Abstract
Assessment of environmental risk for many kinds of chemicals was studied on the survey in a model water area on sunny and rainy weather days during 1997-1999. Environmental risk, ecological risk and human health risk were assessed respectively. The relative ecological risk was indicated by the quotient of each environmental concentration with MTC (maximum tolerable concentration) calculated from the ecological effect data. Relative human health risk was also indicated by the water quality standards or the drinking water concentrations at 10-5 carcinogenic risk level showed in IRIS database. As a result, although both of the relative risks for all tested chemicals were smaller than one at the upper stream in the river, the enlargement of the ecological risk contributed by nonylphenol was found at the lower stream on rainy weather days in particular. The emissions of chemicals contributed on these risks were characterized by the investigation on a branch and drainages flowing between the two sites on sunny days and primary runoff from elevated roads on rainy days.
