Cultured human-cell-based bioassay for environmental risk management

Among bioassays for evaluating various impacts of chemicals on humans and e cosystems, those based on cultured mammalian-cells can best predict acute l ethal toxicity to humans. We expect them to be employed in the future in en vironmental risk management alongside mutagenicity tests and endocrine-disr upting activity tests. We recently developed a disposable bioassay device t hat immobilizes human hepatocarcinoma cells in a small micropipette tip. Th is enables very quick (within 2 h) evaluation of acute lethal toxicity to h umans. For bioassay-based environmental management, 2 promising approaches have been demonstrated by the US-EPA: toxicity identification evaluation (T IE) and toxicity reduction evaluation (TRE). The Japanese Ministry of Envir onment has been supporting a multi-center validation project, aimed at asse mbling a bioassay database. To make full use of these resources, we present a numerical model that describes contribution of individual chemical to ob served toxicity. This will allow the selection of the most effective counte rmeasure to reduce the toxicity. Bioassay-based environmental risk manageme nt works retrospectively, whereas impact assessment using substance flow mo dels and toxicity databases works prospective. We expect that these 2 appro aches will exchange information, act complementarily, and work effectively in keeping our environment healthy in the 21st century.