PESTICIDE RESIDUES IN FOOD - 1984 Sponsored jointly by FAO and WHO EVALUATIONS 1984 The monographs Data and recommendations of the joint meeting of the FAO Panel of Experts on Pesticide Residues in Food and the Environment and the WHO Expert Group on Pesticide Residues Rome, 24 September - 3 October 1984 Food and Agriculture Organization of the United Nations Rome 1985 ACEPHATE Explanation Acephate was evaluated by the Joint Meeting of the FAO Panel of Experts (JMPR) in 1976 (FAO/WHO, 1977) at which time an ADI was established, based on no-effect levels taken exclusively from IBT studies. Additional data were evaluated by the 1982 JMPR (FAO/WHO, 1983) that changed the ADI to a temporary status, as relevant studies from IBT were found to be invalid. Studies required were a multigeneration reproduction study, a delayed neurotoxicity study, and individual animal data from the 28-month toxicity/carcinogenicity rat study. Some of these data have been made available and are summarized in the following monograph addendum. EVALUATION FOR ACCEPTABLE DAILY INTAKE BIOCHEMICAL ASPECTS Absorption, Distribution and Excretion Two male Sprague-Dawley rats received dermally a single treatment with S-methyl-14C-Acephate at level of 10 mg/kg bw. Blood and urine were collected at regular intervals and assayed for total 14C. Acephate and its major metabolite (methamidophos) were also determined in the urine. The 14C-dose was rapidly absorbed into the blood, with the maximum concentration occurring at one to three hours. The 14C content of the blood then decreased with time and a secondary peak was observed at 48 h. The excretion profile of acephate in the urine is similar to the 14C absorption profile into the blood. The maximum concentration of acephate occurred at six and 24 h for the two rats. After three days, approximately 35 percent of the 14C dose was excreted in the urine. Approximately 30 percent of the dermal treatment was excreted as unchanged acephate and 1 percent as methamidophos. The amount of the dose left on the treated area of the rats was not determined (Tucker, 1974). Effects on Enzymes and other Biochemical Parameters The in vitro inhibitory activity (I50) of acephate technical on brain and RBC acetylcholinesterase (AChE) and plasma cholinesterase (ChE) was determined for the rat, monkey and human. The I50 for acephate was between 1 × 10-3 M and 5 × 10-3 M for all enzyme sources. Acephate was approximately 100 000 times less effective than eserine (positive control) as an inhibitor of AChE and 10 000 times less effective as an inhibitor of ChE. The inhibitory effect of acephate was more effective against rat brain and RBC AChE than against monkey and human brain. For plasma ChE, the I50 value was lower for the monkey and human than for the rat. For humans, the inhibitory activity (I50) was in the order: plasma > RBC > brain (Bennett & Morimoto, 1982). I50 VALUES Brain RBC AChE Plasma Rat 1.6 x 10-3 M 1.3 x 10-3 M 4.5 x 10-3 M Monkey 3.4 x 10-3 M 2.7 x 10-3 M 2.3 x 10-3 M Human 5.4 x 10-3 M 2.7 x 10-3 M 1.8 x 10-3 M TOXICOLOGICAL STUDIES Special Studies on Reproduction Rat Groups of six-week-old SPF-CD rats (12 males and 24 females per group) were fed diets containing Acephate (technical, 92.8 percent purity) at levels of 0, 50, 150, or 500 ppm until they were 21 weeks old. At that time they were mated (one male to two females) to start a two-generation (one litter per generation) reproduction study. Diets were maintained during mating, gestation, and lactation. F1 offspring were weaned at three weeks of age, at which time 12 males and 24 females per group were selected to form the basis of F1 generation. The remaining offspring and all F0 parents were sacrificed. The selected animals were reared on their respective diets and mated at 21 weeks of age to produce the F2 generation. For parent animals, observations included regular inspection and regular recording of body weight, food consumption, and food conversion. Sample checks on water consumption were made, and breeding performance was monitored. Litter values were recorded and at termination all animals were subjected to macroscopic post-mortem examination. More detailed macroscopic and microscopic examinations were made on all F1 males; some F1 females failing to produce live young; the majority of F1 females bearing live young; and a small sample (five males and five females per group) of F1 and F2 weanlings. The F1 adults selected for microscopic examinations were also subjected to organ weight