PIRIMICARB JMPR 1978 Explanation Pirimicarb was evaluated by the 1976 Meeting (FAO/WHO, 1977b). A temporary ADI for man was established and temporary MRLs were recommended for a wide range of fruits and vegetables. Additional toxicological and residues data arising from the 1976 review are summarised in this monograph addendum. EVALUATION FOR ACCEPTABLE DAILY INTAKE TOXICOLOGICAL STUDIES Special studies on plant metabolites Rat Groups of 40 rats (20 of each sex) were orally treated with daily doses of 12.5 and 50 mg/kg of the plant metabolite carbamate (R 34 885) for a period of 14 or 28 days. The control group consisted of 10 animals of each sex. The treatment had no effect on the clinical condition, behaviour and mean body weight gain. Either showed the parameters of the haematological and bone marrow examination and the values of the urinalyses any pathological alternations. The results gave no evidence of hypochromic anaemia as suggested in a previous study. The histopathological examination revealed no abnormal findings. In a similar experiment designed to study the inhibition of the cholinesterase activity of the metabolite groups of 10 rats (5 males and 5 females) were treated with daily oral doses of 0, 3 and 12.5 mg/kg for 28 consecutive days. No significant inhibition of the enzyme was found in erythrocytes and brain, whereas the plasma cholinesterase activity showed a depression of 32% compared to control in females after treatment with 28 doses of 12.5 mg/kg (Parkinson, 1978a). Groups of 40 rats (20 males and 20 females) were orally treated with 25 and 100 mg/kg of the plant metabolite 5.6 - dimethyl-2-methylamino-pyrimidin-4-yl dimethylcarbamate (R 34 836) for 14 or 28 days. Additionally a control group consisting of 10 animals of each sex was included into the study. The test compound had no adverse effect when administered at a dose level of 25 mg/kg; at 100 mg/kg however 5 male and 6 female animals died during the study between two and seven doses with clinical signs of cholinesterase inhibition. Some animals at 100 mg/kg lost weight. The examination of blood and bone marrow revealed no abnormal findings and gave no indication for hypochromic anaemia. The results of urinalyses fell into normal limits with the only exception of slightly higher urinary protein values in male animals treated with 14 and 28 doses of 100 mg/kg respectively. No adverse histopathological effects were found at 100 mg/kg. To determine the degree of cholinesterase inhibition groups of 10 rats (5 male and 5 female animals) were orally dosed with 0, 1.5, 5, 25 and 100 mg/kg of the test compound for 28 days. The cholinesterase activity was not affected in erythrocytes and brain, the plasma cholinesterase activity however showed inhibition at 25 mg/kg after 28 days of about 30% in male and about 55% in female animals; after 14 days of treatment with 100 mg/kg the depression was 40%, after 28 days of treatment 63% in female animals only (Parkinson, 1978b). Short-term studies Rat In order to determine a no effect level as regards the growth depression particularly in female rats as found in previous long term studies, groups of 20 female rats were maintained on diets containing 0, 100, 175, 250 and 750 ppm pirimicarb for a period of 8 weeks. The feeding did not adversely affect the general health condition. At 750 ppm reduction of the body weight was observed, accompanied by lower food consumption compared to the control animals, especially in the first half of the study (Paul et al., 1978). In a paired feeding study female rats, fed with dietary levels of 0, 250 and 750 ppm were paired with rats receiving restricted diets at concentrations of 250 and 750 ppm respectively. A treatment related growth depression was observed that was slight at the 250 ppm dietary level and marked at 750 ppm after ad libitum