PESTICIDE RESIDUES IN FOOD - 1979 Sponsored jointly by FAO and WHO EVALUATIONS 1979 Joint meeting of the FAO Panel of Experts on Pesticide Residues in Food and the Environment and the WHO Expert Group on Pesticide Residues Geneva, 3-12 December 1979 CHLOROTHALONIL Explanation Chlorothalonil was evaluated in 1974. In 1977 it was reviewed in the light of information received in response to needs recorded in 1974, also in response to requests for clarification of the past recommendations received from the 9th Session of CCPR. In 1977, temporary MRLs for whole and pulp of bananas were suggested on a basis of a minimum of acceptable data. Since then the results from field trials involving revised patterns of use have been available. The 1977 Meeting also recorded requirements for additional information (i) to resolve the lower dose limits for kidney effects in rats, and (ii) to define the growth reduction after administration of chlorothalonil or its metabolite, 4-hydroxy-2,5,6-trichloro-isophthalonitrile (DAC-3701) in pups relative to ingestion or secretion into milk. Information was also considered to be desirable on (i) observations in humans, (ii) the extent of metabolism to 4-hydroxy-2,5,6-trichloroisophthalonitrile (DAC-3701) in mammals, and (iii) the effects of cooking on residues. The further information received is reviewed in this monograph addendum. EVALUATION FOR ACCEPTABLE DAILY INTAKE BIOCHEMICAL ASPECTS Two groups of 4 male Sprague-Dawley rats, 9 weeks of age, were intubated (following overnight fasting) with polyethylene glycol 400 solutions of <99 percent pure 14C-hydroxy-2,5,6-trichloroisophthalonitrile (DAC-3701) at dosage levels of 4.3 or 42.6 mg/kg body weight. The 14C label was believed to be evenly distributed in the phenyl ring. Following dosing, rats were maintained individually in metabolism cages. Urine, faeces and cage washings were obtained every 24 hours until execution for tissue analysis at 96 hours post-dosing. Cumulative percentage recovery of administered 14C in faeces and urine was unaffected by dose level. However, faecal levels were approximately 10 times greater than urinary levels. At 96 hours, approximately 78% of the administered dose had been recovered in feces (about 70 percent) and urine (about 8 percent). Excretory half-life was about 48 hours. Residues of 14C/gm of tissue was highest in the large intestine (27 and 384 ppm 14C-4-hydroxy-2,5,6-trichloroisophthalonitrile (DAC-3701) equivalents), followed by small intestine (14 and 161 ppm), liver (17 and 139 ppm), and blood (4 and 41 ppm) following 4.3 and 42.6 mg/kg doses. Low levels were found in all other tissues analyzed. Total accountability of 14C was approximately 1O2% at both does levels. The data are suggestive of hepatic conjugation and biliary excretion of the 14C-labelled test material (Jarrett, et al., 1978). TOXICOLOGICAL STUDIES Special Studies on Carcinogenicity Mice Groups of 50 male B6C3F1 mice were fed chlorothalonil (98 percent purity technical material) at either 10,000 ppm for 2 weeks followed by 2,500 ppm for 78 weeks, and a pre-sacrifice withdrawal period of 11-12 weeks (time-weighted average dose 2,688 ppm) or 20,000 ppm for 2 weeks followed by 5,000 ppm for 78 weeks and a 12 week pre-sacrifice withdrawal period (time-weighted average dose 5,375 ppm). Similar groups of female mice were fed either 10,000 ppm for 2 weeks, 5,000 ppm for 10 weeks, and 2,500 ppm for 68 weeks, with an 11 week presacrifice withdrawal period (time-weighted average dose, 3,000 ppm), or 20,000 ppm for 2 weeks, 10,000 ppm for 10 weeks, and 5,000 ppm for 68 weeks, with a 12 week presacrifice withdrawal period (time-weighted average dose, 6,000 ppm). Matched controls comprised 10 male and 10 female mice were maintained for 91 weeks. A dose related decrease in body weight gain in males was observed. Survival, gross, and histopathology were comparable in all groups. Total incidence of male mice with tumors was 