Yoshiyuki Takimoto

Comparative metabolism of fenitrothion in aquatic organisms: I. Metabolism in the euryhaline fish, Oryzias latipes and Mugil cephalus

[14C]Fenitrothion at 0.1 ppm in running water is more rapidly absorbed in the killifish (Oryzias latipes) at 25 than at 15 degrees C to a similar plateau level, and bioaccumulation ratios of fenitrothion are 235 and 339, respectively. Water of higher salinity (23%) resulted in slightly higher accumulation ratios of fenitrothion in both killifish (303) and mullet, Mugil cephalus (179), than fresh water (235 and 30, respectively), but the half-lives are independent of temperature and salinity, with values of 0.24-0.36 day. Fenitrothion was metabolized primarily through hydrolysis by the killifish, demethylation by the mullet, and conjugation of the liberated phenol with glucuronic acid by both species. Although metabolism of the compound was not affected by the different salinities and temperatures in both fish, the glucuronide conjugate was more directly excreted into water under lower temperature and higher salinity conditions. 14C-labeled compounds are distributed primarily in the gall bladder as shown by whole-body radioautography.

Comparative metabolism of fenitrothion in aquatic organisms: III. Metabolism in the crustaceans, Daphnia pulex and Palaemon paucidens

When the waterflea Daphnia pulex and the shrimp Palaemon paucidens were exposed to 1.0 ppb [14C]fenitrothion in a flowthrough system, the concentrations of fenitrothion and 14C in the body reached equilibrium, and the maximum bioaccumulation ratios of fenitrothion were 71 and 6 in the daphnia and shrimp, respectively. These crustaceans primarily metabolized the compound by oxidation of P = S to P = O, hydrolysis of P-O-aryl linkage, and demethylation. The liberated phenol was found to be conjugated with sulfate in the daphnia and with glucose in the shrimp. When the organisms were transferred to a freshwater stream, fenitrothion and its metabolites were rapidly excreted from their bodies, and the half-life of the parent compound was less than 0.2 day in both species.

Comparative metabolism of fenitrothion in aquatic organisms: II. Metabolism in the freshwater snails, Cipangopaludina japonica and Physa acuta

When freshwater snails, Cipangopaludina japonica and Physa acuta, were exposed to 0.1 ppm [14C]fenitrothion in a dynamic flow system, the concentrations of fenitrothion and 14C in the body reached equilibrium on Day 1 of exposure. The maximum bioaccumulation ratios of fenitrothion were 18 and 53 in C. japonica and P. acuta, respectively. These snails metabolized the compound primarily by demethylation, hydrolysis, and reduction. The liberated phenol moiety was found to be conjugated with sulfate in C. japonica and mainly with glucose in P. acuta. When the snails were transferred to a freshwater stream, fenitrothion and its metabolites were rapidly excreted, and the half-life of the parent compound was less than 0.5 day in both snails. Fenitrothion and its decomposition products were mainly distributed in liver of P. acuta, as evidenced by whole-body radioautography.

Fate of fenitrothion in several developmental stages of the killifish (Oryzias latipes)

Abstract14C-Fenitrothion at 0.1 ppm in running water, is rapidly absorbed at each stage of the embryo, yolk sac fry, postlarva, juvenile, and adult of the killifish (Oryzias latipes). The14C and fenitrothion concentrations 2 in organisms including those in eggs produced from mature female reach equilibrium after 1 to 3 days exposure except the juvenile stage, which shows a gradual increase in concentration, and the maximum bioaccumulation ratios 3 of the parent compound ranges from 88- (postlarva) to 540-fold (female adult) relative to the water concentration.Demethylfenitrothion and 3-methyl-4-nitro-phenyl-β-glucuronide are produced at all stages except the embryo, and the highest content of the former compound is produced at the yolk sac fry stage.Once these organisms are transferred to fresh water, the14C and fenitrothion concentrations decrease rapidly with a variation of the half-life of the parent compound from 0.27 day (yolk sac fry) to 1.42 days (embryo). 14C Compounds are primarily distributed in the internal organs, and are also observed in the mature eggs present in the female body by whole body radioautography.

Indoor Behavior and Risk Assessment Following Space Spraying of d-Tetramethrin and d-Resmethrin

To clarify the indoor behavior of insecticides in space spraying, an aerosol canister (containing a mixture of 0.45 g d-tetramethrin and 0.06 g d-resmethrin in a 300-mL product) was applied to a typical Japanese room under various conditions and temporal concentrations in air; floor, walls, and ceiling were monitored. Air concentrations were chiefly dependent on ventilation rates but not on air circulation by an air conditioner. During a periodic spraying, the airborne insecticides did not accumulate in the room, but the floor residues gradually increased with the number of sprayings. After cessation of spraying, however, dislodgeable residues on the floor decreased with time. The time-dependent behavior of d-tetramethrin was simulated by a mathematical model (InPest) developed by the authors, and it was found that the estimated values agreed fully with actually measured values. The simulation model also clarified the amount of insecticide evaporated from the room material, the amount vented to the outdoors, and so on. Indoor exposure levels of d-tetramethrin and d-resmethrin to the rooms occupants were estimated with the monitored concentrations when a 10-sec spraying was done twice a day for 30 days. The margins of safety, which were obtained by dividing the no observed effect levels by the exposure levels, were over 100 for unclothed occupants, even in the room with the windows closed.

