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 FormulaOther Information on Identity and Properties Molecular weight: 265.9 State: White crystalline solid Melting point: 250-251°C Boiling point: 350°C 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 25°C 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 µ 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).
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 315-425°C 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)