30, 18, and 2 percent at control, low, and high dose levels. Malignant tumor incidence was 20, 4, and 2 percent and benign tumors incidence was 10, 12.5, and 0 percent. Comparable percentages in females are total tumors, 30, 12, and 17 percent, malignant tumors, 0, 6, and 8 percent, and benign tumors, 30, 6, and 8 percent in control, low, and high dose levels, respectively. There was no evidence of change in tumor incidence in specific organs or organ systems (NCI, 1978). Rats Groups of 50 male and 50 female Osborne-Mendel rats were dosed with chlorothalonil (technical 98 percent purity, technical 98.5 percent purity, or analytical grade, pure material) at dose levels of either 10,000 ppm for 1 week, followed by 5,000 ppm for 79 weeks and a 30 week presacrifice withdrawal period (time-weighted average dose, 5,063 ppm) or 20,000 ppm for 1 week followed by 10,000 ppm for 79 weeks and a 31 week presacrifice withdrawal period (time-weighted average dose, 10,126 ppm). Contemporary control groups comprised of 10 male and 10 female rats were maintained for 110 weeks. Body weight data showed a dose-related decrease in weight gain in both sexes. During the second year of the study, treated rats showed ataxia, tachypnea hematuria, hyperactivity, vaginal bleeding, a high incidence of abscess formation and bright yellow urine. Survival was decreased in both male test groups. The report indicates the only non-spontaneous pathological lesions noted were a dose-related increase in renal tubular epithelial tumors in both sexes. (Unfortunately, the test and tabular data in the report differ with regard to the incidence of renal tubular epithelial tumors, rendering an evaluation impossible.) The tabular data does not indicate any cause for concern regarding renal tumor incidence (NCI, 1978). A detailed review of the available data on the NCI bioassay indicates that the tabular data on incidence of renal tubular epithelial neoplasms appears to be correct. No reported tumors were noted in the pituitary, where the incidence of adenomas was, in males 0/8, 5/45, and 0/49, and in females 0/10, 3/47, and 3/42 in control, low, and high dose groups. Similar errors were found in the reported incidence of adrenal adenomas, where in the females, the original report indicated 1/10, 0/47, and 0/47, the corrected data indicating 1/10, 9/47, and 9/47 (Weinberg, 1979). Short Term Studies Rat Seven groups of 15 male and 15 female young adult Wister rats were fed 1, 2, 4, 15, 30, 60, or 120 ppm chlorothalonil in the diet for 17 weeks. A concurrent control group of 30 male and 30 female rats were fed normal laboratory chow. All rats were elated to present a healthy appearance throughout the study. Body weight, food consumption, and survival were comparable in all groups. At termination of the study, all rats were sacrificed. Kidney, liver, and thyroid from each animal was removed and grossly examined. Most kidneys had fat-like nodules on them, and a number of livers were mottled and discoloured (Hastings and Jessop, 1975). Histopathology of the kidney has been reported in detail, and although interstitial nephritis and regenerative epithelium were noted, no dose or compound related effects were observed (Busey, 1975). A second examination of the slides of kidney tissue confirmed the absence of dose or compound related effects (Newberne, 1975). COMMENTS A previous Meeting requested additional data which, in part, were made available and reviewed by this Meeting. A detailed histopathology review of the previous study, by two independent pathologists, alleviated the concerns of the previous Meeting on potential kidney effects. Information on pup growth reduction requested by a previous meeting is still lacking, but information was available to indicate that a new 3-generation study is underway. The conflicting data available from the rat carcinogenicity bioassay, especially with regard to the incidence of renal tubular epithelial