ALDICARB First draft prepared by M M. Watson Ministry of Agriculture, Fisheries and Food Harpenden, Hertfordshire, United Kingdom EXPLANATION Aldicarb was evaluated for acceptable daily intake by the 1979 and 1982 Joint Meetings (Annex 1, references 32 and 38). An ADI of 0-0.005 mg/kg bw was allocated by the 1982 Joint Meeting. Since that time additional information has become available, including a new human volunteer study, and the results of these studies were reviewed at the present Meeting. In order to facilitate review of the complete database, summaries of information presented in the reports of the Joint Meetings of 1979 and 1982 are included in this monograph. EVALUATION FOR ACCEPTABLE DAILY INTAKE BIOLOGICAL DATA Biochemical Aspects Absorption, distribution, and excretion Aldicarb is readily absorbed, distributed widely in the body and excreted rapidly in mammals. Radiolabelled aldicarb was administered orally to male rats and residues were analyzed over a 14-day period. Excretion was essentially complete within 4 days (greater than 95% of the administered dose). The major concentrations of metabolites were observed to have been excreted within 24 h of dosing. Four days following acute oral dosing, residues were not detected in animal tissues. In dogs, the excretion pattern of aldicarb administered subacutely was similar to that noted following acute administration in other species. A similar urinary excretion pattern was observed when aldicarb sulfone and aldicarb nitrile were administerd to lactating dairy cows either alone or in combination with one or more aldicarb metabolites. Following a single acute administration of aldicarb, approximately 83% of the dose was eliminated in the urine within 24 h. A minor quantity of residue was eliminated in the faeces and small amount of residues were observed in milk (less than 3% of the administered dose was observed in milk over a 5-day interval). Aldicarb and/or aldicarb sulfone administered as a single oral dose to laying hens were rapidly excreted in the faeces. Minute quantities of terminal residues were observed in eggs on the first day after treatment, but the residue level declined rapidly (Knaak et al., 1966; Andrawes et al., 1967, 1977; Dorough & Ivie, 1968; Sullivan, 1968a,b,c; Dorough et al., 1970; Hicks et al., 1972; Romine, 1973; Sullivan & Carpenter, 1974). A study in goats was conducted to determine the fate, nature and magnitude of aldicarb residues in urine, milk and tissues. Two lactating goats received S-methyl-14C-aldicarb administered in gelatin capsules at a level equivalent to 2.5 ppm in the feed for ten days. A third goat served as the control. The goats were sacrificed within 6 to 8 h after the last dose was given. No toxic effects were noted during the study. Of the applied dose, 61.2% was eliminated in urine, 11.3% in faeces and 1.1% was secreted in milk. Only 0.2% of the applied dose was found in the respiratory gases and < 0.10% in tissues at the end of the ten-day dosing period (Andrawes & Lee, 1986). Biotransformation The metabolic fate of aldicarb has been studied in a variety of vertebrate and invertebrate species. Minor biotransformation differences have been found to occur with respect to quantities of individual metabolites. The basic metabolic profile of aldicarb in all species examined appears to be the same and is shown in Figure 1. Aldicarb is rapidly oxidized to aldicarb sulfoxide, a relatively stable metabolite. Aldicarb sulfoxide is slowly degraded by both oxidative and hydrolytic mechanisms yielding the corresponding aldicarb sulfone and sulfoxide oxime (Knaak et al., 1966; Metcalf et al., 1966; Andrawes et al., 1967, 1977; Bull et al., 1967; Dorough & Ivie, 1968; Sullivan 1968a; Dorough et al., 1970; Hicks et al., 1972; Sullivan & Carpenter, 1974; Andrawes & Lee, 1986). Effects on enzymes and other biochemical parameters As noted with other N-methylcarbamate esters, aldicarb is a readily reversible inhibitor of cholinesterase activity and in vitro studies have shown that cholinesterase inhibition induced by aldicarb and its oxidative metabolites (aldicarb sulfoxide and aldicarb sulfone) can be rapidly reversed by simple dilution. Aldicarb sulfoxide was 47 and 25 times more effective in inhibiting cholinesterase than aldicarb and aldicarb sulfone, respectively, with an insect enzyme preparation, and 23 and 60 times more effective, respectively, when using an RBC preparation obtained from cows (Metcalf et al., 1966; Bull et al., 1967; Chin & Sullivan, 1968). Toxicological studies Acute toxicity studies The acute toxicity of aldicarb and its metabolites has been studied in a variety of mammalian species. A summary of acute toxicity data for aldicarb in shown in Table 1 and for the metabolites in Table 2. Short-term toxicity studies Mice - Aldicarb Groups of 5 mice/sex were fed aldicarb in the diet at dose levels of 0, 0.1, 0.3, 0.6 or 1.2 mg/kg bw/day for 7 days. Mortality was noted in both males and females at the high dose level. Growth was not affected over the course of the study. Liver and kidney weights were also unaffected. A dose level of aldicarb equal to 0.65 mg/kg bw/day for females and 0.75 mg/kg bw/day for males was without substantial effects. The NOAEL in this study was 0.6 mg/kg bw/day (Weil & Carpenter, 1970e).Table 1: Acute toxicity of aldicarb Species Sex Route Vehicle LD50 Reference (mg/kg bw) Rat M oral corn oil 0.84 West & Carpenter (1966b) Rat M oral corn oil 0.93 Striegel & Carpenter (1962) Rat M oral corn oil 0.67-1.23 Carpenter (1963) Nycum & Carpenter (1968b) Rat F oral corn oil 0.62-1.07 Carpenter (1963) Rat F oral gycerol: ethanol 1.0 WHO (1966) Rat F ip corn oil 0.71 Carpenter (1963) Rat M+F ip corn oil 0.44 Carpenter (1963) Rat M ip PEG 0.37-0.44 Weil & Carpenter (1970a) Rat M ip ethanol 0.57 Johnson & Carpenter (1966b) Rat M iv water 0.47 Weil & Carpenter (1970a) Rat M dermal corn oil >10 Field (1979b) Rat F dermal DMP 3.2-7.0 WHO (1966) Rat M dermal water 38.1-44.9 Weil & Carpenter (1968a) Mouse M oral corn oil 0.382 Weil & Carpenter (1972b) Mouse M oral corn oil 0.5 Weil & Carpenter (1972c) Mouse F oral cotton seed 1.5 Dorough et al. (1970) oil Mouse F ip cotton seed 0.3 Dorough et al. (1970) oil Guinea-pig oral corn oil 1.0 Nycum & Carpenter (1968b) Rabbit oral propylene 1.3 Nycum & Carpenter (1968b) glycol Rabbit M dermal corn oil >10 Field (1979a) Rabbit M dermal PEG 5.0 Striegel & Carpenter (1962) Rabbit M dermal dry 141->200 Weil & Carpenter (1968a) Chicken M oral 9 West & Carpenter (1965) Table 2: Acute toxicity of aldicarb metabolites Chemical Species Route Vehicle LD50 Reference (sex) (mg/kg bw) A. nitrile rat oral 570 West & Carpenter (1966b) A. sulfoxide rat (M) oral corn oil 0.49-1.13 Weil & Carpenter (1970a) Nycum & Carpenter (1968b) A. sulfone rat (M) oral corn oil 20-25 Weil & Carpenter (1970a) Nycum & Carpenter (1968b) A. sulfoxide mouse (M) oral corn oil 0.8-1.6 Nycum & Carpenter (1968b) A. sulfone mouse (M) oral corn oil 25 Nycum & Carpenter (1968b) A. sulfoxide guinea-pig oral corn oil 0.8-1.8 Nycum & Carpenter (1968b) A. sulfone guinea-pig oral corn oil >50 Nycum & Carpenter (1968b) A. sulfoxide rabbit oral corn oil 0.4-1.8 Nycum & Carpenter (1968b) Table 2 (cont'd) Chemical Species Route Vehicle LD50 Reference (sex) (mg/kg bw) A. sulfone rabbit oral corn oil 75 Nycum & Carpenter (1968b) A. sulfoxide rat (M) ip water 0.47 Weil & Carpenter (1970a) A. sulfoxide rat (M) ip corn oil 0.71 Johnson & Carpenter (1966b) A. sulfone rat (M) ip PEG 21.2 Weil & Carpenter (1970a) A. sulfoxide rat (M) iv water 0.47 Weil & Carpenter (1970a) A. sulfone rat (M) iv water 14.9 Weil & Carpenter (1970a) A. sulfoxide rabbit dermal water >20 West & Carpenter (1966b) A. sulfone rabbit dermal water >20 West & Carpenter (1966b) 2-methyl-2- (methyl-sulfinyl) propanol-1 rat oral 11 000 Weil & Carpenter (1969b) OH-methyl A rat oral 42.9 Carpenter (1969) A. sulfoxide oxime rat (M) oral 8060 Nycum & Carpenter (1968a) A. sulfone oxime rat (M) oral 1590 Nycum & Carpenter (1968a) A. sulfoxide nitrile rat (M) oral 4000 Nycum & Carpenter (1968a) A. sulfone nitrile rat (M) oral 350 Nycum & Carpenter (1968a) A: aldicarb Mice - Aldicarb/aldicarb metabolites Groups of 3 male and 5 female mice were fed a mixture of aldicarb and aldicarb sulfone (1:1) in the diet at dose levels of 0, 2, 6, 18, or 36 mg/kg bw/day for 7 days. No mortality was noted at any dose level, but severe cholinergic signs of poisoning were observed at the high-dose in males. Depression of growth was observed at the two highest dose levels. Kidney weight was depressed at the highest dose and liver weight was reduced substantially at 6 mg/kg bw/day and above in both males and females. The NOAEL in this study was 2 mg/kg bw/day (Weil & Carpenter, 1970d) Groups of 5 Charles River CD-1 mice/sex were fed aldicarb sulfone in the diet at dose levels of 0, 0.15, 0.6, 2.4, 9.6 or 38.4 mg/kg bw/day for 7 days. Significant body-weight decrease was noted at the highest dose but there were no significant organ weight changes. Cholinesterase activity was not determined (Weil & Carpenter, 1974e). Rats - Aldicarb Groups of 5 rats/sex were fed aldicarb in the diet for 7 days at dose levels of 0, 4, 8 or 16 mg/kg bw/day. Mortality was noted predominantly at the highest dose at which all males and 2 of 5 females died. One of 5 males also died at 8 mg/kg bw/day. There was a substantial reduction in body-weight gain noted at all dose levels. In males, kidney weights were significantly reduced at 8 mg/kg bw/day and liver weight was depressed at 4 and 8 mg/kg bw/day. In females, both liver and kidney weight was significantly depressed at all dose levels (Weil & Carpenter, 1970b). Groups of 5 rats/sex were fed aldicarb in the diet at dose levels of 0, 0.8, 1.6 or 3.2 mg/kg bw/day for 7 days. Growth was depressed at 1.6 mg/kg bw/day and above. There was no mortality attributable to aldicarb. In males, liver weights were depressed in all treatment groups. In females, liver weights were affected only at the highest dose, but the liver to body-weight ratio was reduced at 1.6 mg/kg bw/day and above. Kidney weights were reduced in males at all dose levels and in females only at the highest dose. Cholinesterase activity, measured on the day after the conclusion of feeding, was normal at the highest dose tested with the exception of plasma cholinesterase which was slightly reduced at the highest level (Weil & Carpenter, 1969a). Groups of 10 CFE rats/sex were fed aldicarb in