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 CARBOFURAN Explanation This pesticide was evaluated in 1976 when a temporary ADI and some limits were established. Short term dietary studies in rodents were listed as a requirement for reviewing the temporary nature of the ADI. Findings from comparative biochemical studies with a view to defining the apparent sensitivity of juveniles and further information on residues resulting from approved uses on major crops were also recorded as desirable. At its 11th Session, the CCPR requested clarification of the commodities to be covered by the previously recommended limit for "other animal feeds". New information on these points is reviewed in this monograph addendum. EVALUATION FOR ACCEPTABLE DAILY INTAKE TOXICOLOGICAL STUDIES Special Studies on Cholinesterase Inhibition Groups of rats were fed carbofuran in the diet at dosage levels of 0, 10, 20, and 100 ppm for two years. At periodic intervals, animals were sacrificed and plasma, red blood cell, and brain cholinesterase activity was measured in 10 rats of each dietary level at 6, 12, and 18 months of the study. At 24 months, cholinesterase activity was determined in 20 animals per sex per treatment level. Technical carbofuran was found to cause no physiologically significant depression (<25 percent vs. control) in erythrocyte cholinesterase activity at any dietary level (10, 20 or 100 ppm) in both male and female rats at 6, 12, 18, and 24 months. No depression (< 15 percent vs. control) was observed in brain cholinesterase activity at 10 and 20 ppm in male and female rats at 6, 12, 18 and 24 months. A depression of brain cholinesterase activity was observed at 100 ppm in males at 18 and 24 months, and in females at all time intervals. The cholinesterase inhibition in brain at 24 months was shown to be 21 percent in males and 43 percent in females (Case and Wilson 1979). Special Study on Mutagenicity Carbofuran was tested for mutagenicity by the in vitro Salmonella assay ("Ames test") for screening chemicals for point-mutations. Mammalian metabolism was simulated by the 9000 g fraction of mammalian livers (S-9 mix). All groups were tested with the S-9 mix, and additionally, the highest dose group was tested without an S-9 mix. The following doses were tested: 0, 1.2, 3.7, 11.1, 33.3, and 100 µg/plate. The solvents used were DMSO for carbofuran and distilled water for endoxane (positive control, tested at 500 ug/plate). Doses of up to and including 100 µg/plate did not cause bacterial toxicity. The test provided no indication of mutagenic effect induced by carbofuran. The numbers of mutants neither showed a dose-related increase nor were they doubled. On the other hand, the positive control increased the number of mutants to more than double that found in the negative control (Herbold, 1978). COMMENTS Carbofuran was evaluated for an acceptable daily intake by the Meeting in 1976 and a temporary ADI was established. Preliminary results of a study to define the level causing no cholinesterase depression were reviewed. In addition, data were reviewed which showed no evidence of mutagenic potential as suggested by microbial bioassays. The Meeting was informed that several toxicological studies are in progress and decided to extend the temporary ADI. TOXICOLOGICAL EVALUATION Levels Causing No Toxicological Effect Rat: 10 ppm in the diet, equivalent to 0.5 mg/kg body weight Dog: 50 ppm in the diet, equivalent to 1.25 mg/kg body weight Estimate of Temporary Acceptable Daily Intake for Man 0-0.003 mg/kg body weight RESIDUES IN FOOD AND THEIR EVALUATION RESIDUES RESULTING FROM SUPERVISED TRIALS Brassica leafy vegetables, Maize Leek and Onion Field trials were carried out with granules (Currater 5%) at various locations of Germany, the Netherlands in 1976-1978 and Denmark (Furadan 10) in 