tumors, and of adrenal adenomas precluded a full evaluation of these data. The Meeting agreed to extend the temporary ADI for two years. TOXICOLOGICAL EVALUATION Level Causing No Toxicological Effect Rat: 60 ppm in the diet equivalent to 3 mg/kg body weight. Dog: 120 ppm in the diet equivalent to 3 mg/kg body weight. Estimate Of Temporary Acceptable Daily Intake For Man 0-0.03 mg/kg body weight RESIDUES IN FOOD AND THEIR EVALUATION USE PATTERN Pre-harvest treatments Bananas Chlorothalonil is proposed for use to control foliar diseases of bananas and plantains, primarily by low volume aerial applications of a flowable formulation containing 54% a.i. or a wettable powder containing 75% a.i. This use pattern will result in some applications being made to fruiting plants, however it is common practice to place plastic bags over the developing stems to protect the fruit until harvest. Since this agricultural practice is established in 80% or more of the commercial banana growing areas of the world it will be described in some detail as follows. In 1977, two experiments on bananas were carried out in the Philippines and one in Honduras. In the first Philippine experiment, banana trees received three applications a month for five months followed by two applications per month for six months for a total of twenty seven applications at a rate of 1.75 kg (1.31 kg a.i.) Daconil 2787 W-75/ha/application. On or about April 2, the banana fruit were covered by plastic bags as is the cultural practice in the area of the field tests. The last six applications were made after the bananas were bagged. On June 18, following that day's spray application, fruit for residue determination were collected. In the second Philippine experiment, banana trees received nine applications of Daconil 2787 W-75 at a rate of 1.5 kg a.i./ha/application. The test period lasted 191 days and some banana fruit stems were covered with plastic bags and some left uncovered. Samples for analysis were taken on the day of the final spray application from both bagged and unbagged stems. In the Honduras experiment banana trees received twelve applications of BRAVO 6F at a rate of 1.5 pounds a.i./acre/application over the 103 day test period for a total of 18 lbs. a.i./acre. In the test, some of the banana fruits were covered with plastic bags according to the cultural practice in the area. On the day of the twelfth application replicates consisting of four stems of bagged and four stems of unbagged green bananas were harvested for analysis. Uses on various crops in New Zealand New information on use pattern was received from New Zealand which replaces that previously published in 1974 and 1977 (New Zealand, 1979). Table 1. Uses of Chlorothalonil in New Zealand Crop/Disease Application Rate Preharvest Interval Potatoes/early blight 0.8-1.3 kg ai/ha 7 days Potatoes/late blight Beans/anthracnose 1.2-1.7 kg ai/ha 7 days Brassicas/rust 1.2-1.7 kg ai/ha 7 days Celery/downy mildew 150-200 g ai/100 litres 7 days Cucurbits/leaf spots 150-200 g ai/100 litres 1 day Lettuce 150-200 g ai/100 litres 14 days Use on peanuts in South Africa The Republic of South Africa supplied information on the registered use (Oct. 36/1947) of chlorothalonil on groundnuts (peanuts) for the control of leaf diseases of great economic importance (S. Africa, 1979). The information used is WP 75% at 1125 g/ai/ha with a withholding period of 56 days for peanut foliage as fodder. Use on potatoes in Sweden Information was received from Sweden that chlorothalonil is used in that country mainly against potato blight (Phytophtera) (Sweden, 1979). Since the pre-harvest interval for the bisdithiocarbomates was extended from 1 to 4 weeks, chlorothalonil with a withholding period of only 1 week has come to be used for the last fungicide application before potato haulm desiccation and harvest. Chlorothalonil is also used against disease (Alternaria and Erysiphe) on cucumber (withholding period 