METHAMIDOPHOS EXPLANATION First draft prepared by Dr E.M. den Tonkelaar, National Institute of Public Health and Environmental Protection, Bilthoven, The Netherlands Methamidophos toxicity was evaluated by the JMPR in 1976, 1982 and 1985 (Annex 1, FAO/WHO 1977ab, 1983ab and 1986ac). In 1985 the Meeting allocated an ADI of 0-0.0006 mg/kg bw, based on a complete data package which replaced invalid IBT (Industrial Biotest) data. Because methamidophos is a metabolite of acephate, for which an ADI had been established based on a study in humans, it was decided to re- evaluate methamidophos. This study was considered at the present Meeting as well as new data on in vitro cholinesterase inhibition and on delayed neuropathy. EVALUATION FOR ACCEPTABLE DAILY INTAKE BIOLOGICAL DATA Biochemical aspects Effect on cholinesterase activity The cholinesterase inhibition of methamidophos, acephate and paraoxon (a known strong anticholinesterase) were determined on human erythrocytes and on brain samples of rats, mice and rainbow trout in an in vitro experiment. In all cases, except trout brain cholinesterase, acephate and methamidophos were found to be six and three orders of magnitude weaker than paraoxon, respectively (see Table 1) (Hussain et al., 1985). Table 1. Concentrations of acephate, methamidophos and paraoxon required to inhibit 50% of the activity (I50) of cholinesterases from human erythrocyte, rat, mouse and trout brain in vitro. Chemical Human Rat brain Mouse brain Trout brain erythrocyte Acephate (x 10-2M) 1.9 ± 0.1 0.7 ± 0.008 6.0 ± 2.0 2.8 ± 0.3 Methamidophos (x 10-5M) 2.3 ± 0.3 2.0 ± 0.2 2.0 ± 0.2 5.6 ± 0.9 Paraoxon (x 10-8M) 3.3 ± 0.5 2.3 ± 0.3 5.0 ± 0.8 2200 ± 100 Sprague-Dawley rats (5/sex/group) received single topical applications of analytical grade methamidophos (purity 99.1%) and methamidophos technical (purity 74.7%) at dose levels of 0, 1.0, 2.5, 6.25 or 15.6 mg a.i./rat on a shaved dorsal area ranging from 6.6% to 8.7% of the total body surface area. The rats were sacrificed 24 or 72 hours following application of the test material. Animals were observed daily for toxic signs and mortality; body weight was measured prior to dosing and at sacrifice on day 1 or day 3. Gross pathology and histopathology were performed at sacrifice and plasma, RBC and brain ChE activities were determined. Three-fifths and 2/5 of female rats died during the 24 hour exposure to methamidophos analytical grade and methamidophos technical in the 15.6 a.i./rat dose groups, respectively. After 72-hour exposure to methamidophos technical 1/5 females in the high dose group died. No clinical signs of toxicity were observed at the lowest dose group (1.0 mg a.i./rat). No compound related gross pathological changes were noted at necropsy and no histopathological changes in the skin were found. Dose-dependent significant cholinesterase inhibition was observed in both males and females following treatment with both test materials. For calculation of the dose the amount of active ingredient was determined per cm2 total body surface area. ID50 values were determined to compare the relative sensitivities of each tissue to cholinesterase inhibition. The lowest ID50 values were observed in each tissue after 24 hours for both males and females. RBC and plasma ChE were inhibited to a greater extent by the test materials than brain ChE (see Table 2). No consistent difference in cholinesterase inhibition was observed to be produced by either methamidophos technical or analytical grade (Easter and Rosenberg, 1987). Table 2. ID50 (µg a.i./cm2 total body surface area) 24 hrs. after administration. Test material RBC ChE Brain ChE Plasma ChE males methamidophos (analytical grade) 6.98 23.40 9.51 methamidophos (technical) 10.00 18.55 5.85 females