their diet for 93 days at dose levels of 0, 0.02, 0.1 or 0.5 mg/kg bw/day. One rat per level was killed for cholinesterase (plasma, RBC and brain) determinations at 1, 2, 4 and 29 days of dosing. Mortality was increased and body-weight and food consumption were decreased at the highest level. Histopathology of selected organs was unremarkable and there were no compound-related effects noted. There were no consistent dose-related effects on the cholinesterase determinations, except for plasma cholinesterase depression in both sexes after 30 days at the highest level. There was no indication of how soon after feeding the cholinesterase determinations were performed, which could account for the sporadic results, together with the small number of animals sampled at each interval. The NOAEL in this study was 0.1 mg/kg bw/day (Weil & Carpenter, 1963). Rats - Aldicarb/aldicarb metabolites Groups of 5 rats/sex were fed diets containing aldicarb at dose levels of 0, 0.4, 0.8, 1.6 or 3.2 mg/kg bw/day, or aldicarb sulfoxide at dose levels of 0, 0.4 or 0.8 mg/kg bw/day, or aldicarb sulfone, at dose levels of 0, 0.4, 1.0, 2.5, 5 or 20 mg/kg bw/day, for 7 days. With aldicarb (as with its two major carbamate metabolites) there was a significant growth depression at the highest dose. There were no effects noted with respect to liver or kidney weights. The erythrocyte cholinesterase appeared to be the most sensitive parameter with all three materials tested. The NOAELs, based on erythrocyte cholinesterase depression or decreased body-weight gain over the 7-day treatment period were: aldicarb - 0.8 mg/kg bw/day; aldicarb sulfoxide - 0.4 mg/kg bw/day; and aldicarb sulfone - 2.5 mg/kg bw/day (Nycum & Carpenter, 1968b). Groups of 5 rats/sex received in the diet, aldicarb (0.3 mg/kg bw/day), aldicarb sulfoxide (0.4, 0.8 or 1.6 mg/kg bw/day), aldicarb sulfone (0.6, 5 or 20 mg/kg bw/day), a 1:1 mixture of aldicarb sulfoxide and aldicarb sulfone (1.2 mg/kg bw/day) or a control diet. At the end of the 7 days of feeding, animals were placed on control diets for one day after which they were sacrificed for cholinesterase determination and for examination of liver and kidney. A second one-week feeding trial was performed to compare the data with other strains of rats. Aldicarb sulfoxide was fed to groups of 5 male rats at dose levels of 0, 0.4, 0.8 or 1.6 mg/kg bw/day and aldicarb sulfone was fed to male rats at dose levels of 0, 5 or 20 mg/kg bw/day. As might be expected with the protocol followed in the study, cholinesterase depression was not observed in either plasma, erythrocyte or brain at the conclusion of the study. The second trial using both the same and a different strain of rats was performed in an effort to explain a slight but non-significant inhibition of erythrocyte cholinesterase activity measured in the initial study. Over the course of this study, there were no effects noted on erythrocyte cholinesterase activity (Weil & Carpenter, 1970c). Groups of 5 rats/sex were fed aldicarb sulfoxide in the diet at dose levels of 0, 0.3 or 1.0 mg/kg bw/day and aldicarb sulfone at 0, 2.4 or 16.2 mg/kg bw/day. Animals were sacrificed at 1, 3, 7, 14, 28 and 56 days for cholinesterase analyses. Plasma and erythrocyte cholinesterase activities were measured at the first three time intervals. At the last three time intervals, plasma erythrocyte and brain cholinesterase activities were examined. There was no mortality, but growth was depressed at the highest dose levels with both the sulfoxide and sulfone. Rats administered aldicarb sulfoxide at 1.0 mg/kg bw/day had a slight but significant cholinesterase depression during the study. There were no effects noted at 0.3 mg/kg bw/day. Cholinesterase depression was marked with the aldicarb sulfone consistently throughout the study at the highest dose level of 16.2 mg/kg bw/day (Weil & Cox, 1975). Groups of 10 Wistar rats/sex were administered aldicarb sulfoxide and aldicarb sulfone in a 1:1 ratio, in drinking water, ad libitum, for 29 days. The drinking water levels were 0, 0.075, 0.3, 1.2, 4.8 or 19.2 mg/litre. Plasma and red blood cell cholinesterase levels were determined after 8, 15 and 29 days of treatment. Brain cholinesterase was measured at termination. Animals were continuously exposed to the test substances in water until blood samples were taken or sacrifice was performed. There was no mortality and food and water consumption values together with body- weight gains were significantly decreased in both sexes at the high- dose level when compared to controls. Significant depression of plasma, RBC and brain cholinesterase, in both sexes, occurred at the highest dose level. The data demonstrate that a level of 4.8 mg/litre of aldicarb sulfoxide:aldicarb sulfone in water is without effect on cholinesterase (plasma, RBC, brain) in either sex. Based on the actual concentrations being approximately 80% of the nominal concentrations, the NOAEL was roughly 3.8 mg/litre, equivalent to 0.4 mg/kg bw/day (Mirro et al., 1982). Groups of 15 rats/sex were fed aldicarb sulfoxide in the diet at dose levels of 0, 0.125, 0.25, 0.5 or 1 mg/kg bw/day for 6 months. Animals were sacrificed at 3 months and at the conclusion of the study for cholinesterase determinations and for gross and microscopic examination of liver and kidneys. There was no mortality noted during the course of the study, although growth, especially in males, at 0.25 mg/kg bw/day and above was reduced. Cholinesterase activity was substantially reduced, at the three highest dose levels, especially in plasma and erythrocytes of males. Gross examination of liver and kidneys revealed no abnormalities attributable to aldicarb. The NOAEL in this study was 0.125 mg/kg bw/day (Weil & Carpenter, 1968b). In an attempt to resolve the question of cholinesterase depression and rapid recovery, groups of 5 rats/sex were fed aldicarb sulfoxide for one week or one week plus one day of control diets at a dose level of 1 mg/kg bw/day. When the study was concluded (within one week), animals were sacrificed at 0 and 24 h after the dietary feeding interval (the 24 h animals were fed control diets). Cholinesterase depression was noted at the 0 h sacrifice in erythrocyte and plasma preparations. Administration of a control diet for one day (24 h sacrifice) completely reversed the cholinesterase depression noted when animals were sacrificed without any recovery interval (Weil & Carpenter, 1970c). Groups of 5 rats/sex were fed aldicarb sulfoxide in the diet at dose levels of 0, 0.0625, 0.125, 0.25, 0.5 or 1.0 mg/kg bw/day for 3 and 6 months after which some of the animals were sacrificed immediately and others were placed on a control diet for 24 h prior to sacrifice and cholinesterase analysis. Cholinesterase activity in the brain was unaffected by aldicarb sulfoxide. Plasma and erythrocyte cholinesterase was substantially reduced at the 0 h sacrifice in both sexes. Males were slightly more sensitive with depression being noted at 0.25 mg/kg bw/day and above, while with females depression was noted at 0.5 mg/kg bw/day and above. There was no cholinesterase depression noted in any of the animals treated for either 3 months or 6 months when the animals were allowed to recover from cholinesterase depression for a one day recovery interval. The NOAEL in this study was 0.125 mg/kg bw/day (Weil & Carpenter, 1968b). In a series of studies similar to those reported with aldicarb sulfoxide, groups of rats were fed aldicarb sulfone at dietary concentrations at dose levels of 0, 0.2, 0.6, 1.8, 5.4 or 15.2 mg/kg bw/day for 6 months. Animals were sacrificed at 3 and 6 months for examination of liver and kidney abnormalities and for evaluation of cholinesterase activity. Cholinesterase determinations were made at the end of the 3 and 6 month intervals with rats fed continuously until sacrifice or rats were allowed to consume a control diet for 24 h prior to sacrifice and determination of cholinesterase activity. There was no mortality over the course of the study. Transient but significant growth depression was noted at the highest level in the longer study. There were no effects noted with respect to food consumption or on gross and microscopic examinations of liver and kidneys. Plasma, erythrocyte and brain cholinesterase were significantlv depressed at 5.4 mg/kg bw/day and above. Erythrocyte cholinesterase depression was also noted at 1.8 mg/kg bw/day. There was no cholinesterase depression noted at 0.6 mg/kg bw/day in any of the tissues examined. In the study to evaluate recovery of cholinesterase activity, when animals were allowed to equilibrate for one day on control diets, all depressed cholinesterase values returned to normal. The NOAEL in this study was 0.6 mg/kg bw/day (Weil & Carpenter, 1968c). Groups of rats were fed aldicarb oxime at dose levels of 0, 31.25, 62.5, 125, 250, 500 or 1000 mg/kg bw/day for 7 days. There was no mortality over the course of the study. Growth was slightly reduced at the initiation of the study at dose levels of 125 mg/kg bw/day and above, but at the end of one week only the two highest dose levels appeared to show a retardation in growth. Gross changes were noted in both liver and kidneys at the two highest dose levels in both males and females. The NOAEL in this study was 62.5 mg/kg bw/day (Weil & Carpenter, 1974b). Groups of 5 rats/sex were fed the hydrolytic metabolite of aldicarb (2-methyl-2-(methylsulfinyl)propanol-1) for 7 days at dose levels of 0, 500 or 1000 mg/kg bw/day. Growth was depressed at both dose levels in males but only at the highest dose level in females. In females, while growth was depressed within one day of treatment, the animals appeared to recover during the rest of the week. There was no apparent effect on major organs, although, in females at the highest dose level, kidney weights were slightly depressed. Cholinesterase activity was not measured (Weil & Carpenter, 1969b). Rabbits - Aldicarb Four groups, each of 5 male rabbits with abraded skin, were administered aldicarb 10G formulation at dose levels of 0, 5, 10 or 20 mg/kg bw/day, for 6 h per day, 5 days per week, for 15 days. Water was added periodically during the exposure time to the dressing containing the aldicarb treatment, simulating a condition of excess perspiration. One additional group was administered 20 mg/kg bw/day to intact, unabraded skin with no water added to the dressing. Animals treated with aldicarb under a dry condition with unabraded skin