4. Assessment of Human Health Risks from Metals in Urban Stormwater Based on Geochemical Fractionation and Bioavailability

Risks posed by metals in stormwater is directly influenced by their geochemical fractionation and, in turn, the bioavailability. Therefore, accurate quantification of the risks from metals should be undertaken by considering these two key aspects. This chapter presents a novel approach to quantify the human health risks of metals, among the common stormwater pollutants found in urban areas, considering their geochemical fractionation and bioavailability characteristics. Stormwater quality and quantity modelling approaches were used to convert metal build-up loads to corresponding metal concentrations in stormwater. The results of the modified risk assessment discussed in this chapter highlights the drawbacks in using classical health risk indices and the importance of upgrading the risk assessment methods to avoid the over-estimation of risk posed by metals. Based on the modified hazard index, there is a low or no health risk from metals in stormwater runoff originating from the urban land uses investigated in this study.