or restricted feeding. The results indicate that the growth depression seems not to be due to reduced palatability of the supplemented food (Richards et al., 1978). Dog To define the susceptibility to haemolytic anaemia in the beagle strain (Jackson et al., 1977) another study was undertaken employing the foxhound an experimental animal. Groups of dogs received pirimicarb at dietary levels of 0 (2 animals) and 2 mg/kg b.w. (2 animals) over a period of 16 weeks. A third group (6 animals) was maintained on a diet containing the test compound at a level of 25/50 mg/kg The dose level of 50 mg/kg was subsequently reduced back to 25 mg/kg as noon an marked haematological changes appeared. The treatment was followed by a recovery period from week 17-23. One dog of the 25/50 mg/kg group was killed after a 2-week treatment with 50 mg/kg pirimicarb, showing behavioural changes and clinical deterioration as weight loss, inappetence and ataxia. Loose faeces were seen in dogs from all treatment groups. At 25 mg/kg vomiting was observed sporadically. Over the first 4 weeks the male animals showed reduced body weight gains. At 50 mg/kg usually a few hours after feeding excessive salivation occurred; some dogs showed toxic effects as laboured respiration, vomiting, bloody faeces and flaccid muscles. The weight loss in some animals was accompanied by a slight reduction in food intake. The treatment at 50 mg/kg was associated with marked anaemia characterised by reduction in haemoglobin, packed cell volume and erythrocyte count and an increase in reticulocytes. The direct Coombs test failed to produce positive results (Jackson and Royle, 1978a). The examination of the bone marrow revealed a tendency to an increased number of normoblasts and towards suppressed activity (hypoplasia). Anaemia, reticulocytosis and bone marrow changes were reversible and normal values were measured after the recovery period. Maximum inhibition of plasma cholinesterase activity of about 50-79% and 80-90% was measured at the 25 mg/kg and the 50 mg/kg dose level respectively. No dose-related alternations as regards the biochemical parameters GOT, GPT, SAP, Glucose and BUN and the common parameters of urinalyses were found at any dose level. No abnormal macroscopic findings were detected. Owing to the small number of control animals the significance of various alterations in relative organ weight particularly of the kidney and the spleen can't be determined (Fox, 1978). Monkey Groups of 4 rhesus monkeys (2 of each sex) were orally treated with 2 and 25 mg/kg pirimicarb over a period of 91 days; additionally 2 monkeys were used as controls. The treatment had no effect on mortality, appearance, behaviour and body weight gain. The parameters of the haematological examinations and the results of urinalyses were within normal limits. There was no evidence of haemolytic anaemia and all direct Coombs tests were negative throughout the dosing period. The results of clinical chemistry with respect to the parameters of Bilirubin, LAP, SGOT, SGPT, SAP, total serum protein, plasma glucose, plasma urea showed no abnormal alterations. A dose-related inhibition of the cholinesterase activity in erythrocytes of 16 and 38% and in plasma of 8 and 74% was found at the dose levels of 2 and 25 mg/kg 2 hours after dosing. The examination of the bone marrow revealed no pathological findings. The few incidental macroscopic findings are not attributable to treatment and the organ weights were considered to be within normal limits (Heywood et al., 1977). In a similar study, groups of 4 rhesus monkeys of each sex were orally dosed with 0, 2, 7 and 25 mg/kg pirmicarb for up to 17 weeks, followed by a recovery period of 8 weeks. The survival, appearance and behaviour were not adversely affected by treatment and the only clinical effect was loose faeces in animals