1975. The treatments were in accordance with recommended uses. The details are summarized in Table 1. Table 1. Residues Resulting from Supervised Trials with Carbofuran (Years 1975-1978) Single applications Residues1 in mg/kg, at intervals (days) after application Crop granules at a.i. 50-51 59-62 70 79-80 92 104-109 115-125 136-151 161-176 Cabbage 0.1 g/m 13.4 6.4 8.2 7.6 /savoy/ 0.1 g/m 0.3 0.1 0.1 0.1 0.1 g/m 2.02 1.12 2.43 0.26 Kohlrabi 0.1 g/m 0.2 0.2 <O.1 <0.1 0.1 g/m 0.15 0.12 <0.1 <0.1 0.1 g/m 23.72 0.192 23.22 0.54 Cabbage 0.5 kg/ha 0.07 0.04 1 kg/ha 0.1 0.05 2kg/ha 0.3 0.23 Kohlrabi 0.5 kg/ha <0.05 <0.05 1.0 kg/ha 0.05 <0.05 2.0 kg/ha 0.07 0.1 Leek 0.06 g/m <0.1 <0.1 0.06 g/m <0.05 <0.05 1.25 kg/ha 0.5 0.26 0.13 Onions 0.5 kg/ha 0.07 0.04 0.06 0.05 g/m <0.1 <0.1 0.05 <0.1 <0.1 1.5 kg/ha <0.1 1.5 kg/ha <0.1 Table 1. Continued... Single applications Residues1 in mg/kg, at intervals (days) after application Crop granules at a.i. 50-51 59-62 70 79-80 92 104-109 115-125 136-151 161-176 Maize 0.075 g/m 0.3 0.7 0.4 <0.13 0.075 g/m 0.4 0.6 0.3 <0.13 0.075 g/m 0.3 0.8 0.9 <0.13 1 Sum of carbofuran and 3-hydroxy carbofuran 2 leaf samples 3 in kernel Alfalfa Carbofuran (as Furadan 4F) was applied to mixed stands of alfalfa at a rate of 0.3, 0.6, 1.12 kg a.i/ha 7, 14, 28 days before harvest respectively in 10 states of US with two replicates at each location. Carbamate and phenolic residues were determined. The limit of determination was 0.25 mg/kg for each carbamate derivatives and 0.5 mg/kg for the phenols. The composition of stands varied between: alfalfa 50-80%, orchard grass 20-50%, bromegrass 15-50% fescue 0-10%, other grass weeds 0-15%. The average moisture content of samples was 76% (66-86%). The residue found was mainly 3-OH-carbofuran. Intact carbofuran was detected /0.26 mg/kg only in one of the 60 treated samples. 12 samples were analysed for phenols but residues were at or below the limit of determination /0.5 mg/kg/ (FMC 1976a). The total carbamate residues /mg/kg/ ranged at does rates: 0.3 kg ai./ha 0.25-4.54 / 7 days after treatment/ 0.6 kg ai./ha 0.29-4.4 /14 days after treatment/ 1.12 kg ai./ha 0.25-3.18 /28 days after treatment/ Alfalfa and bromegrass samples were taken from 11 locations of Canada. The treatments were made (with Furadan 4.8 F) at dose rates of 0.3 kg a.i/ha and 2 × 0.15 kg a.i/ha. Samples were analysed for the residues of carbofuran (CF), 3-hydroxycarbofuran (3OHCF), their phenols and 3-ketocarbofuran phenol. The carbamate residues are summarised in Table 2. Measurable phenol residues (2.09, 1.46 mg/kg) were only found 1 day after treatment in alfalfa and none was in bromegrass (FMC 1976b). The results of these experiments agree with those discussed above. The low or not detectable residues soon after the treatments may be due to rainfall which appears to remove the carbofuran carbamate residues from the plant surfaces of alfalfa and bromegrasses. The quantity of rain after the treatments was as follows: No. of exp. Rain /mm/ after treatment /days/ 2 3.2 mm /2/ 39.5 mm /3/ 6.6 mm /4/ 58.1 /5/ 4 2.7 mm /3/ 1 mm /4/ 19.6 mm /5/ 6 6.6 mm /0/ 1.7 mm /1/ 2.5 mm /2/ 7 16.2 mm /3/ Table 2. Residues of Carbofuran and 3-hydroxycarbofuran resulting from Supervised Trials in Canada in 1976 Spray application Residues in mg/kg, at intervals/days/after application Crop No. rate kg a.i./ha 0 1 3 7 14 dry /14/ (4.8F formulation) CF 3OHCF CF 3OHCF CF 3OHCF CF 3OHCF CF 3OHCF CF 3OHCF Alfalfa 2 0.15 4.66 nd 3.50 nd 1.3 nd 0.93 nd nd nd <0.5 <0.5 3.8 nd 4.37 nd 0.9 nd 0.50 nd nd nd <0.5 <0.5 Alfalfa 2 0.15 5.09 nd 2.33 nd nd <0.5 nd <0.5 nd <0.5 nd <0.5 6.4 nd 3.9 <0.5 nd <0.5 nd <0.5 nd <0.5 nd <0.5 Bromegrass 2 0.15 9.79 nd 7.5 nd 5.38 1.0 nd 0.97 nd <0.5 nd 1.3 14.2 nd 10.3 nd 3.42 1.0 nd <0.5 nd <0.5 nd 0.98 17.9 nd nd 0.52 Bromegrass 2 0.15 5.03 nd 2.67 nd <0.5 <0.5 nd nd nd nd nd <0.5 4.28 nd 1.94 nd 0.77 <0.5 nd nd nd <0.5 nd <0.5 Alfalfa 2 0.15 3.86 <0.5 3.16 0.58 <0.5 0.88 nd <0.5 nd <0.5 nd <0.5 4.76 0.58 3.2 1.85 <0.5 1.02 nd <0.5 nd nd nd nd Bromegrass 2 0.15 15.7 nd nd <0.5 nd nd nd nd nd nd nd nd 14.6 nd nd nd nd nd nd nd nd <0.5 nd nd Alfalfa 2 0.15 14.4 nd 8.35 nd nd <0.5 nd 0.5 nd 0.56 nd 0.8 7.07 nd 5.58 nd nd 0.74 nd 0.63 nd 0.5 nd 1.0 Alfalfa 1 0.3 15.1 5.29 nd 2.08 nd 2.4 nd 0.98 nd 4.3 14.3 5.38 nd 2.14 nd 2.16 nd 1.72 nd 4.24 Alfalfa 1 0.3 9.46 4.07 nd 1.62 nd 1.40 nd 1.45 <0.5 4.88 9.58 4.07 nd 2.35 nd 1.53 nd 1.60 <0.5 3.66 Alfalfa 1 0.3 10.4 0.7 3.53 2.14 0.76 3.5 nd 1.79 12 nd 2.5 2.62 0.5 2.9 nd 1.18 nd = non detectable Egg Plants Egg plants from three locations in Mexico were analysed for carbofuran and 3-hydroxy-carbofuran. Treatment was one soil application (as Furadan 3 G at 2 kg ai/ha following by three individual foliar applications of 75 WP at 1 kg ai/ha per application. Sampling was 7 and 14 days after treatment. No residues were detected at <0.05 mg/kg limit (FMC 1977a). Garlic Garlic cloves were treated with 30% seed treater at a rate of 0.5% ai/100 kg of seed immediately before planting in Argentina. Samples were taken at harvest 176 days after planting and 0.18 mg/kg carbofuran but none of 3-hydroxy-carbofuran were detected. Potatoes Potatoes from test plots located in ten different states of US were analysed for carbamate and phenolic residues of carbofuran. The treatments were 3.4 kg ai/ha (Furadan 10G) at planting plus 3 times of 11 kg ai/ha foliar spray (Furadan 4 F)/experiment A/ applied with a dose of 6 times 1.1 kg ai/ha/experiment B/. The total residue values in each sample have been calculated by adding in nondetectable residues as being equal to the limit of determinations and placing a "less than" prefix with the sum. The limit of determination for the various compounds analysed was not reported. The average residue in 10 samples taken at the same time, was calculated by adding in ND as zero and less than values in as the listed number disregarding the less than symbol (FMC 1978a). The average, minimum and maximum residue values found after application are listed in Table 3. In Canada, Furadan 1OG and 4.8 F were applied on potato field to give a total toxicant per hectare ranging from 2.2-3.1 kg. At harvest the residues (carbofuran and 3-hydroxycarbofuran) in 8 samples fell in the range of 0.01-0.17 mg/kg. The harvested tubers were stored at 5°C and analysed for carbofuran and 3-hydroxycarbofuran at 0, 30, 60, 90 days. The total residues were in the range of 0.06-0.11 mg/kg after 90 days. There was no evidence for conversion of parent compound to its metabolite during storage (Canada). Carbofuran applied at a dosage rate of 5-10 kg ai/ha at seeding in four supervised trials resulted in nondetectable residues in potatoes 134 days after treatment in Finland. Table 3. Residues in Potatoes mg/kg Days Experiment A Experiment B after carbamates Phenols carbamates phenols Treatment average min. average min. average min. average min. max. max. max. max. ND 0.1 ND 0.2 0-2 0.1 0.64 0.4 1.03 0.05 0.2 0.34 0.7 ND 0.1 ND 0.1 12-15 0.08 0.23 0.3 0.48 0.06 0.1 0.3 0.5 ND ND ND 0.2 27-43 0.05 0.3 0.02 0.45 0.05 0.16 0.34 0.06 Soybean Two separate plots were treated with a foliar spray (Furadan 4F) at a rate of 0.28 kg ai/ha. One plot received a single application and was sampled 63 days after treatment. The second plot was treated twice and the samples were taken 36 days after last application. The observed carbamate residue was solely carbofuran in the range of 0.05-0.1 mg/kg (FMC 1979b). Sweet Corn Sweet corn at various locations of U.S. was treated (with Furadan 10G) at rates of: - 4.5 kg ai/ha in furrow at planting; - 2.24 kg ai/ha at planting as a band of 29-37 cm width; - 4.5 kg ai/ha in furrow