analysis. Significantly reduced water consumption was recorded at 500 ppm for both sexes of F0 and F1 generations and at 150 ppm for F0 females. Food consumption and food conversion were unaffected by treatment. Overall body weight changes were variably affected but no consistent dose-related effects. However, [illegible text] demonstrated decreased body [illegible text] during lactation. Pregnancy rate for all F0 generation dose groups, including control, was low. Pregnancy rate for F1 generation was decreased at 50 and 500 ppm, and only slightly at 150 ppm. Duration of gestation was unaffected by treatment. There were no effects on organ weights, macroscopic or microscopic changes related to treatment. For both generations viable litter size of all test groups was lower than that of controls, with initial differences at birth maintained or enhanced during lactation. The difference was statistically different only for the 150 and 500 ppm groups. There were slightly lower litter weights in test groups at birth, enhanced during lactation, such that by day 21 post partum a significant dosage-related trend for reduced litter weight was evident for both generations. Intergroup differences from controls was statistically significant at 150 and 500 ppm in both generations. Histopathological examination of weanlings was unremarkable. Dietary concentrations of 150 and 500 ppm acephate adversely affected reproductive performance and rearing of offspring during lactation. As many effects were also observed at 50 ppm. A clear no-effect level was not determined (Palmer, et al. 1983). Special Studies on Mutagenicity See Table 1. Mouse Groups of CD-1 mice (75 males and 75 females/group) were given diets containing acephate (purity not reported) at levels of 0, 50, 250, or 1 000 ppm for 104 weeks. The mice were observed daily for signs of toxicity, moribundity and mortality. Detailed observations were recorded weekly. Individual body weights and food consumption values were recorded weekly for the first eight weeks of study and monthly thereafter. Haematology was conducted on ten mice/sex/group at study termination. An interim sacrifice of ten mice/sex/group was conducted at 12 months of study. No compound- or dose-related changes in appearance, behaviour, or mortality were noted. Group mean body weights and average food consumptions were decreased for the 250 and 1 000 ppm mice when compared to the controls. No changes were seen in the haematological parameters. No compound-related gross necropsy lesions were observed for mice that died during the first 12 months of study. However, lung foci were observed grossly and alveolar macrophages identified microscopically at the 12-month interim sacrifice in the high dose group. At 12 months there were also microscopically visible compound-related liver hypertrophy and pigmented macrophages present among the high-dose males and females. TABLE 1. Special Studies on Mutagenicity Test Organism Test Substance Result Reference GENE MUTATION STUDIES Bacteria S. thyphimurium Acephate techn. -TA100: 7 samples weakly Bullock, (eight samples) mutagenic without metabolic Carver & activation in the range Wong 2-50 mg/plate, one sample 1982a negative without metabolic activation in the range 0.01-50 mg/plate; -TA98 and TA1537:4 samples tested were not mutagenic without metabolic activation in the range 10-50 mg/plate. Acephate techn. -TA100:5 samples weakly Bullock, (six samples) mutagenic without metabolic Carver & activation in the range 2-50 Wong mg/plate; 1 sample inconclusive. 1982b Acephate techn. -Very weakly mutagenic to Simmon (93.5% purity) TA100 at doses above 2.5 1979 mg/plate, with and without metabolic activation. Acephate -Positive TA100 without Moriya, metabolic activation at et al. concentration of 5 mg/plate 1983 and higher; Negative TA1535, TA1537, TA1538, TA98. TABLE 1. (continued) Test Organism Test Substance Result Reference E.coli WP2 her Acephate -Positive Moriya, et al. 1983 E.coli WP2 Acephate techn. -No significant increase of Simmon (93.5% purity) revertants, with and without 1979 activation, at doses up to 10 mg/plate. Yeasts and Fungi S. cerevisiae D3 Acephate techn. -Increased mitotic recombination Simmon (93.5% purity) with and without metabolic 1979 activation, at concentrations of 1 to 5%. S. cerevisiae D7 Acephate techn. -Induction of mitotic crossing Mortelmans, (93.5% purity) over and gene conversion in Riccio & the 3 to 5% range, with and Shepherd without metabolic activation. 