FENAMIPHOS JMPR 1974 IDENTITY Fenamiphos is a draft ISO common name. Chemical name O-ethyl O-(3-methyl-4-methylthiophenyl) isopropylphosphormidate. O-ethyl 4-(methylthio)-m-tolyl isopropylphosphoramidate. Synonyms Nemacur(R), phenamiphos, Bayer 68138. Structural FormulaMolecular weight 303.3 Empirical Formula: C13H22NO3PS Other information on identity and properties State: brown semi-solid (technical) white crystals (pure) Melting Point: 46°C (technical) 49°C (Pure) Vapour pressure: 10-6mm Hg (at 30°C) Solubility: in water approx. 700 mg/l at 20°C slightly soluble in most organic solvents Specific gravity (melt): 1.14 Hydrolytic stability in propanol/water (1:1) at 40°C: 40% degradation after 14 days at pH 2 no degradation after 50 days at pH 7 half life of 31.5 hours at pH 11.3 Formulations: 5% Granular, 10% Granular, 400 E.C. (Emulsifiable concentration 400 g/l) Purity The minimum purity is 87%. Maximum levels of the individual impurities are shown in Table 1. TABLE 1 Impurities (maximum levels) in technical fenamiphos Compound Maximum level (%w/w) O,O-diethyl isopropylphosphoramidate 3.0 4-methylthiocresol 0.5 O,O-bis[(4-methylthio)-3-ethylphenyl] isopropylphosphoramidate 2.0 O,O-diethyl O-[(4-methylthio)-3-methylphenyl] phosphate 1.0 O-ethyl O-[(4,6-bismethylthio)-3-methylphenyl] isopropylphosphoramidate 3.0 O-ethyl O,O-bis-[(4-methylthio)-3-methylphenyl] phosphate 8.0 O-ethyl O-[(4-methylthio)-3-methylphenyl] phosphate 1.0 water 0.3 EVALUATION FOR ACCEPTABLE DAILY INTAKE BIOCHEMICAL ASPECTS Biotransformations The two major metabolites identified following injection into bean, tomato, peanut and potato stems were O-ethyl O-4-methylsulfinyl-m-tolyl isopropylphosphoramidate and O-ethyl O-4-methylsulfonyl-m-tolyl isopropylphosphoramidate, the sulphoxide and sulphone of the thio-ether (Waggoner, 1972). A third metabolite (apparently a more potent inhibitor of cholinesterase) was not identified but was considered to be a further metabolite resulting from the sulphoxide. Further details of this study are given in the section "Fate of residues in plants". Small residues of the unknown metabolite may be of toxicological significance because of the potent anticholinesterase properties. The metabolic fate of labelled fenamiphos was studied in vivo in rats and in vitro with rat liver microsomes. The compounds were labelled in the ethyl (14C) isopropyl, (14C) or the thiomethyl (3H) positions. In vivo fenamiphos is excreted within 12-15 hours following a single oral dose of 2 mg/kg. In the in vitro studies a small quantity of an unknown metabolite possibly resulting from the N-dealkylation of fenamiphos was observed (Khasawinah and Flint, 1972). Apart from this minor component, metabolism in animals and plants follows the same pattern: oxidation of the thioether to the sulphoxide and sulphone, dearylation to yield the methyl thioether phenol (or its sulphoxide and sulphide) and potentially dealkylation of the ethyl, isopropyl or isopropylamide moiety of the phosphate ester. Treatment of rats with fenamiphos sulphoxide or sulphone produced the same excretion pattern and almost identical urinary metabolites (Gronberg, 1969). When fenamiphos sulphoxide was given to a lactating cow (Gronberg et al., 1974) the identified components of the residue were fenamiphos, its sulphoxide and its desisopropyl derivative, and the phenols of phenamiphos, its sulphoxide and its sulphone. An unidentified metabolite was also detected. Quantitative details are given in the section "Fate of residues in animals". Effects on enzymes and other biochemical parameters Fenamiphos, as are other organophosphate esters, is an inhibitor of cholinesterase enzymes. The in vitro I50 values were as follows: Rat serum - 5.1 x 10-5M. Rat erythrocyte - 6.3 x 10-4M. Rat brain - 2.1 x 10-4M. The maximum inhibition of whole blood cholinesterase in vivo occurred in rats three hours after dosing. In vivo sensitivity of cholinesterase reflects the in vitro I50 values with plasma cholinesterase being more sensitive to inhibition than the erythrocyte enzyme (Löser and Kimmerle, 1971). The metabolites of fenamiphos are more active inhibitors than the parent molecule (Waggoner, 1972). In vitro inhibition of horse serum cholinesterase showed relative values for fenamiphos < sulfoxide = sulfone < sulfoxide metabolite. In vitro I50 values of chicken and monkey liver aliesterase (triacetin hydrolysis) and monkey cholinesterase are as follows: Chicken (aliesterase): 4.2 x 10-5M. Monkey (aliesterase): 1.0 x 10-6M. Monkey (cholinesterase): 4.6 x 10-6M. (Coulston and Wills, 1974) On the basis of some preliminary electrophysiological studies with the cat, it was estimated that a threshold dose of fenamiphos might fall in the range of 0.8 to 1.5 mg/kg (Coulston and Wills, 1974). TOXICOLOGICAL STUDIES Special studies on carcinogenicity Mouse Groups of Charles River random bred Swiss white mice (125 males and 125 females/group) were fed fenamiphos in the diet at 0, 25 and 50 ppm for eighteen months in a study specifically designed to evaluate the carcinogenic potential of the compound. Additional groups of mice were fed 10 ppm N-nitrosodiethylamine for eighteen months (125 males and 125 females); 40 ppm for six months (60 males and 60 females); and 1000 ppm benzidine (100 females) for eighteen months as positive controls. Fenamiphos did not affect the incidence or pattern of mortality. Clinical chemistry studies performed at 18 months were normal. No signs of tumour formation were observed on gross or microscopic examination which were attributed to fenamiphos (Smith et al., 1972). Special studies on mutagenicity Mouse Groups of twelve male mice were administered fenamiphos intraperitoneally at 0, 0.25 and 0.50 mg/kg and mated for six consecutive weeks to virgin females in a standard dominant lethal test. A positive reference (methyl methanesulphonate) was used in this experiment. Fenamiphos did not induce alterations in male germinal cells which would be expected to lead to an early embryo mortality (Arnold et al., 1971). Special studies on neurotoxicity Hen Groups of hens (eight per group) were fed fenamiphos in the diet at levels of 0, 1, 3, 10, and 30 ppm for thirty days. At the end of the feeding experiment some animals were sacrificed and the remainder were observed for four weeks for neurological signs of poisoning. Food consumption was depressed at 30 ppm and the average body weight and growth of the animals at this same level was reduced. Cholinesterase (whole blood) depression was observed at thirty days at 3, 10 and 30 ppm, although cholinergic signs of poisoning were not observed at any time. There were no indications of delayed neurotoxic effects and microscopic examination of brain, spinal cord, and sciatic nerve (stained with H&E) did not indicate delayed neurological involvement with fenamiphos (Kimmerle, 1970; Spicer, 1970). Groups of hens (ten per group) were orally administered an LD50 dose of fenamiphos (5.0 mg/kg). The birds were observed for three weeks and sacrificed. No evidence of delayed neurotoxicity was observed either clinically or histologically while positive signs were observed with TOCP (Kimmerle, 1971; Spicer, 1971). Special studies on potentiation Rat Male rats were tested orally with fenamiphos (SRA 3886) in combination with disulfoton or E 154 and no potentiation of the acute toxicity was noted (Kimmerle, 1972c). Special studies on reproduction Rat A standard three generation, two litters per generation, reproduction study was performed with fenamiphos. Four groups of animals, consisting of ten male and twenty female rats per group, were fed fenamiphos at 0, 3, 10, and 30 ppm in the diet throughout the study period including mating, gestation, and suckling. Immediately after birth, pups were examined for malformations prior to either preparing for another generation or sacrifice. Five weanling rats per group of the F3b generation were sacrificed and macroscopic and microscopic examinations performed on the major tissues and organs. There were no apparent differences with regard to reproduction parameters including fertility, litter size, lactation index, growth of young, or on examination for malformation in any of the animals exposed to fenamiphos levels up to and including 30 ppm in the diet. It was concluded that fenamiphos had no influence on the reproduction of rats at