methamidophos (analytical grade) 4.94 14.04 1.61 methamidophos (technical) 5.41 8.33 0.57 Special study on pharmacokinetics Male Wistar rats were given atropine sulfate (100 mg/kg i.p.) 10 to 15 minutes prior to i.v. dosing with 10 mg/kg methamidophos (purity 74%) in propylene glycol. At various time intervals after dosing blood was taken and methamidophos values in plasma were analysed. Pharmacokinetic values were calculated using a one compartment model: t1/2 = 1.5 hr; Vd(volume of distribution)=0.81 L/kg; C1(clearance)= 5.8 mL/min/kg; kel(elimination constant)=0.45 hr-1. The volume of distribution of 0.81 L/kg indicates that methamidophos is not highly tissue bound (Eigenberg et al., 1983). Toxicological studies Acute toxicity studies The acute toxicity of methamidophos is presented in Table 3. Short-term studies In a range finding study, groups of Wistar rats (10/sex/group) were exposed to aerosols containing methamidophos (purity 75.7%) at mean concentrations of 0 (vehicle=polyethylene glycol/ethanol), 1.4, 5.4 or 33.1 mg/m3 6 hours per day for 5 days. The only effects observed were cholinergic signs and a significant depression of cholinesterase activity in plasma and brain as well as a reduced male body weight gain on day 5 occuring at 33.1 mg/m3 only. The NOAEL in this study was 5.4 mg/m3 (Pauluhn, 1987a). Groups of Wistar rats (10/sex/group) were exposed to aerosols containing methamidophos (purity 73%) at mean concentrations of 0 (air), 0 (vehicle=polyethylene glycol/ethanol), 2.6, 12.0 or 48.4 mg/m3 6 hours per day, 5 days per week over a period of 3 weeks (head/nose exposure). Cholinergic symptoms were observed at 48.4 mg/m3. Body weight was slightly reduced in high dosed rats. Reduced ALAT, urea and creatinine values were observed at 48.4 mg/m3. Cholinesterase activities were significantly depressed in plasma (35-88%), erythrocytes (20-25%) and in brain (20-74%) at 12.0 and 48.4 mg/m3. In the urine, acidification was observed at 48.4 mg/m3. Relative adrenal weight was increased and relative thymus, liver and spleen weight were decreased in high dose male rats. There were no signs of specific organ damage or local damage to the respiratory tract. The NOAEL in this study was 2.6 mg/m3 (Pauluhn, 1987b). Groups of Wistar rats (10/sex/group) were exposed to 0 (air), 0 (vehicle=polyethylene glycol/ethanol), 1.1, 5.4 or 23.1 mg methamidophos (purity 73.4%)/m3 6 hours per day, 5 days a week for 3 months. Two additional satellite groups (10/sex/group), of which one was exposed to the vehicle aerosol and the other to 23.1 mg methamidophos/m3, served as recovery groups with a 6-week exposure- free recovery period. Observations included clinical signs, body weight, haematology, biochemistry, urinalysis, cholinesterase inhibition in plasma, erythrocytes and brain, lung function tests, acetylcholine (ACH) provocation test, ophthalmoscopy, gross pathology, organ weights and histopathology. Table 3. Acute toxicity of methamidophos in animals. Species Sex Route LD50 LC50 Purity Reference (mg/kg b.w.) (mg/m3) Rat M** oral 161 95.3% Flucke, 1990a 142 98.5% 163 97.8% M, F Inhal. 213 75.7% Pauluhn, 1987a (4 hr) Hen F oral 48 72.5% Pauluhn and Kaliner, 1984 180* oral 251# 95.3% Flucke, 1990b 432# 98.5% 823# 96.5% dermal 50 74% Flucke, 1985 Turkey F Oral 15* 72.5% Pauluhn and Kaliner, 1984 Hen 1 test compound: (±)-methamidophos 2 test compound: (+)-methamidophos 3 test compound: (-)-methamidophos * 50 mg atropine sulphate/kg b.w. was administered i.m. 5 min. before the test compound. ** unfasted rats # The enantiomers also differed in that the symptoms and recovery period lasted longer, and mortalities occurred later with (-)-methamidophos that in the case of (+)-methamidophos. Cholinergic symptoms were observed at 23.1 