2 days), and Botrytis on ornamentals in glasshouses. Formulations: WP 75% (in glasshouses, however, as a 20% fumigant) at a rate of application of 1.2-1.5 kg/ha. RESIDUES RESULTING FROM SUPERVISED TRIALS Bananas Some of the bananas obtained during the experiments referred to under `Use Pattern' were analysed green as harvested, others after ripening with ethylene in the laboratory. They were also examined before and after placement in a washing tank and treatment for 15 minutes with 400 ppm a.i. thiabendazole flowable and 1% alum according to common commercial practice. Whole fruit, edible pulp and surface extractions were examined from each handling and treatment level and 6 to 8 replicate analyses were undertaken on each sample of treated bananas. In Philippine experiment (1) no residue equal or greater than 0.02 mg/kg was found on washed or unwashed green whole bananas, or edible pulp from green bananas, washed or unwashed ripe whole bananas or edible pulp from ripe bananas. Treated and nontreated samples gave identical results. In Philippine experiment (2), unbagged whole fruit from treated areas contained a maximum chlorothalonil residue of 0.11 mg/kg (mean, 0.04 mg/kg). Post-harvest washing reduced the mean value from 0.04 to 0.01 mg/kg. Bananas protected by plastic bags during treatment contained no residue of chlorothalonil above 0.01 mg/kg and no detectable residue of DAC-3701. The levels of chlorothalonil obtained by macerated extraction were comparable to those obtained by surface stripping. Edible pulp from treated bananas contained no residues of chlorothalonil or DAC-3701 at the detection limit of 0.01 mg/kg. In the Honduras experiment, unwashed bananas from unbagged plots had a maximum residue of 0.17 mg/kg with a mean of 0.08 mg/kg which was reduced to 0.02 mg/kg by washing. No DAC-3701 residues greater than 0.01 mg/kg were found in any samples including the edible pulp. No chlorothalonil residues greater than 0.01 mg/kg were found in edible pulp. Onions (Canada) In Ontario, Canada, chlorothalonil (as Bravo 5F) was applied to onions (var. Autumn spice) at 1.6 kg ai/ha (3.25 L product in 561.1 L water/ha) by a 16-nozzle sprayer in a single spray with the following results (Canada, 1979): Table 2. Residues following spraying onions (Ontario) Days after application chlorothalonil DAC-3701 0-before spray ND (< 0.05) ND (<0.002) 0-after spray 13 0.24 2 7.7 0.15 4 5.8 0.03 6 2.7 0.01 8* 1.4 0.003 10-older outer leaves 2.4 0.008 10-all leaves* 1.5 0.01 10-younger leaves 0.51 0.005 14 0.93 0.005 15 2.2 0.01 22 0.29 ND (<0.002) The chlorothalonil residues decayed with a half-life of about 3 days while the 4-hydroxy metabolite (DAC-3701) was fairly constant at about 0.5% of the total residue. Selection of 10% of the initial fungicide as an unacceptable level suggest a 7-10 day protection period. Grapes (Canada) In two experiments in Ontario, chlorothalonil was applied to grapes at 1.3-1.9 kg ai/ha as either 7.2 F or 500 F flowable or 75% WP formulations for 3-6 applications in one case or a single late season application of WP in the second case (Canada, 1979). Harvest residues on grapes 46 days-post-spray were 0.8 mg/kg for 6 applications and 0.6 mg/kg for 3 applications for the 75% WP. The flowable formulations gave 1.0 and 3.3 mg/kg for 6 applications and 2.5 and 1.7 mg/kg for 3 applications. Residues of DAC-3701 were 0.006 mg/kg (6 applications) and 0.002 mg/kg (3 applications) for the WP whereas the flowable formulations gave 0.014 and 0.017 mg/kg (6 applications) and 0.008 mg/kg (3 applications). An August application of the WP degraded slowly from 7.5 to 4.9 and 3.1 mg/kg after 7 and 14 days respectively and remained at 1.6-2.5 mg/kg between 21 and 36 days post-spray. The 4-hydroxy metabolite residues declined from 0.09 mg/kg to 0.013 over about the same period. Although some mild phytotoxicity was noted for the flowable formulations, the possible use of such grapes for wine