dietary levels up to and including 30 ppm (Löser, 1972c; Cherry et al., 1972). Special studies on teratogenicity Rabbit Groups of fifteen artificially inseminated rabbits were orally administered fenamiphos at levels of 0, 0.2, and 0.4 mg/kg/day. Positive control groups (oral treatment with thalidomide (37.5 mg/kg/day)) were concurrently run with this experiment. All animals were treated from day 6 through 18 of gestation and sacrificed on day 29. At day 29 the young were examined for 24 hours, sacrificed and examined after skeletal staining. At the high level of treatment of fenamiphos, 2/12 instances of abortion and 2/12 premature deliveries were observed. No external or internal abnormalities were observed in the foetuses following treatment. With the exception of the animals at the high level of treatment where a few aborted or delivered prematurely, no effects on reproduction were observed with fenamiphos (Ladd et al., 1971). Acute toxicity TABLE 2 Acute toxicity of fenamiphos LD50 Animal Sex Route (mg/kg) References Rat M oral 2.4-15.6 Löser and Kimmerle, 1971 Kimmerle and Solmecke, 1971a Rat F oral 2.3-19.4 Kimmerle, 1972c Crawford and Anderson, 1974 DuBois et al., 1967 Rat M ip 3.0-3.7 ibid. Rat F ip 4.2-4.9 Löser and Kimmerle, 1971 Rat M dermal 73-500 DuBois et al., 1967 Rat F dermal 84-154 Kimmerle and Solmecke, 1971a Mouse M oral 22.7 Löser and Kimmerle, 1971 Mouse M&F ip 3.4 DuBois at al., 1967 Guinea Pig M oral 56-100 ibid. Löser and Kimmerle, 1971 Kimmerle and Solmecke, 1971a Guinea Pig M ip 17.3 DuBois et al., 1967 TABLE 2 (Cont'd.) LD50 Animal Sex Route (mg/kg) References Rabbit M oral 10-17.5 Löser and Kimmerle, 1971 Kimmerle and Solmecke, 1971a Cat M oral Ca.10 Löser and Kimmerle, 1971 Kimmerle and Solmecke, 1971a Dog M oral Ca.10 Löser and Kimmerle, 1971 Kimmerle and Solmecke, 1971a Hen F oral 5.3 Löser and Kimmerle, 1971 Kimmerle and Solmecke, 1971a TABLE 3 Acute toxicity of metabolites and impurities of fenamiphos LD50 Species Sex Route (mg/kg) References Fenamiphos-sulphoxide Rat F oral 10-25 Thyssen, 1974a Fenamiphos-solphone Rat F oral 10-25 ibid. 4-methylthio-m-cresol Rat M oral 1418 Crawford and Anderson, 1974 Rat F oral 1333>2500 ibid. Thyssen, 1974c 3-methyl-4-methylthiophenol Rat M oral 1418 Crawford and Anderson, 1974 Rat F oral 500-1000 Thyssen, 1974d 1175 Crawford and Anderson, 1974 3-methyl-4-methanesulphonylphenol Rat M oral 1250 ibid Rat F oral 1000 Thyssen, 1974e 1854 Crawford and Anderson, 1974 Impurities identified as components of the technical mixture (aryldiamide, diarylamide, diaryl ethyl ester, diethyl ester, diethylmonamide, di-SCH3 compound, ethyl aryl ester, ethyldiamide, and 4-methylthio-3-cresol) were tested for their acute toxic properties to rats. At a dosage of 1.5 times the acute LD50 of fenamiphos none of the materials were toxic (Crawford and Anderson, 1973b). Technical fenamiphos administered to the skin of rabbits as an acetone solution at 50 mg/kg resulted in a slight erythema and was not considered as a primary irritant. Technical fenamiphos applied to the conjunctival sac of rabbits (100 mg/kg as a crystalline material) was irritating to the eye. This irritation was believed to be a mechanical rather than a physiological effect (Crawford and Anderson, 1971). A 15% granular formulation was examined for dermal and inhalation toxicity properties and at the highest level examined (200 mg/kg and 20 mg/l respectively) no toxicity was observed (Crawford et al., 1970b; Crawford and Anderson, 1972a). The rat oral LD50 of a 15% granular formulation was 66.6 mg/kg for male rats and 62.7 mg/kg for female rats (DuBois and Kinoshita, 1970). A 5% or 10% granular formulation, administered at up to 500 mg/kg to the backs of rats resulted in depressed cholinesterase activity values. Mortality was not observed at the maximum dose tested and it was considered that the granular formulation was not a dermal hazard although the material was rapidly absorbed into the body (Kimmerle and Solmecke, 1971b). The acute dermal toxicity and dermal and eye irritation properties of a liquid formulation (37.4% a.i.) were tested in rabbits. The acute LD50 was 75.7 mg/kg and 71.5 mg/kg to male and female rabbits respectively (Crawford et al., 1970a; Crawford and Anderson, 1972b). When applied to intact and abraded skin at a dose of 0.25 ml (0.085 mg a.i.), fenamiphos was not found to be a primary irritant. Fenamiphos (0.1 ml, equivalent to 0.034 mg a.i.) was an irritant when applied to the conjunctival sac of rabbits. Control formulation data were not reported (Crawford and Anderson, 1973c). The acute rat oral LD50 of a 35% liquid formulation was calculated to be 24.8 mg/kg (equivalent to 8.7 mg fenamiphos /kg). Inhalation toxicity studies with this preparation using a small particle size distribution (1-3 microns) resulted in an LC50 value of 0.175 and 0.091 mg/l following one and four hour exposure respectively (DuBois and Kinoshita, 1971). Studies with rodents administered fenamiphos by inhalation at doses up to 0.23 mg/l for one to four hours exposure as a static spray showed that rabbits and guinea pigs were more tolerant of the acute effects than rats and mice. A one hour LC50 value for mice was 0.06 mg/l and for rats 0.23 mg/l while rabbits and guinea pigs were unaffected at these concentrations (Kimmerle and Solmecke 1971a; 1972b). Acute oral administration of 2.5 mg/kg to rabbits had no effect on several liver function tests including BSP, SGPT and SDH activity at 1 and 24 hours and seven days after treatment (Kimmerle and Solmecke 1971a). Studies performed on male rats indicated that, following poisoning, the administration of atropine and/or 2-PAM or Toxogonin would reduce the acute lethal dose by a factor of approximately two. As with other organophosphorus compounds, rapid administration of atropine and oxime reactivator following poisoning would afford some protection and would alleviate the cholinergic signs of poisoning (Kimmerle, 1972a; DuBois et al., 1967). Short term studies Rat Groups of rats (fifteen males and fifteen females per group, thirty males and thirty females were used as controls) were fed fenamiphos in the diet at 0, 4, 8, 16, and 32 ppm for twelve weeks. Male and female rats from the highest dose group exhibited signs of cholinergic stimulation in the first two months of the test. Behavioral differences in all other groups were not apparent. There were no differences from the control in the average of any group with regard to food consumption and growth. With the exception of cholinesterase inhibition, there was no apparent effect on group averages of haematological parameters examined. Plasma cholinesterase depression was observed at 8 ppm. A no-effect level, based upon plasma cholinesterase, was observed at 4 ppm. Gross and microscopic pathological examination was performed on tissues and organs at the conclusion of the experiment. A slightly increased liver weight, observed in males at 16 and 32 ppm, was not reflected in the calculation of relative organ-to-body weight ratios nor in the histological examination. Based on cholinesterase depression, 4 ppm in the diet was a no-effect level in this experiment (Löser, 1968b; Mawdesley-Thomas and Urwin, 1970a). Groups of male rats (15 per group) were administered fenamiphos orally or by intraperitoneal injection daily, 5 days/week for 60 days. The animals all survived a dose range of 1.5 (ip) to 1.7 (oral) mg/kg/day with no evidence of a cumulative toxicological effect due to fenamiphos (Kimmerle and Solmecke, 1971a). In an earlier study female rats survived daily ip administration of 1 mg/kg for 60 days while 40% of those administered 2 mg/kg did not survive. All rats died at 3 mg/kg administered by intraperitoneal injection (DuBois and Flynn, 1968). These studies indicate little if any cumulative toxicity. Dog Groups of beagle dogs (two males and two females/group) were fed fenamiphos in the diet at 0, 2, 6, and 18 ppm for three months. Behavioral abnormalities, evidenced by signs of cholinergic stimulation, were evident at 18 ppm in the diet and growth of females at this high level was reduced. Average haematological and clinical chemistry values including liver function tests, kidney function tests and urinalyses were not apparently affected by fenamiphos in the diet. Averages of plasma and red blood cell cholinesterase values were depressed