showed normal weight gains and no apparent effects as a result of the treatment. Administration of aldicarb under conditions where the dressing was wet and the skin abraded resulted in reduced body-weight at a dermal dose of 5 mg/kg bw/day and above. During the interim where dermal treatment was not applied, recovery of growth was extremely rapid. Plasma cholinesterase activity was inhibited at the two highest dose levels. There were no other adverse effects on haematology or clinical chemical parameters and limited organ weight analysis and microscopic examination of several major tissues showed no pathological effects attributable to aldicarb. Almost identical results were also obtained in a similar study in rats (Carpenter & Smyth, 1966; Weil & Carpenter, 1968a). Rabbits - Aldicarb metabolites Aldicarb sulfone (technical and 75 WP) were administered to the unabraded, but closely clipped, ventral surface of rabbits (6 males/group, 5 days/week for 19 applications) at dosages of 4.8 mg/kg bw/day for 75 WP and 3.5, 7.0 or 14.0 mg/kg bw/day for technical aldicarb sulfone. No mortality, skin irritation or cholinesterase depression were observed. However, rabbits were removed from treatment 19 h prior to sampling for cholinesterase analyses, which could account for the lack of cholinesterase depression. Body-weight was significantly depressed in the high-dose level rabbits. There were no reported treatment-related effects on organ weights and necropsy findings were unremarkable (Weil et al., 1977). Dogs - Aldicarb Groups of 2 beagle dogs/sex were fed aldicarb at dose levels of 0, 0.2, 0.3 or 0.7 mg/kg bw/day for 7 days. There was no mortality over the course of the study. Plasma, erythrocyte and brain cholinesterase activities, measured one day after conclusion of the dietary treatment, were normal. Gross liver and kidney weights and organ to body-weight ratios were unaffected by aldicarb in the diet (Weil & Carpenter, 1973). Groups of 4 beagle dogs/sex were fed aldicarb in the diet for five days per week at dose levels of 0, 0.2, 0.3 or 0.7 mg/kg bw/day for 100 days. There was no mortality over the course of the study and growth was comparable within all dosage groups. A slightly decreased testes weight and a slight increase in adrenal weight were observed at the highest level in males, but there were no effects in females on any of the tissues and organs examined. Microscopic analysis did not suggest any abnomalities including tissues where gross changes had been seen to occur. Cholinesterase values, as well as other clinical chemistry and haematology parameters, were unaffected by the presence of aldicarb in the diet, however, the animals had been removed from aldicarb exposure for 24 to 48 h prior to cholinesterase analyses. The NOAEL in this study was 0.3 mg/kg bw/day (Weil & Carpenter, 1974c). Groups of 3 beagle dogs/sex were fed aldicarb in the diet at dose levels of 0, 0.025, 0.05 or 0.1 mg/kg bw/day, 5 days per week for 2 years. There was no mortality over the course of the study and growth and food consumption data were comparable to control values. Haematology parameters and clinical chemistry values, evaluated at five intervals over the course of the study were normal. Plasma and erythrocyte cholinesterase, evaluated over the course of the study, did not differ from control values. At the conclusion of the study brain cholinesterase, while somewhat lower at the high dose level, was not statistically different from controls. Gross and microscopic examination of tissues and organs showed no lesions which could be attributable to the presence of aldicarb in the diet at dose levels up to and including 0.1 mg/kg bw/day (Weil & Carpenter, 1966c). A two-week range-finding study was conducted in beagle dogs to select dose levels for a subsequent one-year dog study. Aldicarb was fed to groups of 1 male and 1 female at dietary concentrations of 0, 1, 3, 10, 30 or 100 ppm. There was no mortality during the study, but tremors and slight ataxia were observed at 30 and 100 ppm, and soft faeces were noted more frequently in these dogs. Food consumption was depressed in all treated males, particularly at the highest dose, and slightly depressed in the 100 ppm female. Body- weight losses were noted in the 100 ppm group and in the 30 ppm male. Red blood cell and plasma cholinesterase inhibition exceeded 25% at doses of 3 ppm and greater. Brain cholinesterase inhibition exceeded 25% for the 30 and 100 ppm group males (no calculation was possible in the female groups due to presumed technical error) (Hamada et al., 1985b). As a clear NOEL for cholinesterase depression was not demonstrated in the first study, a second two-week dietary dose range-finding study was conducted to select the dose levels for a subsequent one-year dog study. Aldicarb was fed to groups of 1 male and 1 female at dietary concentrations of 0, 0.1, 0.3, 1, 3 or 10 ppm. There was no mortality during the study and no treatment-related clinical signs were observed. Body-weight change and food consumption were unaffected by treatment. Maximum plasma and erythrocyte cholinesterase inhibition occurred immediately following the two-hour feeding and lasted approximately 4 h after the dosing period. Erythrocyte and plasma cholinesterase inhibition (> 25% compared to the mean pre-study value) occurred in the 10 ppm group on both days 7 and 14. There was no inhibition of brain cholinesterase and no other compound-related effects noted. The NOAEL in this study was 3 ppm, equal to 0.096 mg/kg bw/day (Hamada, 1987b). In a five-week study, conducted in order to further investigate the cholinesterase inhibition dose response curve, aldicarb (99.7%) was fed at dietary concentrations of 0, 0.35, 0.7, or 2 ppm, to 3 groups of 6 beagle dogs/sex. There were no mortalities nor any changes in body-weight gain, food consumption, clinical symptoms or gross pathology indicative of a compound-related effect seen during the study. Plasma cholinesterase inhibition over 20% when compared to the control occurred only in the highest dose group. Red blood cell cholinesterase activity inhibition was not observed in any dose group and brain cholinesterase activity was not measured. No adverse effects were observed at 2 ppm (equal to 0.06 mg/kg bw/day) and the NOEL for any symptoms including plasma cholinesterase depression was 0.7 ppm (equal to 0.02 mg/kg bw/day) (Hamada, 1991). In a 52-week oral toxicity study in beagle dogs, groups of 5 dogs/sex were fed dietary concentrations of 0, 1, 2, 5 or 10 ppm aldicarb (95.5%) daily for 52 weeks. The study was designed to produce maximum cholinesterase depression by limiting feeding time to two hours per day to mimic a bolus administration of aldicarb. Erythrocyte and plasma cholinesterase activities were measured from blood samples collected approximately 2 h after the daily feeding period to minimise dissociation of the carbamate-cholinesterase- complex. Aldicarb at up to 10 ppm (equal to 0.241 mg/kg bw/day) caused no observable effects other than inhibition of cholinesterase activity. Inhibition of erythrocyte and brain cholinesterase activity was restricted to dogs receiving 5 or 10 ppm. The NOEL for plasma cholinesterase inhibition was 1 ppm, equal to 0.027 mg/kg bw/day, while if the changes in the plasma enzyme activity are discounted, the NOAEL was 2 ppm, equal to 0.054 mg/kg bw/day (Hamada, 1988). An inhalation study was conducted to determine the toxicity of pyrolysis products of cigarettes made from tobacco pretreated with aldicarb. Twelve beagle dogs (two animals/sex/dose), which had been initially conditioned prior to commencement of the test to smoking 10 cigarettes per day via tracheostomy, were exposed to untreated, low-level and high-level treated cigarettes on a schedule of two successive cigarettes 5 times per day, 5 days per week for a total of 19 exposure days. Whole blood cholinesterase was monitored throughout the study with samples taken before smoking, after 4 and after 10 cigarettes. All effects observed in this study were apparently due to inhalation of cigarette smoke. No inhibition of cholinesterase was seen in any treatment group (Coate et al., 1982). Dogs - Aldicarb metabolites Groups of 3 beagle dogs/sex were fed aldicarb sulfoxide in the diet at dose levels of 0, 0.0625, 0.125, 0.25 or 0.5 mg/kg bw/day 5 days per week for 3 months. There was no mortality over the course of the study. Slight body-weight changes were noted in many of the dogs at the highest dose level within the first week of treatment but thereafter the body-weight changes were similar to but lower than control values. No effects on haematologic and blood chemistry parameters were observed. Cholinesterase depression measured 24-48 h after the final exposure was not observed in plasma, erythrocytes or brain of any of the animals at the conclusion of the study. Gross and microscopic examination of tissues and organs did not show any adverse effects attributable to the presence of aldicarb sulfoxide. The NOAEL in this study was 0.25 mg/kg bw/day (Weil & Carpenter, 1968b). Groups of 3 dogs/sex were fed aldicarb sulfone in the diet at dose levels of 0, 0.2, 0.6, 1.8 or 5.4 mg/kg bw/day 5 days per week for 90 days. There was no mortality over the course of the study. Slight body-weight depression was noted at the highest dose level, although the body-weight was not statistically lower than control levels. There were no effects noted with respect to biochemical and haematologic parameters and gross and microscopic examination of tissues and organs revealed no effects attributable to the presence of aldicarb sulfone in the diet. Cholinesterase depression was not observed, but dogs were removed from treated diet prior to cholinesterase determinations. The NOAEL in this study was therefore greater than 5.4 mg/kg bw/day (Weil & Carpenter, 1968c). In a two-week range-finding study, aldicarb sulfone was fed to six groups of 1 male and 1 female beagle dog at dietary concentrations of 0, 3, 10, 30, 100 or 300 ppm. There was no mortality during the study, but emesis, tremors and decreased food consumption were observed in the high-dose group. Inhibition of cholinesterase (> 25%) occurred at 10 ppm and over in both sexes for plasma cholinesterase, and 100 ppm and over for red blood cell and brain cholinesterase (Hamada et al., 1985a). In a one-year feeding study, aldicarb sulfone was administered to four groups of 6 beagle dogs/sex at dietary concentrations of 0, 5, 25 or 