indicated that the higher residue levels associated with these treatments should be considered for recommending maximum residue limits. * mean of 2 sample replicates. Potatoes, Tomatoes (New Zealand) Information on supervised trials from New Zealand showed that potatoes treated 10 times at 1.7 kg ai/ha with a preharvest interval of 6 days had non-detectable (20-5 mg/kg) residues (New Zealand, 1979). Tomatoes treated 5 times with 180 g ai/100 litres (1.5 kg ai/ha) had residues of 11.4, 2.8, 0.9, N.D., and N.D. at preharvest intervals of 1, 3, 7, 10 and 14 days respectively. Peanuts (South Africa) Information from South Africa on residues on peanut foliage (leaves) following treatment by 4 applications at 10 day intervals at a rate of 1125 g ai/ha is shown in the following table (South Africa, 1979). Table 3. Residues on peanut foliage (South Africa) Days after chlorothalonil DAC-3701 last treatment mg/kg mg/kg 0-1 57.5:55.0 0.5:0.5 0 77.5:80.0 0.7:0.8 1 68.0:74.0 0.6:0.6 7 39.0:47.0 0.3:0.4 14 20.5:25.0 0.3:0.2 28 7.0:8.5 0.2:0.3 Recovery at 5 mg/kg = 80% for chlorothalonil and 70% for DAC-3801. Limit of detection = 0.1 mg/kg. FATE OF RESIDUES General Since hexachlorobenzene (HCB) can and does occur as a manufacturing impurity in chlorothalonil, the question arises as to the extent of its occurrence in the residue spectrum of chlorothalonil. Information from the manufacturer indicates that specifications permit no more than 0.02% in W-75 wettable powder. At a typical application rate of 1.5 kg a.i./ha this would result in approximately 0.3 g of HCB per hectare per application. Since the agricultural practice on bananas could result in as many as twenty-seven applications, a total calculated HCB residue of 8.1 g/ha is theoretically possible assuming no losses by volatilization or rain wash-off. However, since HCB is not systemic, any traces of residue would occur on the peel where it could be largely removed by the usual washing process and would not occur in the edible pulp. The situation with respect to other commodities requiring a multiplicity of applications merits investigation. In storage and processing The effects of cooking on chlorothalonil and DAC-3701 were investigated using plain water, green beans, and tomatoes in four cooking techniques. Fifty gram samples of water, chopped green beans, and tomatoes were each fortified with 14C-chlorothalonil and cooked for 10 minutes in a vessel containing 20 ml of boiling water. The cooking methods were: (1) in a 600 ml beaker without a cover, (2) in a 500 ml flat bottomed flask fitted with a reflux condenser, (3) in a 500 ml flat bottomed flask fitted with a distillation column and an acetone trap cooled in dry ice/acetone, (4) in a 6 qt. pressure cooker with and without a tightly sealed cover. A similar group of test samples were also fortified with 14C-DAC-3701 and subjected to cooking methods (1) and (4). After using appropriate extraction and cleanup procedures, the residues were quantitated by liquid scintillation counting and characterized by thin layer chromatography and autoradiography. Separate tests without cooking gave complete recovery of the fortified 14C-radioactivity under all test conditions indicating that the extraction and partition procedures were reliable. The results of the cooking experiments are shown in Tables 4, 5 and 6. For all three test samples, cooking under open conditions resulted in volatilization of chlorothalonil (94-98% loss) whereas cooking under closed conditions resulted in partial hydrolysis to DAC-3701 and either 3-cyano-2,4,5,6-tetrachlorobenzamide (water) or unidentified residues (tomatoes and beans). Only chlorothalonil was found in the distillate. Pressure cooking without a cover resulted in loss of a major portion of the chlorothalonil through volatilization. However, with the cover tightly sealed (15 Psi), the major portion of the chlorothalonil remained unchanged and no significant amounts of DAC-3701 