submitted by Diamond Shamrock Chemical Co. (Unpublished)

    Duggan, R.E. and Cook, H.R. (1971). National food and feed monitoring
    Program. Pestic. Monit. J., 5:37-43.

    Gutenmann, W.H. and Lisk, D.J. (1966). Metabolism of Daconil and
    Dacthal pesticides in lactating cows. J. Dairy Sci., 49:1272-1276.

    Hastings, T.F. and Jessup, D.C. (1974). 3-Generation reproduction
    study in albino rats using DAC-3701 in the diet. Report from BIO/TOX
    Research Laboratories, Inc. Submitted to WHO by Diamond Shamrock
    Chemical Co. (Unpublished)

    Holliday, W., Schadeberg, K., Goode, J. and Keplinger, M. (1973).
    Twenty-one day subacute aerosol inhalation toxicity study with Bravo
    6F(R) in albino rats. Report from Industrial Bio Test Laboratories,
    Inc. (Unpublished)

    Holsing, G. and Shott, L. (1970). Two year dietary administration
    - rats. Report from Hazelton Laboratories Inc. submitted by Diamond
    Shamrock Chemical Co. (Unpublished)

    Holsing, G. and Voelker, R. (1970). Final report 104 week dietary
    administration - dogs. Report from Hazelton Laboratories Inc.
    submitted by Diamond Shamrock Chemical Co. (Unpublished)

    Kunkel, J.F. (1967a). Absence of 14C movement in crop plant organs
    after topical application and soil amendment studies with isotopic
    Daconil 2787. Report to Diamond Shamrock Chemical Co. (Unpublished)

    Kunkel, J.F. (1967b). Movement of 14C in or on roots of crop species
    grown in soil amended with isotopic Daconil 2787. Report to Diamond
    Shamrock Chemical Co. (Unpublished)

    Legator, M. (1974). Mutagenic Testing with DAC 2787. Report from
    Division of Genetics, Roger Williams General Hospital and Brown
    University, Division of Biological and Medical Sciences submitted by
    Diamond Shamrock Chemical Co. (Unpublished

    McLeod, H.A., Mendoza, C., Wales, P. and McKinley, W.P. (1967).
    Comparison of various carbon adsorbents and quantitative elution and
    separation of forty-two pesticides from a carbon-Solka Floc cleanup
    column. J. Ass. off. analyt. Chem., 50:1216-1228.

    McLeod, H.A. and Ritcey, W.R. (1973). Analytical methods for pesticide
    residues in foods. Information Canada, Ottawa, Canada.

    McMahon, B.M., Sawyer, L.D. and Corneliussen, P.E. (editors) (1973).
    Pesticide analytical manual. Volume 1. Methods which detect multiple
    residues. Food and Drug Administration, Washington, D.C.

    Mills, P.A., Bong, B.A., Kamps, L.R. and Burke, J.A. (1972). Elution
    solvent system for Florisil column cleanup in organochlorine pesticide
    residue analyses. J. Ass. off. analyt. Chem., 55:39-43.

    Osadchuk, M., Romach, M. and McCully, K.A. (1971). Cleanup and
    separation procedures for multi-pesticide residue analysis in
    monitoring and regulatory laboratories. Proc. Second Intern. IUPAC
    Congress Pestic. Chem. Vol. IV, Methods in Residue Analysis, p.
    357-383. A.S. Tahori (editor), Gordon and Breach Science Publishers,
    New York.

    Paynter, O. (1965a). Oral dose range - dogs - final report. Report of
    Hazelton Laboratories Inc. submitted by Diamond Shamrock Chemical Co.
    (Unpublished)

    Paynter, O. (1965b). Repeated dermal application - rabbits. Report
    from Hazelton Laboratories Inc., submitted by Diamond Shamrock
    Chemical Co. (Unpublished)

    Paynter, O. (1966). Reproduction - rabbit. Report from Hazelton
    Laboratories Inc. submitted by Diamond Shamrock Chemical Co.
    (Unpublished)

    Paynter, O. (1967a). Three generation reproduction study - rats.
    Report from Hazelton Laboratories Inc. submitted by Diamond Shamrock
    Chemical Co. (Unpublished)

    Paynter, O. (1967b). Ten week amino acid feeding study - rats. Report
    from Hazelton Laboratories Inc. (Unpublished)

    Paynter, O. (1967c). Final report - two year dietary feeding - rats.
    Report from Hazelton Laboratories Inc. (Unpublished)

    Paynter, O. and Busey, W. (1967). Long term (76 weeks) feeding study,
    rats, DAC 2787. Final Report from Hazelton Laboratories Inc.
    (Unpublished)

    Paynter, O. and Crews, L. (1967). Final report - two year dietary
    feeding - rats. Report from Hazelton Laboratories Inc. (Unpublished)

