This book discusses the physicochemical changes (transformations) that metals deposited on urban road surfaces undergo during dry weather periods, in order to provide insights into their potential impacts on stormwater quality. Based on extensive field experiments, and laboratory and data analyses, it examines transformation characteristics of metals with respect to the particle size of road dust, antecedent dry days and land uses. Further, it proposes a new risk-assessment methodology, improving the original human health-risk indices based on the transformation characteristics and potential bioavailability of metals in order to evaluate the risks posed by metals in stormwater. This book is of interest to researchers and decision-makers developing appropriate pollution mitigation measures to enhance the quality of stormwater, targeting the effective reuse of stormwater in urban areas.