1980 CHROMOSOMAL EFFECTS Cytogenetics-In Vitro Mouse Lymphoma Acephate -Dose-related increase in Kirby L5178Y Cells (98.7% purity) mutation frequency both with 1982a and without metabolic activation at TK+/-locus, in the range 500-5000 ug/ml. Acephate -Dose-related increase in Kirby mutation frequency both with 1982b and without metabolic activation at TK+/-locus, in the range 500-5000 ug/ml. TABLE 1. (continued) Test Organism Test Substance Result Reference -Dose-related increase in Jotz & mutation frequency both with Mitchell and without metabolic activation 1980 at TK+/-locus, in the range 1000-5000 ug/ml. Chinese Hamster Acephate -Dose-related increase of Evans & ovary cells Sister Chromatid Exchange, Mitchell in vitro with and without metabolic 1980 activation at concentrations of 125-2000 ug/ml. Cytogenetics-In Vivo Mouse Bone Acephate -Negative for Chromosomal Esber Marrow (98.7% purity) aberrations at doses of 1982 11.2-112 mg/kg bw. Acephate -Negative for Sister Chromatid Cimino & (98.7% purity) Exchange (some cell cycle Brusick delay) at doses of 29-96 mg/ 1983 kg bw. Monkey Acephate -Negative for Chromosomal Cummins Lymphocytes (98.7% purity) aberrations and Sister 1983 Chromatid Exchange at dose of 2.5 mg/kg bw/day. Micronucleus Test Mouse Acephate -No increase of incidence of Kirkhart micronucleated polychromatic 1980 erythrocytes at doses of 75-300 mg/kg bw. TABLE 1. (continued) Test Organism Test Substance Result Reference Dominant Lethal Mouse Acephate -Negative at dose of 50-500 Eisenlord (99%) mg/kg in the diet. 1982 DNA damaqe and repair Unscheduled DNA Acephate -Increase without metabolic synthesis (93.5% purity) activation at doses of 1 mg/kg WI - 38 cells and higher. Doubtful result with metabolic activation. Differential toxicity S. typhimurium Acephate -Negative Mortelmans SL4525(rec+)- (93.5% purity) & Riccio SL4700(rec-) 1981 S. typhimurium Acephate -Negative Mortelmans TA1978(UVrB+)- (93.5% purity) & Riccio TA1538(UVrB-) 1981 Special Studies on Carcinogenicity (See also under long-term studies) At terminal autopsy a dose-related increase of lung foci was macroscopically observed in males at 250 and 1 000 ppm, and in females of all the treated groups (6, 24, 53 and 73 percent for control, 50, 250 and 1 000 ppm groups, respectively). Liver masses or hyperplastic nodules were present in 64.7 percent of the high-dose females, but were not significantly different from controls in the other two groups. In males, the incidence of liver masses or nodules were comparable in all groups. At terminal sacrifice there was a statistically significant increase in the mean relative weight of liver, ovaries and brain of high-dose females, and testes and brain of high-dose males. At the terminal sacrifice, an increased incidence of hyperplastic nodules and hepatocellular carcinoma was microscopically observed only in the livers of the high-dose females when compared to controls. Hepatocyte hypertrophy, nuclear enlargement (karyomegaly) and intranuclear inclusion bodies were increased only in the two highest-dose groups (both males and females) in a dose-related manner. Mononuclear inflammatory cell foci were increased in treated groups of males in a dose-related manner. Lung lesions included alveolar hyalinosis and dark-pigmented alveolar macrophages which were increased in all treated groups in a dose-related manner, while eosinophilic foreign bodies were increased only in the highest-dose groups (both males and females). Increased incidence of acute rhinitis was also observed in all treated groups in a dose-related manner. Dark pigment in the reticuloendothelial cells of mediastinal lymph nodes was observed to be increased and dose-related in all male treated groups and in the females at the two highest doses. Incidence of neoplastic lesions was comparable with respect to type and site among all groups, except for the increase of hepatocellular carcinomas in high-dose females (Geil & Richtter, 1981). Special Studies on Skin Sensitization Twenty male Hartley albino guinea-pigs received dermal applications of Acephate at the concentration of 35 percent w/w in saline solution which was previously determined to be the maximum non-irritant concentration. The positive control material, 1-chloro-2,4-dinitrotoluene 0.1% w/w in saline solution, and the saline vehicle were similarly each tested in ten male guinea-pigs. The induction phase of the study consisted of ten repeated topical applications, 0.4 ml of the test solution, on alternate days over a 22-day period. Fourteen days following