mg/m3. In the same dose group body weight as well as food consumption were significantly reduced in both male and female rats. Ophthalmoscopy, haematology and urinalysis were unremarkable. At 23.1 mg/m3 ASAT and LDH concentrations were significantly increased in males. Protein, cholesterol and glucose were significantly decreased in both high dose male and female rats. Creatinine was significantly decreased at 5.4 and 23.1 mg/m3 in both sexes. Significant cholinesterase inhibition (>30%) was observed in plasma and brain in rats at 5.4 and 23.1 mg/m3. Liver N-demethylase was significantly decreased in rats at the highest dose level. The lung function tests performed at the end of the exposure period gave no indications of functional lung damage. In an acetylcholine provocation test, basal lung function parameters were not changed but an increased reactivity of the bronchial musculature to an acetylcholine aerosol was observed at dose levels of 5.4 mg/m3 and higher. In rats at 23.1 mg/m3, absolute and relative spleen weight were significantly decreased, and relative brain, and absolute and relative adrenal weight were increased, at the same dose level. At gross pathology and histopathology no evidence of treatment related organ damage or of local damage to the respiratory tract was observed. A dose related increase in reticulum cells and an increase in neutrophilic myelocytes in both male and female rats were observed at 5.4 and 23.1 mg/m3 at the bone marrow morphological examinations. At the end of the recovery period, changes in biochemical parameters and cholinesterase returned to normal. The NOAEL in this study is 1.1 mg methamidophos/m3 (Pauluhn, 1988). Special studies on delayed neurotoxicity Chickens Acute neurotoxicity was studied in 30 adult Leghorn hens after the simultaneous oral administration of 75 mg methamidophos and 400 mg trimethylphosphate (TMPO)/kg bw, followed after 21 days by 50 mg methamidophos and 264 mg trimethylphosphate/kg bw (both under atropine protection). Two independent positive control groups of 5 hens were administered 375 mg triorthocresylphosphate (TOCP)/kg bw once. The negative control group received the solvents (water and polyethylene glycol/ethanol for TMPO) under atropine protection twice at an interval of 21 days. After the first administration of the combination 15/30 hens died. No mortalities were observed after the second administration. From the 27th post-observation day onwards, 7/15 surviving hens exhibited an incipient uncoordinated gait, but progression was not observed. Delayed paralysis was not observed and after morphological examination of the nerve tissues no indication for induced neuropathy was provided. All hens in the positive control group showed delayed paralysis and morphological nerve damage (Pauluhn and Kaliner, 1984). Groups of 3 hens received single oral doses of 0 (corn oil), 27.5 or 55 mg/kg bw methamidophos EC 63.3%. After 24 hours blood samples were taken and the birds were killed and then brain, blood, liver, heart, spleen and kidney tissues were collected for enzyme assays. No effects were observed on the activity of glutathione-S-transferase (GST) and brain neurotoxic esterase (NTE). Blood and heart cholinesterase were inhibited, but acid phosphatase (AP) was increased in brain, blood and liver tissues of the treated hens. Another group of 10 hens received daily doses of 5.5 mg/kg methamidophos EC 63.3% for 60 days, under atropine protection with an observation period of 72 days. A control group received corn oil for 60 days. The hens were observed for any abnormalities in the ability to walk or any clinical delayed neuropathic symptoms. Treated hens had signs of cholinergic toxicity, especially in the first week of treatment. Two and 3 