【Special Issues:Bioassay with Molecular Techniques】
Evaluation of Waste Toxicity with Yeast DNA Microarray
Emiko Kitagawa* and Hitoshi Iwahashi*
*National Institute of Advanced Industrial Science and Technology, Human Stress Signal Research Center
† Correspondence should be addressed to Hitoshi Iwahashi:
（1-1-1 Higashi, Tsukuba, Ibaraki, 305-8566 Japan）

Abstract
It is a major concern in environmental protection that not only controlled substances but also numerous unknown chemicals are present in the environmental waste（s）. We present here a novel approach for the biological risk assessment, namely development of a DNA microarray-based technology that can be used to qualitatively assess multiple toxicities at the level of gene expression. As an example, we investigated wastes from incinerator, which is composed of complex components/compounds. Burned ash, the main waste from incinerator, was found to cause strong alteration of yeast gene expression. It was more complex than the effect seen by individual chemical components, and cell respiration was observed to be strongly affected by the burned ash. The possibility of mutagenesis was also suggested on the basis of the altered expression of DNA repair-related genes. Usually, in order to reduce toxicity, burned ash is vitrified and the wash water from the stack gas is treated before environmental discharge. Therefore, we also evaluated five more samples from the incineration processes. Evaluation of the vitrified products showed that the vitrification process reduced the toxicity effectively. However, the wash water revealed high levels of transcriptional toxicity even after its treatment, suggesting that the waste water treatment process needs further improvement. In conclusion, using our global gene expression profile-based bioassay, we could not only evaluate the effects of environmental wastes, such as burned ash, but also examine each major step during the waste production and release process into the environment.

Key words: microarray, yeast, burned ash, incineration facility