were detected. The later result is postulated to be due to instant sublimation which prevented hydrolysis. The parallel experiments with 14C-DAC-3701 indicated that DAC-3701 is stable and neither chemical change nor loss will occur during cooking. Grape juice In the previously described experiments in Canada (see "Residues from Supervised Trials"), the effect of 3- and 6-spray programmes of 3 formulations of chlorothalonil on carry-over of residues into grape juice are shown in table 7 (Canada, 1979). Table 4. Effect of cooking on 14C-chlorothalonil with water 14C-Chlorothalonil Recovery of 14C-radioactivity (dpm) Fortified Organic Aqueous Sample (dpm) Phase Phase Distillate Total Loss, % Open beaker 1,000,000 29,400 2,700 - 32,100 96.8 Reflux 1,000,000 987,160 7,335 - 994,495 0.6 Distillation 1,000,000 800,400 10,500 200,500 1,011,400 0.0 Table 5. Effects of cooking on 14C-chlorothalonil with tomatoes 14C-Chlorothalonil Recovery of 14C-radioactivity (dpm) Fortified Organic Aqueous Sample (dpm) Phase Phase Distillate Total Loss, % Open beaker 1,400,000 20,500 7,065 - 27,565 98.0 Reflux 1,000,000 797,100 346,430 - 1,041,160 0.0 Distillation 1,000,000 805,600 14,600 107,100 927,300 7.3 Table 6. Effects of cooking on 14C-chlorothalonil with green beans. 14C-Chlorothalonil Recovery of 14C-radioactivity (dpm) Fortified Organic Aqueous Sample (dpm) Phase Phase Distillate Total Loss, % Open beaker 1,400,000 59,000 27,420 - 86.420 93.8 Reflux 1,000,000 772,080 269,080 - 1,041,100 0.0 Distillation 1,000,000 786,000 7,200 160,000 953,200 4.7 Table 7. Residues in Grapes and Juice (Canada) Formulation Grape berries, mg/kg Grape juice, mg/kg and program chlorothalonil DAC-3701 chlorothalonil DAC-3701 Full season: 6 applications 75 W.P. 0.3 <0.002 0.3 0.0005 7.2 F 0.8 0.006 0.7 0.0005 500 F 1.6 0.008 0.9 0.002 Late season: 3 applications 75 W.P. 0.2 <0.002 0.3 <0.0005 7.2 F 0.7 0.011 0.8 <0.0005 500 F 0.6 0.006 0.2 0.004 Check <0.002 <0.002 <0.001 <0.0005 EVIDENCE OF RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION Chlorothalonil is detectable by the analytical methods employed for the Total Diet Study conducted in the United States by the Food and Drug Administration. During the 1976 and 1977 periods, no residues of chlorothalonil were detected at a sensitivity of slightly less than 0.01 mg/kg (Weasel, 1979). Finland and Sweden In the course of monitoring of imported produce during 1978 (Finland, 1979), several lots of imported fruits, vegetables, and rootcrops were analysed with detectable residues only in the following cases: strawberries, 3 samples, 0.02-0.15 mg/kg; chinese lettuce, 6 samples, 0.01-0.86 mg/kg; peaches, 2 samples, 0.12-1.2 mg/kg. In Sweden, thirty-four samples of Swedish potatoes were analysed during 1979 (Sweden 1979). No sample contained detectable levels (0.005 mg/kg) of chlorothalonil. METHODS OF RESIDUE ANALYSIS A specific GLC method for chlorothalonil and its major metabolite, 4-hydroxy-2,5,6-trichloroisophthalonitrile (DAC-3701) in soil, water, green leafy vegetables, tomatoes, and dry oily crops such as soybeans, dry beans, and peanuts has been developed and published (Ballee, 1976). Recoveries ranged from 85-100% for both compounds at a sensitivity level of 0.01 mg/kg. The method of analysis used in the field trials on bananas (Diamond Shamrock, 1979a) was essentially the same as that reported in the initial evaluation of chlorothalonil (FAO, 1975) differing only in details such as the composition of the Florisil eluting mixtures used - 20% dichloromethane in hexane (Eluent A) and 50% dichloromethane, 1.5% acetonitrile, 48.5% hexane (Eluent C) instead of 5% acetone, 95% dichloromethane for chlorothalonil and 50% acetone, 50% dichloromethane for DAC-3701 - and in the use of 1-n-propyl-3-p-tolyltriazene to form the propyl ether of DAC-3701 instead of diazomethane to form the methyl ether. Although the propylated DAC-3701 has desirable GLC properties, its use cannot be