| Research Abstract |
Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/DFs) and dioxin-like polychlorinated biphenyls (DL-PCBs) are ubiquitous and persistent in the environment and magnify in organisms through the food web. These compounds finally accumulate in humans. It is well known that some of these compounds are extremely toxic to organisms. In Japan, specific congeners and isomers were applied to agricultural fields as herbicides, i.e. pentachlorophenol and 2,4,6-trichiorophenyl 4-nitrophenylether (CNP), contaminated with octachlorinated dibenzo-p-dioxin(OCDD), and 1,3,6,8- and 1,3,7,9-tetrachlorinated dibenzo-p-dioxins(TCDDs), respectively. Consequently, it is necessarily to evaluate their dispersion from agricultural fields and their presence in environmental matrices. PCDD/DFs in soils of agricultural fields were entered into river through run off caused by rice farming. It is estimated that PCDD/DFs mainly presented in soil particles less than 5μm diameter. Then PCDD/DFs that adsorbed on
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the soil particles deposited to river and coastal bottom sediments. To evaluate dioxin contamination in vegetable, congener analyses of PCDD/DFs and DL-PCBs were performed on three kinds of vegetables (43 individuals). The total dioxin concentrations and toxic equivalent quantity (TEQ) levels in samples ranged from 0.19 to 16 pg/g wet weight and 0.002 to 0.071 pg TEQ/g wet weight, respectively. 1,3,6,8- and 1,3,7,9-TCDDs were main contributors of total dioxin concentrations detected in the vegetable samples. It imply that vegetables must be contaminated by these compounds in agricultural fields during growing. A relatively high concentration of dioxins was found in cucumber samples. The analytical results of PCDD/DFs and DL-PCBs in freshwater and coastal fishes show that these compounds detected in all samples investigated. Impurities of CNP and PCP as herbicides for paddy field were thought as PCDD/DFs sources of fish samples. Whereas Japanese fish samples, 1,3,6,8- and 1,3,7,9-TCDDs and OCDD levels in Chinese fish samples were not so high as the Japanese samples. Dioxins and DL-PCBs in ten species of wild birds collected from Japan were analyzed. The results revealed that the concentrations and homologue / isomer profiles were species-specific, featuring with their unique habitats and feeding habits. It seems to be that the impurities of pesticides such as 1,3,6,8- and 1,3,7,9-TCDDs could be degraded in the birds although intake through their foods such as fish. Japanese human blood samples collected from differently-aged individuals have been analyzed for PCDD/DFs and DL-PCBs. The concentration ranges of PCDDs, PCDFs and DL-PCBs were 58-930, 7.4-37 and 3,100-23,000pg/g, respectively, on a lipid weight basis. TEQ levels were calculated to be 7.0-46pg/g on a lipid weight basis. The levels of 1,3,6,8- and 1,3,7,9-TCDDs in human blood samples were less than detection limit. Statistical analysis indicated a correlation between an increased total TEQ level and increased age. TEQ level of a person aged 60 years is about twice times higher than a person aged 20 years. By these results it is able to make sense out of what had appeared the distributable properties of dioxins which were ever applied as impurities of herbicides to agricultural fields. Less
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