An exploratory study of urban runoff toxicity

An exploratory study of urban runoff toxicity was undertaken at 14 urban si tes, including two sites receiving runoff from major multi-lane divided hig hways (> 100,000 vehicles.day(-1)). To assess various types of toxicity, a battery of tests was used including Daphnia,nngna, Microtox(TM), sub-mitoch ondrial particles, and the SOS Chromotest (for genotoxicity). The whole dat a set comprised almost 70 samples and 350 test results, which were reduced to toxicity point values using a toxicity scale. About two fifths of all da ta did not show any toxic responses, one fifth indicated severe toxicity, o ne fifth confirmed toxicity, and one fifth potential toxicity. When compari ng urban stormwater toxicity to that of multi-lane divided highway (MLDH) r unoff the main difference was noted for the severe toxicity level; almost 2 0% of MLDH samples were severely toxic compared to 1% of urban stormwater s amples. The MLDH data were obtained at the edge of the pavement, and althou gh attenuation of runoff toxicity during transport can be expected, particu larly in grassed swales, additional research is required. (C) 1999 IAWQ Pub lished by Elsevier Science Ltd. All rights reserved.