the tenth induction application, the test animals were challenged by applying the respective test material. Very slight to well-defined irritation was observed after the last induction application. No sensitization responses were observed either for the animals challenged with Acephate or for the vehicle control animals (Silveira, 1982). Toxicity See Table 2. TABLE 2. Acute Toxicity of Acephate Animal Sex Route Compound LD50 Reference Purity Rat M+F oral 98.7% 1.3-0.93 Duke,1982 g/kg bw Mouse M oral 98.7% 403 Esber, F oral 98.7% 323 1982 g/kg bw Special Studies on Antidotes The LD50 values for groups of male and female Sprague-Dawley rats treated with atropine sulphate (10 mg/kg bw) 15 minutes following oral dosing with technical Acephate, were 4.2 and 6.6 times higher, respectively, than the LD50 of groups receiving no antidote. Similarly, the LD50 of groups of male and female Sprague-Dawley rats treated with pralidoxime chloride (2-PAM) (50 mg/kg bw/i.m.) 15 minutes following oral dosing with Acephate technical, were each 2.9 times higher than the LD50 of groups receiving no antidote (Duke, 1982). Short-Term Studies Monkey - oral Two male and two female cynomolgus monkeys (Macaca fascicularis) received technical Acephate (98.7 percent pure) by oral gavage at doses of 0 or 2.5 mg/kg bw/day for up to 34 consecutive days (33 days for males, 34 days for females). No noteworthy differences between groups were observed with respect to clinical signs, food and water consumption, body weight changes, physical examination, haematology, blood chemistry (except cholinesterase activity), urinalysis, organ weights or macroscopic pathology at terminal autopsy. Cholinesterase activities were assayed in red blood cells and plasma every two days and in brain at sacrifice. Erythrocyte acetyl- and plasma acetyl- and butyrylcholinesterase activities were depressed in all treated monkeys compared to control animals. Maximum inhibition was observed after approximately six days for plasma cholinesterases and 14 days for erythrocyte cholinesterase. Mean inhibition (relative to mean pre-treatment values) of 42 percent (males) and 43 percent (females) was recorded for plasma acetylcholinesterase activity and 37 percent (males) and 40 percent (females) for plasma butyrylcholinesterase activity during days 6 to 34. Mean inhibition of 53 percent (males) and 47 percent (females) for erythrocyte acetylcholinesterase activity was recorded during days 14 to 34. No erythrocyte butyrylcholinesterase activity was detected in treated or control animals. There was no relevant difference in the pattern of inhibition between plasma acetyl and butyryl activity or between sexes for each cholinesterase parameter. Brain cholinesterase activity after four weeks of treatment was lower in all treated animals compared to controls. Compared to contemporaneous control values treated animals showed mean inhibition of 16 percent (males) and 32 percent (females) for butyrylcholinesterase activity and 50 percent (males) and 43 percent (females) for acetylcholinesterase activity. Thus, brain cholinesterase inhibition was similar to (acetylcholinesterase) or less marked than (butyrylcholinesterase) that recorded for blood. These levels of cholinesterase inhibition were without any visible cholinergic signs (Cummins, 1983). Long-Term Studies (see also under Special Studies on Carcinogenicity) Rat Groups of Sprague-Dawley CD rats (75 males and 75 females per group) received Acephate technical (92.4 percent purity) in the diet at dose levels of 0, 5, 50, and 700 ppm for 28 months. Interim sacrifices were performed on ten animals/sex/group at four and 12 months and on four or five sex/group at 22 months. Physical observations for signs of toxic or pharmacological effects and palpations for tissue masses were performed weekly throughout the study. Body weights and food consumption were monitored and clinical laboratory evaluations (haematology, clinical chemistry, cholinesterase activity, and urinalysis) were performed periodically on ten animals/sex/group. Ophthalmoscopic examinations were performed periodically on all animals. Complete gross post-mortem examinations were conducted on all animals and microscopic examinations were performed on all tissues from control and high-dose animals and on gross lesions, tissue masses, eyes and adrenals from low- and mid-dose animals. Organ weights were recorded at interim and terminal necropsies, and organ/body weight ratios were calculated. Evaluation of mortality, physical