at 4 ppm in the plasma of both males and females. At 2 ppm no effect on the average red cell cholinesterase values was found while plasma cholinesterase was depressed (20-30%) in both sexes. Gross morphological examination of tissues and organs at the conclusion of the study indicated no abnormal effects of fenamiphos in the diet (Löser, 1968a). Groups of beagle dogs (two males and two females/dose, three of each sex were used in the control group) were fed fenamiphos in the diet at levels of 0, 1, 2 and 5 ppm for twelve weeks. There was no effect of feeding fenamiphos at levels up to and including 5 ppm in the diet on the average of any of the parameters examined including haematology, liver function tests, clinical chemistry tests, kidney function tests, and gross and microscopic examination of tissues and organs. As with other studies, cholinesterase was the only parameter significantly affected, with the females being more susceptible than the males and the plasma being more sensitive to inhibition than red blood cell. Erythrocyte cholinesterase was unchanged at 2 ppm while plasma cholinesterase was slightly depressed. One ppm in the diet had no effect on plasma cholinesterase. As the depression of plasma cholinesterase was minimal and transient at 2 ppm it might be considered that this would be a no-effect level in this experiment (Löser, 1969; Mawdesley-Thomas and Urwin, 1970b). As an extension of the previous short term study in dogs (Löser, 1969), an additional two male and two female dogs were fed fenamiphos in the diet at 10 ppm for three months. Two male and two female animals were also maintained as a control. There was no mortality over the course of the experiment and a very slight deviation in the average body weight of both males and females was noted. Because of the small sample population, the slight weight differences cannot be fully evaluated. There was no effect of feeding fenamiphos on any of the haematological parameters examined. Urinalysis, clearance examinations, blood sugar and cholesterol were normal over the course of the experiment. Cholinesterase activity was significantly depressed in both plasma and erythrocytes and in both male and female dogs. In addition, several abnormalities were noted with regard to some of the serum enzyme parameters related to liver function after three months of feeding, especially in male dogs. Alkaline phosphatase and SGPT activity were significantly increased. Following gross and microscopic examination of tissues and organs, no significant differences were noted between the control and those animals fed 10 ppm. The abnormal findings in some enzyme parameters related to liver functions, predominantly in males at three months of feeding 10 ppm in the diet, were not accompanied by pathological findings at autopsy nor confirmed in another test where fenamiphos was fed at levels of 18 ppm in the diet. They are considered a transient occurrence and not directly related to the presence of fenamiphos in the diet (Löser, 1970; Thompson et al., 1972a). Groups of pure bred beagle dogs (four males and four females per group) were fed fenamiphos in the diet at levels of 0, 0.5, 1, 2, 5, and 10 ppm for two years. There were no significant effects noted with fenamiphos at any dietary level with regard to growth, food consumption or any of the standard clinical and physiological examinations made during the course of the study. One dog died after being fed 0.5 ppm in the diet. This dog was considered to have died of pneumonia and its death was not related to administration of fenamiphos. Gross and histological examinations of all tissues and organs at the conclusion of study did not reveal any abnormal developments considered to have been a result of feeding fenamiphos. The only significant physiological effect observed was anti-cholinesterase activity which was marginally depressed in plasma at 2 ppm. As with other species, the plasma appears to be the most sensitive indicator of exposure with a no-effect level being 1 ppm in the diet (equivalent to 0.029-0.036 mg/kg/day) (Löser, 1972b; Thompson et al., 1972b). Long term studies Rats Groups of SPF derived Wistar strain (forty males and forty females per group, eighty males and eighty females used as controls) were fed fenamiphos in the diet, at concentrations of 0, 3, 10, and 30 ppm for two years. Behavioral abnormalities were evident, as signs of cholinergic stimulation, only during the first six weeks of feeding at 30 ppm. After six weeks of feeding, the obvious anticholinesterase effect disappeared and was not evident for the remainder of the two year study. There were no differences in averages at any feeding level on growth, mortality, food consumption, haematological values, clinical chemistry values or liver and kidney function tests. Urine examinations as well as blood sugar and cholesterin values were normal. Thyroid weights and thyroid-to-body weight ratios of females were heavier than normal at 30 ppm. All other major tissues and organs appeared normal under gross and microscopic examination. The thyroid weight in females at 30 ppm was high but was not accompanied by an abnormal tumour development, goitre or by unusual histological findings. Cholinesterase determinations indicated that plasma cholinesterase was the most sensitive parameter. At 10 ppm in the diet, fenamiphos inhibited plasma cholinesterase. No significant effects were observed at 3 ppm in the diet (equivalent to 0.17-0.23 mg/kg bw/day) (Löser, 1972a; Cherry and Newman, 1973). COMMENTS Fenamiphos, an acutely toxic organophosphate ester, is rapidly absorbed as evidenced by rapid onset of cholinergic signs of poisoning. In animals fenamiphos is rapidly degraded, predominantly through oxidation to acutely toxic products. Fenamiphos does not appear to affect biochemical systems other than cholinesterase. Testing for the delayed neurotoxic effect commonly seen with TOCP was negative. Short term and long term dietary studies in both rats and dogs have indicated, with the exception of cholinesterase depression, no unusual effects. In long term studies with rats, transient behavioural abnormalities were observed during the first six weeks of feeding, which disappeared and were not evident for the remainder of the study. Female rats are more susceptible than males to cholinesterase depression. Plasma cholinesterase depression is a better indicator of exposure than red blood cell cholinesterase. Based on plasma cholinesterase depression, a no-effect level in a two-year rat study is considered to be 3 ppm in the diet and in a two year dog study, 1 ppm in the diet. Long term studies in rats and mice reported to the Meeting did not show a carcinogenic effect. Although there are no studies available in man, sufficient data are available and the Meeting allocated an ADI using the more sensitive species, the dog. TOXICOLOGICAL EVALUATION Level causing no toxicological effect Rat: 3 ppm in the diet equivalent to 0.17 mg/kg bw. Dog: 1 ppm in the diet equivalent to 0.029 mg/kg bw. ESTIMATE OF ACCEPTABLE DAILY INTAKE FOR MAN 0 - 0.0006 mg/kg bw. RESIDUES IN FOOD AND THEIR EVALUATION USE PATTERN Fenamiphos is an organophosphorus compound with a systemic action and a powerful nematicidal effect. It is active against root-knot, cyst-forming and free-living nematodes and has important applications against sucking insect pests and spider mites. Fenamiphos is commercially used in the USA, Australia, Spain, the Cameroons, Caribbean, Chile, Columbia, Costa Rica, Ecuador, Guatemala, Ivory Coast, Jamaica, Martinique, Mexico, Nicaragua, San Salvador and Uruguay. Registration proceedings and trials are in progress in several other countries. Fenamiphos is formulated as 5 and 10% granules and as a 40% emulsifiable concentrate. Pre-harvest treatments Fenamiphos is formulated as a granular product and as an emulsifiable concentrate. Both formulations are recommended chiefly for treatments in banana, pineapple, vegetable (tomatoes, brassicas, peppers, eggplants), tobacco, coffee, groundnut and citrus crops. Application is usually made to the soil at sowing, planting and transplanting, and in established crops. The general dose rate is 5 to 10 kg active ingredient per hectare for broadcast (overall) application, but is reduced for band application according to band width. Furthermore, the emulsifiable