Assessment of Antifouling Biocides Contaminations in Maizuru Bay, Japan

The concentrations of organotin compounds in the aquatic environment of Maizuru Bay and their spatial distribution are discussed. The concentrations of tributyltin (TBT) compounds in water samples ranged from 0.001 to 0.002 μg l⁻¹, and monobutyltin compounds were the dominant species among the butyltin compounds. TBT concentrations in Maizuru Bay are low compared with other coastal waters of Japan. Drastic differences in TBT concentrations were not observed among the Maizuru Bay sites. Phenyltin compounds were not detected in the water samples. Concentrations of TBT and triphenyltin (TPT) in sediment from Maizuru Bay ranged, respectively, from 0.9 to 11 μg kg⁻¹, from 0.2 to 17 μg kg⁻¹ dry weight (dw). TBT concentrations in Maizuru Bay were lower than those in other coastal areas of Japan. TPT concentrations were greater than TBT concentrations in the fishing port. The concentrations of TBT and TPT in blue mussels (M. galloprovincialis) from Maizuru Bay were in the range of 2.4 to 9.3 μg kg⁻¹ and 0.2-13 μg kg⁻¹ wet weight (ww), respectively. A tolerable average residue level (TARL) was estimated at 74.8 μg kg⁻¹ from a tolerable daily intake (TDI) of 0.25 bis(tributyltin)oxide μg kg⁻¹ body weight day⁻¹. TBT concentrations detected in blue mussel samples were lower than the TARL values. The acceptable concentration of TPT, which were calculated using acceptable daily intake instead of TDI, was 127 μg kg⁻¹. Concentrations of TPT in blue mussel samples were also lower than the TARL. TBT compounds in blue mussel samples were at similar levels among the various sampling sites, indicating that TBT is not currently being used in ship hull paints; the ratios of degradation products of TBT and TPT were greater than those of the parent compounds. Concentrations of alternative biocides in water samples were also investigated in the bay. Although Sea-Nine 211, M1, and Pyrithiones were not detected, Diuron and Irgarol 1051 were detected at 0.010-0.257 and at 0.002-0.018 μg l⁻¹, respectively. Concentrations of Diuron were great in the shipping route and near the shipyard, whereas the concentration of Irgarol 1051 was great at the fishing port. Concentrations of Diuron and Irgarol 1051 in sediment from Maizuru Bay ranged, respectively, from <0.08 to 12, from <0.08 to 9.8 μg kg⁻¹ dw, respectively. Despite being a semi-enclosed bay, we found that sediment in Maizuru Bay is not contaminated by alternative biocides to the degree found in other coastal areas. Copper concentrations of sediment were at ordinary levels, and those of blue mussels were slightly lower than those reported previously in other coastal areas of Japan. In both the sediment and blue mussels, there was no correlation between the presence of copper and antifouling biocides.