of all treatment groups. At 25 mg/kg a slight reduction In body weight gain was observed in the female animals. The results of haematological investigations gave no indication of a treatment-related anaemia. The parameters of clinical chemistry and urinalyses varied within normal limits. The inhibition of the cholinesterase activity in erythrocytes was 19, 18 and 31% and in plasma it was 23, 35 and 63% at the dose levels of 2, 7 and 25 mg/kg respectively. The cholinesterase activity measured after 2 weeks after cessation of treatment was normal. The findings of the bone marrow examinations were normal as well as any macroscopic post mortem findings. No group differences in organ weights were discovered. In the direct Coombs test sporadically positive reactions were found (Heywood et al., 1978a). Additional serological studies on monkeys confirmed the weak positive reactions in the Coombs test in some animals treated with 0, 2, 7 and 25 mg/kg pirimicarb (Jackson and Royle, 1978b). As could be demonstrated in a test performed on 30 untreated monkeys isolated positive reactions can occur spontaneously (Heywood et al., 1978b; Jackson and Royle, 1978c). COMMENTS Previous studies in beagle dogs showed that the oral administration of pirimicarb caused haemolytic anaemia at dose levels of 10 mg/kg b.w. Concern was expressed by the 1976 Meeting regarding the pathogenesis of the condition and the susceptibility of other species than beagle dogs. Studies were performed recently in the foxhound strain. The same haematologic changes were found after oral treatment with 50 mg/kg. However, studies on rhesus monkeys with administration of oral daily doses of 25 mg/kg for 17 weeks did not show my signs of haemolytic anaemia. The toxic response of the dog therefore seems to be species specific. Significant dose-related cholinesterase inhibition in plasma was observed in dogs and monkeys at dose levels of 25 mg/kg and above. The additional studies in dog (foxhound) confirm the no effect level established at the 1976 Meeting. Additionally the results of supplementary rat studies were submitted to consider the previously observed growth impairment in female rats at 250 ppm in the diet. In one of the presented studies a no effect level of 250 ppm was noted. In a corresponding paired feeding study a slight reduction in body weight gain at 250 ppm compared to the control was observed, suggesting 250 ppm to be the borderline of biological effect. Growth impairment was not caused by diminished food intake. Special studies on two plant metabolites 5,6-dimethyl-2-methyl formamido-pyrimidin4-yl dimethyl-carbamate (R 34 885) and 5,6-dimethyl-2-methylamino-pyrimidin-4-yl dimethylcarbamate (R 34 836) could not confirm the abnormal haematological findings of hypochromic anaemia noted in previous studies which were reported at the 1976 Meeting. Data on carcinogenicity of pirimicarb were not submitted. New data reduced some of the concerns of the previous Meeting and allowed a higher value for the temporary ADI. TOXICOLOGICAL EVALUATION Level causing no toxicological effect Monkey: 2 mg/kg body weight day Rat: 175 ppm in the diet equivalent to 9 mg/kg body weight Dog: 1.8 mg/kg body weight day Estimate of temporary acceptable daily intake for man 0-0.01 mg/kg b.w. RESIDUES IN FOOD AND THEIR EVALUATION RESIDUES RESULTING FROM SUPERVISED TRIALS Residues data in fruit and vegetables were reviewed at the 1976 Meeting. Additional data an alfalfa and cereals is reviewed below. Alfalfa (Medicago sativa) At 0.07-0.14 kg ai per ha, pirimicarb controls the blue aphid, Acyrthosiphon kondoi and the pea aphid, Acyrthosiphon pisum, on alfalfa. The major use of alfalfa is as hay. Freshly cut green standing alfalfa is also used as animal feed, cut either on an "as needed" basis or for ensilation. Seventeen alfalfa residue trials were conducted