Toxicological Evaluation of Waste-Water Samples to Appropriately Sensitized Cultured Fathead Minnow Cells Compared with the Microtox Assay

We have previously shown that a good correlation exists between in vitro cytotoxicity data to cultured fathead minnow (FHM) fish cells and fish lethality data for a series of 50 chemicals belonging to very different chemical classes (Brandao et al. 1992). A comparable correlation was observed for the in vitro toxicity of 45 pesticides to goldfish GF-scale (GFS) cells (Saito et al. 1991). A good correlation between the cytotoxicity of inorganic metal compounds to FHM cells and the in vivo toxicity to Daphnia magna was also observed (Dierickx and Bredael-Rozen 1996), but the FHM assay was less sensitive than fish and Daphnia assays. In order to allow the use of the FHM assay for environmental water samples, its sensitivity was highly increased by adding sodium dodecyl sulfate (SDS) and buthionine sulfoximine (BSO), a glutathione synthesis inhibitor (Griffith 1982), to the assay system (Dierickx 1998). However, when so sensitised FHM cells were used to measure the toxicity of surface-water samples, it appeared that too many false-positives were obtained, at least when compared to the Microtox assay (Dierickx et al. 2000), and ascribed to the addition of SDS. We searched for assay conditions without SDS resulting in an intermediate toxic effect between the original (Brandao et al. 1992) and the highly sensitive assay (Dierickx 1998). This adapted assay system was then applied for measuring the toxicity of waste-water samples, from which the toxicity was also measured by the Microtox method.