hens died after 5 and 11 doses, respectively. None of the surviving 5 hens showed signs of leg weakness or ataxia throughout 60 days of the experiment or after 72 days (El-Sebae et al., 1987). The effect on neurotoxic esterase (NTE) was studied after dermal application of 200 mg methamidophos (73.0%)/kg b.w. to 9 Leghorn chickens under atropine protection. This dose represented 4 x the LD50 without atropine protection. A positive control group and a negative control group (9/group) received 100 mg TOCP/kg b.w. orally and 5 ml Cremophor EL (2% v/v)/kg b.w. in demineralized water, respectively. NTE activity in the nerve tissue (brain and spinal cord) was determined after 24 and 48 hours and seven days post- application in 3 chickens/group. A mean inhibition of approximately 60% occurred in the brain after 24 and 48 hours and approximately 46% in the spinal cord after 24 hours. An inhibition of over 80% in all cases in both nerve tissues was observed in the positive controls at these times. According to the authors an inhibition of 70-80% within 1-40 hours after administration is necessary for induction of delayed neuropathy. This threshold value was not reached after a dose of methamidophos which was about 4 x the LD50 for dermal exposure (Flucke and Eben, 1988). The effect on NTE in the nervous tissues and lymphocytes of hens was also studied after the oral administration of 50 mg/kg b.w. racemic methamidophos (purity 95.5%) and the enantiomers (+)- and (-)- methamidophos (dose levels: 50, 100 or 400 mg/kg b.w. and 50, 200 or 400 mg/kg b.w., respectively) under atropine protection. The highest doses of the (+) and (-) enantiomers were about 10 and 5 times the LD50 respectively. NTE activity in brain, spinal cord, sciatic nerve and lymphocytes was determined 24 and 48 hours and 7 days after administration. About 60-85% inhibition occurred in the brain and spinal cord after administration of racemic methamidophos, which could be reactivated. (+)- Methamidophos showed greater inhibition (up to 100% in brain at 400 mg/kg b.w.) but nearly complete reactivation (>80%) of the inhibited NTE occurred, whereas at 400 mg/kg bw (-)- methamidophos up to 58 and 84% inhibition in brain after 24 and 48 hours, respectively, was observed, of which only a small fraction could be reactivated. Irreversible NTE inhibition levels of nearly 90% to almost 100% were observed with TOCP, which was used as a positive control, at oral doses of 100 and 300 mg/kg b.w. (Flucke and Eben, 1990). Two hundred mg/kg b.w. methamidophos (purity 74%) was dermally applied twice at an interval of three weeks to 30 chickens under atropine protection. A control group of 6 animals and a positive TOCP group of 5 animals were also used. Ten of 30 chickens died after the first treatment and one died after the second treatment. No delayed neurotoxic damage was observed as confirmed by a negative clinical test for neurotoxicity (forced movement) and the absence of basic histomorphological variations between the chickens treated with methamidophos and those in the negative control group. The TOCP group developed neuropathy (Flucke and Kaliner, 1985). Groups of white Leghorn hens (16/group) were orally administered by gavage 0, 0.3, 1.0 or 3.0 mg methamidophos (purity 76%)/kg bw 5 days a week for 3 months. Ten hens/group were examined for delayed neurotoxicity and plasma cholinesterase activity; NTE activities in the brain and spinal cord were determined in 6 hens/group. Two hens in the control group and 2 hens in the high dose group died during the study (deaths were not considered to be treatment-related). Somnolence and slight emaciation as well as a decreased mean body weight were observed in hens at 3 mg/kg b.w., but there were no signs of ataxia. Plasma