in seven States of the USA during 1975 and 1976, including four aerial trials. Samples for residue analysis normally consisted of 0.5-1 kg of mature crop derived from 3-4 replicate plots. Samples were usually transferred to cold storage at -18°C within three hours of harvest, prior to analysis by gas chromatography (Edwards et al., 1977). Residues on green standing alfalfa decay rapidly; 50-75% of the initial residue is lost in 1-3 days. One or more days after the last application of 0.07-0.14 kg ai per ha, residues of pirimicarb plus its two carbamate-containing plant metabolites, II and III were less than 50 mg/kg experssed as pirimicarb equivalents on a dry weight basis - see Table 1 and Figure 1 (Cox, 1977; Edwards et al., 1977). During the seven days after spraying, total pyrimidine-carbamate residue levels in alfalfa hay, determined on a fresh weight basic, did not decrease markedly because moisture loss from the cut crop acted as a concentration step. However, when calculated on a dry-weight basis, total carbamate residues were seen to decrease; although the rate of decay was somewhat lower than that found in standing green alfalfa, residue levels in hay were still smaller than those on standing green alfalfa determined on a dry-weight basis. Residues were consistently below 20 mg/kg in hay, on a dry-weight basis, after last spraying at 0.07-0.14 kg ai per ha (Table 2) (Cox, 1977; Edwards et al., 1977). Cereals (Wheat, Triticum spp., Barley, Hordeum vulgare and Oats, Avena sativa) At 0.125-0.25 kg ai per ha pirimicarb controls the grain aphid, Macrosiphum avenae, on cereals. Spraying is conducted at an immature growth stage, normally several weeks before harvest. Residue trials have been conducted in Australia, South Africa, Canada, Denmark, Germany, the Netherlands and the UK. Approximately 1 kg samples were normally transferred to a deep freeze within a few hours of harvest. Residues of pirimicarb and its two major carbamate-contained plant metabolites were usually determined by the gas-chromatographic method. As in the case of alfalfa residues of pirimicarb on green standing cereals decay rapidly, 50% of the initial residue being normally lost within 1-3 days. One day or more after the application of 0.25 kg ai per ha, residues of pirimicarb plus its two carbamate-containing plant metabolites, II and III, were less than 5 mg/kg expressed as pirimicarb equivalents - Table 3 and Figure 1 (Dick, 1978; Kennedy, 1978). There was no obvious difference between residues on immature ears and stalks (Dick, 1978). No residues were detected in grain and straw harvested three weeks or more after spraying at 0.125-0.3 kg ai, per ha (limit of determination; normally 0.01-0.04 mg/kg). See Table 4 (Dick, 1978; Kennedy, 1978). TABLE 1. Residues of pirimicarb in green standing alfalfa ("green chop"), USA 1975-76 Application No. of Pre-harvest Total carbamate rate applications Interval residues (kg ai/ha) (days) (mg/kg) Range Mean 0.07 1-3 0 1.4-26 13 1 1.3-14 6.2 2 0.92-9.7 3.9 3 0.92-6.4 3.7 7 0.48-3.5 2.1 0.14 1-4 0 6.6-79 27 1 3.1-45 12 2 1.9-46 8.7 3 1.0-27 6.5 7 0.57-11 3.0 0.28 1-4 0 12-38 29 1 6.8-22 14 2 5.5-14 9.5 3 2.6-11 7.4 7 1.0-5.8 2.6 * expressed as mg/kg pirimicarb equivalents and on a dry weight basis. TABLE 2. Residues of pirimicarb in alfalfa hay, USA 1975-76 Application No. of Pre-harvest Total carbamate rate applications interval residues (kg ai/ha) days (mg/kg) Range Mean 0.07 1-3 0-3 0.29-12 3.6 6-7 0.81-5.1 2.3 0.14 1-4 0-3 0.55-11 2.9 6-7 0.41-7.5 2.3 0.28 2-4 0-3 1.0-14 5.3 6-7 1.4-8.1 4.2 * expressed as mg/kg pirimicarb equivalents on a dry weight basis. TABLE 3. Residues of pirimicarb in green standing wheat and barley, 1973-78 Country Application Pre-harvest Total carbamate rate interval residues (kg ai/ha) (days) (mg/kg)* Range Mean Wheat Canada 0.14 1-2 0.89-3.9 