concentrate is suitable for dip treatments of banana seedlings and for foliar spraying of pineapples. Details of uses and recommendations are given in Table 4. TABLE 4 Use Pattern of fenamiphos (All applications are pre-harvest against nematodes) No. of Application rate treatments Crop a.i. Type of Application Formulation1 per year Bananas 1.5-2.5 g/m2 At planting G 3.0 g/plant Soil treatment in established crop G 3-4 4-5 kg/ha In irrigation canals or direct to soil EC 2 1-1.5 g/corm Dip treatment pre-planting plus soil application EC 2 or 1.5 g/ planting position (but no more than total of 3 g/ planting position) G Pineapples 10-40 kg/ha Broadcast treatment pre-planting of crowns and slips G 5-20 kg/ha Broadcast treatment pre-planting of crowns and slips in combination with G 3-5 kg/ha foliar spraying 3 in post-planting LC established crop 15 kg/ha Foliar spray application at planting, repeat after an interval of 2 months EC 2 TABLE 4 (Cont'd.) No. of Application rate treatments Crop a.i. Type of Application Formulation1 per year Tomatoes 1-2.5 g/m2 Immediately before or after sowing G 5-10 kg/ha Broadcast/overall application G, pre-planting EC Brassicas 5-8 kg/ha Broadcast/overall application G, pre-planting EC Tobacco 1-2.5 g/m2 Before or immediately after sowing or G 0.1-0.2 g/plant at transplanting or in established crop G 1 5-10 kg/ha Broadcast/overall application G, pre-planting EC Coffee 1-2.5 g/m2 Seedbed treatment G 1.5-2.5 g/shrub In established crop G 2-3 Groundnuts 3-5 kg/ha Broadcast/overall application G, pre-sowing LC 1 Cucurbitaceae 0.15-0.2 g/ Band application planting hole or at sowing G 1.5-2.5 kg/ha Peppers 5-8 kg/ha Broadcast application at sowing or at transplanting G 1 Eggplant 5-8 kg/ha Broadcast application at sowing or at transplanting G 1 Citrus 1-1.5 g/m2 Seedbed treatment G 2-3 g/tree Treatment in nursery G 1.5-3 g/tree In established crop G, LC 2-3 TABLE 4 (Cont'd.) No. of Application rate treatments Crop a.i. Type of Application Formulation1 per year Potatoes 5-10 kg/ha Broadcast/overall G, EC, treatment pre-planting LC 1 Pyrethrum 5-8 kg/ha Broadcast application at planting G Ornamentals 1.5-3 g/m2 In established crops G Cotton 1.7-3.5 kg/ha Band application (band width of G, 30-45 cm.) at sowing LC Beets 3-(6) kg/ha Band application immediately after sowing or during G, emergence EC Soybeans 5-8 kg/ha Broadcast/overall application G, pre-sowing LC 1 Beans 5-8 kg/ha Broadcast application pre-sowing G 1 Grapes 2-3 g/plant G 1 Strawberries 10 kg/ha Broadcast application pre-planting G 300 g/1000 Post-planting or G metres of row post-harvest Lawns 10-20 kg/ha Broadcast application G 1 G = Granules; EC = Emulsifiable concentrate; LC = Liquid concentrate. Post-harvest treatments No recommended uses. Other uses Fenamiphos is recommended for use on ornamentals (granular formulation). RESIDUES RESULTING FROM SUPERVISED TRIALS The residues of fenamiphos together with its sulphoxide and sulphone resulting from supervised trials in a wide range of crops are shown in Table 5. In most crops, residues were below 0.05 mg/kg. The exceptions were grapes, lettuce, potatoes, strawberries and tomatoes which contained up to about 0.1, 0.5, 1, 0.7 and 0.3 mg/kg respectively. Residues in tobacco were much higher, with respective maximum levels in green, cured and fermented tobacco of about 12, 140 and 100 mg/kg. FATE OF RESIDUES In animals A feeding study was carried out on a lactating dairy cow to determine whether fenamiphos sulphoxide, found in plants as the major metabolite, would be incorporated into milk and animal tissues either as the intact compound or in metabolized form (Gronberg et al., 1974. See also "Biotransformations"). A single dose of 0.8 mg/kg body weight, corresponding to 27 ppm in the diet, of ring-14C fenamiphos sulphoxide was administered. Four hours after application the label was distributed as follows. Urine 39%, faeces <0.1%, rumen 47%, tissues 1.4%, bile 0.1%, omasum, abomasum and milk <0.1% each; total recovery 88%. The following compounds were found: fenamiphos (I), fenamiphos sulphoxide (II), desisopropyl-fenamiphos (III), phenol of fenamiphos (IV), phenol of fenamiphos sulphoxide (V), phenol of fenamiphos sulphone (VI) and "unknown" (VII). The levels of these residues in tissues and milk are shown in Table 6. Of the dose, 18% was reduced to the parent fenamiphos, apparently by microorganisms. At 4 hours 82% of the activity in whole blood and 87% of the activity in urine was identified as conjugated phenols. The residues of fenamiphos in poultry eggs and tissues were determined by Gronberg et al. (1973). Laying hens were fed for 14 days with carbon-14 ring-labelled fenamiphos in feed at 0.06, 0.18 and 0.65 ppm concentration. During this time, residues in eggs were below the detection limit of 0.003 mg/kg. At slaughter, all tissue residues from birds given feed containing 0.65 ppm were below the limit of determination of 0.003 to 0.005 mg/kg, although very low residues were detectable in some tissues. TABLE 5 Residues of fenamiphos and metabolites resulting from supervised trials Rate of Residues, fenamiphos and application Interval No. of sulphoxide and sulphone, mg/kg Crop Country Formulation1 (kg a.i./ha) (days) analyses Range Average Apples Australia 10% G 22.4 334 1 n.d.2 n.d.2 Bananas, Central peel America 10% G 2.8-12 g a.i./plant 1-195 41 <0.025-0.3 <0.025 pulp <0.025 <0.025 Bananas, Ivory Coast 5% G 10 g a.i./plant 1-14 4 <0.02 <0.02 peel pulp <0.02 <0.02 peel 28-88 3 0.06-0.1 0.07 pulp 0.03-0.08 0.05 Broccoli USA 3% G; 15% G 6.72 65-101 8 <0.01-0.04 0.02 15% G 10.0 92 1 0.2 0.2 Brussels Sprouts USA 3% SC; 15% G 6.72-10.0 107-133 5 <0.01-0.02 <0.01 Cabbage USA 3% SC; 15% G 6.72-10.0 55-108 14 <0.01-0.02 0.01 TABLE 5 (Cont'd.) Rate of Residues, fenamiphos and application Interval No. of sulphoxide and sulphone, mg/kg Crop Country Formulation1 (kg a.i./ha) (days) analyses Range Average Australia 40% EC 4.5 42-106 6 n.d.2 n.d.2 Carrots USA 15% G 6.72 96-160 9 <0.01-0.05 0.01 Cauliflower USA 3% SC; 15% G 6.72-10.0 97-111 12 <0.01-0.04 0.02 Coffee Brazil - 1-2 g a.i./plant 14-15 6 <0.02-0.07 0.05 beans, Central green America 28-30 6 <0.02-0.09 0.05 56-62 4 <0.02-0.05 0.03 90 2 0.03; 0.05 0.04 Cottonseed USA 3% SC; 15% G 1.12 157-196 10 <0.01 <0.01 Cotton USA 3% SC; gin trash 15% G 1.12 161-196 8 <0.01 <0.01 Cotton USA 3% SC; foliage 15% G 1.12 143-148 4 <0.01-0.1 0.04 Grapefruit USA 3% SC; peel 15% G 33.6 - 50.4 183-184 1 <0.01 <0.01 pulp <0.01 <0.01 whole fruit <0.01 <0.01 TABLE 5 (Cont'd.) Rate of Residues, fenamiphos and application Interval No. of sulphoxide and sulphone, mg/kg Crop Country Formulation1 (kg a.i./ha) (days) analyses Range Average Grapes Australia 5% G 43% EC 5.6 - 14.7 145-147 2 n.d.2 n.d.2 22.0 145-147 1 0.03 0.03 44.0 145-147 1 0.08 0.08 Leaf-lettuce USA 3% SC 11.2 46 1 0.3 0.3 Head USA lettuce, 3% SC; head 15% G 11.2 61-72 4 0.02-0.1 0.08 wrapper leaves 0.09-0.5 0.3 discard leaves 0.09-6.5 1.9 Lemons, USA whole fruit 3% SC 33.6 184 1 0.01 0.01 Limes, USA 3% SC; whole fruit 15% G 33.6 147 2 <0.01 <0.01 Melons Guatemala Australia 5% G Egypt 40% EC 1.6-10.0 56-112 5 n.d2-0.05 n.d.2 Oranges, USA 3% SC; 22.4-50.4 182-366 4 <0.01-0.1 0.04 peel 10% G; 15% G TABLE 5 (Cont'd.) Rate of Residues, fenamiphos and application Interval No. of sulphoxide and sulphone, mg/kg Crop Country Formulation1 (kg a.i./ha) (days) analyses Range Average pulp 4 <0.01 <0.01 whole fruit 5 <0.01-0.02 0.01 whole fruit Australia 5% G; 40% EC 11.2-22.4 21-139 10 n.d.2 n.d.2 Peanuts, USA 3% SC; kernels 10% G 4.51-13.45 122-148 5 <0.01-0.02 <0.01 shells (0.01-0.2 0.06 vines 98-148 5 0.02-4.3 2.3 Pineapples Hawaii, USA 3% SC; 10% G 44.8-112 238-658 10 <0.01-0.03 <0.01 3% SC (foliar spray) 5.6 1-29 20 <0.02-4.0 0.5 Potatoes USA 3% SC; 15% G (row appl) 6.1 41-58 3 <0.02-1.2 0.7 71-106 7 <0.01-1.0 0.15 Potatoes, USA, Canada, 3% SC; whole Fed. Rep. of 15% G Germany, UK, (broadcast Australia 4-5-11.2 67-203 23 n.d.2-0.45 0.07 peel 1 0.07 0.07 TABLE 5 (Cont'd.) Rate of Residues, fenamiphos and application Interval No. of sulphoxide and sulphone, mg/kg Crop Country Formulation1 (kg a.i./ha) (days) analyses Range Average flesh 1 0.07 0.07 Sweet USA 3% SC; Potatoes 15% G (broadcast) 6.72 108-143 8 <0.01-0.04 0.01 3% SC; 15% G (row appl) 4.0-6.1 108-143 8 <0.01-0.06 0.01 Soybeans, USA 3% SC; bean, green 15% G 11.2 75-117 12 <0.01-0.09 0.04 vine, green 75-117 12 <0.01-12 2.9 bean, dry 131-159 11 <0.01-0.03 0.01 Strawberries Australia 5% G 40% EC 16.5-22.5 36-121 6 0.03-0.7 0.2 Sugarbeets, USA 3% SC; tops 15% G 6.72-10.0 119-187 9 <0.01-0.08 0.01 beets <0.01-0.03 0.01 Tangerines, USA 3% SC; peel 15% G 33.6 247-251 2 0.07; 0.3 0.2 pulp 2 <0.01; 0.03 0.02 whole fruit 1 0.03 0.03 TABLE 5 (Cont'd.) Rate of Residues, fenamiphos and application Interval No. of sulphoxide and sulphone, mg/kg Crop Country Formulation1 (kg a.i./ha) (days) analyses Range Average Tobacco Australia 40% EC 50-95 4 0-5-4.8 1.9 Tobacco, USA 3% SC; 6.72 4 3 0.9-7.8 3.5 green 15% G 7 3 0.8-7.0 2.9 11 3 0.8-3.3 1.8 14 3 1.4-12 5.2 21 3 1.2-4.9. 