cholinesterase (after 4 weeks) and NTE activity in the spinal cord (after 12 weeks) were inhibited at 1 mg/kg bw (23 and 22%, respectively) and 3 mg/kg bw (48% and 41%, respectively). NTE activity in the brain was only inhibited (17%) in the highest dose group. No dose related effects including neuropathological changes were observed grossly or microscopically. The NOAEL for general toxicity and plasma cholinesterase and NTE inhibition was 0.3 mg/kg bw/day (Sachsse et al., 1987). Special studies on genotoxicity The results of a cytogenetic assay in Chinese hamster ovary cells and an unscheduled DNA synthesis test in rat primary hepatocytes are described in Table 4. Table 4. Results of genotoxicity assays on methamidophos. Test system Test object Concentration Results Reference Cytogenetics Chinese 3150,4200 and equivocal8 Murli, 1990 assay 1 hamster 5250 µg/ml2 ovary cells (without action3) 1250,2500, negative 3750 and 4990 µg/ml (with action4) UDS assay Rat 0.001 to 10 negative Curren, 1988 hepatocytes µl/ml5,6,7 1 Both with and without rat liver S9 fraction 2 Test article purity = 74.5% 3 Mitomycin was used as positive control 4 Cyclophosphamide was used as positive control 5 Test article: Monitor technical (purity 71.2%) 6 Dose levels > 3.0 µl/ml were too toxic to be evaluated for UDS. 7 7,12-dimethylbenz(a)anthracene was used as a positive control 8 Slight increases in chromosome aberations were found at cytotoxic doses Special studies on skin sensitization Repeated application (via a modified Buehler method) of methamidofos technical (purity 73.8%) at a concentration of 25% w/w in distilled water to the shaven backs of Hartley guinea pigs did not cause allergic sensitization (Cushman, 1984). Observations in humans Cholinesterase inhibition In an oral dosing study, human volunteers were given combinations of acephate and methamidophos. Groups of 3 males and 3 females received 0.1, 0.2, or 0.3 mg/kg bw/day of a methamidophos/acephate combination (1:9) for 21 days followed by a 7-day recovery period after which the dose for each group was increased to 0.4 mg/kg bw/day (females only) for 10 days. Groups of 2 males and 2 females received 0.1 or 0.2 mg/kg bw/day of a methamidophos/acephate combination (1:4) for 21 consecutive days. In none of the groups was any effect noted on erythrocyte cholinesterase. Plasma cholinesterase activity was affected in the 1:9 groups in males at 0.3 mg/kg bw/day and only slightly in females at 0.4 mg/kg bw/day. Plasma cholinesterase inhibition in the 1:4 group was observed at 0.2 mg/kg bw/day. The NOAEL in this study was 0.3 mg/kg bw/day for the combination 1:9 and 0.2 mg/kg bw/day for the combination 1:4, with methamidophos concentrations of 0.03 and 0.04 mg/kg bw/day, respectively (Garofalo, 1973). The raw data were validated and support the above conclusions regarding cholinesterase activities. Acephate and methamidophos were detected in urine and blood from the subjects, but urine samples were only collected periodically and excretion data were not calculated (Cavalli, 1978). Information was obtained from the manufacturer concerning 36 cases of intoxication by methamidophos in the Federal Republic of Germany during 1978-1982. These were mainly the result of misuse of the compound (painting hop poles). Efficient warnings prevented further accidents. These cases could not be used for evaluation of a delayed haemotoxic potential because not enough information was available (Machemer, 1988). COMMENTS An in vitro experiment found that methamidophos inhibited cholinesterase at a much higher rate than acephate. The I50 for human erythrocyte cholinesterase and rat brain cholinesterase were of the same order of magnitude. Delayed neurotoxicity has been studied in hens following oral and