at planting and twice (with Furadan 3G) at a rate of 0.56 kg ai/ha as foliar spray; - 1.12 kg ai/ha in furrow at planting and four times (with Furadan 4F) at a rate of 0.56 kg ai/ha at intervals of 4-6 days during ear formation. The carbofuran and hydroxycarbofuran residues in the cobs, kernels, husks and stalks were determined using nitrogen selective Coulson detector. The limit of determination was 0.05 mg/kg for carbofuran and 0.1 mg/kg for 3-hydroxycarbofuran. The kernels contained no detectable residues regardless of type of treatment. The residues in cobs were at or about the limit of determination. The highest residue (4.09 mg/kg) was observed in stalk 87 days after treatment (FMC 1976c, 1976 d). The ranges of residues measured are summarized in Table 4. Sugarcane Supervised trials were carried out in South Africa at dose rates of 3 kg ai/ha (registered dosage) and 4.5 kg ai/ha. The residue in sugar cane was lower than limit of determination (0.2 mg/kg) in both experiments. Table 4. Residues of Carbofuran and 3-hydroxyfuran in Sweet Corn Sample Dose Rate Days Minimum - maximum residues mg/kg Type No. Kg a.i./ha Lapsed CF 3OHCF Total Reference Cobs 16 4.5 66-111 nd 0.1 nd nd nd 0.1 MC-1371 Kernels 16 nd nd nd nd nd nd Husks 16 nd 0.35 nd 0.95 nd 1.3 nd 0.99 nd 3.1 nd 4.09 Cobs 2 4.5+2 × 0.56 28 0.09 0.1 0.13 0.14 0.22 0.26 Kernels 2 nd nd nd nd nd nd Husks 2 0.1 0.2 0.5 0.7 0.9 1.2 Stalks 2 0.33 0.7 0.9 1.24 1.2 1.94 Cobs 16 2.24 76.81 nd nd nd nd nd nd Kernels 16 nd nd nd nd nd nd Husks 16 nd 0.1 nd 0.1 nd 0.2 Stalks 16 nd 0.1 nd 0.14 nd 0.24 Cobs 10 4.5+3 × 0.56 7 nd 0.08 nd nd nd 0.08 Kernels 10 7 nd 0.05 nd nd nd 0.05 Husks 10 7 0.06 0.44 nd 0.45 0.08 0.89 Stalks 6 21-27 0.2 0.38 0.37 1.82 0.59 2.19 Tobacco Burley tobacco fields at five locations of U.S. were treated (with Furadan 10 G or 4 F) before planting at a dose rate of 4.5 kg ai/ha; another 12 plots received 6.73 kg ai/ha. Upon harvesting each tobacco plant was separated into upper, middle and lower leaves for separate analysis. All samples were taken at normal harvest and then commercially air cured before analysis. Following the 4.5 kg/ha dose, the total carbamate residues found (CF + 3OHCF) ranged from non-detectable to a maximum of 13.6 mg/kg in lower leaves, 8.27 mg/kg in middle leaves and 4.72 mg/kg in upper leaves. The quantitable residue found averaged 24.3% carbofuran and 75.7% 3-hydroxycarbofuran (FMC 1977b). While the total residue ranged from non-detectable to 19 mg/kg at 6.73 kg ai/ha. The average residue was 2.84 mg/kg for the 72 samples analysed (FMC 1979c). The limit of determination was 0.5 mg/kg for carbofuran and 1.0 mg/kg for 3-hydroxy carbofuran in both experiments. Tomatoes Two foliar sprays (of Furadan 4.8 F) were applied to ripe tomatoes in Canada. Samples were taken 1, 3, 6, 10 an 27 days after treatment. The carbamate residues on fruit declined from 0.25 mg/kg one day after last application to non-detectability at ten days, with limit of determination 0.05 mg/kg (FMC 1975). Experiments on 9 plots treated at planting (with Furadan 10 G) at a dose rate of 3.36 kg ai/ha in a 29 cm band resulted in non-detectable residues in the fruits (FMC 1977c). FATE OF RESIDUES In Animals The bio-availability of bound (i.e. unextractables) and conjugated (i.e. water solubles) carbofuran residues from bean plants was investigated by administering the radioactive residues orally to female rats. Whereas the water-soluble metabolites were eliminated primarily in the urine, most of the bound residues were excreted in the faeces. In both cases, biliary excretion was minor (Marshall and Dorough, 1977). Carbofuran was degraded rapidly also in laying hens (Hicks et al., 1970); 54% of the dose was hydrolyzed after only 6 hours, and 72% had been hydrolyzed by the end of 24 hours. Laying hens eliminated most