2.5 28 3 0.4-4.2 1.7 35 3 0.25-3.6 1.4 36-148 13 0.02-4.8 1.0 air cured 88-106 2 3.2; 4.2 3.7 flue cured 85 2 11; 13 12 cured 75-91 6 4.5-140 33 aged 75-92 3 5.7-16 11 fermented 89 1 98 98 Tomatoes USA, 3% SC; Canada 15% G 11.2-16.8 61-89 10 <0.01-0.3 0.1 TABLE 5 (Cont'd.) Rate of Residues, fenamiphos and application Interval No. of sulphoxide and sulphone, mg/kg Crop Country Formulation1 (kg a.i./ha) (days) analyses Range Average Australia 5% G; 40% w/v 9.8-11.2 78-161 5 <0.05 <0.05 Fed. Rep, of Germany 5% G 9.8-12.2 79-161 5 n.d.3 n.d.3 1 EC = emulsifiable concentrate; G = granules; SC = spraying concentrate. n.d. = <0.01. 2 <0.01 mg/kg. 3 <0.05 mg/kg. TABLE 6 Residues, mg/kg, in tissue and milk of cow fed fenamiphos sulphoxide (Gronberg et al., 1974) Compound1 Fat Meat Liver Kidney Milk I 0.004 n.d.2 0.006 n.d. n.d. II n.d. n.d. 0.002 n.d. 0.002 III 0.002 n.d. 0.005 0.16 0.004 IV 0.005 0.001 0.029 0.86 0.005 V 0.003 0.003 0.021 0.36 0.025 VI n.d. n.d. n.d. 0.01 0.004 VII 0.002 0.005 0.036 0.25 0.020 1 For identities of compounds, see text. 2 n.d., not detectable, = <0.001 mg/kg. In plants Various investigations of the metabolism of fenamiphos in plants and soil demonstrate the rapid thiooxidation of the parent compound to the sulphoxide and sulphone. Both metabolites are detoxified by hydrolysis, generally followed by glucosylation of the phenolic products. Fenamiphos-14C,3H was injected into the stems of beans, tomatoes, peanuts and potatoes and the plants were harvested at 7, 14, 21 and 28 days (Waggoner, 1972. See also "Biotransformations"). Two major metabolites were identified by TLC, isotopic ratios, IR, and MS as the sulphoxide and sulphone of fenamiphos. The sulphoxide was the major metabolite, accounting for 33-41% of the residue, followed by the sulphone (31-33%), both after 7 days' treatment. Two minor metabolites containing intact phosphoramidate structures accounted for not more than 1.5 and 0.2% of the total residue. Khasawinah studied fenamiphos metabolism in carrots (1973a), tomatoes (1973b), cabbages (1973c), soybeans (1972b) and tobacco plants (1971) following soil application, and in snap beans (1972a) after both soil treatment and stem injection; 14C-ring, 14C-1-ethyl and 3H-methylthio labelled fenamiphos were used. Carrots readily absorbed and metabolized fenamiphos and its major soil foliage and 14C from the ethyl group was detected in the foliage and carrots. This 14C was probably incorporated into lipids, pigments, sugars and structural elements such as cellulose. Water-soluble residues were mainly conjugates of the sulphoxide and sulphone phenols. No parent fenamiphos was detected. Residues of the sulphoxide and sulphone were below 0.06 mg/kg in both carrots and foliage. At the end of the growing period, soil residues were 2.7 mg/kg fenamiphos equivalents (one third of the amount applied) of which 65% consisted of the sulphoxide and sulphone in the ratio 4:1. Results with tomatoes were similar. Sulphoxide and sulphone residues reached a peak of 0.2-0.3 mg/kg 30-40 days after treatment, and no parent compound was detected later than 40 days. The results showed the stability of the thio-methyl-ring linkage. Comparable results were obtained with head cabbage. An organosoluble polar metabolite with an apparently intact phosphoramidate structure was detected soon after treatment and declined gradually to insignificant levels. In tobacco plants the sulphoxide reached a peak in less than one week, and then decreased as the sulphone increased. At the end of the growing period the ratio of sulphoxide to sulphone was about 3:2. Soybeans were planted in soil that had been treated with 14C-ethyl, 3H-methylthio fenamiphos and cropped with tobacco for one growing season. The soil at soybean planting contained 0.65 mg/kg fenamiphos sulphoxide, 0.07 mg/kg fenamiphos sulphone and 0.18 mg/kg fenamiphos equivalents as unextractable material. Nineteen days old soybean seedlings contained 16.9 mg/kg (fresh weight basis) of these two soil metabolites in a sulphoxide: sulphone ratio of 73:17. In the mature plant (150-day growing period), the total concentration of the two metabolites, found in equal proportions, was 3.5 mg/kg in the dry leaves and 0.19 mg/kg in the dry beans. The water-soluble radioactivity consisted mainly of the glucose conjugate of the sulphone phenol. The insoluble radioactivity was not characterized. The fate of 14C1-ethyl and 3H-methylthio fenamiphos was investigated in snap beans following stem injection and soil treatment in systems designed for the recovery of the applied nematicide. The study demonstrated volatile 14C radioactivity, presumably as CO2. 40% of the stem-injected and 12% of the soil-applied fenamiphos was recovered in this form. Volatile tritium radioactivity was less, 7.4% and 1.3% of the amounts applied by stem-injection and soil treatment, respectively. The metabolites formed by both methods of application were fenamiphos sulphoxide, fenamiphos sulphone and the sulphoxide and sulphone phenols in the free form or conjugated with glucose. The metabolism of similarly labelled fenamiphos applied by stem injection, soil drench or spray to fruited pineapple plants was studied by Flint (1973). Soil treatment at 20 pounds a.i./acre resulted in maximum total radioactive residues in fruit of 0.086 mg/kg fenamiphos equivalents at 90 days after treatment. Metabolites identified in fruit and foliage were identical to those previously found in several other plant and animal systems. In soil and water Khasawinah (1970) treated the top 1.5 cm of a sandy loam soil, in which tobacco was growing, with labelled fenamiphos. One third of the applied amount was taken up by the growing plants during an 11-week period. The major product in the soil was the sulphoxide, with small quantities of the sulphone. No hydrolysis products of the parent compound or its oxidation products were detected in the soil extracts. None of the radioactivity was leached into the drainage water, and all of it remained in the root zone. About 22% of the radioactivity remaining in the soil after 177 days was bound to clay particles and was unextractable. Fenamiphos was studied for soil runoff, leaching, adsorption, and stability in water by Flint et al. (1971) and Church (1971). It was moderately adsorbed by sandy loam and silt loam soil. Fenamiphos residues in runoff water were less than 3.4% of the applied compound over a 37-day interval during which 2.3 to 3.7 inches of irrigation were applied; the application rate of fenamiphos was 22.5 kg a.i./ha. The leaching of fenamiphos from the three types of soil was inversely proportional to the adsorptivity of the soils. It was estimated that 111 inches of rainfall would be needed for clay loam soil and 75 inches for sandy loam to leach fenamiphos to a depth of 12 inches. Fenamiphos was relatively stable in aqueous systems at pH 5 and 7 in the laboratory but declined rapidly with a half-life of 4.8 days in a simulated field pond at PH 7 and average temperature of 29°C. The leaching of "aged" fenamiphos residues in sandy loam soil was investigated by Tweedy et al. (1974). Ring-14C fenamiphos was incubated with sandy loam soil under greenhouse conditions for 30 days and then applied to the top of a sandy loam soil column 2.9 inches in diameter and 12 inches high. Distilled water, equivalent to 0.5 acre-inch/day was added daily for 45 days. Of the radioactivity recovered from the system, 77.5% was found in the top fourth of the column and only 2.3% was recovered in the leachate. The majority of the activity, 65%, apparently did not move at all. The metabolism of fenamiphos soil residues under aerobic and anaerobic conditions