observations, haematology, clinical chemistry (except cholinesterase activity), and urinalysis revealed no significant differences between control and treated animals, which were considered compound-related. A slight, transient increase in the incidence of aggressive behaviour and/or increased activity occurred in high-dose animals during the first six months. Body weights of high-dose males were significantly lower (4-18 percent) than those of control males throughout the study. Also, the feed efficiency in high-dose males was significantly lower than in control males. Although the ophthalmoscopic examinations revealed a variety of abnormalities more frequently in treated than in control animals, they were not considered compound-related, due to the infectious or traumatic origin and the unilateral nature of many of the observations. Plasma and erythrocyte cholinesterase activities were significantly lower than control activities at most intervals for high-dose males and females. Mean plasma and erythrocyte cholinesterase activity ranged from 28 to 90 percent and 31 to 79 percent of control activity, respectively, for high-dose animals and 62 to 106 percent and 58 to 111 percent of control activity for mid-dose animals. No statistically significant decreases in plasma and erythrocyte cholinesterase activity occurred in low-dose animals. Mean brain cholinesterase activity of mid- and high-dose (but not low-dose) animals was significantly lower than control activity at all intervals (17 to 34 percent of control in high-dose animals and 55 to 67 percent in mid-dose animals). Statistically significant differences in organ weights and organ/body weight ratios occurred sporadically in mid- and high-dose animals with no consistent dose-related pattern. Grossly observable abnormalities were most common in the lung, liver, kidneys, pituitary glands and subcutaneous tissue, but there was no significant difference in the incidence between control and treated groups. Microscopically various non-neoplastic lesions were observed in most of the organs, lungs and kidney being most frequently affected. The incidence of these lesions does not indicate a treatment-related effect. Various neoplasms were observed in different organs and tissues examined microscopically. Based on these examinations, the number of neoplasm-free animals, the number of animals with benign neoplasms only and the number of animals with malignant neoplasms were similar among groups. Neoplasms most commonly observed were those of the pituitary gland. They were more frequent in female rats of all groups compared to males. There was no significant difference in the number of pituitary neoplasms between treated and control groups. Mammary gland neoplasm represented the second largest group; the incidence was 33/75 in control females compared to 43/73 in the high-dose group. The incidence of neoplasm of adrenal medulla was increased in all males of the treated group; however, historical control data demonstrate the relatively low control value for the present study and the great variability in the incidence of this neoplasm. Statistical analysis of these data was inconclusive. The incidence of thyroid gland neoplasm, though slightly increased in the high-dose group of both male and female rats when compared to controls, was below the mean value of the laboratory's historical control groups. The 5 ppm dose-level (equal to 0.2-0.6 mg/kg bw/day) may be considered the no-effect level for the parameters investigated (Auletta & Hogan, 1981). COMMENTS Acephate was first evaluated by the JMPR in 1976 and most recently re-evaluated in 1982, when invalid IBT studies and consideration of additional data caused the ADI to be changed to a temporary ADI with requirements for a multigeneration reproduction study, a delayed neurotoxicity study and data for individual animals in the 28-month rat toxicity/carcinogenicity study. A two-generation, one-litter-per-generation study showed that Acephate adversely affected reproduction and neonatal weight gain during lactation, but it was considered to be an inadequate study (JMPR report, 1982). The 28-month rat toxicity study showed no consistent biologically significant increased incidences of neoplasia, and mutagenicity tests were mostly negative. The previously requested delayed neurotoxicity study was not presented. In view of the inadequate multigeneration study and the lack of a delayed neurotoxicity study, only a temporary ADI, with a high safety factor, was allocated. Level Causing no Toxicological Effect Rat: 5 ppm in the diet, equivalent to 0.25 mg/kg bw. Dog: 30 ppm in the diet, equivalent to 0.75 mg/kg bw. Estimate of Temporary Acceptable Daily Intake for Humans 0 - 0.0005 mg/kg bw FURTHER WORK OR INFORMATION Required (by 1987): 1. An adequate multigeneration study, with two litters per generation. 