100 ppm. In this study, samples for cholinesterase determinations were taken approximately two hours after feeding in order to measure maximum cholinesterase inhibition. No treatment-related clinical signs were seen. Body-weight gain was slightly reduced in the high-dose males and females. There was a slight decrease in the spleen weights of the mid- and high-dose females and in the thyroid/parathyroid weight of the high-dose females when compared to respective control values. These changes were not seen in the males. Slight treatment-related effects were noted in the mandibular lymph nodes of the high-dose males and females, and adrenal cortex of the high-dose females. The NOAEL based on depression of erythrocyte and plasma cholinesterase activity was 25 ppm, equal to 0.54 mg/kg bw/day (Hamada, 1987a). Monkeys As a result of reports of alleged illness associated with consumption of watermelons and cucumbers illegally treated or contaminated with aldicarb in 1985, two studies were conducted to evaluate the acute toxicity of aldicarb residues in food commodities. Two crops were chosen for the studies: bananas as a representative of a registered food crop in the USA, and watermelons as a representative of a non-registered food crop from the cucurbit family. (Suggestions had been made that some possible natural component in cucurbits might synergise aldicarb toxicity). Bananas were treated with approximately ten times the recommended label rate and watermelons were treated at 13.44 kg ai/ha, to ensure adequate residues in the fruit. Each study was performed using 3 Cynomolgus monkeys/sex, with an additional group of 3 monkeys/sex serving as a control (total of 12 animals per study). Following analytical determination of actual residues in the two commodities to be consumed, (approximately 0.3 ppm in bananas and 5 ppm in watermelons), intake of the treated crops was adjusted with control fruit to provide a dose of exactly 0.005 mg aldicarb/kg bw. The animals were offered the fruit as the first meal of the day, and consumed it immediately. Individuals were monitored for clinical signs at regular intervals, and plasma and erythrocyte cholinesterase activities were measured pre-dose, then at 1, 2, 4, 6, 12, 18 and 24 hours post-feeding. In both studies, there was no evidence of acute cholinergic distress or any signs of over-exposure in any animal. Depression of plasma cholinesterase activity was evident within 1-4 h after ingestion and reached a maximum of 32 to 36% at 2 h after feeding (banana trial) and 36 to 37% at 1 h after feeding (watermelon trial). Erythrocyte cholinesterase activity was not depressed in either study. Rapid recovery of all enzyme activity was observed. There was no indication in these studies that components in watermelons potentiate aldicarb toxicity (Trutter, 1987a,b). Long-term toxicity/carcinogenicity studies Mice - Aldicarb Groups of 50 B6C3F1 mice/sex (25 of each sex were used as controls) were fed aldicarb at dietary concentrations of 0, 2 or 6 ppm for 103 weeks in a carcinogenicity bioassay. A preliminary dietary study (using 10 mice/sex fed dietary concentrations of aldicarb of 0, 0.5, 1.0, 2.5, 5, 10, 20 or 40 ppm for 13 weeks) showed no significant effects on microscopic examinations of the 0, 20 and 40 ppm levels. In the long-term carcinogenicity study there was no mortality attributable to aldicarb. A variety of benign and malignant tumours, occurring at different sites in both control and aldicarb-treated mice, were not unusual for this strain of mice and were evaluated to be independent of the administration of aldicarb. Gross and microscopic examination of tissues, organs and all gross lesions was performed and it was concluded that aldicarb was not carcinogenic for the B6C3F1 strain of mice of either sex (NIH, 1979). Groups of 44 CD-1 mice/sex were fed aldicarb at dose levels of 0, 0.1, 0.2, 0.4 or 0.7 mg/kg bw/day for 18 months. Mortality was evident in males at the two highest dose levels and in females at the three highest dosage levels during the first two and one-half months of the study. Following this period, aldicarb was admixed with the diet in a different manner which appeared to eliminate its acutely toxic effects. (In the early parts of the study, aldicarb was mixed in a dry fashion using a finely ground aldicarb preparation. At the 2.5 month interval, aldicarb was dissolved in acetone and the acetone-aldicarb solution was dispersed in the diet at a more uniform rate. It was assumed that consumption of small crystalline particles of aldicarb may have led to the high mortality during the initial phases of the study). At the high dose level in males there was a statistically significant increase in hepatomas found predominantly in the survivors at the termination of the study and an increase in lymphoid neoplasias which occured in the mice that died. None of the male mice surviving at the end of the study were found to have lymphoid neoplasias. There were no significant increases in any other types of tumours at dose levels of 0.4 mg/kg bw/day and below (Weil & Carpenter, 1972c). Groups of 50 male CD-1 mice were fed aldicarb at dose levels of 0, 0.1, 0.3 or 0.7 mg/kg bw/day in an effort to verify the results of the previous mouse carcinogenicity bioassay. A group of 150 mice were used as concurrent controls with a mouse being sacrificed for each treated animal that died during the course of the study. Diets were prepared by dissolving aldicarb in acetone and mixing the solution with the diet. The aldicarb was the same sample as used in the previous study and the duration of the study was approximately the same as in the previous trial. There was no mortality observed in the study as a result of aldicarb in the diet. At the end of 18 months cumulative mortality at all dose levels was the same as noted in controls. There was no effect of aldicarb on growth in any of the groups. An examination of the animals that died during the course of the study and those that were sacrificed at the end of 18 months was made and the data compared with control values. There was no significant association between aldicarb in the diet and the formation of tumours, particularly with respect to the incidence of hepatomas, lung adenomas, and lymphoid neoplasias. The data were evaluated with respect to the mice that died, those that survived the test and the total of all animals. It was concluded that the administration of aldicarb at levels up to and including 0.7 mg/kg bw/day for approximately 18 months did not result in a higher than normal incidence of tumours and the inclusion of aldicarb in the diet of CD-1 mice did not result in an increased incidence of carcinogenic response (Weil & Carpenter, 1974d). Groups of C3H/Hej male mice were administered aldicarb dissolved in acetone, dermally 3 times a week for 28 months by applying a brush full of an acetone solution to the shaved back of the mice. For the first 2 weeks, treatment was performed 3 times a week using a 0.25% solution in acetone. After 2 weeks this was reduced to a twice weekly application. This dosing regimen was maintained for 2 months and further reduced thereafter to a concentration of 0.125% which was maintained for the rest of the study. While there was some aldicarb-induced mortality noted over the course of the study this mortality was not substantially different from that noted with control applications. There were no substantial differences with respect to the incidence or onset of tumours. Two growths, a haemangioma and a thymoma, were noted in the animals administered aldicarb. Neither of these internal growths was accompanied by cutaneous papillomas or carcinomas and were considered to be spontaneous growths unrelated to treatment. Aldicarb, administered dermally to this sensitive species, did not induce any incidence of malignancy (Weil & Carpenter, 1966b). Mice - Aldicarb metabolites Groups of Charles River CD-1 mice (50/sex/group) were administered 0, 0.15, 0.6, 2.4 or 9.6 mg aldicarb sulfone/kg bw/day via the diet for 18 months. Aldicarb sulfone did not affect tumour incidence or produce any pathological alteration in this strain of mouse (Woodside et al., 1977b). Rats - Aldicarb Groups of 20 rats/sex were fed aldicarb for 2 years at dose levels of 0, 0.005, 0.025, 0.05 or 0.1 mg/kg bw/day. Additional groups of 16 rats/sex were maintained for serial sacrifices at 6 and 12 months. There was no mortality, attributable to the presence of aldicarb. Growth was normal at all dose levels as was consumption of food and behavioural characteristics. Results of gross examination of liver and kidney weight at 6 months and at one year did not differ from control values. Haematologic determinations in the highest dose level and control groups were normal. Blood and brain cholinesterase activity, measured at 6 and 12 months, were normal. Microscopic examination of tissues and organs for histopathologic occurrences and neoplasms showed the incidence of lesions to be similar in aldicarb-treated and in control groups. An apparent no-effect-level in this study is 0.1 mg/kg bw/day (Weil & Carpenter, 1965). Groups of 50 F344 rats/sex (25/sex for controls) were fed aldicarb in the diet at dietary concentrations of 0, 2 or 6 ppm for 103 weeks. A preliminary study used 10 rats/sex, with dietary concentrations of 0, 5, 10, 20, 40, 80, 160 or 320 ppm for 13 weeks. Microscopic examinations performed on male and female rats of the 0 and 80 ppm dose levels at the conclusion of the preliminary trial showed no significant effects. In the long-term carcinogenicity study, there was no mortality attributable to aldicarb in the diet. A variety of benign and malignant tumours occurring at different sites in both control and aldicarb treated rats were not unusual for this strain of rat and were evaluated to be independent of the administration of aldicarb. Gross and microscopic examination of tissues, organs and all gross lesions was performed and it was concluded that aldicarb was not carcinogenic for the F344 strain of rat of either sex at dietary concentrations of up to 6 ppm (NIH, 1979). Rats - Aldicarb/Aldicarb metabolites Groups of 20 rats/sex were fed aldicarb for 2 years at dose levels of 0 or 0.3 mg/kg bw/day. In addition, groups of rats were fed aldicarb sulfoxide (0.3 or 0.6 mg/kg bw/day), aldicarb sulfone (0.6 or 2.4 mg/kg bw/day) or a 1:1 mixture of aldicarb sulfoxide and aldicarb sulfone (0.6 or 1.2 mg/kg bw/day). There was no significant