was investigated by Shaw and Flint (1974). Fenamiphos, labelled with tritium in the methylthio group or with carbon-14 uniformly throughout the aromatic ring, was used in this study. The results indicated that anaerobic conditions arrested further degradation while aerobic incubation allowed continued metabolism. Essentially no 14C or 3H radioactivity was lost during incubation indicating stability of the aromatic ring system. The major metabolite was fenamiphos sulphoxide with some further thio-oxidation and hydrolysis observed under aerobic conditions. The effect of fenamiphos on soil microbial populations was studied by Houseworth and Tweedy (1972) using Indiana clay loam and Commerce silt loam soils. The soils were treated with 50 and 250 mg/kg of the pesticide and maintained at 50% field moisture capacity for 56 days. At intervals, samples of soil were removed from each treatment and assayed for populations of bacteria, fungi and Actinomycetes. Fenamiphos had no significant effect on them under the conditions of the experiment. The photodecomposition of thin films of fenamiphos was investigated by Khasawinah and Sandie (1974). Thin films of dual labelled ethyl-1-14C, methylthio-3H fenamiphos were coated on glass plates and silica gel coated glass plates and exposed in the open air for about three weeks. Fenamiphos was rapidly oxidized to its sulphoxide and then to the sulphone. Some hydrolysis of the sulphone occurred after long intervals, especially on glass. The results of some studies in the USA of the persistence of fenamiphos and its oxidation products in various types of soil were available to the Meeting. They are reproduced in Table 7. In storage and processing The effect of alkali refining and steam deodorization on residues in cottonseed and soybean oils was studied in laboratory simulation experiments by Thornton (1973a) and Olson (1972b, 1974). In cottonseed, the two processes in combination removed 98.5% of the fenamiphos, 98.4% of the sulphoxide and 88% of the sulphone. Since the sulphone would constitute only a small proportion of a naturally occurring residue, the combined processes would remove nearly all the residue. In soybeans, the effects of the processes on sulphoxide residues was studied, as this is the main component of the residue after long post-treatment intervals. The simulated refining process removed 96% of the sulphoxide, and deodorization removed 38%. A hypothetical residue of 0.42 mg/kg should therefore be reduced to 0.01 mg/kg by the two steps. The effect of citrus processing on residues of fenamiphos sulphoxide was investigated by Olson (1972a). Commercial citrus processing involves liming and drying of the chopped solids in the preparation of cattle feed. Fenamiphos sulphoxide, the main metabolite in crops, was resistant to the liming step but 39% of the residue was removed by drying. To prepare citrus oil, an aqueous emulsion is centrifuged vigorously. 99% of any fenamiphos sulphoxide present in the emulsion would be removed from the oil by this procedure. TABLE 7 Persistence of fenamiphos + sulphoxide + sulphone in various soils in the USA1 Residue, phenamiphos + sulphoxide + sulphone, mg/kg, after interval, days2 0 30-40 80-100 180-200 360-400 Soil Range Mean Range Mean Range Mean Range Mean Range Mean Silt loam 1.2-15 7.7 5.4-12 9.4 0.8-15 6.9 0.1-6.5 2.5 0.1-2.5 1.1 Clay 1.0-1.7 1.3 3.7 3.7 1.5-2.7 2.1 0.6-1.3 1.0 0.6-0.7 0.7 Sand muck 5.1-6.3 5.7 5.1-5.8 5.4 0.1 0.1 0.7-1.0 0.8 0.4-0.6 0.5 Sand 5.5 5.5 0.3-0.6 0.5 0.1-0.2 0.2 0.06-0.07 0.07 0.03-0.04 0.04 Sand clay 6.8-8.5 7.7 3.0-4.9 3.9 0.5-1.2 0.8 0.1 0.1 0.1 0.1 Fox sand 4.3-9.2 6.7 6.8-8.0 7.4 3.1-3.2 3.1 1.0-1.3 1.1 0.9-1.0 0.9 Peat 15-16.5 16 17-20 18 12.5-17 15 6.8-8.8 7.4 6.3-7.2 6.8 Low humus 13-17 15 4.6-6.6 5.5 3.6-6.6 5.1 1.2-3.3 2.2 0.3-0.6 0.4 1 Fenamiphos was added to soils at 10mg/kg level as granules or spray concentrate. 2 Usually two or three analyses at each interval. Olson (1970a) studied the fate of residues on pineapple crowns. The fresh crowns were dipped in an aqueous emulsion of spraying concentrate containing 0.12% fenamiphos, and allowed to drain dry. The surface residue immediately after treatment amounted to about 30 mg per crown, of which about half could be removed by extracting with water. Seven days after treatment, aqueous extraction removed about one-third of the original residue. Surface extraction with benzene, however, removed virtually all the initial deposit (29 mg per crown) but only 27% (8 mg) after 7 days. Storage of broccoli, carrots, peanut kernels, pineapple fruit and potatoes at -18° to -23°C for two years showed no significant loss of fenamiphos, the sulphoxide or the sulphone (Anonymous, 1973). There was no significant loss of residues (parent + sulphoxide + sulphone) in field-treated potatoes or of fenamiphos from potatoes fortified in the laboratory when cooked at 100°C for 30 minutes in sealed jars (Thornton, 1972). METHODS OF RESIDUE ANALYSIS A specific gas-chromatographic procedure for the determination of residues of fenamiphos and sulphoxide and sulphone in various crops, animal tissues and milk is described by Thornton (1969, 1971a). Following initial extraction, the extract is oxidized with potassium permanganate to convert fenamiphos and its sulphoxide to the sulphone. The sulphone is then determined by gas chromatography with alkali flame ionisation detection. Recoveries from a variety of crops and animal tissues fortified with fenamiphos or its metabolites at the blending step were generally between 75 and 110%. Interference studies by Thornton (1971b, 1973b) and Olson (1970d, 1971b,c) have shown the method to be specific in the presence of other possible organophosphorus compounds. The limit of detection is about 0.02 mg/kg. The determination of residues of fenamiphos and its metabolites in tobacco and tobacco smoke was successfully investigated by Olson (1971a) with the Thornton (1971a) method. This method should be suitable for regulatory purposes. The determination of fenamiphos residues in soil by thermionic emission gas chromatography is described by Olson (1970b). The soil sample is extracted in a Soxhlet apparatus, using a 1:1 chloroform-methanol solvent mixture. The solvent is evaporated and the residue oxidized and chromatographed. Recoveries of fenamiphos and its metabolites were 80-107%. The sensitivity of the method is approximately 0.02 mg/kg. Olson (1970c) has also extended the procedure to a number of other organophosphorus pesticides. NATIONAL TOLERANCES REPORTED TO THE MEETING National tolerances reported to the Meeting are shown in Table 8. TABLE 8 National tolerances reported to the Meeting Safety Tolerance Interval Count Crop mg/kg (days) Australia Tomatoes, brassicas, cucurbits, lettuce, citrus, pineapples, grapes, bananas, ginger No residue Spain Tobacco sugarbeets, etc. (industrial purpose), bananas 60 USA Bananas, citrus 0.1 180 APPRAISAL Fenamiphos is a systemic nematicide which gives good control of root-knot cyst forming and free living nematodes. It is also effective against sucking insect pests and spider mites. It is formulated as 5% and 10% granules and as an emulsifiable concentrate (40%). Both formulations are recommended chiefly for treating bananas, pineapples, tomatoes, brassicas, eggplant, tobacco, groundnuts, citrus crops, ornamentals and pyrethrum. It is chiefly applied to the soil at sowing or planting. The general dose rate is 5-10 kg active ingredient/ha for broadcast application, but is reduced for band application. The emulsifiable concentrate is especially suitable for dip treatment of banana seedlings and for foliar spraying of pineapples. Fenamiphos is commercially used in Australia, USA, some Central and South American countries, Spain, the Cameroons and the Ivory Coast. Various investigations of the metabolism of fenamiphos in plants and soil demonstrate the rapid thio-oxidation of the parent compound to the sulphoxide and sulphone. In general the major part of the residue in crops and soil is the sulphoxide, followed by the sulphone. Both are relatively persistent. Both metabolites are detoxified by hydrolysis, usually followed by conjugation of the phenolic products as glycosides. Little or none of the parent fenamiphos seems to be present in most crops at harvest. Micro-organisms in soil do not seen to be affected by fenamiphos. The