recommended due to toxicological hazards associated with the derivitizing agent which has led to its general lack of availability. The original recommended procedure using diazomethane is therefore still the method of choice for determining DAC-3701. As the data herein shows, there is no significant difference in residue results obtained on whole bananas either by surface stripping or by maceration; due to the additional cleanup required when maceration is used the surface stripping technique is preferred. The mean recovery for whole bananas was 93% for chlorothalonil and 84% for DAC-3701; on macerated whole bananas the figures were 72% and 83% respectively. The mean recovery for edible pulp was 71% for chlorothalonil and 64% for DAC-3701. For screening purposes where only chlorothalonil and not the sum of the residues of chlorothalonil plus DAC-3701 is required, the multiresidue method described in the U.S. Food and Drug Administration Pesticide Analytical Manual (PAM), Vol. I, sections 212.1 plus 252 for nonfatty foods can be used. The procedure yields a partial (75%) recovery and has a limit of 0.005 mg/kg. Alternately PAM I, 212.2 can be used; also with a limit of 0.005 mg/kg. For fatty foods PAM I, 212.2 plus 252 can be used with a limit of 0.03 mg/kg fat. NATIONAL MRLs REPORTED TO THE MEETING Country Commodity MRL United States Banana (whole) 0.5 mg/kg Banana (pulp) 0.05 " " New Zealand Celery 15 " " Lettuce 10 " " Beans, brassicas, cucurbits, tomatoes 5 " " South Africa Shelled Ground Nuts 0.1 " " APPRAISAL Chlorothalonil was re-evaluated in response to information desired by the 1977 Joint Meeting on the effects of cooking on residues and to a request from the 1979 Codex Committee on Pesticide Residues to review the recommended temporary maximum residue limits on bananas (whole and pulp) in light of extensive new data available from field trials reflecting improved agricultural practice. In tests conducted in Honduras and the Philippines, repeated low volume aerial applications of chlorothalonil formulations were made on bananas for control of foliar diseases. Although this use will result in some applications being made to fruiting plants it is common practice to place plastic bags over the developing stems to protect the fruit until harvest. Samples of mature banana fruits from bagged and unbagged stems were analyzed for chlorothalonil and its metabolite DAC-3701. No residues (<0.01 mg/kg) of chlorothalonil or DAC-3701 were detected in edible pulp of any samples. Commercial washing of the banana fruits prior to export resulted in an average of 75% reduction in residual chlorothalonil. The data support a reduction in the recommended temporary maximum residue limits from 4 mg/kg (whole banana) and 0.1 mg/kg (banana pulp) to 0.2 mg/kg (whole banana) and 0.05 mg/kg (banana pulp). Data on residues in onions, grapes, potatoes, and tomatoes from supervised trials in various countries were available. These confirmed the previous recommendations for onions, potatoes, and tomatoes and permit the recommendation of a temporary MRL for grapes. Although it is theoretically possible to have a detectable residue of the manufacturing impurity hexachlorobenzene on whole bananas if many repeat applications are made, calculations based on a specification of not more than 0.02% HCB in a commercial formulation indicate that this would not be a problem in bananas since no residues should occur in edible pulp. The situation for other agricultural commodities needs investigation and clarification. Chlorothalonil would be detected by the multiresidue methods of analysis for fatty and non-fatty foods described in the FDA Pesticide Analytical Manual, Vol. I, and equivalent procedures utilized in other countries but DAC-3701 would not. Therefore the multiresidue methods are useful for screening purposes, but if the presence of chlorothalonil is indicated, need to be followed by the more specific methods developed