For comprehensive hazard assessment of environmental water samples with lower toxicity, simple bioassay using human cell lines with brief vacuum condensation have been applied to samples from Lake Kasumigaura, Lake Suwa, and Lake Biwa. The samples from Lake Kasumigaura both in 1999 and 2000 showed a similar seasonal variation in cytotoxicity: the cytotoxicity was detected significantly during summer season and peaked in August. The samples from Lake Biwa and Lake Suwa also showed weak but significant cytotoxicity during summer season of 2000.
Based on behavior during pretreatment with various cartridge columns, toxic substances existing in the samples were suggested to be hydrophobic with molecular weight less than 3,000. No significant correlation between the cytotoxicity and water quality data except phycocyanin level was observed among samples from Lake Kasumigaura. No specific agricultural chemicals or heavy metals were detected at the level sufficient to show the cytotoxicity alone.
These results indicate that this bioassay system is quite useful for comprehensive assessment of toxicity existing in environmental water. However, to integrate this kind of indices in environmental management process, systematic and continuous accumulation of bioassay data on water samples with authentic water quality data must be essential.