of the radioactivity in the excreta, in which the 3-hydroxycarbofuran was identified as the major metabolite. Additionally, free and conjugated forms of 3-ketocarbofuran, carbofuran phenol, 3-hydroxycarbofuran phenol, 3-ketocarbofuran phenol, N-hydroxymethylcarbofuran and 3-hydroxy-N-hydroxymethyl carbofuran were detected in excreta, liver and gizzard. The eggs of laying hens (Hicks et al., 1970) given an oral dose of radio-labelled carbofuran [0.3 mg 14C carbofuran/kg body weight; 2.7 mg ring 14C carbofuran/kg body weight] contained only small amounts of carbofuran equivalents not exceeding 0.02 mg/kg. All tissues taken from the laying hens for analysis at 6 and 24 hours contained residues [maximum levels in liver and kidney amounted to 2.6 mg/kg carbofuran equivalents]. None was detected thereafter in tissues of hens treated with ring 14C carbofuran, although certain tissues from the 14C carbofuran-treated hens contained residues at 3 days. The authors considered that some of the 14CO carbofuran equivalents may have been naturally occurring chemicals, which was in agreement with the findings obtained in the feeding studies on cows (JMPR 1976). In Plants Carbofuran was rapidly taken up by plants through the roots from soil, water or nutrient solution and translocated mainly into the leaves (Ashworth and Sheets 1972, Penner and Early 1973). The rapidity of carbofuran degradation differed in the various plant species and the main metabolite was identified as 3-hydroxycarbofuran. Soybean seeds and kernels of maize contained only 0.0l% of the applied radioactivity (Talker et al., 1977) or non-detectable residues - 0.01 mg/kg - (Turner and Caro 1973) respectively at harvest following soil treatment. Residues in following crops: No residues of carbofuran plus 3-hydroxycarbofuran were found in carrots grown after maize in treated soil. The limit of determination was 0.1 mg/kg. In lettuce planted after savoy cabbage, residues of carbofuran plus 3-hydroxycarbofuran amounted to 0.3-0.4 mg/kg 129 days after the final application, and to n.d.-0.1 mg/kg after 140 and 147 days. In Soil The influence of different parameters on carbofuran degradation in soil was studied. Degradation was seen to accelerate with increasing pH in laboratory experiments (Stanovick, 1968; Getzin, 1973) and in field trials (Caro et al., 1973). Degradation was accelerated also by higher temperature and water contents of the soils (Caro et al., 1973; Talakar et al., 1977b). Talekar et al. (1977b) noted that in subtropical soils, carbofuran was more persistent during the dry and relatively cooler autumn and winter months than in summer. After ten months, only 0.6% of the residues present initially could be recovered as parent compound. In laboratory studies, flooding of soils was likewise found to accelerate degradation (Venkateswarlu et al., 1977). Only 20 to 35% of carbofuran remained intact after 40 days of flooding, except in a relatively acid soil /PH 4.2/ from which 77% unchanged parent compound was recovered. On the other hand, in a laboratory study, the rate of carbofuran dissipation was observed to increase, in the order: sandy loam, silt loam, muck soil (Stanovick, 1968). Getzin (1973) found that the effect of soil sterilization upon the degradation rate of carbofuran varied in different soils. Whereas only slight or no differences were noted in silt loam and organic soils, the rate of degradation was slower in irradiated, sterilized clay loam. Williams et al. (1976b) found that the rate of degradation of carbofuran was forty times greater in non-sterile soil during the second week after application. Carbofuran seemingly is metabolized to a lesser extent in soil than in animals and plants. Several authors (Stanovick, 1968; Caro et al., 1973; Getzin, 1973) found that unchanged parent compound accounted for