    Paynter, O. and Murphy, J. (1967). Sixteen week dietary feeding -
    dogs. Report from Hazelton Laboratories Inc., submitted by Diamond
    Shamrock Chemical Co. (Unpublished)

    Powers, M. (1965). Acute oral administration - rats. Report from
    Hazelton Laboratories Inc. submitted by Diamond Shamrock Chemical Co.
    (Unpublished)

    Ryer, F.H. and Sullivan, J.B. (1966). Radiotracer metabolism study.
    Report from Hazelton Laboratories Inc., submitted by Diamond Shamrock
    Chemical Co. (Unpublished)

    Skinner, W.A. and Stallard, D.E. (1967). Daconil 2787(R) animal
    metabolism studies. Report from and submitted by Diamond Shamrock
    Chemical Co. (Unpublished)

    Stallard, D.E. and Wolfe, A.L. (1967). The fate of
    2,4,5,6-tetrachloroisophthalonitrile (Daconil 2787(R)) in soil.
    Report from Diamond Shamrock Chemical Co. (Unpublished)

    Sterner, W. and Loveless, L. (1963). A study of the subacute toxicity
    of tetrachloroisophthalonitrile to rats. Report from International
    Bio-Research, Inc. (Unpublished)

    Teeters, W. (1966). In vivo assay of spasmodic activity, mice, DAC
    2787. Final report from Hazelton Laboratories Inc. (Unpublished)

    Turner, N.J. and Lamont, D. (1965). Control of fungal diseases in the
    greenhouse with thermally induced dusts of
    tetrachloroisophthalonitrile. Contr. Boyce Thomson Inst. Pl. Res.,
    23:51-54.

    Turner, N.J., Limpel, L.E., Battershell, R.D., Bluestone, H., Lamont,
    D. (1964). A new foliage protectant fungicide,
    tetrachloroisophthalonitrile. Contr. Boyce Thomson Inst. Pl. Res.,
    22:303-310.

    Wazeter, F. (1971). Acute oral LD50 in male albino rats. Report from
    International Research and Development Corporation. (Unpublished)

    Wazeter, F. and Goldenthal, E. (1972). Acute oral toxicity in beagle
    dogs. Report from International Research and Development Corporation.
    (Unpublished)

    Wolfe, A.L. and Stallard, D.E. (1968a). Analysis of tissues and organs
    for storage of the Daconil metabolite
    4-hydroxy-2,5,6-trichloroisophthalonitrile. Diamond Shamrock
    Chemical Co. (Unpublished)

    Wolfe, A.L. and Stallard, D.E. (1968b). The fate of DAC-3701
    (4-hydroxy-2,5,6-trichloroisophthalonitrile) in soil. Diamond Shamrock
    Chemical Co. (Unpublished)

    Wolfe, A.L. and Stallard, D.E. (1969). Residues in milk from cows fed
    2,4,5,6-tetra-chloroisophthalonitrile. Diamond Shamrock Chemical Co.
    (Unpublished)

    Wolfe, A.L. and Stallard, D.E. (1970a). Residues in milk from cows fed
    2,5,6-trichloro-4-hydroxyisophthalonitrile. Diamond Shamrock Chemical
    Co. (Unpublished)

    Wolfe, A.L. and Stallard, D.E. (1970b). Residues in tissues of dairy
    cows fed Daconil 2787 and 2,5,6-trichloro-4-hydroxyisophthalonitrile.
    Diamond Shamrock Chemical Co. (Unpublished)

    Wolfe, A.L. and Stallard, D.E. (1970c). Analytical method for
    determination of Daconil 2787 and DAC-3701 residues. Diamond Shamrock
    Chemical Co. (Unpublished)
    


    See Also:
       Toxicological Abbreviations
       Chlorothalonil (EHC 183, 1996)
       Chlorothalonil (HSG 98, 1995)
       Chlorothalonil (ICSC)
       Chlorothalonil (Pesticide residues in food: 1977 evaluations)
       Chlorothalonil (Pesticide residues in food: 1981 evaluations)
       Chlorothalonil (Pesticide residues in food: 1983 evaluations)
       Chlorothalonil (Pesticide residues in food: 1985 evaluations Part II Toxicology)
       Chlorothalonil (Pesticide residues in food: 1987 evaluations Part II Toxicology)
       Chlorothalonil (Pesticide residues in food: 1990 evaluations Toxicology)
       Chlorothalonil (Pesticide residues in food: 1992 evaluations Part II Toxicology)
       Chlorothalonil  (IARC Summary & Evaluation, Volume 30, 1983)
       Chlorothalonil  (IARC Summary & Evaluation, Volume 73, 1999)