2.4 5 0.76 7 < 0.04-0.98 0.51 South Africa 0.25 1 0.84-1.1 0.96 2 0.80-1.0 0.91 4 0.52-0.65 0.60 7 0.27-0.52 0.41 Germany 0.25 0 2.5-4.7 3.8 1 0.58-3.4 2.4 3 0.13-2.6 1.6 7 0.04-1.5 0.99 TABLE 3 (Continued) Country Application Pre-harvest Total carbamate rate interval residues (kg ai/ha) (days) (mg/kg)* Range Mean Australia (0.025% ai 0 5.9 spray) 2 3.3 7 0.33 South Africa 0.5 1 2.0-2.6 2.3 2 1.5-2.0 1.7 4 1.3-1.3 1.3 7 0.62-1.0 0.79 Germany 0.5 0 2.2-2-4.5 3.1 1 0.47-1.7 1.2 3-4 0.19-1.0 0.48 7-8 0.05-0.21 0.21 Barley Canada 0.14 1 2.6 5 0.51 7 0.42 * expressed as mg/kg pirimicarb equivalents on a fresh weight basis. TABLE 4. Residues of Pirimicarb in cereal grains and straw, 1968-78 Application Pre-harvest Total carbamate Country rate interval residues (kg ai/ha) (days) (mg/kg)* Range Mean 1. Wheat grain Canada 0.125-0.14 14 <0.04 23 <0.04 92 <0.04 TABLE 4 (Continued) Application Pre-harvest Total carbamate Country rate interval residues (kg ai/ha) (days) (mg/kg)* Range Mean Denmark 0.125 33 <0.01 <0.01 Germany 13-15 <0.01 <0.01 18-21 <0.01 <0.01 Holland 56 <0.01 <0.01 Denmark 0.28-0.3 33 <0.01 <0.01 Germany 6-9 <0.01-0.12 0.05 21-22 <0.01 <0.01 39-42 <0.01 <0.01 Holland 7 <0.01 <0.01 14 <0.01 <0.01 56 <0.01 <0.01 UK 70 <0.1** <0.1** 75-103 <0.01 <0.01 Barley grain Canada 0.14 14 0.09 45 <0.04 Oat grain Canada 0.14 52-71 <0.04 <0.04 2. Wheat straw Germany 0.125 18-21 <0.01 <0.01 UK 0.28 75-103 <0.01 <0.01 Barley straw Canada 0.14 14 0.26 * expressed as mg/kg pirimicarb equivalents on a fresh weight basis ** determined colorimetrically; limit of determination 0.1 mg/kgFATE OF RESIDUES In plants Data reviewed by the 1976 Meeting showed that pirimicarb is rapidly lost from plants after spraying. Half of the initial residue is lost in 1-3 days. Volatilisation affords the primary means of loss: the higher the ambient temperature, the greater the percentage of pirimicarb lost by volatilisation (FAO/WHO, 1977b). Pirimicarb also undergoes photochemical and metabolic degradation. The major carbamate-containing degradation products are compounds II And III (Figure 1). Other degradation products include the hydroxypyrimidines V, VI and VII, which can be present either free or as conjugates, and guanidine and its 1-methyl and III methyl derivatives. A further metabolite on cabbages has been characterized by its facile degradation to the hydroxypyrimidine V and another metabolic component was characterized as re-crystallising with 1,1-dimethylguanidine but not susceptible to desorption from charcoal with a solution containing a large quantity of 1,1-dimethylguanidine (Teal and Skidmore, 1978). Some of the residue is not extracted by conventional techniques, 14% of the radioactivity associated with cabbage leaves 3´ weeks after applying 2 - 14C-labelled pirimicarb was not extracted by maceration with methanol (Teal, 1978). In lettuce plants sprayed with 2- 14C-labelled pirimicarb four weeks prior to harvest, 25% of the radioactivity associated with the plants could not be extracted with ethanol. Pirimicarb compounds III and VI and the three guanidines mentioned above were all shown to be minor constituents of this unextracted residue. Approximately 40% of the unextracted radioactivity was associated with the cellulose and hemicellulose of the plant (FAO/WHO, 1977b). The fate of pirimicarb on alfalfa (Davis and Hemingway, 1978a) is similar to that reviewed previously on lettuce, cabbage, peach leaves and sugar beet leaves. In animals An oral dose of pirimicarb is rapidly excreted by cows, principally in the urine. The biotransformation of pirimicarb in cows is similar to that in rat and dog. Only traces of residues are transferred to milk and tissues (FAO/WHO, 1977b). When a single oral dose of 2-14C-labelled pirimicarb was administered to a cow at 1 mg/kg (equivalent to approximately 33 ppm in the diet), the