dermal exposures. Methamidophos inhibited NTE and elicited signs of delayed neuropathy at dose levels which were higher than the LD50, indicating that the potential to induce delayed neuropathy was low. A NOAEL of 0.3 mg/kg bw/day was demonstrated in a 90-day oral neurotoxicity study in hens. Inhibition of erythrocyte cholinesterase was not found in a short-term study in humans in which dose levels up to 0.3 mg/kg bw/day of a combination of one part methamidophos with nine parts acephate or 0.2 mg/kg bw/day of a combination of one part methamidophos with four parts acephate were given. The estimations of the NOAEL for methamidophos in this study were 0.03 and 0.04 mg/kg bw/day, respectively. These data from humans were used in allocating the ADI. In allocating the ADI it was assumed that the effects observed after administration of the mixture were due solely to methamidophos. TOXICOLOGICAL EVALUATION Level causing no toxicological effect Rat: 2 ppm in the diet, equal to 0.1 mg/kg bw/day Dog: 2 ppm in the diet, equal to 0.06 mg/kg bw/day Chicken: 0.3 mg/kg bw/day Human: 0.04 mg/kg bw/day Estimate of acceptable daily intake for man 0-0.004 mg/kg b.w. Studies which will provide information valuable in the continued evaluation of the compound Further observations in humans. REFERENCES Cavalli, R.D. (1978) Data validation Industrial Bio-Test report no. 636- 02498. A study on the effects of orthene and monitor on plasma and erythrocyte cholinesterase activity in human subjects during subacute oral administration. Submitted to WHO by Chevron Chemical Company, Richmond, CA, USA. Curren, R.D. (1988) Unscheduled DNA synthesis in rat primary hepatocytes. Test article: Monitor technical. Unpublished report no. 1119, from Microbiological Associates, Inc. Submitted to WHO by Bayer AG, Leverkusen, Germany. Cushman, J.R. (1984) Modified Buehler test for the skin sensitization potential of methamidophos technical (SX-1490). Unpublished toxicological report no. 596 from Chevron Environmental health Center, Richmond, California, USA. Submitted to WHO by Bayer AG. Easter, M.D. and Rosenberg, D.W. (1986) The cholinesterase inhibition potential of analytical grade methamidophos (SX-1672) and methamidophos technical (SX-1490) following topical application of a single dose to male and female rats. Unpublished toxicological report SOCAL 2211 from Chevron Environmental Health Center, Richmond California, USA. Submitted to WHO by Bayer AG. Eigenberg, D.A., Pazdernik, T.L. and Doull, J. (1983) Haemoperfusion and pharmacokinetic studies with methamidophos in the rat. Fund. Appl. Toxicol., 3, 490-501. El-Sebae, A.H., Ahmed, N.S., El-Gendy, K.S., El-Bakary, A.S. and Soliman, S.A. (1987) Methamidophos (Tamaron) - a delayed neuropathic compound to man, but negative to chickens. Proc. 2nd Nat. Conf. on Pests and Dis. of Veg. and Fruits, Ismailia, Egypt, October, 1987, 475-485. Flucke, W. (1985) SRA 5172 TA (Tamaron TA) (c.n. methamidophos) Study for acute dermal toxicity to the chicken (Gallus domesticus). Unpublished toxicological report no. 13780 from Institute of toxicology Bayer AG. Wuppertal-Elberfeld. Submitted to WHO by Bayer AG. Flucke, W. (1990a) Methamidophos (Tamaron): Racemate and Enantiomers. Study for acute oral toxicity to rats. Unpublished report 19034 from Bayer AG, Fachbereich toxicologie, Wuppertal. Submitted to WHO by Bayer AG. Flucke, W. (1990b) Methamidophos (Tamaron): Racemate and enantiomers. Study for acute oral toxicity to the hen (Gallus domesticus). Unpublished report 19091 from Bayer AG, Fachbereich toxikologie, Wuppertal. Submitted to WHO by Bayer AG. Flucke, W. and Eben, A. (1988) SRA 5172 TA (Tamaron TA) - Study for the effect on the neurotoxic esterase (NTE) after dermal administration to chickens. Unpublished