Aquatic sediments are now acting as a major source of toxic chemica1s, such as dioxins, PAHs and TBT. In this paper, we report recent trend in sediment quality standard with special reference to London Convention and postulate importance of promoting the study on the fate and transport of chemicals contaminated in the sediments.

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Guidance to the OECD Test Guideline 218/219, Sediment Toxicity Test using a midge, is given. To develop the sediment toxicity test procedure using Chironomus yoshimastui, ring-tests were carried out in Japan in 2003 and 2004. The result in 2004 showed that the toxic values taken at different laboratories were consistent but with some variance, and the all tests were valid regarding to the validity criteria of the Test Guidelines.

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Chlorate (chlorate ion: ClO3-) is one of the by-product substances of chlorine dioxide used as an alternative disinfectant of chlorine. In this study, the toxicity of chlorate was evaluated by bioassay using different developmental stages in the life cycle of three kinds of seaweeds ( red macroalgae Porphyra yezoensis, brown macroalgae Undaria pinnatifida and green macroalgae Ulva pertusa). In the static exposure tests, the 4-day lowest-observed effect concentration (LOEC) values of chlorate were estimated as 1000mg/L for the growth (cell-division) rate of P. yezoensis conchospores and 320mg/L for the germ-tube length of U. pinnatifida zoospores, respectively. In the flow?through exposure tests, the 14-day LOEC values to the rate of thalli growth of each seaweed were estimated as 1mg/L for P. yezoensis, 100mg/L for U. pinnatifida and 1mg/L for U. pertusa, respectively, and the thalli of P. yezoensis and U. pertusa were more sensitive to toxicity of chlorate than that of U. pinnnatifida. The bioassay results suggest the necessity for controlling the concentration of chlorate in the final effluent when chlorine dioxide is dosed to disinfect secondary effluent in the wastewater treatment plant.

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To evaluate the acute and subchronic toxicity of 4-methyl-2,4-bis(4-hydroxyphenyl)pent-1-ene (MBP), a metabolite of bisphenol A (BPA; 2,2-bis(4-hydroxyphenyl)propane), on three species invertebrates, two of which are the crustaceans, Americamysis bahia (A. bahia) and Daphnia magna (D. magna), and free-living nematode Caenorhabditis elegans (C. elegans) were used in this study. The 48-h LC₅₀ values of MBP and BPA for A. bahia were estimated to be 0.43 and 1.34 mg/l, and the 48-h LC50 of those were estimated at 2.75 and 12.84 mg/l for D. magna, respectively. In C. elegans, the 24-h LC₅₀ values of MBP and BPA were estimated to be 78.2 and 324.7 mg/l. Moreover, to compare the subchronic toxicity effect of MBP and BPA on the invertebrates, we performed the growth-maturation and reproduction test using C. elegans. Although there were no significant differences on body length, the percentage of gravid worm and fecundity at the concentrations of BPA tested in this study, the lowest-observed-effect concentrations (LOECs) of MBP for growth, development and fecundity in C. elegans were estimated to be 67.1 mg/l. Therefore, these results suggest that MBP has high lethal toxicity against both aquatic and soil invertebrates when compared with BPA.

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Concentrations of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzo-furans (PCDFs), non ortho polychlorinated biphenyls (no-PCBs), and mono ortho polychlorinated biphenyls (mo-PCBs) in the sediment and the benthos which were collected from the head and entrance of Osaka Bay were measured. These dioxins concentrations in the sediment of the bay head were from 14 to 25 times as high as those in the sediment of the bay entrance. These differences of dioxins concentrations would be explained by the content of organic matter. The concentration ratios of dioxins between the benthos and the sediment were decreased in order of mo-PCBs, no-PCBs, PCDFs, and PCDDs. This result shows that mono and non ortho PCBs are more easily accumulated than PCDD/Fs by the benthos. The concentrations of PCDD/F isomers chlorinated in 1 and 3 (6 and 8) positions were relatively high in the benthos.

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