Indoor Behavior and Risk Assessment Following Residual Spraying of d-Phenothrin and d-Tetramethrin

To clarify the indoor behavior of insecticides in residual spraying equivalent to a crack and crevice treatment, an aerosol canister (containing a mixture of 0.9 g d-phenothrin and 1.1 g d-tetramethrin in a 300-mL product) was applied to a typical Japanese room under various conditions, and temporal concentrations in air and on the floor, walls, and ceiling were monitored. Air concentrations were chiefly dependent on ventilation rates but not on air circulation. During a periodic spraying, the airborne insecticides did not accumulate in the room, but the floor residues gradually increased with the number of sprayings. After cessation of spraying, however, dislodgeable residues on the floor decreased with time. The time-dependent behavior of d-phenothrin was simulated by a developed simulation model (InPest), which helped a more comprehensive understanding of the insecticide behavior. Indoor exposure levels of d-phenothrin and d-tetramethrin to room occupants were estimated with the monitored concentrations when a 2.5-min spraying was done four times over an 8-week period. The margins of safety, which were obtained by dividing the no observed effect levels by the exposure levels, were over 100 for unclothed occupants, even in a room with the windows closed.

Effect of metabolism on bioconcentration of geometric isomers of d-phenothrin in fish

Abstract Yearling carp (Cyprinus carpio) were exposed to d-phenothrin (a 1:4 mixture of d-cis and d-trans isomers) in the absence and the presence of piperonyl butoxide under the flow-through test condition and the bioconcentration factors (BCFs) of the geometric isomers were separately evaluated. It was demonstrated that BCF values for the d-cis isomer were significantly higher by 1.1 to 2.2-fold than those for the d-trans isomer and the subsequent exposure in the presence of piperonyl butoxide resulted in elevated BCF values for the d-cis isomer, but no remarkable change in BCFs was observed for the d-trans isomer. The elevation observed here was presumably attributable to a reduced elimination caused by inhibited oxidative reactions characteristic to the d-cis isomer. The contribution of biotransformation to the elimination rate constant ( K 3 K 2 was estimated to be 2.3–11. Thus, the result was well explained by a distinct oxidative metabolism of the d-cis isomer and a significance of metabolism in bioconcentration phenomenon was exemplified.

The inorganic and organic characters for predicting bioconcentration on wide variety of chemicals in fish.

The applicability of Fujitas inorganic (i) and organic (o) characters as descriptors for predicting bioconcentration factor (BCF) in fish was investigated with a wide variety of organic chemicals. Among 612 BCF data recently released by National Institute of Technology and Evaluation (NITE), the values for the chemicals with a molecular weight of less than 600 and the 1-octanol/water partition coefficient (log P ) of less than six were extracted and analyzed. By applying theoretically derived model equation, a good relationship between these BCF and each Fujitas i: o was established. Statistical analyses and model validations revealed that the estimations of our approach were very excellent. More precise predictions were attained than those by using other published models, especially, for chemicals such as disperse dye having hetero atoms.

Analytical methods for Sumithion in technical products and formulated materials

As Sumithion or O,O-dimethyl O-(3-methyl-4-nitrophenyl) phosphorothioate has the chemical structure similar to methylparathion or ethylparathion, the analytical methods for the latter compounds can generally be applied to Sumithion with slight modifications. Titration of reduced Sumithion with standardized sodium nitrite (Anonymous 1965 a and b), measurement of 3-methyl-4-nitrophenol formed by alkaline hydrolysis (Anonymous 1964, 1964 a and c; Kovac and Fodrekova 1965, Suzuki 1972), or colorimetric determination of reduced Sumithion according to Averell-Norris (1948) are among the analytical methods analogous to those for methylparathion or ethylparathion. More recently, a gas chromatographic method of analysis has been elaborated which, if applied appropriately, can determine Sumithion content in both technical products and formulated materials more easily and more accurately than some of the foregoing methods. This section deals in detail with several of the representative methods of analysis, stressing the availability and the advantage and disadvantage of each as compared with others.

Metabolism of fungicide diethofencarb in grape (Vitis vinifera L.): Definitive identification of thiolactic acid conjugated metabolites

The metabolic fate of diethofencarb (isopropyl 3,4-diethoxycarbanilate) separately labeled with (14)C at the phenyl ring and 2-position of the isopropyl moiety was studied in grape (Vitis vinifera L.). The acetonitrile solution of (14)C-diethofencarb at a rate of 500 g a.i. ha(-)(1) was once applied topically to fruits or leaves at the maturity stage of fruits (PHI 35 days), and the plants were grown in the greenhouse until harvest. In the grape plants, diethofencarb was scarcely translocated to the untreated portion and was degraded more in the fruit as compared to the leaf. For the fruit, diethofencarb primary underwent O-deethylation at the 4-position of the phenyl ring to form the phenolic derivative, isopropyl 3-ethoxy-4-hydroxycarbanilate (0.9% of the total radioactive residue, TRR). This metabolite was successively transformed via conjugation with glucose at the phenolic hydroxy group (8.1-18.1% TRR) or with thiolactic acid at the 5-position of the phenyl ring (1.5-1.7% TRR). The thiolactic acid conjugate was further metabolized mainly to two different types of glucose conjugates at the 4-position of the phenyl ring (8.7-13.5% TRR) and the hydroxy group in the thiolactic acid moiety (6.4-7.3% TRR), as evidenced by (1)H NMR and atmospheric pressure chemical ionization-liquid chromatography-mass spectrometry together with cochromatographies with synthetic standards.