dissipation of residues in soil depends on the type of soil, increasing in the order peat < silt loam < clay = sand. Fenamiphos is only very slowly leached from soil. Following application in accordance with good agricultural practice, the maximum residue levels of fenamiphos including its sulphoxide and sulphone in Brussels sprouts, cotton seed, cabbage, carrots, cauliflower, grapefruit, lemons, limes, melons, oranges (pulp), peanut kernels, pineapples, soybeans (dried) and sugar beets are at or below 0.05 mg/kg. Higher residues are found in some other crops. Typical maximum residues are: grapes 0.1 ppm, lettuce 0.5 ppm, potatoes 1 ppm, strawberries 0.7 ppm, tomatoes 0.3 ppm and tobacco (green) 12 ppm, (cured) 140 ppm (fermented) 100 ppm. Data for fenamiphos residues in tobacco smoke are not available. Processing cottonseed or soybeans to oil removed 98-99% of the residues and processing citrus to cattle feed removed about 40%. Cooking potatoes had no significant effect. In a laboratory experiment approximately one third of the fenamiphos originally applied was extractable with water from the surface of the crowns of pineapples seven days after dipping in an aqueous emulsion containing 0.12% fenamiphos. Residues in eggs and tissues from hens fed for 14 days with 14C ring-labelled fenamiphos in feed at 0.65 ppm were below 0.005 mg/kg. Residues in milk and tissues of a dairy cow fed once with a dose corresponding to 27 ppm fenamiphos sulfoxide in the diet were below 0.01 ppm. Specific gas-chromatographic procedures for the determination of residues of fenamiphos, its sulphoxide and sulphone in various crops, animal tissues, milk and soil have been elaborated. The initial extract is oxidized with permanganate to convert fenamiphos and its sulphoxide to the sulphone. The sulphone is determined with an alkali flame ionisation or flame photometric detector. Limits of detection are about 0.02 ppm, and recoveries higher than 75%. The methods should be suitable for regulatory purposes. RECOMMENDATIONS The following limits refer to fenamiphos including its sulphoxide and sulphone, expressed as fenamiphos. TOLERANCES Tolerance Crop (mg/kg) Bananas, coffee beans (green and roasted, grapes, sweet potatoes 0.1 Broccoli, Brussels sprouts, cabbage, carrots, cauliflower, citrus fruits, cottonseed, melons, peanut kernels, pineapples, soybeans (dried), sugar beets 0.05* * At or about the limit of determination. TEMPORARY TOLERANCES Temporary tolerance Crop (mg/kg) Potatoes, tomatoes 0.2 FURTHER WORK OR INFORMATION REQUIRED (by 1977) 1. Further data on which to judge the residues in or on potatoes and tomatoes. 2. Adequate residue data on which to base recommendations for tolerances for other crops (e.g. beans, cucumbers, lettuce, peppers and strawberries). DESIRABLE 1. Brain cholinesterase and behavioural studies in animals exposed to low levels for extended periods. 2. Observations in man. 3. Additional studies on the potentiation effects with other organophosphorus pesticides. 4. Residue data for raw agricultural products moving in commerce. 5. Further residue data for different crops from supervised trials including data on rates and frequencies of application, soil, foliar or other treatment and pre-harvest intervals, especially for broccoli and tangerines. REFERENCES Anonymous. (1973) The effect of frozen storage at 0 to -10°F on Nemacur residues in peanut meat, broccoli, carrot roots, potatoes, pineapple fruit. Chemagro Report No. 36132, 36318, 36319, 36320, 39094. Arnold, D., Keplinger M. and Fancher, O. (1971) Mutagenic study with Nemacur(R) (BAY 68138) Technical in albino mice. Report from Industrial BioTest Laboratories, Inc., submitted by Bayer AG. (Unpublished). Cherry, C., Urwin, C. and Newman, A. (1972) Pathology report of BAY 68,138. Rat breeding study. Report from Huntingdon Research Centre, submitted by Bayer AG. (Unpublished). Cherry, C. and Newman, A. (1973) Pathology report of Bayer 68,138. Chronic toxicological studies in rats. Report from Huntingdon Research Centre, submitted by Bayer AG. (Unpublished). Church, D.D. (1971) Nemacur - leaching, runoff and water stability. Chemagro Report No. 26 849. Coulston, F. and Wills, J.H. (1974) Summary of research of the Institute of Comparative and Human Toxicology, Albany Medical College, on fenamiphos. Report submitted by Bayer AG. (Unpublished). Crawford, C., Anderson, R. and Nelson, D. (1970a) The skin and eye irritating properties of BAY 68,138 3 lb/gal S.C. to rabbits. Report from Chemagro Division of Baychem Corporation, submitted by Bayer AG. (Unpublished). Crawford, C., Anderson, R. and Nelson, D. (1970b) The acute inhalation toxicity of Nemacur(R) 15% granular to rats. Report from Chemagro Division of Baychem Corporation, submitted by Bayer AG. (Unpublished). Crawford, C, and Anderson, R. (1971) The skin and eye irritating properties of Bay 68138 technical to rabbits. Report from Chemagro Division of Baychem Corporation, submitted by Bayer AG. (Unpublished). Crawford, C. and Anderson, R. (1972a) The acute dermal toxicity of Nemacur(R) technical to rabbits. Report from Chemagro Division of Baychem Corporation, submitted by Bayer AG. (unpublished). Crawford C. and Anderson, R. (1972b) The acute dermal toxicity of Nemacur(R) 3 lbs/gal. spray concentrate to rabbits. Report from Chemagro Division of Baychem Corporation, submitted by Bayer AG. (Unpublished). Crawford C. and Anderson, R. (1973a) The dermal toxicity of Nemacur(R) 15% granules to rats. Report from Chemagro Division of Baychem Corporation, submitted by Bayer AG. (Unpublished). Crawford, C. and Anderson, R. (1973b) Comparative oral toxicity in rats of several impurities and a technical compound of Nemacur(R) with analytical grade Nemacur(R). Report from Chemagro Division of Baychem Corporation, submitted by Bayer AG. (Unpublished). Crawford C. and Anderson, R. (1973c) The eye and skin irritancy of Nemacur(R) 2 lb/gal spray concentrate to rabbits. Report submitted by Bayer AG. (Unpublished). Crawford, C. and Anderson, R. (1974) The acute oral toxicity of two Nemacur(R) phenolic metabolites and MTMC to male and female rats. Report from Chemagro Division of Baychem Corporation, submitted by Bayer AG. (Unpublished). DuBois, K., Flynn, M. and Kinoshita, F. (1967) The acute toxicity and anticholinesterase action of Bayer 68138. Report from University of Chicago. (Unpublished). DuBois, K. and Flynn, M. (1968) The subacute parenteral toxicity of BAY 68138 to rats. Report from University of Chicago, submitted by Bayer AG. (Unpublished). DuBois, K. and Kinoshita, F. (1970) Acute oral and dermal toxicity of a granular formulation of BAY 68138. Report from University of Chicago, submitted by Bayer AG. (Unpublished). DuBois, K. and Kinoshita, F. (1971) The acute oral and inhalation toxicity of a Nemacur(R) (BAY 68138) formulation to rats. Report from University of Chicago submitted by Bayer AG. (Unpublished). Flint, D.R. (1973) The metabolism of Nemacur in pineapple. Chemagro Report No. 39 119. Flint, D.R., Church, D.D., Shaw, H.R. and Armour, J., II. (1971) The mobility and persistence of Nemacur in soil and water. Chemagro Report No. 29 974. Gronberg, R.R. (1969) The metabolic fate of ethyl-4-(methylthio)-m-tolyl isopropylphosphoramidate (BAY 68138), ethyl-4-(methylsulfinyl)-m-tolyl isopropylphosphoramidate (BAY 68138 sulfoxide) and ethyl-4-(methylsulfonyl)-m-tolyl-isopropylphosphoramidate (BAY 68138 sulfone) in white rats. Report No. 26759 from Chemagro Division of Baychem Corporation, submitted by Bayer AG. (Unpublished). Gronberg, R.R., Flint, D.R. and Pither, K. (1974) The metabolic fate of Nemacur sulfoxide administered orally to a lactating dairy cow. Report No. 41104 from the Chemagro Division of Baychem. Corp., submitted by Bayer AG. (Unpublished). Gronberg, R.R., Simmons, C.E. and Shaw, H.R., II. (1973) Residues of Nemacur in poultry eggs and tissue. Report No. 35995 from the Chemagro Division of Baychem Corporation, submitted by Bayer AG. (Unpublished). Houseworth, L.D., and Tweedy, B.G. (1972) Effect of Nemacur on microbial populations. Chemagro Report No. 34 990. Khasawinah, A.M. (1970) The fate of Nemacur in soil. Chemagro Report No. 28 796. Khasawinah, A.M. (1971) Metabolism of Nemacur in tobacco plants. Chemagro Report No. 29 142. Khasawinah, A.M. (1972a) Metabolism of Nemacur in snap beans grown in closed glass chambers. Chemagro