radioactivity was quantitatively recovered during the following twelve days, principally in the urine (95.6%) but also in the faeces (4.3%). Only 0.29% of the radioactivity was recovered in the milk. The maximum residue in the milk (0.25 mg/kg pirimicarb equivalents) was detected one hour after dosing; 80-90% of the residue was due to the hydroxypyrimidines V, VI and VII (Figure 1). Subsequent residues were 0.06 mg/kg pirimicarb equivalents or less. The maximum residue in fat and meat tissues after twelve days was only 0.04 mg/kg pirimicarb equivalents (FAO/WHO, 1977b). When 2-14C-labelled pirimicarb was administered to a lactating goat for seven days at a rate equivalent to 37 ppm in the diet, 96% of the radioactivity recovered in the excreta was in the urine. Hydroxypyrimidines constituted the major residues - compound VI 35%, compound VII 29% and compound V 2% of the radioactivity in the urine. The total radioactive residue in the milk reached plateau levels of 0, 12 and 0.3 mg Pirimicarb equivalents /kg in the morning and afternoon milkings respectively. Hydroxypyrimidines again constituted the major components - VI and VII together accounting for more than 56% of the radioactivity and V 5%. The goat was sacrificed four hours after receiving the last dose. In the tissues the levels of radioactivity, in pirimicarb equivalents, were muscle 0.45 mg/kg, fat, 0.18 mg/kg, liver 1.8 mg/kg and kidney 2.3 mg/kg. Approximately 50-60% of the extractable radioactivity in muscle, liver and kidney was due to the hydroxypyrimidines V, VI and VII, the two latter predominating (Davis and Hemingway, 1978b). The hydroxypyrimidines V-VII are also major metabolites in the rat and dog and are of low mammalian toxicity (FAO/WHO,1977b). In no instance were residues of pirimicarb or its carbamate-containing metabolites detected in this study. The remainder of the radioactivity present in tissues and milk was due to a mixture of polar, water-soluble compounds (Davis and Hemingway, 1978b). Groups of three barren Friesian cows were maintained for 28-29 days on diets containing approximately 20, 60 and 200 ppm pirimicarb, applied as a spray to pelleted grass nuts. The majority of milk samples obtained from the 20 ppm group did not contain detectable carbamate residues (ie pirimicarb plus its two carbamate-containing metabolites II and III; limit of determination 0.01 mg/kg pirimicarb equivalents). Only trace residues were found in milk obtained from the 60 ppm group - up to approximately 0.02 mg/kg. Milk samples from the 200 ppm group contained mean residues of 0.07 mg/kg (range 0.02 - 0.13 mg/kg). Two animals in each group were sacrificed after 28-29 days and the third after a further seven days on untreated diet. Total carbamate residues in meat tissues were normally non-detectable (ie less than 0.01 mg/kg pirimicarb equivalents) at all dose levels. Trace residues were detected in a few muscle and fat samples but the total carbamate residue was consistently below 0.05 mg/kg in all groups (Edwards et al., 1978). An oral dose of pirimicarb is rapidly excreted by hens. Only traces of residues are transferred to eggs and tissues and the hydroxypyrimidines V-VII constitute the major components of these residues. When a single oral dose of 2-14C-labelled pirimicarb was administered at 8 mg/kg to a hen in peak egg production, 88% of the administered radioactivity was recovered from the excreta during the following three days (Hendley at al., 1978). When 2-14C-labelled pirimicarb was administered to two hens in full egg production, at a rate equivalent to 6 ppm in the diet for fourteen days, total radioactive residues in eggs reached a plateau of 0.05-0.06 mg pirimicarb equivalents/kg in 5-8 days, when the residue in the yolk was approximately twice that in the albumen. The hydroxypyrimidines V-VII (Figure 1) constituted approximately 50% of the total radioactivity in the yolks, with compounds VI and VII predominating (each approximately 20% of the radioactivity in eggs). The pyrimidine-carbamates I-IV together represented approximately 8% of the total radioactivity in the yolks, the remainder of the radioactivity was either not solubilised or was more polar than compound VII. The hens were sacrificed three hours after receiving the last dose. The tissues contained approximately 0.15 mg/kg (muscle), 0.35 mg/kg (liver) or 0.02 mg/kg (fat) pirimicarb equivalents. 