toxicological report no. 17268 from Bayer AG Toxicology division, Wuppertal. Submitted to WHO by Bayer AG. Flucke, W. and Eben, A. (1990) Methamidophos: racemate and enantioners. Study for effect on NTE (neuropathy target esterase) in hens following oral administration. Unpublished report no.: 19092 from Bayer AG Fachbereich Toxikologie, Wuppertal. Submitted to WHO by Bayer AG. Flucke, W. and Kaliner, G. (1985) SRA 5172 TA (Tamaron TA) (c.n. methamidophos) Study for acute neurotoxicity to the chicken after dermal administration. Unpublished report no. 13852 from Bayer AG Institute of toxicology. Submitted to WHO by Bayer AG. Garofalo, M. (1973) A study on the effects of orthene and monitor on plasma and erythrocyte cholinesterase activity in human subjects during subacute oral administration. Industrial Bio-Test Laboratories, Inc. unpublished report no. 636-02498. Submitted to WHO by Chevron Chemical Company, Richmond, CA, USA. Validated by United States Environmental Protection Agency. Hussain, M.A., Mohamad, R.B. and Oloffs, P.C. (1985) Studies of the toxicity, metabolism, and anticholinesterase properties of acephate and methamidophos. J. Environ. Sci. Health. B20(1), 129-147. Machemer, L. (1988) Expertise on the question: Does methamidophos induce delayed neuropathy? Unpublished report (January 8, 1988) from Bayer AG Fachbereich Toxikologie, Wuppertal. Submitted to WHO by Bayer AG. Murli, H. (1990) Mutagenicity test on SRA 5172 in an in vitro cytogenetic assay measuring chromosomal aberration frequencies in chinese hamster ovary (CHO) cells. Unpublished report no. R4935 from Hazleton Laboratories America, Inc. Submitted to WHO by Bayer AG. Pauluhn, J. (1987a) SRA 5172 TA (c.n. methamidophos) Study for acute inhalation toxicity to the rat to OECD guideline no. 403. Unpublished report no. 15661 from Bayer AG Institute of Toxicology, Wuppertal. Submitted to WHO by Bayer AG. Pauluhn, J. (1987b) SRA 5172 (Common name: methamiphos, the active integredient of MonitorR) Study of the subacute inhalation toxicity to rats in accordance with OECD guideline no. 412. Unpublished report no. 16069 from Bayer AG Fachbereich toxikologie, Wuppertal. Submitted to WHO by Bayer AG. Pauluhn, J. (1988) SRA 5172 (Common name methamidophos, the active ingredient of MonitorR) Study of the subchronic inhalation toxicity to rats in accordance with OECD guideline no. 413. Unpublished report no. 16578 from Bayer AG Fachbereich toxikologie, Wuppertal. Submitted to WHO by Bayer AG. Pauluhn, J. and Kaliner, G. SRA 5172 and trimethylphosphate (TMPO) (c.n. methamidophos) Study for the combination's acute neurotoxicity to hens and turkey hens. Unpublished report no. 13056 from Bayer AG Institute of toxicology, Wuppertal. Submitted to WHO by Bayer AG. Pauluhn, J., Machemer, L and Kimmerle, G. (1987) Effects of inhaled cholinesterase inhibitors on bronchial tonus and on plasma and erythrocyte acetylcholine esterase activity in rats. Toxicology 46, 177-190. Sachsse, K., Oharek, A., Zbinden, K., Madoerin, K., Luetkemeier, H., Wilson, J., Terrier, Ch. and Vogel, W. (1987) 3-Month subchronic delayed neurotoxicity study with SRA 5172 (c.n. methamidophos) in the hen. Unpublished report no.: R 4106 from RCC AG, Switzerland.
See Also: Toxicological Abbreviations Methamidophos (HSG 79, 1993) Methamidophos (ICSC) Methamidophos (JMPR Evaluations 2002 Part II Toxicological) Methamidophos (Pesticide residues in food: 1976 evaluations) Methamidophos (Pesticide residues in food: 1979 evaluations) Methamidophos (Pesticide residues in food: 1981 evaluations) Methamidophos (Pesticide residues in food: 1982 evaluations) Methamidophos (Pesticide residues in food: 1984 evaluations) Methamidophos (Pesticide residues in food: 1985 evaluations Part II Toxicology)