for chlorothalonil and DAC-3701 for regulatory compliance. The effect of cooking upon chlorothalonil with plain water, tomatoes, or green beans was evaluated. Under open cooking conditions, chlorothalonil was lost (94-98%) through volatilization. Under closed cooking conditions, hydrolysis to 4-hydroxy- 2,5,6-trichloroisophthalonitrile (DAC-3701) and 3-cyano-2,4,5,6-tetrachlorobenzamide (DS-19221) occurred. When cooked in a tightly sealed pressure cooker, chlorothalonil remained unchanged. Under similar test conditions, neither losses nor chemical changes were observed, for DAC-3701. RECOMMENDATIONS A temporary maximum residue limit for grapes is recommended in addition to those temporary MRL's previously recommended. The temporary maximum residue limits recommended in 1977 for bananas are amended as follows: Preharvest interval on which recommendations are based; Commodity Limit, mg/kg days Grapes 5 46 Bananas (whole) 0.2 none Bananas (pulp) 0.05 none FURTHER WORK OR INFORMATION Required by 1981: 1. Studies to define the growth reduction after administration of chlorothalonil or its major metabolite (DAC-3701) in pups relative to ingestion or secretion into milk. Desirable 1. Experimental information on the possible occurrence of hexachlorobenzene residues on crops requiring multiple applications. 2. Results of on-going studies on the effects of cooking under closed conditions on residue levels and composition. 3. Elucidation of the discrepancies in the carcinogenicity studies. 4. Observations in occupationally exposed humans. 5. Information on the extent of metabolism of chlorothalonil in mammals. REFERENCES Ballee, D.L., Duane, W.C., Stallord, D.E.,and Wolfe, A.L. "Analytical Methods for Pesticides and Plant Growth Regulators," Vol. VIII, pp. 263-274 (1976). Edited by Gunter Zweig and Joseph Sherma. Academic Press, Inc., New York, N.Y., publishers. Busey, W.M. Histopathological Incidence Data - Kidney. (1975) Unpublished Report by Experimental Pathology Laboratory, Inc. Submitted by Diamond Shamrock Corporation. Canada. Information provided by national government. (1979). Diamond Shamrock. Residue Chemistry. Results of tests on the amount of residues remaining (on bananas), including a description of the analytical method. (1979a) Unpublished report. Diamond Shamrock. Effect of cooking upon 2,4,5,6-tetrachloroisophthalonitrile (chlorothalonil, DS-2787) and 4-hydroxy-2,5,6-trichloroisophthalonitrile (DS-3701). Report Document Number: 283-3EF-79-0058-001. (1979b) Unpublished report. Finland. Information provided by national government. (1979). Hastings, T.F. and Jessop, D.C. 4-month Dietary Toxicity Study-Rats. Chlorothalonil. Final Report. (1979) Unpublished Report by Bio/Tox Research Laboratories, Inc. Submitted by Diamond Shamrock Corporation. Jarrett, R.D., Stallard, D.E., and Bachand, R.T. Absorption, Excretion and Tissue Distribution of Orally Administered 14C-4-Hydroxy-2,5,6-Trichloro-isophthalonitrile (14C-DAC 3701) in Male Sprague-Dawley Rats. (1978) Unpublished Report by T.R. Evans Research Centre Submitted Diamond Shamrock Corporation. NCI. Bioassay of Chlorothalonil for Possible Carcinogenicity. United States Department of Health, Education, and Welfare, Publication No. (NIH) 78-841 (1978). Newberne, P.K. (1975) Unpublished Report by the Department of Nutritional Pathology, Massachusetts Institute of Technology, submitted by Diamond Shamrock Corporation. New Zealand. Information provided by national government. (1979). South Africa. Information provided by national government. (1979). Sweden. Information provided by national government. (1979). Weinberg, M.S. Review of Bioassay Study of Chlorothalonil Performed for the National Cancer Institute by Gulf South Research Institute Phase 1: Rat Study. (1979) Unpublished Report by Booz, Allen, and Hamilton, Inc. Submitted by Diamond Shamrock Corporation. Weasel, J.R. Private Communication. (1979).
See Also: Toxicological Abbreviations