mortality observed over the course of the study with any of the individual chemicals or the mixture of sulfoxide and sulfone. In the initial phases of the study, there was a slightly higher mortality noted in the high-dose level of aldicarb sulfoxide and in the group receiving the combined aldicarb sulfoxide and aldicarb sulfone. A slight increase in mortality was also noted at the latter part of the study with aldicarb sulfoxide. Growth was slightly depressed at the high-dose level of the sulfoxide:sulfone mixture, primarily in males. There were no apparent effects on growth with respect to the aldicarb, aldicarb sulfoxide or aldicarb sulfone administered alone. Haematological values observed at various intervals over the course of the study did not differ from controls. Cholinesterase determinations were made periodically over the course of the study (6, 12 and 24 months). Plasma, erythrocyte and brain cholinesterase were examined only at a 24-h interval after animals were removed from test diets. There was a slight depression of plasma cholinesterase noted in males administered the high-dose level of the combination aldicarb sulfoxide and sulfone at the 24-month interval. A repeat of the analyses within the final week of the study showed a slight depression in all chemical groups with respect to plasma cholinesterase. There were no effects noted at any interval with respect to red blood cell or brain cholinesterase. The plasma cholinesterase depression noted at the 24-month interval was limited to male rats. An evaluation of the incidence of tumours suggested that there was no statistical difference between treated and control groups. Gross and microscopic examination of tissues and organs at various periods over the two-year test interval showed that these sporadically distributed lesions could not be considered to be indicative of damage induced by aldicarb, its major metabolites, or the combination of the sulfoxide and sulfone (Weil & Carpenter, 1972a). Reproduction studies Rats - Aldicarb Groups of rats (8 male and 16 female rats per group) were fed aldicarb at dietary concentrations at doses of 0, 0.05 or 0.1 mg/kg bw/day for approximately 90 days and mated to initiate a 3- generation, one litter per generation reproduction study. Dietary administration was continuous throughout the study. In addition to the reproduction indices (fertility, gestation, viability and lactation) the F3 generation was maintained for an additional period and tissues from these animals were histologically examined at either weaning or at 90 days of age. In all groups, the reproduction indices from the aldicarb-treated animals were similar to the control group. Body-weights of both male and female pups at weaning were similar to control values as were results of gross and microscopic examinations of tissues and organs in the F3 weanling and 90-day old animals. In all three generations, with all criteria examined, there were no effects of aldicarb on reproduction at a dose level of 0.1 mg/kg body-weight (Weil & Carpenter, 1964). Groups of rats (10 male and 20 female per group) were administered aldicarb in the diet at doses of 0, 0.2, 0.3 or 0.7 mg/kg bw/day for 100 days prior to pairing and mated to initiate an additional 3-generation (one litter per generation) reproduction study. Dietary administration was continuous throughout the study. A larger group was used for the F2 generation (15 male and 25 female rats) as male pups of this generation were maintained on aldicarb diets for 148 days and subjected to a (modified) dominant lethal (mutagenesis) bioassay where they were mated with groups of untreated virgin females for a period of 10 weeks. Each female in the group was mated with 2 treated males and allowed to maintain pregnancy until day 12 when they were sacrificed and examined. There was some mortality over the course of the study which was associated with lung infection and not as a result of aldicarb in the diet. At the high-dose level, body-weights of both male and female F2 pups were lower than the control values. Overall, there were no effects on any of the reproduction indices (fertility, gestation, viability, or lactation). Gross and microscopic examinations of the parents and pups of the high level and control groups showed no effects attributable to aldicarb. The dietary dominant lethal mutagenesis bioassay showed no statistical differences between the aldicarb-treated rats and controls with respect to early or late fetal death or any other parameter examined (Weil & Carpenter, 1974a). Rats Aldicarb metabolites Aldicarb sulfone (99.76% pure) was fed to groups of 10 male and 20 female rats at dietary concentrations at doses of 0, 0.6, 2.4 or 9.6 mg/kg bw/day for approximately 100 days. Rats were then mated to initiate a three-generation, one litter per generation, reproduction study. Dietary administration was continuous throughout the study. Male rats fed 9.6 mg/kg bw/day exhibited reduced body-weights. There were no differences from the control with regard to fertility, gestation survival or viability indices. It was determined that aldicarb sulfone, at levels up to and including 9.6 mg/kg bw/day, was without adverse effects on reproduction under the conditions of this study (Woodside et al., 1977a). Special studies on embryo/fetotoxicity Rats - Aldicarb Using a test protocol where both the reproductive and teratologic potential of aldicarb was evaluated, groups of pregnant rats were fed aldicarb at dietary concentrations at dose levels of 0, 0.04, 0.2 and 1.0 mg/kg bw/day. Females from each of the dietary groups were assigned to one of three treatment groups: (1) aldicarb administered in the diet throughout pregnancy or until pups were weaned; (2) aldicarb administered in the diet from day 0 to day 7 of gestation; (3) aldicarb administered in the diet from day 5 to day 15 of gestation. Five or six females from each group were sacrificed and examined on day 20 of pregnancy and a similar number of females were allowed to bear, nurse and wean the pups. There were neither gross manifestations of teratogenicity in any of the pups carried by females administered aldicarb at dose levels of up to 1 mg/kg bw/day nor was there apparent interference with the reproductive process by any of the dosage regimens used in this study. The administration of aldicarb at dose levels up to and including 1.0 mg/kg bw/day had no apparent effect on the growth of pregnant females during the course of the study (Weil & Carpenter, 1966a). Pregnant Sprague-Dawley rats were given aldicarb by gavage at levels of 0, 0.125, 0.25 or 0.5 mg/kg bw/day on gestational day 6 through day 15. Maternal toxicity was indicated, at the highest dose, by reduced weight gain and food intake during the treatment and post-treatment period as well as by the occurrence of three maternal deaths and, at the two highest levels, by reduced food consumption during treatment. Gestational parameters, including ovarian corpora lutea, number of implantations per litter and sex ratio were unaffected by treatment. Fetal body-weight per litter was significantly reduced at 0.5 mg/kg bw/day. There was no increase in the incidence of external or skeletal malformations. A significantly increased incidence of dilated lateral ventricles with tissue depression was observed only at 0.5 mg/kg bw/day. No increased incidence of malformation was observed in the absence of clear maternal toxicity nor were these malformations accompanied by more severe malformations. The NOEL was 0.125 mg/kg bw/day for maternal toxicity and 0.25 mg/kg bw/day for embryo-fetal toxicity and teratogenicity (Tyl & Neeper-Bradley, 1988). Rats - Aldicarb metabolites The aldicarb sulfone reproduction study incorporated a teratology bioassay. The animals were divided into 4 groups and orally dosed with 0, 0.6, 2.4 or 9.6 mg/kg bw/day at one of the following time intervals of gestation: 0-20 days, 6-15 days, or 7-9 days. All animals were sacrificed before parturition (day 20) and the fetuses examined for skeletal and visceral changes. Anomalies were essentially non-existent and there was no indication of structural abnormalities produced under the conditions of the study at levels up to and including 9.6 mg/kg bw/day (Woodside et al., 1977a). Rabbit - Aldicarb A range-finding study was conducted with aldicarb in rabbits to determine dosage levels of aldicarb for a teratology study. Pregnant Dutch belted rabbits (5/dose) were dosed by oral gavage at 0.1, 0.25, 0.5, 0.75 or 1.0 mg/kg bw/day on days 6 to 27 of gestation. Two does in the high-dose group and one doe in the second highest group died during the study. Increased incidences of decreased defecation (all except low-dose group) and soft stools (two highest dose groups) were noted. Maternal body-weight losses or markedly decreased maternal body-weight gain during the treatment and gestation intervals were observed at 0.25 mg/kg bw/day and greater. Of the uterine parameters measured, there was an increase in the mean post-implantation loss in the high-dose group. Dosage levels of 0.1, 0.25 and 0.5 mg/kg bw/day were selected for the definitive study (Aldridge et al., 1983). Pregnant Dutch belted rabbits (16/dose) were dosed by oral gavage at 0.1, 0.25, or 0.5 mg/kg bw/day on days 7 to 27 of gestation. Signs of maternal toxicity in the treated groups included small amount of stool, pale kidneys and hydroceles on oviducts. A loss in body-weight occurred in the 0.25 and 0.5 mg/kg bw/day dosage groups during gestation days 7 to 27. A decline in the number of viable fetuses per doe was observed in all treatment groups (8.7, 5.0, 6.5 and 6.2 for the control, 0.1, 0.25 and 0.5 mg/kg bw/day treatment groups, respectively). This can be explained by an unusually high number of implantations in the control group (9.8, 6.1, 7.2 and 7.8 implantations per doe in the control, 0.1, 0.25 and 0.5 mg/kg bw/day treatment groups, respectively). There was no clear dose-effect relationship. There were also no increases in post-implantation losses (1.1, 1.1, 0.7 and 1.7 post-implantation losses for the control, 0.1, 0.25 and 0.5 mg/kg bw/day treatment groups, respectively) these figures falling within the historical control range. There was no meaningful difference in any of the other developmental parameters nor in the number of developmental variations or malfunctions between the control and treatment groups. Aldicarb did not produce a teratogenic response when administered orally to