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The present study reports an in vitro screening method for contaminants in sediment samples utilizing an RTG-2 cell line. This technique integrates cytotoxicity testing with analytical chemistry with the aim of achieving a toxicity evaluation of the sediment sample. The toxic effect of individual organotin (OT) compounds and their presence in the sediment sample is the focus of the present study; however, other contaminants are also discussed. The following OT compounds: tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPT), diphenyltin (DPT), and a sediment solvent extract are exposed to the RTG-2 fish cell line. Both the alamar blue (AB) and neutral red (NR) assays are used to assess cytotoxicity after 24-h and 96-h exposure. Methodology for preparation of a sediment solvent extract suitable for biological testing and analytical determination is also described. With the RTG-2 cells, the AB and NR assays had comparable sensitivity for each individual OT compound exposure after 24 h, with TPT being the most toxic compound tested. The individual OT compound concentrations required to induce a 50% toxic effect on the cells (369 ng ml TBT, 1,905 ng ml DBT) did not equate to the concentrations of these contaminants present in the sediment extract that induced a 50% effect on the cells (294 ng ml TBT, 109 ng ml DBT). The solvent extract therefore exhibited a greater toxicity, and this suggests that the toxic effects observed were not due to OT compounds alone. The presence of other contaminants in the solvent extract is confirmed with chemical analysis, warranting further toxicity testing of contaminant mixtures and exposure to the cell line to further elucidate a complete toxicity evaluation. Environ. Toxicol. Chem. 2011;30:154-161. © 2010 SETAC [ABSTRACT FROM AUTHOR]

Caging studies have been previously reported to be useful for providing valuable information on biological effects of mollusks over short periods of time where resident species are absent. The degree of imposex in caged dog whelk (Nucella lapillus), was measured using the vas deferens sequence index (VSDI) and the Relative Penis Size Index (RPSI) and the extent of shell thickening in caged Pacific oyster (Crassostrea gigas) was investigated at t = 0 and t = 18 weeks. Nucella lapillus, when provided with mussels as a food source at the control site at Omey Island on the west Irish coast, did not demonstrate imposex features, whereas those transplanted to port areas did. Dunmore East exhibited the highest level of imposex (3.25 VDSI and 2.37 RPSI). Shell thickening was evident in C. gigas transplanted to Dunmore East, with low effects evident at the control location, Omey Island, and Dublin Bay at t = 18 weeks. Dry weight whole-body concentrations of organotins were most elevated in all species held at Dunmore East compared with other locations. Greatest δ15N and δ13C enrichment was observed within the tissues of the predatory N. lapillus in all three test sites. Increased assimilation in the Dublin Bay oysters might have been influenced by the presence of more nutrients at this location. Surficial sediment organotin levels were most elevated in the Dunmore East <2-mm fraction (22,707 μg tributyltin/kg dry weight), whereas low organotin levels were determined from Dublin and Omey Island sediments. The valuable application of cost-effective caging techniques to deliver integrated biological effects and chemical measurements in the absence of resident gastropod populations in potential organotin/tributyltin hotspot locations is discussed. [ABSTRACT FROM AUTHOR]