48-63% of the radioactivity in liver and muscle was due to the hydroxypyrimidines V-VII, compounds VI and VII again predominating. No more than 3.5% of the radioactivity in the tissues was due to the pyrimidine-carbamates I-VI (Figure 1). About 25% of the radioactivity in the tissues was due to compounds more polar than the hydroxypyrimidine VII, including a conjugate or conjugates of VI Hendley et al., 1978). When a hen in full egg production was given nine daily doses of 2-14C-labelled pirimicarb at a rate equivalent to 60 ppm in the diet, levels of total radioactivity in eggs and tissues were greater than those in the equivalent hens dosed at the 6 ppm rate by the expected factor of 10 (Hendley et al., 1978). Groups of 40 hens in maximum egg production were maintained for up to 28 day on diets containing 1.5, 4.6 and 14 ppm total pyrimidine carbamates. Approximately 90% of the administered carbamate mixture was pirimicarb itself and 10% the carbamate metabolites II and III. No residues of either pirimicarb or compounds II and III were detected in either yolks or albumen of the eggs or in muscle and skin at sacrifice (limits of determination: 0.01 mg/kg for pirimicarb, 0.01-0.02 mg/kg for compounds II and III determined jointly). Trace total carbamate residues in liver did not exceed 0.05 mg/kg pirimicarb equivalents (Edwards and Dick, 1978). METHODS OF RESIDUE ANALYSIS A gas chromatographic method using a nitrogen-selective detector to determine residues of pirimicarb plus its two major carbamate containing plant metabolites (II and III, Figure 1) was reviewed by the 1976 meeting as the preferred crop residue method (FAO/WHO, 1977b). With modified extraction procedures, this method is suitable for the determination of these residues in products of animal origin. Milk and eggs are extracted with a mixture of acetonitrile and chloroform. Tissues are extracted with methanol in the presence of anhydrous sodium sulphate. Clean-up by solvent partition and determination by gas chromatography are as reviewed at the 1976 Meeting (ICI Ltd., 1978). Acetonitrile/chloroform has been shown to be an efficient solvent for extracting aged residues of pirimicarb and of the two metabolites from milk. Greater than 80% extraction efficiency was obtained. The low residue levels in tissues precluded a meaningful extractability study but by analogy with studies on the extractability of these compounds from a wide range of crop substrates, methanol is considered to be the most acceptable extraction solvent for tissues (Edwards et al., 1978;). Mean percentage recovery values for samples fortified in the range 0.005/0.01-0.01/0.25 mg/kg were 76-92% for milk, 76-98% for egg fractions, 80-89% for cow tissues and 62-96% for hen tissues (Edwards et al., 1978; Edwards and Dick, 1978). APPRAISAL Further data on residues of pirimicarb on alfalfa, wheat, barley and oats were reviewed, together with information concerning likely levels in milk, eggs and meat arising from treated animal feeds. Available methods of analysis have been improved and extended to cover products of animal origin. The data provided are sufficient to recommend additional temporary maximum residue limits for residues of pirimicarb in alfalfa, barley, oats, milk, meat and eggs. No data were available on