rabbits by gavage at dosage levels up to 0.5 mg/kg bw/day (Leng et al., 1983). Special studies on genotoxicity Results of genotoxicity tests are summarised in Tables 3 and 4 (for in vitro and in vivo tests with aldicarb) and Table 5 (for in vitro tests with aldicarb metabolites). Table 3: Results of in vitro genotoxicity assays on aldicarb Test System Test Object Concentration Purity Results Reference Ames test S. typhimurium 50-5000 µg/plate nk Negative Godek et al. (1980c) TA98,TA100,TA1535, TA1537,TA1538 Reverse E. coli WP2 nk nk Negative Dunkel et al. (1985) mutation assay Reverse S. cerevisiae nk nk Negative Guerzoni et al. (1976) mutation assay HGPRT forward CHO cells 1000-5000 µg/ml nk Negative Stankowski et al. (1985a) mutation assay SCE Human nk nk Weak Debuyst & Larebeke (1983) mutation assay lymphocytes Positive Cytogenetics Human 10-250 µg/ml nk Weak Cid & Matos (1984) mutation assay lymphocytes Positive UDS Rat hepatocytes 0.16-5000 µg/ml nk Negative Godek et al. (1984a) DNA damage S. typhimurium > 500 µg/disc nk Positive Rashid & Mumma (1986) TA 1538 uvrB TA 197 nk: not known Table 4: Results of in vivo genotoxicity assays on aldicarb Test System Test Object Concentration Purity Results Reference Micronucleus Mouse 0.001-0.01 93.47% Negative Ivett et al. (1984) test mg/kg bw Micronucleus ICR mouse 0.1-0.4 99.7% Negative Ivett (1990) test mg/kg bw Dominant Wistar rat 0.2-0.7 99.2% Negative Weil & Carpenter (1974a) lethal test mg/kg bw Table 5: Results of in vitro genotoxicity assays on aldicarb metabolites Test System Test Object Concentration Purity Results Reference Ames test S. typhimurium 50-5000 µg/plate nk Negative Godek et al. (1980b) TA98,TA100,TA1535, sulphoxide TA1537, TA1538 Ames test S. typhimurium 100-10000 µg/plate nk Negative Godek et al. (1980a) TA98,TA100,TA1535, sulphone TA1537, TA1538 HGPRT forward CHO cells 500-1500 µg/ml nk Negative Stankowski et al. (1985b) mutation assay sulphone Cytogenetics CHO cells 50-500 µg/ml nk Negative San Sebastian et al. (1984) mutation assay sulphone UDS Rat hepatocytes 0.1-3000 µg/ml nk Negative Godek et al. (1984b) sulphone nk: not known Special studies on skin and eye irritation and sensitization Administration of aldicarb to the conjunctival sac of rabbits did not produce ocular irritation or corneal damage. Ocular irritation studies were performed at doses that were lethal without indication of ocular damage. Furthermore, there was no evidence of dermal irritation when aldicarb was applied to the shaved, abraded backs of rabbits (Striegel & Carpenter, 1962). There was no indication of a sensitization reaction induced by aldicarb. Male guinea-pigs were administered aldicarb by multiple subdermal applications (0.7 mg/kg body-weight) and re-administered aldicarb three weeks later by a similar intradermal administration. There was no suggestion of sensitization in any of the animals tested (Pozzani & Carpenter, 1968a). Skin sensitization to aldicarb sulfone (UC 21865, technical) or a 75% WP formulation was evaluated in albino guinea-pigs (Hartley Strain) using a modified Landsteiner technique. Neither substance was determined to be a sensitizer under the conditions of this study (Conroy & Carpenter, 1977). Special studies on delayed neurotoxicity Hens - Aldicarb Groups of 6 adult chickens were administered aldicarb as a single oral dose of 4.5 mg/kg bw or as daily oral doses of 0, 2.25 or 4.5 mg/kg bw/day for 30 days. A positive control group, treated with 100 mg of TOCP, was used to produce typical delayed neurotoxic signs of poisoning. While there was some weight loss, which was correlated with the dose of aldicarb administered, the only neurological effects attributable to aldicarb were acute signs of poisoning noted in the first two or three days of treatment. Neither ataxia nor hind limb paralysis were noted over the course of the study. Aldicarb did not induce a delayed neurotoxic syndrome similar to that induced by certain organophosphate esters (Johnson & Carpenter, 1966a). Hens - Aldicarb metabolites A group of 40 adult white Leghorn hens were intubated to receive 250 mg/kg bw aldicarb sulfone suspended in maize oil. Two other groups, each with 10 hens, received either TOCP (500 mg/kg bw) or maize oil alone, and served as positive and negative control groups respectively. There were no neurological effects other than acute cholinergic signs of poisoning in the TOCP dosed group. No histological examination was performed, owing to the lack of demonstrated neurotoxic signs. Aldicarb sulfone did not cause delayed neurotoxic reactions under the conditions of the study (Babish & Salerno, 1977). Special studies on behaviour The effects of acute administration of aldicarb and aldicarb sulfoxide on avoidance behaviour in rats was compared to a variety of other carbamate esters. Rats were trained and evaluated for their ability to avoid electrical shock in standard avoidance behaviour tests. Aldicarb and aldicarb sulfoxide were administered by intraperitoneal injection and the rats were evaluated for their ablity to avoid shocks over a 6 h period following administration. The lowest beviourally effective dose was found to be 0.266 mg/kg bw which, when compared to the acute ip LD50 value, was noted to have a smaller ratio of behaviour effects to acute LD50 than any of the other carbamates tested. These data suggest that the level of aldicarb needed to produce measurable avoidance is greater (closer to a fatal dose and less likely to be achieved at the suggested use level) than the chemicals to which it was compared. Additionally, the activity over the 6-h period was seen to rapidly decline again attesting to the transient nature of the cholinesterase inhibition (Johnson & Carpenter, 1966b). Special studies on immune responses Aldicarb was evaluated for its ability to modulate the immune response in two strains of mice. The B6C3F1 mouse was chosen because it is the strain used by the US National Toxicology Program for immunotoxicology studies, and the hybrid Swiss Webster mouse was included because aldicarb had been reported to suppress the splenic plaque-forming cell response to sheep red blood cells in an inverse dose-response fashion (Olson et al., 1987). An attempt was made to reproduce these findings and to expand the data base using more standardised techniques with the B6C3F1 strain. Aldicarb was administered in the drinking water ad libitum for 34 consecutive days to female mice of both strains at dosages ranging from 0.1 to 1000 µg/litre in 10-fold increments (equivalent to 0.04 to 364 mg/kg bw/day). Aldicarb had no effects on body-weights or organ weights, on numbers or types of circulating white blood cells, or on the microscopic pathology of the thymus, spleen, liver, kidneys, or lymph nodes. Also unaffected were the number of antibody forming cells in the spleen and the amount of circulating antibody in the blood. Aldicarb had no effect in either strain on in vivo host resistance to infectious viral challenge, on the capacity of B- and T-lymphocytes to respond to nonspecific mitogens, or on the ability of T-lymphocytes to recognize genetically different cell types in a mixed lymphocyte culture. In this study, subchronic exposure to aldicarb in the drinking water of mice had no effect on any measured immunological function or toxicological parameter (Thomas et al., 1987). In another study, adult female B6C3F1, mice received distilled water only or water containing 1.0, 10 or 100 µg/litre of aldicarb daily for 34 days. To further develop an immune profile of the compound, following aldicarb exposure, the ability of splenic natural killer (NK) cells as well as specifically sensitized cytotoxic T-lymphocytes to lyse YAC-1 lymphoma and, P815 tumour cells, respectively, was evaluated. To complement the functional assays, the impact of aldicarb exposure on spleen cell viability, splenic cellularity and the percentages and absolute numbers of total T-cells, T-suppressor, T-helper and B-cells was evaluated. The results of this study demonstrated that aldicarb did not impact upon the functional ability of interferon-induced splenic NK cells to lyse YAC-1 lymphoma target cells. Aldicarb had no effect on the functional capacity of cytotoxic T-lymphocytes to recognize allogeneic cells in vivo and undergo differentiation and lysis of these cells in a short-term 51-Cr release assay. The numbers and percentages of T-cell subpopulations and B-cells in the spleen also were not significantly affected. In addition, aldicarb had no significant effect on body-weights, on spleen cellularity or cell viability or on absolute weights of lymphoid organs. The absence of statistically significant effects on any of these parameters indicated that aldicarb did not have adverse effects on the immune system of mice (Thomas et al., 1990). Special studies on pesticide antagonistic agents Following acute oral administration to rats, aldicarb has been shown to induce a strong muscarinic action at excretory, bronchial and cardiac nerve sites. A nicotinic effect was also shown to occur at myoneural junctions. The parasympathetic signs of poisoning were readily reduced following atropine administration. Administration of atropine and 2-PAM, alone, or in combination, showed that while atropine was a more effective antidote, 2-PAM was also active. While it has been shown that aldicarb elicits a strong muscarinic action as well as nicotinic action at myoneural sites, the control of signs of poisoning from both mechanisms appears to be somewhat difficult to achieve. Atropine has been shown to be an effective antidote to block the muscarinic effects, but decamethonium, commonly used to block the nicotinic effects, has been shown to be somewhat ineffective. Additional studies to influence the nicotinic actions by such drugs as tubocurare also failed to completely eliminate nicotinic activity. Further studies confirmed the therapeutic effects of a variety of oximes (P2S and obidoxime) in reducing the acute toxic signs of poisoning associated with aldicarb. (Johnson & Sullivan, 1968a,b; Natoff & Reiff, 1973). Special studies on pesticide interactions Aldicarb was administered orally to male rats alone and in combination with a series of eight organophosphate esters or one carbamate ester, all anti-cholinesterase agents, to examine the potential interactive or additive effects. Results of the study, using proportions of the acute lethal dose of each material alone and in combination with