Microbial community in a groundwater sample did not degrade 0.1μg Carbon/ml of 2, 4-dichlorophenol (DCP). DCP was degraded when the water sample was amended with phosphate or ammonium nitrate. The density of the degrader, as measured by the most probable number (MPN) method using a DCP-spiked mineral-salt (MS) medium, increased to 10⁴-10⁵cell/ml irrespective of the amendment with the mineral nutrients. These results suggested that phosphate or ammonium nitrate was required by the DCP degrader not for growth but for the expression of an ability to degrade 0.1μg DCP-C/ml in the groundwater. Three bacterial isolates from the groundwater showed different mineral requirements for expressing the ability to degrade 0.1μg DCP-C/ml. Namely, the pure culture of one isolate degraded 0.1μg DCP-C/ml in filter-sterilized groundwater only when amended with ammonium nitrate; another isolate degraded DCP partially when amended with phosphate; and the other isolate degraded DCP irrespective of amendment with the mineral nutrients. The cell density of each isolate increased to 10⁶-10⁷cell/ml irrespective of the amendment with these mineral nutrients. Possible reasons for the discrepancy in the response to these mineral nutrients in the degradation of DCP by the microbial community and by the bacterial isolates are discussed.

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Methanesulfonates of phenol and hydroxy heteroaromatic compounds possessing an isobutylthio substituent were synthesized and their lethal activity against six species of insects and mites was tested. The insecticidal spectrum and potency of these aryl methanesulfonates varied according to the aromatic moiety. Compounds the aryl moiety of which is phenyl, pyridyl, pyrazinyl and thiazolyl showed high insecticidal activity to N. cincticeps, N. lugens and C. pipiens. For high insecticidal activity, the isobutylthio group was required at the β (meta) position with regard to the sulfonate side chain. The corresponding and sulfones showed high inhibitory activity to acetylcholinesterase preparations from N. cincticeps, housefly heads and bovine erythrocytes.

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The herbicide isouron [3-(5-tert-butyl-3-isoxazolyl)-1, 1-dimethylurea] was mineralized to 31 and 25% in sewage samples at 0.01 and 0.1ppm, respectively, but only 7% was mineralized in river-water samples in a 120-day period. Although most of the radioactivity remained, only 66 to 68% of the initial isouron was found in the river-water samples. Data suggest that isouron was converted mainly to organic compounds, presumably by metabolism. Mineralization occurred in microbial environments prevailing in the seawage. A partial pathway involved in the microbial degradation of isouron in the aqueous environments is proposed. Metabolites, 3-(5-tert-butyl-3-isoxazolyl)-1-methyl-1-formylurea and N-[5-(1, 1-dimethyl-2-hydroxyethyl)-3-isoxazolyl]carbamic acid were identified in the sewage samples, these two compounds were not previously found among metabolic products of isouron in soils.

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The metabolic fates of procymidone [N-(3, 5-dichlorophenyl)-1, 2-dimethylcyclopropane-1, 2-dicarboximide, Sumilex^®] in rats and mice were examined. After [phenyl-¹⁴C]procymidone was administered orally to male rats and mice at 100mg/kg, the radiocarbon was rapidly and almost completely excreted into excreta of both animals, mainly into the urine, within 7 days after administration. ¹⁴C-Levels in the blood of both species were fairly constant for 2-12hr, reaching maximum at 12hr in rats and at 2hr in mice after administration. The ¹⁴C-levels decreased with the biological half-lives of 12hr in rats and 10hr in mice from 8 to 72hr after administration. In both species, the major metabolic reactions were oxidation of one of the methyl groups to carboxylic acid via hydroxymethyl and cleavage of the imide linkage. No marked species differences in metabolism were observed.