residues in other grains each as maize or rice. RECOMMENDATIONS The following temporary maximum residue limits refer to the sum of pirimicarb, its N-formyl(methylamino) analogue (desmethylformanido pirimicarb) and desmethyl pirimicarb. Commodity Temporary MRL (mg/kg) Alfalfa (green) 50 (dry weight basis) Alfalfa hay 20 (dry weight basis) Barley 0.05* Oats 0.05* Eggs 0.05* Meat 0.05* Milk 0.05* * At or about the limit of determination. FURTHER WORK OR INFORMATION Required (by 1980) 1. Carcinogenicity study in an appropriate mammalian species using a currently acceptable protocol. REFERENCES Fox, T. Pirimicarb dietary toxicity study in foxhounds. Unpublished (1978) report from Hazelton Laboratories Europe Ltd., No. 1371-72/2, submitted by ICI Ltd. Heywood, R., Sortwell, R.J., Pulsford, A.H., Brown, G. and (1977) Street A.E. Pirimicarb preliminary oral toxicity study in rhesus monkeys (repeated dosages for 13 weeks). Unpublished report from Huntingdon Research Centre, No. 164/77825, submitted by ICI Ltd. Heywood, R., Sortwell, R.J., Pulsford, A.H., Brown, G. and 1978a Street, A.E. Pirimicarb oral toxicity study in rhesus monkeys (repeated dosage for 17 weeks, followed by a recovery period of 8 weeks). Unpublished report (final report) from Huntingdon Research Centre, No. 198/78444, submitted by ICI Ltd. Heywood, R., Sortwell, R.J., Pulsford, A.H. and Brown, G. (1978b) Pirimicarb comparative data from naive rhesus monkeys (white blood cell counts and Direct Coombs Tests). Unpublished report from Huntingdon Research Centre, No. ICI 219/78445, submitted by ICI Ltd. Jackson, J.A., Chart, I.S., Sanderson, J. H. and Garner, R. (1977) Pirimicarb induced immune hemolytic anaemia in dogs. Scand. J. Haematol. 19, 360-366. Jackson, J.A. and Royle, G. Pirimicarb: dietary toxicity study (1978a) in foxhounds. "Addendum: results of additional aerological investigations". Unpublished report from ICI Central Toxicology Laboratory, No. CTL/P/420, submitted by ICI Ltd. Jackson, J.A. and Royle, G. Pirimicarb: oral toxicity study in (1978b) rhesus monkeys. "Addendum: results of additional aerological investigations". Unpublished report from ICI Central Toxicology Laboratory No. CTL/P/421, submitted by ICI Ltd. Jackson, J.A. and Royle. G. Pirimicarb: comparative data from 1978c) naive rhesus monkeys (white blood cell counts and Direct Coombs Tests). "Addendum: results of additional haematological and serological investigations". Unpublished report from ICI Central Toxicology Laboratory, No. CTL/P/419, submitted by ICI. Kennedy, S.H. Residues data on pirimicarb in cereals: Canada. (1978) ICI Plant Protection Division data (unpublished). Parkinson, G.R. Pirimicarb metabolite R 34 885: subacute oral (1978a) toxicity to rats. Unpublished report from ICI Central Toxicology Laboratory, No. CTL/P/402, submitted by ICI. Parkinson, G.R. Pirimicarb metabolite R 34 836: subacute oral (1978b) toxicity to rats. Unpublished report from ICI Central Toxicology Laboratory, No. CTL/P/401, submitted by ICI. Paul, J.D., Richards, D., Banham, P.B. and Weight, T.M. (1978) Pirimicarb: growth study to determine a no effect level in the female rat. Unpublished report from ICI Central Toxicology Laboratory No. CTL/P/408 submitted by ICI. Richards, D., Banham, P.B. and Weight. T.M. Pirimicarb paired (1978) feeding study in a female rat. Unpublished report from ICI Central Toxicology Laboratory, No. CTL/P/407, submitted by ICI. Teal, G. and Skidmore, M.W. Pirimicarb: metabolism on cabbage plants (1978) in the field, ICI Plant Protection Division Report No. RJ00033A (unpublished).
See Also: Toxicological Abbreviations Pirimicarb (Pesticide residues in food: 1976 evaluations) Pirimicarb (Pesticide residues in food: 1979 evaluations) Pirimicarb (Pesticide residues in food: 1981 evaluations) Pirimicarb (Pesticide residues in food: 1982 evaluations)