aldicarb, showed a simple additive effect with all materials tested. Aldicarb was not found to potentiate the acute oral toxicity of other anticholinesterase agents. Further studies were reported on the potential interaction of aldicarb with alpha-naphthol, aldicarb sulfoxide with aldicarb sulfone and aldicarb sulfone with parathion administered orally and aldicarb with alpha-naphthol or with carbaryl administered by the intraperitoneal route. In no case were any interactions greater tban the predicted additive effects (West & Carpenter, 1966a; Weil & Carpenter, 1970a). Observations in humans Groups of 4 adult male volunteers were administered aldicarb orally in aqueous solution at dose levels of 0.025, 0.05 or 0.1 mg/kg body-weight. Clinical signs of poisoning were recorded and whole blood cholinesterase activity was measured up to 6 h after administration of the sample. Total urine voided was collected and aldicarb-excretion patterns for the initial 8 h after dosing were evaluated. In addition, spot samples were taken at 12 and 24 h. Acute signs of poisoning, typical of anticholinesterase agents, were observed at the high-dose level within 1 h after administration of aldicarb. There were no signs of poisoning observed at the 0.05 mg/kg body-weight dose level. Cholinesterase depression was observed in all volunteers prodominantly within 1-2 h after treatment. Within the first six hours of treatment almost all cholinesterase depression and clinical signs of poisoning were diminished. Examination of urinary excretion patterns showed that approximately 10% of the administered dose was excreted as carbamates (toxic residues) within the first 8 h interval. Cholinesterase analyses confimed the same rapid inhibition and recovery pattern with man as had been observed in experimental animals (Haines, 1971). In another study, two additional subjects were administered aldicarb in water solution at dose levels of 0.05 and 0.26 mg/kg body-weight. Acute signs of poisoning were recorded at the higher- dose level and atropine was administered to aid recovery. No signs of poisoning were recorded with the lower-dose level. Urinary excretion of carbamate residues within 24 h accounted for approximately 10% of the administered dose (Cope & Romine, 1973). A double blind, placebo controlled study has been conducted, in which aldicarb was given as a single oral dose to healthy male and female subjects. The doses administered were: placebo (22 subjects - 16 males and 6 females), 0.01 mg/kg bw (8 males), 0.025 mg/kg bw (8 males and 4 females), 0.05 mg/kg bw (8 males and 4 females) and 0.075 mg/kg bw (4 males). Subjects were screened before entry by general medical history and examination and laboratory tests including haematology, clinical chemistry and urinalysis. Clinical measurements were made at intervals before and after dosing. These included vital signs, (systolic and diastolic blood pressure, pulse rate), pulmonary function tests, pupil size, electrocardiographs, salivation and clinical signs of nausea, vomiting, diarrhoea, sweating, abdominal cramps, involuntary movement and slurred speech. Samples were taken for urinalysis, clinical chemistry (including red blood cell and plasma cholinesterase activity) and haematology evaluation before and after dosing. Urine and blood were collected for aldicarb analysis. The results of these latter analyses were not reported. There were no clinically significant changes in vital signs, pupil size, pulmonary function, ECG's, salivation, clinical signs, clinical chemistry (apart from cholinesterase), haematology or urinalysis in the study. Cholinesterase activity in red cells and plasma was maximally depressed at one hour after dosing and had recovered by 8 h in all subjects. The fall in activity was dose- related. Only marginal depression of cholinesterase activity (< 20%) was seen in erythrocytes from patients treated with 0.01 or 0.025 mg/kg bw and in plasma at 0.01 mg/kg bw. Depression in cholinesterase activity > 20% was seen in erythrocytes at 0.05 and 0.075 mg/kg bw and in plasma at 0.025, 0.05 and 0.075 mg/kg bw. No serious adverse events occurred. The minor adverse events which were recorded were similar to those reported in other volunteer studies. Only one subject (0.075 mg/kg bw group, actual dose 0.06 mg/kg bw) developed symptoms which were reported to be related to aldicarb. The NOAEL in this study should be based on depression (> 20%) in erythrocyte cholinesterase activity and was thus 0.025 mg/kg bw (Nimmo et al., 1992). Fifteen male volunteers participated in a study in Panama to evaluate human exposure in a banana plantation where Temik-15G was applied under natural conditions. Temperatures ranged from 24 °C to 32 °C with 80% to 90% relative humidity. The workers used three different types of hand-held applicators. Blood samples were taken from all volunteers prior to initiating the test and immediately following each 6 h working period for estimation of blood cholinesterase activity. Samples were obtained in the field and analyzed 1-2 h later in the laboratory. Only two workers showed greater than 25% reduction in their blood cholinesterase activity (29% and 50%). Spontaneous reversibility was evident in both cases. The worker with 50% reduction showed 25% recovery within 3 h. Blood samples from the other worker indicated 100% recovery 24 h later. Results of blood analyses indicated that cholinesterase activity was below the normal range (population) in samples collected from six workers during the second day of the study. Cholinesterase activity in all samples taken during the first and third day of the study were within the normal range. No clinical signs of aldicarb-induced intoxication were found, although one individual presented symptoms of nausea, stomachache and headache (Union Carbide, 1979). A series of human exposure episodes was reported occurring as a result of a variety of field and glasshouse conditions in an effort to assess the potential for human harm from exposure under actual occupational conditions. In several instances, slight blood cholinesterase depression attested to the actual exposure situation. Exposure data, as indicated by cholinesterase depression or urinary excretion, suggested that there was no change in the general health of workers exposed under any of the working conditions. Although there were acute clinical signs of poisoning there was no indication that the workers exposed were harmed once removed from exposure situation (Williams, 1966; Burrows et al., 1970; Wakefield et al., 1973; Shrivastava, 1975; Pandey, 1977). From 1966 to 1979, 133 cases of apparent over-exposure to aldicarb formulations were reported. Of these cases, 40 were confirmed aldicarb poisoning episodes where clinical diagnosis and/or urinalysis for aldicarb and its metabolites were performed. As has been the case with other carbamate insecticides, the acute signs of toxicity are rapidly dissipated, although atropine therapy and hospitalization have been useful therapeutic regimens (Abdalla, 1977, 1979). Several deaths have been reported, but all of these have been attributed to suicide or gross neglect (Lee, 1984). California reported that in 1974, 1975 and 1976 a total of 10, 14 and 13 cases of human illnesses were reported, respectively. In these incidents, people were directly exposed to aldicarb and illness was brought on by dermal, inhalation and in one instance, ocular exposure. While most illnesses resulted from aldicarb exposure in loading or applying the formulated pesticide, some illness has been reported from the handling of plants and soils treated with aldicarb (Peoples et al., 1977). Several misuses of aldicarb on watermelons and cucumbers have been reported in the literature. Goes et al. (1980) reported on a suspected food-borne intoxication in Nebraska associated with the consumption of aldicarb-contaminated hydroponically grown cucumbers. Two episodes were reported (April 1977: 9 cases; July 1978: 5 cases). Neither cholinesterase determinations nor urine residue determinations were performed in any of these patients. Four cucumbers (two in the supermarket and two in the greenhouse were analyzed and aldicarb content was 6.6 and 10.7 mg/kg (supermarket) 0 and 9.9 mg/kg (greenhouse). No data are available on cucumbers actually eaten and no attempts to correlate symptoms and aldicarb consumption were made. Hirsch et al. (1987) reported over 300 alleged intoxications in Canada following ingestion of aldicarb contaminated cucumbers (residue levels up to 26 mg/kg). In only five cases involving 13 patients, were any remaining portion of the cucumbers consumed still available for analyses. Goldman (1990) reported on four outbreaks of aldicarb poisoning having occurred in California and other states in the USA from 1978 to 1988. Outbreak 1: watermelons, 1985 Outbreak 2: watermelons, 1987 Outbreak 3: cucumbers, 1988 Outbreak 4: cucumbers, 1978 (corresponds to Goes (1980) publication). In the first outbreak, 1376 people allegedly became ill due to consumption of contaminated watermelons. Of this total, 308 were considered by the authors themselves as unlikely (235) or incomplete (73). Nevertheless, only 28 cases were supported by positive findings of aldicarb residues in the food commodity. All the other cases were only supported by self-diagnosis. An epidemiological study of potential adverse health effects of aldicarb metabolites in drinking water was performed. In two surveys conducted on Long Island, New York, the major cohorts were selected on the basis of aldicarb levels in their drinking water. Levels of contamination were generally 4-12 µg/litre, but a maximum of 400 µg/litre was reported. Questionnaires to determine water and food consumption, symptoms experienced, and diagnosed illnesses were sent to 1035 residents of 462 households. Although the initial survey indicated a possible association between the incidence of diarrhoea and levels of aldicarb in the water, the follow-up study, focusing on children, did not confirm this association. No relationship was detected between food consumption or water source and adverse health symptoms, and self-reported physician-diagnosed illnesses for 1974-1979 were not significantly related to levels of aldicarb in the water (Whitlock et al., 1982). Another survey attempted to relate self-reported symptoms suggestive of peripheral neuropathy to aldicarb levels in drinking water in Suffolk County, New York. The response rate