The adverse effects of rainwater and artificial urban runoff (an imitation of urban runoff during rainfall event) were investigated using a battery of bioassays employing three test species. Urban dusts were collected at three representative sites; commercial, industrial and highway areas. The water quality parameters of rainwater and artificial runoff revealed low hardness (23.4 ∼ 34.2 mg·L−1 as CaCO3) and alkalinity (7.0 ∼ 34.2 mg·L−1 as CaCO3). High toxicities were observed in the bioassays for the artificial runoffs. The average toxic units for D. magna, S. capricornutum, and O. latipes were 1.26(±0.84), 1.34(±1.10) and 2.05(±1.08), respectively. Of these species, O. latipes revealed significantly higher toxicity compared to D. magna and S. capricornutum (p<0.05). Embryo lesions were observed with 6.25% treatments, and these significantly increased at 12.5% treatments (p<0.05). The EC50 values for each artificial runoff were 22.5, 22.6 and 25.4% for commercial, industrial and highway areas, respectively. With 12.5% treatment, significant delays in hatching times were observed (p<0.05); all embryos tested did not hatched at 100% treatment. Similarly, a significant decrease in hatching success was observed at every sampling point from 25% treatment (p<0.05). The adverse effects of artificial runoff on the three test species suggests that urban surface runoff can cause significant impairment in aquatic ecosystems.

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