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Degradation of racemic, (R)- and (S)-salithion (2-methoxy-4H-1, 3, 2-benzodioxaphosphorin-2-sulfide) in two types of Japanese upland soils was studied by using ¹⁴C preparations uniformly labeled at the phenyl ring. (R)-Rich salithion was recovered from soils treated with racemic salithion after aerobic incubation, whereas racemic salithion was recovered from sterilized soils. When each enantiomer of salithion was applied separately, the (S)-enantiomer disappeared 1.5-1.7 times faster than the (R)-enantiomer in both soils. Larger amounts of bound ¹⁴C residues were observed in soils treated with (S)-salithion. Similar fates between the enantiomers of salithion under sterilized conditions suggested that the stereoselective degradation of salithion in soils was attributable to the properties of salithion-degrading soil microorganisms. No epimerization of the enantiomers of salithion was observed in soils.

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Fenitrothion microcapsule was compared with fenitrothion 60% emulsifiable concentrate in applicability to insect-proof plywood. Microencapsulated fenitrothion was more stable than fenitrothion formulated in emulsifiable concentrate in four kinds of adhesives, especially in highly alkaline adhesives such as alkaline phenol resin, in which nonencapsulated fenitrothion easily decomposed when the adhesive was hardened. The efficacy of plywood containing fenitrothion microcapsule against Lyctus brunneus was excellent. Fenitrothion microcapsule was more effective than fenitrothion emulsifiable concentrate to be used for insect-proof plywood, because it retained residual efficacy at a smaller dosage even after stored in severe conditions regardless of the sort of adhesives used with.

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Penetration and dermal accumulation of topically applied vamidothion, carbaryl and fenvalerate were investigated in the common cutworm epidermal tissue mounted on a diffusion cell system. At low doses, carbaryl showed the highest penetration rate followed by vamidothion. The penetration rate of fenvalerate, in contrast, was extremely slow. At high doses, the penetration rate decreased especially with carbaryl and fenvalerate. The dose-dependent penetration was analysed with Michaelis-Menten type kinetics. The maximum penetration rate (V) and Michaelis constant (Km) calculated by computer simulation for vamidothion, carbaryl and fenvalerate were 0.021, 0.015 and 0.0029μg/hr, and 0.072, 0.016 and 0.29μg, respectively. Besides the Michaelis-Menten type pathway, an additional process under first order kinetics was proposed; the first order rate constant, k_n was 42, 6.5, and 0.74×1C^-3 hr^-1 for vamidothion, carbaryl and fenvalerate, respectively. At a low dose (0.1μg/individual), the radioactivity accumulated in the dermal tissue did not show a significant variation, the ratio being within 10 to 20% of the applied dose regardless of insecticides. The ratio decreased as the applied dose increased especially with fenvalerate. Effects of combination of these insecticides on penetration and tissue accumulation were investigated. Vamidothion decreased both penetration and tissue accumulation of ¹⁴C-carbaryl, while vamidothion altered only tissue accumulation of ¹⁴C-fenvalerate. The inconsistent interaction implied that factors other than simple diffusion governed by Fick's low had affected insecticide penetration through the insect cuticle.

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Bond strength in the lowest excited singlet state and enthalpy changes in reaction estimated by semiempirical AM1 calculations showed that β cleavage proceeds more favorably than α cleavage at the carbamoyl moiety of O-aryl N-methylcarbamates. The spin density at each atom of a phenoxy radical derivative formed via β cleavage indicated that radical reactivity are higher at the oxygen atom and the o- and p-positions of the phenyl ring. In subsequent photo-Fries rearrangement, cyclohexadienone intermediates were theoretically suggested. Regioselectivity in the rearrangement was well elucidated by enthalpy changes along the proposed photodegradation pathways and the spin density of the phenoxy radicals.

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Male Fischer 344 rats were exposed to Chloropicrin (CP) vapor for 4hr by whole-body, nose-only and dermal exposures. Each exposure was followed by a 14-day observation period. The LC₅₀ values for the whole-body and nose-only exposures were 14.4 and 6.6ppm, respectively. In the dermal exposure experiment, no deaths occurred in the rats exposed to CP vapor at a mean actual concentration of 25.0ppm. In the whole-body exposure experiment, CP vapor produced a biphasic toxic manifestation. The first phase lasted about 3 days after exposure, and the second phase was between post-exposure days 6 and 14. Irritation and/or damage to the respiratory tract was mainly observed in both phases. Most deaths occurred within 24hr after exposure. The rest were caused by a high exposure concentration, and the dead animals were found on post-exposure day 9. In the nose-only exposure experiment, toxic effects were observed only in the first phase and they were similar to those in the whole-body exposure experiment. All deaths occurred within 24hr after exposure. In the dermal exposure experiment, no toxic effects were observed. These results indicated that acute dermal toxicity of CP vapor due to whole-body exposure was minimal compared to acute inhalation toxicity, and that restraint of experimental animals during the nose-only exposure increased the acute inhalation toxicity of CP vapor.