was less than 20%. Responses were classified as "probably", "possibly", or "vaguely" suggestive of a neurologic syndrome. A significant correlation with aldicarb concentration was obtained only by combining all three categories of response, including reports of just one symptom or of symptoms not forming any cohesive syndrome. The authors concluded that further study was needed (Sterman & Varma, 1983). A pilot epidemiological study by Fiore et al. (1986) evaluated a wide range of clinical immunological parameters in 23 women exposed to aldicarb in their drinking water and in a non-exposed control group. The groups did not differ in any immunological parameters except in T8-Lymphocytes: the number was considered as elevated in five exposed and in one control. Observation of an elevated stimulation assay response to one of the large number of antigens (Candida) was not considered as toxicologically significant, nor was it attributed to aldicarb exposure. In a follow-up study, five women of the preceeding group and still exposed to aldicarb were examined versus previous control women plus women previously exposed but for whom exposure no longer occurred (e.g., change in water supply due to addition of a charcoal filter). According to the authors, this follow-up study confirmed the previous results, except for increased response to Candida antigens which was no longer present (Mirkin et al., 1990). COMMENTS Aldicarb is rapidly absorbed, widely distributed in the body and rapidly excreted. Metabolism appears to be similar in all species studied, aldicarb being rapidly metabolised to aldicarb sulfoxide, which is more slowly degraded to aldicarb sulfone. All metabolites are quickly eliminated from the body, 80-90% being excreted within 24 h. Elimination was complete by the fifth day after dosing and no bio-accumulation was seen. Aldicarb has high acute toxicity in a wide variety of mammalian species. Signs of toxicity are those commonly associated with acetylcholinesterase inhibition by a carbamate insecticide: cholinergic signs of poisoning, which are alleviated rapidly on cessation of exposure. Aldicarb sulfoxide is a more potent inhibitor of acetylcholinesterase than aldicarb itself, while aldicarb sulfone is considerably less toxic than either aldicarb or the sulfoxide. WHO has classified aldicarb as extremely hazardous (WHO, 1992). Short-term and long-term studies have been performed in rats, mice and dogs with aldicarb and aldicarb metabolites, both individually and in combination. Toxicity tests employing mixtures of aldicarb or aldicarb sulfoxide with aldicarb sulfone are of interest because aldicarb sulfoxide and aldicarb sulfone are the terminal residues potentially consumed by humans. Cholinesterase depression is the most significant indicator of toxicity that can be evaluated. However, considerable attention must be paid to the methods of sample collection and determination of cholinesterase activity. Continuous administration of aldicarb to the test animals until collection of samples for analysis is important, as is rapid analysis under carefully controlled conditions. No-effect levels in the various studies which included evaluation of cholinesterase inhibition are summarized in Table 6. No distinction is made in this table for the methods of determining cholinesterase activity. It is now considered inappropriate to use no-adverse-effect levels from many of the earlier repeat-dose studies for the derivation of an ADI, because animals were not dosed for 24-48 h prior to collection of tissue samples for measurement of cholinesterase activity. In the most recent dog studies, which were conducted in a manner designed to maximize detection of cholinesterase depression, the overall NOEL was 0.02-0.03 mg/kg bw/day, but the NOAEL (which discounts inhibition of plasma cholinesterase only) was 0.05-0.06 mg/kg bw/day. Results of repeat-dose studies with aldicarb demonstrate that the method of administering the test material to the test animals can greatly modify the apparent toxicity of aldicarb and its metabolites. Mice, rats and dogs have tolerated daily doses equal to the LD50 incorporated into the diet for 7 days to 2 years. Doses which caused death in less than 2 h when administered as a bolus, caused no death and only moderate cholinesterase depression when given in the diet. Two dietary carcinogenicity studies have been conducted with aldicarb in rats and three in mice. A dermal carcinogenicity study has also been conducted with aldicarb in mice and dietary studies have been carried out with aldicarb sulfone in mice and aldicarb sulfoxide in rats. Aldicarb was not carcinogenic in mice and rats. Two reproduction studies have been conducted in rats with aldicarb and one with aldicarb sulfone. There were no effects on reproductive performance at doses up to 0.7 mg/kg bw/day aldicarb or 9.6 mg/kg bw/day aldicarb sulfone. Aldicarb did not display any teratogenic potential in rats or rabbits in studies which included maternally toxic doses. After reviewing the available genotoxicity data, the meeting concluded that aldicarb, aldicarb sulfoxide and aldicarb sulfone are not genotoxic. In a range of special studies in animals (involving delayed neurotoxicity, behaviour, antagonistic agents and pesticide interactions) aldicarb displayed no results which gave cause for concern. There was no evidence of immuno-toxicity in mice in a number of functional assays of cell-mediated immunity and in host resistance to respiratory infection. Epidemiological studies provided no convincing evidence that aldicarb could significantly alter immunological function in humans. In addition to the above epidemiological studies, studies conducted in 1982 and 1983 attempted to correlate any potential adverse health effects with the occurrence of aldicarb in drinking water. Although the authors concluded that further study was needed, there was no clear evidence that aldicarb contamination of drinking water generally at concentrations of about 4-12 µg/litre, but at a maximum concentration of 400 µg/litre was related to any health effects. The anticholinesterase potential of aldicarb has been extensively investigated in human. These studies revealed the same pattern of rapid cholinesterase inhibition and rapid recovery seen in experimental animals. Transient erythrocyte cholinesterase depression was seen at single doses of 0.05 mg/kg bw, and the NOAEL for cholinesterase depression (discounting changes in plasma enzyme activity) was 0.025 mg/kg bw. A number of poisoning incidents have been reported in the agricultural use of aldicarb, but there has been no indication that the workers exposed were harmed once removed from the exposure source. Although several deaths have been reported, all of these have been attributed to suicide or gross neglect. A number of food-borne aldicarb intoxications have been reported in the literature. These have all been associated with misuse and reliable quantification of the dose of aldicarb involved has always proved difficult, if not impossible. An ADI was allocated using a 10-fold safety factor applied to the NOAEL for depression of erythrocyte cholinesterase activity in human volunteers. TOXICOLOGICAL EVALUATION Level causing no toxicological effect Rat: 0.1 mg/kg bw/day (93-day dietary study) Dog: 0.05 mg/kg bw/day (52-week study) Human: 0.025 mg/kg bw (double-blind, placebo controlled volunteer study) Estimate of acceptable daily intake for humans 0-0.003 mg/kg bw Studies which will provide information valuable in the continued evaluation of the compound Further observations in humans, including information regarding the correlation of blood cholinesterase depression and clinical signs and symptoms. Table 6: Summary of no effect levels in repeat dose toxicity studies which included cholinesterase investigations Species Duration Test Material Dosages* NOAEL** Effects at higher doses Mouse 7 days Aldicarb 0,0.1,0.3,0.6,1.2 0.6 Mortality Mouse 7 days Aldicarb: 0,2,6,18,36 2 Kidney and liver weight A. sulfone reduction, growth 1:1 depression Rat 7 days Aldicarb 0,4,8,16 NE Mortality, growth depression, kidney and liver weight reduction Rat 7 days Aldicarb 0,0.8,1.6,3.2 NE Growth depression, kidney and liver weight reduction Rat 93 days Aldicarb 0,0.02,0.1,0.5 0.1 Mortality, growth depression Rat 2 years Aldicarb 0,0.005,0.025, >0.1 No effects seen 0.05,0.1 Table 6 (cont'd) Species Duration Test Material Dosages* NOAEL** Effects at higher doses Rat 7 days Aldicarb 0,0.4,0.8,1.6,3.2 0.8 Growth depression, A. sulfoxide 0,0.4,0.8 0.4 RBC cholinesterase A. sulfone 0,0.4,1.0,2.5,5,20 2.5 depression Rat 29 days A. sulfoxide: 0,0.0074,0.03, 0.4 Growth depression, A. sulfone 0.12,0.47,1.67 in brain, plasma and RBC 1:1 drinking water cholinesterase depression Rat 6 months A. sulfoxide 0,0.125,0.25,0.5,1 0.125 Growth depression, brain, plasma and RBC cholinesterase depression Rat 6 months A. sulfoxide 0,0.0625,0.125, 0.125 Plasma and RBC 0.25,0.5,1.0 cholinesterase depression Rat 6 months A. sulfone 0,0.2,0.6,1.8, 0.6 Brain, plasma and RBC 5.4,15.2 cholinesterase depression Rat 7 days A. oxime 0,31.25,62.5,125, 62.5 Growth depression, 250,500,1000 minor liver and kidney changes Dog 7 days Aldicarb 0,0.2,0.3,0.7 >0.7 No effects seen Dog 100 days Aldicarb 0,0.2,0.3,0.7 0.3 Minor organ weight changes Dog 2 years Aldicarb 0,0.025,0.05 >0.1 No effects seen 0.1 Dog 2 weeks Aldicarb 0,0.022,0.068, NE Brain, plasma and RBC cholinesterase depression 0.192,0.609,1.42 Dog 2 weeks Aldicarb 0,0.003,0.008, 0.096 Brain, plasma and RBC cholinesterase depression 0.027,0.096,0.28 Dog 5 weeks Aldicarb 0,0.012,0.024, >0.06 No effects seen 0.06 Dog 52 weeks Aldicarb 0,0.027,0.054, 0.054 RBC and plasma 0.131,0.241 cholinesterase depression Table 6 (cont'd) Species Duration Test Material Dosages* NOAEL** Effects at higher doses Dog 3 months A. sulfoxide 0,0.0625,0.125, 0.25 Transient growth 0.25,0.5 depression Dog 3 months A. sulfone 0,0.2,0.6, >5.4 No effects seen 1.8,5.4 Dog 1 year A. sulfone 0,0.11,0.59, 0.11 RBC and plasma 2.25 cholinesterase depression * mg/kg bw/day equivalence, by dietary administration, unless otherwise stated. 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See Also: Toxicological Abbreviations Aldicarb (EHC 121, 1991) Aldicarb (HSG 64, 1991) Aldicarb (ICSC) Aldicarb (Pesticide residues in food: 1979 evaluations) Aldicarb (Pesticide residues in food: 1982 evaluations) Aldicarb (IARC Summary & Evaluation, Volume 53, 1991)