| Co-Investigator(Kenkyū-buntansha) |
TANAKA Junko Department of Hygiene, Hiroshima University School of Medicine., 医学部, 助手 (70155266)
IMADA Atsushi Department of Hygiene, Hiroshima University School of Medicine., 医学部, 助手 (00112201)
HIRAOKA Yukio Department of Hygiene, Hiroshima University School of Medicine., 医学部, 講師 (00144816)
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| Research Abstract |
We carried out some experiments in order to ascertain the effects of the degradation products on organisma. A fenitrothion (MEP) emulsion, which is an organic phosphorous in secticide used quite frequently in Hiroshima prefecture, was used as an experimental chemical. MEP emulsion adjusted to pH 8, pH 10, and pH 14 was degraded by exposing it to natural sunlight in winter with heat. When approximately 90% of the MEP concentration in each original MEP emulsion was degraded, the exposure was discontinued (Original degraded solution). In carrying out exposure experiments, each original degraded solution was diluted with dechlorinated tap water containing Tween 80 to various kinds of MEP concentrations (Degraded solution) and each degraded solution was used for the following exposure experiments. A medaka egg obtained in our laboratory was exposed to 200 ml of the degraded solution and the untreated MEP emulsion containing various kinds of MEP concentrations for 5 days from 4 to 5 hours af
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ter fertilization. Subsequently, they were reared carefuly in the dechlorinated tap water until they grew up 3-month-old fish. On the other hand, in the case of exposure experiments using pregnant mice, variously set MEP concentrations of 3 kinds of the degraded solutions, and the untreated MEP emulsion were administered subcutaneously to the back of a pregnant mouse from the 3rd fetal day to 15th fetal day in continuity. Its abdomen was opened and the fetuses were obtained in the 18th fetal day, at which time they were observed. In addition, experiments which examined LD50 of 3 kinds of the degraded solutions, and the untreated MEP emulsion were carried out according ot Behrens' method. From the results of exposure experiments using the medaka egg, it was found that the hatching rate and the rate of survival in 3 kinds of the degraded solutions tended to be lower than that in the untreated MEP emulsion, and that an incidence of abnormal fry in the 3 kinds of the degraded solutions tended to be higher than that of the untreated MEP emulsion. On the other hand, from the results of exposure experiments using pregnant mice, it was found that a maternal death, a decrease of fetus weight, and an enhancement of acute toxicity were caused by some degraded solutions. Consequently, as it was pointed out that the toxicity of degradation products also should not be neglected, it is inferred that the investigation involving the toxicity of the degradation products should be carried out when a safe assessment of agricultural control chemicals is considered. Less
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