In vitro tools for the toxicological evaluation of sediments and dredged materials: intra- and inter-laboratory comparisons of chemical and bioanalytical methods.

The implementation of in vitro bioassays for the screening of dioxin-like compounds (DLCs) into management guidelines of dredged material is of increasing interest to regulators and risk assessors. This study reports on an intra- and inter-laboratory comparison study between four independent laboratories. A bioassay battery consisting of RTL-W1 (7-ethoxy-resorufin-O-deethylase; EROD), H4IIE (micro-EROD), and H4IIE-luc cells was used to assess aryl hydrocarbon receptor-mediated effects of sediments from two major European rivers, differently contaminated with DLCs. Each assay was validated by characterization of its limit of detection (LOD) and quantification (LOQ), z-factor, reproducibility, and repeatability. DLC concentrations were measured using high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) and compared to bioassay-specific responses via toxicity equivalents (TEQs) on intra- and inter-laboratory levels. The micro-EROD assay exhibited the best overall performance among the bioassays. It was ranked excellent (z-factor = 0.54), reached a repeatability > 75%, was highly comparable (r 2 = 0.87) and reproducible (83%) between two laboratories, and was well correlated (r 2 = 0.803) with TEQs. Its LOD and LOQ of 0.5 and 0.7 pM 2,3,7,8-TCDD, respectively, approached LOQs of HRGC/HRMS measurements. In contrast, cell lines RTL-W1 and H4IIE-luc produced LODs > 0.7 pM 2,3,7,8-TCDD, LOQs > 1.7 pM 2,3,7,8-TCDD, and repeatability < 70%. Based on the data obtained, the micro-EROD assay is the most favorable bioanalytical tool, and via a micro-EROD-based limit value, it would allow for the assessment of sediment DLC concentrations; thus, it could be considered for the implementation into testing and management guidelines for dredged materials.

Bioanalytical and instrumental screening of the uptake of sediment-borne, dioxin-like compounds in roach (Rutilus rutilus).

To examine the uptake of dioxin-like compounds (DLCs), common roaches (Rutilus rutilus) were exposed for 28 days to differently contaminated sediments from two major European rivers in a purpose-built facility. Dietary transfer of DLCs was investigated by exposing fish to sediments inoculated or non-inoculated with black worms (Lumbriculus variegatus). Dioxin-like polychlorinated biphenyls (DL-PCBs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), measured via high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) in sediments and whole fish, were used to calculate toxicity equivalent quotients (TEQs). TEQs were compared with biological toxicity equivalent quotients (BEQs) determined via the 7-ethoxyresorufin-O-deethylase (EROD) assay, performed with mammalian (H4IIE) and fish (RTL-W1) liver cell lines. TEQs and BEQs indicated an uptake of sediment-borne DLCs by roach, which was independent of sediment contamination levels, but rather reflected sediment-specific characteristics. For most sediment treatments, DLC uptake did not increase with time. Highest congener-specific uptake (DL-PCB 123) was 10-fold compared to control. Exposure to worm-inoculated sediment of highest overall DLC contamination caused a 2-fold (TEQ and H4IIE BEQ) greater uptake of DLCs by fish compared to the respective non-inoculated treatment. H4IIE cells showed the greatest sensitivity (0.37 ± 0.25 pM TCDD) and the strongest correlation with TEQs (r (2) = 0.79), hence, they seem to be best suited for DLC screening of sediments and biota, amended by compound-specific instrumental analysis if required.