2. An appropriate delayed neurotoxicity study. Desirable: Observations in humans. REFERENCES Auletta, C.S. & Hogan, G.K. A life-time oral toxicity/carcinogenicity 1981 study with technical RE-12420 in rats. Report Project No. 782135 from Big Dynamics Inc., New Jersey, submitted by Chevron, USA to WHO. (Unpublished) Bennett, E.L. & Morimoto. H. The comparative in vitro activity of 1982 Acephate technical on brain, erythrocyte and plasma cholinesterases from the human, monkey, and rat. Chevron study S-2150 from University of California, submitted by Chevron, USA to WHO. (Unpublished) Bullock, C.H., Carver, J.H. & Wong, Z.A. Salmonella mammalian 1982a microsome mutagenicity test (Ames test) with eight samples of Chevron Acephate Technical. Report Socal 1189 from Chevron Environmental Health Center, California, submitted by Chevron, USA to WHO (Unpublished). Bullock, C.H., Carver, J.H., & Wong, Z.A. Salmonella mammalian 1982b microsome mutagenicity test (Ames test) with six samples of Chevron Acephate Technical and purified. Report Socal 1215 from Chevron Environmental Health Center, California, submitted by Chevron, USA to WHO. (Unpublished) Cimino, M.C., & Brusick, D.J. Mutagenicity Evaluation of Chevron 1983 Acephate Technical in the sister chromatid exchange assay in vivo in mouse bone marrow, final report. S-2166, LBI Project No. 22204, Litton Bionetics, Inc., submitted by Chevron USA to WHO. (Unpublished) Cummins, H.A. Orthene technical: Cholinesterase inhibition and 1983 cytogenetics in the monkey. Report No. 82/CHE 001/313 from Life Science Research, England, submitted by Chevron, USA to WHO. 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Report from SRI 1980 International, California, Project No. LSU-7558-19, EPA contract No. 68-02-2947, submitted by Chevron, USA to WHO. (Unpublished) Moriya, M., Ohta, T., Watanabe, K., Miyazawa, T., Kato, K., & Shirasu, 1983 Y. Further mutagenic studies on pesticides in bacterial reversion assay systems. Mutat. Res. 116: 185-216. Mortelmans, K.E., Riccio, E.S., & Shepherd, G.F. In vitro detection of 1980 mitotic crossing-over, mitotic gene conversion, and reverse mutation with S. Cerevisiae D7 for seven pesticides. Report from SRI International, California, Project No. LSU-7558-20, EPA contract No. 68-02-2947, submitted by Chevron, USA to WHO. (Unpublished) Mortelmans, K.E., & Riccio, E.S. Differential toxicity assays of 1981 nineteen pesticides using Salmonella tiphimurium strains. Report from SRI International, California, Project No. LSU-7558-26, EPA Contract No. 68-02-2947, submitted by Chevron, USA to WHO. (Unpublished) Palmer, K.A., Barton, S.J., Offer, J.M., Gregson, R.L., Gibson, W.A. & 1983 Almond, R.H. Effect of technical RE-12420 on reproductive function of multiple generations in the rat. Report CHR 11/81957 from Huntingdon Research Centre, England, submitted by Chevron, USA to WHO. (Unpublished) Silveira, R.F. Modified BUEHLER test for the skin sensitization 1982 potential of Chevron Acephate technical (SX-1102). Report Socal 1840 from Chevron Environmental Center, California, submitted by Chevron, USA to WHO. (Unpublished) Simmon, V.F. In vitro microbiological mutagenicity and unscheduled DNA 1979 synthesis studies of eighteen pesticides. Report from SRI International, California, EPA publication 600/1-79-041 submitted by Chevron, USA to WHO. Tucker, B.V. S-methyl-14C-Orthene. Dermal treatment of rats. Report 1974 No. 721.11 from Chevron R. & D. Department, California, submitted by Chevron, USA to WHO. (Unpublished)
See Also: Toxicological Abbreviations Acephate (ICSC) Acephate (Pesticide residues in food: 1976 evaluations) Acephate (Pesticide residues in food: 1979 evaluations) Acephate (Pesticide residues in food: 1981 evaluations) Acephate (Pesticide residues in food: 1982 evaluations) Acephate (Pesticide residues in food: 1984 evaluations) Acephate (Pesticide residues in food: 1987 evaluations Part II Toxicology) Acephate (Pesticide residues in food: 1988 evaluations Part II Toxicology) Acephate (Pesticide residues in food: 1990 evaluations Toxicology) Acephate (JMPR Evaluations 2002 Part II Toxicological) Acephate (JMPR Evaluations 2005 Part II Toxicological)