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Relationships between the degradation rate of the herbicide pyrazoxyfen (2-[4-(2, 4-dichlorobenzoyl)-1, 3-dimethylpyrazol-5-yloxy]-acetophenone) and soil properties were investigated. In the experiment, pyrazol-3-¹⁴C-labeled and unlabeled pyrazoxyfens were incubated in five paddy soils under flooded and upland conditions. The degradation rate of pyrazoxyfen differed greatly according to the properties and conditions of soils. Pyrazoxyfen tended to degrade rapidly in mineral soils and slowly in humic volcanic ash soils with its half-life being 3-5 and 5-34 days, respectively. In the same soil, the degradation was faster under flooded conditions (half-life of less than 10 days) than under upland moisture conditions (half-life of 4-34 days). Under all the experimental conditions the degradation rate was negatively correlated with the cation-exchange capacity and the organic-matter content of a soil. The correlation was also negative with the C/N ratio and the maximum water holding capacity, but the correlation coefficient differed according to experimental conditions.

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Without pretreatment of Ushiku loam upland soil with the organophosphorus insecticide salithion (2-methoxy-4H-1, 3, 2-benzodioxaphosphorin-2-sulfide), the ratios of salithion-degrading bacteria, actinomycetes and fungi to the corresponding total microorganisms in the soil were 14, 44 and 16%, respectively. Among them, Acinetobacter sp. (B-60) degraded 82% of applied 10-ppm salithion in culture during 8hr of incubation. The high degrading activity of this strain was probably due to its high salithion-demethylating activity. Agrobacterium sp. (B-7, B-15 and B-17) degraded 51-62% of applied salithion during 48hr. This high degrading activity of the strains was probably due to their high activity in cleaving the P-O-aryl bond of salithion than the other microorganisms. The degrading activity of isolated actinomycetes and fungi was not as high as that of the bacterial strains. None of the isolated microorganisms grew with salithion as a sole carbon source, while some strains used salithion as a sole phosphorus source. Demethylation and cleavage of P-O-aryl and P-O-aralkyl linkages of salithion were the first metabolic processes by the isolated soil microorganisms.

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Metabolism of (R)_P- and (S)_P-salithion (2-methoxy-4H-1, 3, 2-benzodioxaphosphorin-2-sulfide) by four bacterial strains, three Agrobacterium sp. (B-7, B-15, and B-17) and one Acinetobacter sp. (B-60) isolated from Ushiku loam upland soil was studied using ¹⁴C preparations uniformly labeled at the phenyl ring. The (S)_P-enantiomer was metabolized by B-7 3.1 times faster than the (R)_P-enantiomer, and the stereoselectivity was derived from the stereo-selective cleavages of P-O-aryl and P-O-aralkyl linkages of salithion. Both (R)_P- and (S)_P-enantiomers were metabolized by B-15 at similar rates, with similar metabolite distribution. By B-17 the (S)_P-enantiomer was metabolized 3.5 times faster than the (R)_P-enantiomer, with difference in metabolism. Cleavages of the P-O-aryl and P-O-aralkyl linkages were main metabolic pathways of the (S)_P-enantiomer, whereas demethylation a main metabolic pathway of the (R)_P-enantiomer. Both salithion enantiomers were metabolized rapidly by B-60, and the metabolic pathway of each enantiomer was in contrast to that by B-17. Neither of the salithion enantiomers was epimerized by any of the bacterial strains examined. Such stereoselectivity in metabolism agrees with stereoselective degradation of salithion in soil.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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