Health Impact Assessment of New Urban Water Concepts

Abstract

Water features in urban areas are increasingly perceived by citizens as a positive element because they provide aesthetic quality to the neighbourhood and offer recreation opportunities. They may also lead, however, to increased health risks due to the potential presence of waterborne pathogens. Exposure of humans to pathogens in urban water occurs through recreational activities, household uses, occupational exposure, consumption of crops irrigated with contaminated water, or accidentally. Research is needed on the health risks derived from urban water exposure to inform urban water authorities and help them to implement risk control and mitigation measures. In this thesis, the microbial health risks of several urban water features have been assessed using Quantitative Microbial Risk Assessment (QMRA) tools. The studied water concepts are several features from an urban area (including a river, a lake, a sedimentation pond, a pond in the park, a wadi), a water plaza, reclaimed water used for crop irrigation, and drinking water produced from groundwater during the 2009 Q Fever outbreak. Pathogens studied include Campylobacter, Cryptosporidium, adenovirus, norovirus, Legionella pneumophila, Coxiella burnetii and cyanobacteria. Faecal indicators and microbial source tracking tools were also used. The water features assessed showed high risks of gastrointestinal diseases (through Campylobacter or norovirus) but low risks of respiratory illness (legionellosis and Q fever). Higher concentration of Campylobacter, resulting in higher gastrointestinal risks, were found when human faecal contamination was present. Gastrointestinal disease risks were high even when faecal indicators were below the threshold for excellent bathing water quality according to the Bathing Water Directive. Higher risks are expected in the future due to warmer climate, and higher frequency and strength of rain events. Measures should be taken to reduce health risks (e.g., remove cross-connections in separate sewers, add extra barriers for the use of reclaimed water).