Report No. 34 992. Khasawinah, A.M. (1972b) The uptake and metabolism of Nemacur soil residues by soybean plants. Chemagro Report No. 35012. Khasawinah, A.M. (1973a) Metabolism of Nemacur in carrots. Chemagro Report No. 36005. Khasawinah, A.M. (1973b) Metabolism of Nemacur in tomatoes. Chemagro Report No. 38501. Khasawinah, A.M. (1973c) The metabolism of Nemacur in cabbage. Chemagro Report No. 39120. Khasawinah, A.M. and Flint, D.R. (1972) Metabolism of Nemacur(R) [ethyl-4-(methylthio)-m-tolyl isopropylphosphoramidate] by rat liver microsomes in vitro. Report No. 34217 from Chemagro Division of Baychem Corporation, submitted by Bayer AG. (Unpublished). Khasawinah, A.M. and Sandie, F.E. (1974) Photodecomposition of thin films of Nemacur. Chemagro Report No. 39217. Kimmerle, G. (1970) Subchronic neurotoxicity studies on chickens. Report from the Institute for Toxicology, submitted by Bayer AG. (Unpublished). Kimmerle, G. (1971) Acute neurotoxicity studies on hens. Report from Institute for Toxicology, submitted by Bayer AG. (Unpublished). Kimmerle, G. and Solmecke, B. (1971a) BAY 68138 toxicological studies. Report from Institute for Toxicology, submitted by Bayer AG. (Unpublished). Kimmerle, G. and Solmecke, B. (1971b) Granular formulation. Acute dermal toxicity on rats. Report from the Institute for Toxicology, submitted by Bayer AG. (Unpublished). Kimmerle, G. (1972a) Antidotal experiments on rats. Report from the Institute for Toxicology, submitted by Bayer AG. (Unpublished). Kimmerle, G. (1972b) Acute inhalation toxicity study with Nemacur(R) active ingredient on rats. Report from the Institute for Toxicology, submitted by Bayer AG. (Unpublished). Kimmerle, G. (1972c) Acute toxicity of SRA-3886 in combination with S-276 and with E-154 to rats. Report from Institute for Toxicology, submitted by Bayer AG. (Unpublished). Ladd, R., Jenkins, D., Keplinger, M. and Fancher, O. (1971) Teratogenic study with Nemacur(R) technical in albino rabbits. Report from Industrial BioTest Laboratories, submitted by Bayer AG. (Unpublished). Löser, E. (1968a) Subchronic toxicological studies on dogs. Report from the Institute for Toxicology, Farbenfabriken Bayer AG. (Unpublished). Löser, E. (1968b) Subchronic toxicological studies on rats. Report from the Institute for Toxicology, submitted by Bayer AG. (Unpublished). Löser, E. (1969) Subchronic toxicological studies on dogs (3 month feeding test). Report from the Institute for Toxicology, submitted by Bayer AG. (Unpublished). Löser, E. (1970) Subchronic toxicological studies on dogs. Report from the Institute for Toxicology, submitted by Bayer AG. (Unpublished). Löser, E. and Kimmerle, G. (1971) Acute and subchronic toxicity of Nemacur(R), active ingredient. Pflanzenschutz-Nachr. Bayer, 24(1):69-113. Löser, E. (1972a) Chronic toxicological studies on rats (2 year feeding experiment). Report from the Institute for Toxicology, submitted by Bayer AG. Löser, E. (1972b) Chronic toxicological studies on dogs (2 year feeding experiment). Report from the Institute for Toxicology, submitted by Bayer AG. (Unpublished) Löser, E. (1972c) Generation studies on rats. Report from the Institute for Toxicology, submitted by Bayer AG. (Unpublished). Mawdesley-Thomas, L. and Urwin, C. (1970a) Pathology report of BAY 68138. Subchronic toxicological studies in rats. Report from Huntingdon Research Centre, submitted by Bayer AG. (Unpublished). Mawdesley-Thomas, L. and Urwin, C. (1970b) Pathology report of BAY 68138. Subchronic toxicity tests in dogs. Report from the Huntingdon Research Centre, submitted by Bayer AG. (Unpublished). Olson, T.J. (1970a) Residues on the surface of fresh pineapple crowns treated with an aqueous emulsion of S.C. formulation of Nemacur. Chemagro Report No. 28014. Olson, T.J. (1970b) Determination of Nemacur residues in soil by thermionic emission gas chromatography. Chemagro Report No. 28731. Olson, T.J. (1970c) Determination of Dasanit, Guthion, Metasystox R, Nemacur and trichlorfon in soil by thermionic emission gas chromatography. Chemagro Report No. 27835. Olson, T.J. (1970d) An interference study for the determination of residues of Nemacur on pineapple. Chemagro Report No. 28723. Olson, T.J. (1971a) Determination of Nemacur residues in tobacco and tobacco smoke. Chemagro Report No. 30448. Olson, T.J. (1971b) An interference study for the determination of residues of Nemacur on cotton and tomatoes. Chemagro Report No. 30095. Olson, T.J. (1971c) An interference study for the Nemacur crop residue method for bananas. Chemagro Report No. 31041. Olson, T.J. (1972a) The effect of citrus processing on residues of Nemacur sulfoxide. Chemagro Report No. 34050. Olson, T.J. (1972b) Effect of commercial soybean oil processing on residues of Nemacur sulfoxide. Chemagro Report No. 33461. Olson, T.J. (1974) The effect of alkali refining on Nemacur residues in cottonseed oil. Chemagro Report No. 40113. Shaw, H.R. and Flint, D.R. (1974) The metabolism of Nemacur soil residues under aerobic and anaerobic conditions. Chemagro Report No. 39909. Smith, P., Wright, P. and Keplinger, M. (1972) Eighteen month carcinogenic study with Nemacur(R) (BAY 68138) in Swiss white mice. Report from Industrial BioTest Laboratories, submitted by Bayer AG. (Unpublished). Spicer, J. (1970) Pathology report of BAY 68138. Subchronic neurotoxicity tests on hens. Report from the Huntingdon Research Centre, submitted by Bayer AG. (Unpublished). Spicer, J. (1971) Pathology report of BAY 68138. Hen study. Report from Huntingdon Research Centre, submitted by Bayer AG. (Unpublished). Thompson, C., Newman, A. and Urwin, C. (1972a) Pathology report of BAY 68138. Subchronic toxicity study in dogs. Report from the Huntingdon Research Centre, submitted by Bayer AG. (Unpublished). Thompson, C. Newman, A. and Urwin, C. (1972b) Pathology report of BAY 68138. Chronic toxicity study in dogs (administration in diet for 2 years). Report from Huntingdon Research Centre, submitted by Bayer AG. (Unpublished). Thornton, J.S. (1969) A gas chromatographic method for the determination of Nemacur and metabolite residues in crops. Chemagro Report No. 25402. Thornton, J.S. (1971a) Determination of residues of Nemacur and its metabolites in plant and animal tissues. J. agr. Food Chem., 19 (5):890-893. Thornton, J.S. (1971b) An interference study for the residue method for Nemacur and metabolites. Chemagro Report No. 25533. Thornton, J.S. (1972) Effect of cooking on residues of Nemacur in potatoes. Chemagro Report No. 35314. Thornton, J.S. (1973a) Effect of alkali refining and deodorization on residues of Nemacur and metabolites in cottonseed oil. Chemagro Report No. 35345. Thornton, J.S. (1973b) An interference study for the Nemacur residue method. I. Additional compounds not previously tested. Chemagro Report No. 36 142. Thyssen. (1974a) Nemacursulfoxid, Akute Toxizitat bei Ratten. Report from Institute for Toxicology, submitted by Bayer AG. (Unpublished). Thyssen. (1974b) Nemacursulfon, Akute Toxizitat bei Ratten. Report from Institute for Toxicology, submitted by Bayer AG. (Unpublished). Thyssen. (1974c) 4-methyl-mercapto-m-Kresol, Akute Toxizitat bei Ratten. Report from Institute for Toxicology, submitted by Bayer AG. (Unpublished). Thyssen. (1974d) 3-methyl-4-methyl-mercaptophenol, Akute Toxizitat bei Ratten. Report from Institute for Toxicology, submitted by Bayer AG. (Unpublished). Thyssen. (1974e) 3-methyl-4 methan-sulfonyl phenol, Akute Toxizitat bei Ratten. Report from Institute for Toxicology, submitted by Bayer AG. (Unpublished). Tweedy, B.G. and Houseworth, L.D. (1974) Leaching of "aged" Nemacur residues in sandy loam soil. Chemagro Report No. 40 506. Waggoner, T.B. (1972) Metabolism of Nemacur [ethyl 4-(methylthio)-M-tolyl isopropylphosphoramidate] and identification of two metabolites in plants. J. agr. Food Chem., 20(1):157-160.
See Also: Toxicological Abbreviations Fenamiphos (ICSC) Fenamiphos (Pesticide residues in food: 1977 evaluations) Fenamiphos (Pesticide residues in food: 1978 evaluations) Fenamiphos (Pesticide residues in food: 1980 evaluations) Fenamiphos (Pesticide residues in food: 1985 evaluations Part II Toxicology) Fenamiphos (Pesticide residues in food: 1987 evaluations Part II Toxicology) Fenamiphos (Pesticide residues in food: 1997 evaluations Part II Toxicological & Environmental) Fenamiphos (JMPR Evaluations 2002 Part II Toxicological)