most of the radioactive residue. Getzin (1973) established that most of the radioactivity - up to 79% - from the degraded carbonyl-labelled carbofuran was expired as CO2. With ring 14C carbofuran, an increase in soil-bound radioactivity was observed as time progressed. Metabolites detected were carbofuran phenol (Stanovick, 1968; Getzin, 1973, Gupta and Dewan, 1975) which accounted for a maximum of 0.8% of the total activity added as carbofuran 3-keto-carbofuran which accounted for 5-10% of the carbofuran present and 3-keto-carbofuran phenol (Caro et al., 1973); Gupta and Dewan, 1975 and Talekar et al., 1977b). Carbofuran phenol was immediately bound to the soil constituents and slowly metabolized by micro-organisms (Stanovick, 1968; Getzin, 1973). 3-ketocarbofuran disappeared from the soil at about the same rate as carbofuran (Caro et al., 1973). In soil 3-hydroxycarbofuran, the principal carbofuran metabolite in some plants and animals, either was not found at all (Gupta and Dean, 1975) or was recovered only in traces (Caro et al., 1973; Talekar et al., 1977b). On the other hand, Thinrumurthi et al. (1975) found in experiments with unlabelled carbofuran at 1 kg ai/ha that 3-hydroxycarbofuran was the principal metabolite in soil, reaching a maximum of 12.70 mg/kg on Day 20. In Water The rate of hydrolysis is strongly pH-dependent. In buffer solution at pH 5/28°C the carbofuran was stable for 28 days, 48.4% of carbofuran remained unchanged at pH 7/28°C after 21 days, while 50% of the compound hydrolysed at pH 9/26°C in 0.46 days. (Cook and Robinson 1972). The results are in good agreement with the findings of other authors (McDonald, 1972, Metcalf, 1968). In field experiments, the behaviour was studied in rice paddy water (Deuel, 1975). Applied in granular form (as Curaterr) to flood water, carbofuran was dissipated within 96 hours. No significant levels of 3-keto or 3-hydroxycarbofuran were found in the water. Metcalf et al. (1974) treated water with 0.1 mg/kg carbofuran. At 13-20°C the residues declined from 0.08 mg/kg immediately after treatment to 0.01 mg/kg on Day 21 post-treatment. At temperatures of 23-32°C, no more residues were detectable after only 7 days. In Processing Tomato fields were treated at planting (with Furadan 10 G) at a dose rate of 3.36 kg ai/ha in a 29 cm band. The crops were processed. Samples were taken from tomatoes, juice, puree, juice pomace and puree pomace and were analysed for the carbamate and phenolic residues of carbofuran. All samples contained residue of less than the 0.05 mg/kg limit of determination. Since all processed products of tomatoes are acidic, any carbamate or phenol residues in tomato samples should likely be present in the processed products. Thus the negative results indicate that the residues in tomatoes are much lower than the 0.05 mg/kg limit of determination (FMC 1977c). EVIDENCE OF RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION 26 samples of barley, sugarbeet, maize, onion, rape, carrot, known to have been treated with carbofuran at sowing were taken and analysed for carbofuran, but none contained detectable residues (Hungary, 1979). NATIONAL MRLs REPORTED TO THE MEETING Country Crops MRLs in Preharvest mg/kg Intervals/days Argentina Apples, pear 60 peaches 45 tobacco, tomatoes no waiting-times corn, potatoes fixed Austria general 35 Belgium sugar-beet, corn grains 0 corn fodder 0.5 general 150 Brazil milk 0.02 rice 0.2 30 cabbages 1 90 peanut and cotton seed 0.1 14 Canada carrots, rutabages, turnips 0.5 corn, grain 0.1 strawberries 0.4 Country Crops MRLs in Preharvest mg/kg Intervals/days Cyprus potatoes, bananas vegetables, beans, brassicas tomatoes, eggplants, cucumbers, onions, etc, groundnuts, fodder beets, tobacco 21-28 Fed. Republic corn, hops, beets fixed by registered of Germany application cabbage 70 wine grapes 56 German potatoes 21 Democratic drift-treated cultures Republic /provisions/ 21 drift-treated cultures /fodder/ 14 Hungary general 0.1 30 Italy sugar-beet 0.1 Kenya maize grain 0.1 sugar cane 0.1 rice 0.2 turnips 0.5 Mexico alfalfa 7-14 cotton 10 sugar cane 17 potatoes 14 Netherlands onions 0.1 others 0 New Zealand grapes, pipfruit 42 pastures 42 Switzerland Field applications 21 mushrooms 0.8 corn 0.1 Spain beet, corn, sorghum 60 South Africa corn, fodder 56 mealies/green 0.2 sugar cane Country Crops MRLs in Preharvest mg/kg Intervals/days Taiwan vegetables 15 fruits 10 rice 21 APPRAISAL Carbofuran is applied at planting or sowing or as foliar treatment at various times during the growing season. Trials indicate that the residues in treated crops such as egg plant, potatoes, soybean sweet corn, tomatoes are generally very low or not detectable even if a foliar treatment was applied shortly before harvest. Only plants having a large leaf surface such as alfalfa, cabbage, forage, grasses, maize and tobacco, contain high residues, which consist mainly of the intact carbofuran and the conjugated 3-hydroxycarbofuran. The residue found in mixed stands of alfalfa and forage grasses is covered by the limit given for alfalfa. There are no data available for the residue in fodder beet or animal feeds other than those discussed in 1976 or in this addendum, and no new data were provided for Brussels Sprouts. Most of the bound residues in bean plants administered orally to female rats were excreted in the faeces, whereas the conjugated metabolites were excreted in the urine. Carbofuran was degraded rapidly in laying hens and eliminated in the faeces, in which 3-hydroxycarbofuran was the major metabolite. The eggs contained less than 0.02 mg/kg residues calculated as carbofuran. No residues of carbofuran or 3-hydroxycarbofuran were found in carrots grown after maize, but in lettuce planted after cabbage, the residue amounted to 0.3-0.4 mg/kg 129 days after the final application. The degradation of carbofuran in soil is influenced by several factors such as pH, humidity, temperature, soil type and microbial activity. Carbofuran phenol was immediately bound to the soil and slowly metabolized by micro-organisms. The new information on methods of analysis supports the conclusions of the 1976 Meeting. RECOMMENDATIONS In the light of the data available, the limits recommended previously for "fodder beets" and "other animal feeds not otherwise listed" are withdrawn. The limit for sugar beet leaves in amended. The remaining recommendations of the previous Meeting are supported by more recent studies. In addition, new limits are recommended for kohlrabi and egg plants, as follows: New or Amended Recommendations Commodity Temporary MRL, Pre-harvest intervals on which mg/kg recommendations are based/days Egg plants 0.1 14 Kohlrabi 0.1 80 Sugar beet leaves 0.2 FURTHER WORK OR INFORMATION Required by July 1980: 1. Submission of the long-term feeding studies in appropriate species. 2. Teratogenicity and reproduction studies. Desirable: 1. Comparative animal studies to evaluate the apparent sensitivity of juveniles with respect to adults. 2. Observations in occupationally exposed people. 3. Further information on the level of residues in brassica cole leafy vegetables, especially Savoy cabbage and Brussels sprouts, and in bulb vegetables resulting from approved uses of carbofuran. 4. More information on use patterns on sugar cane and on the residue in the cane, raw sugar and refined sugar. 5. 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See Also: Toxicological Abbreviations Carbofuran (ICSC) Carbofuran (Pesticide residues in food: 1980 evaluations) Carbofuran (Pesticide residues in food: 1996 evaluations Part II Toxicological) Carbofuran (JMPR Evaluations 2002 Part II Toxicological)