Quantification of Waterborne Pathogens and Associated Health Risks in Urban Water

Citizens are exposed to microbial hazards in urban waters. To quantify health risks associated with this exposure, pathogen concentrations in an urban river, lake, rainwater sedimentation pond, a pond in a park, and a wadi, were assessed. <i>E. coli</i> concentrations were variable in all locations, with mean values ranging between 1.2 × 10² (lake) and 1.7 × 10⁴ (sedimentation pond) cfu (colony forming units)/100 mL. High concentrations of <i>Campylobacter</i> were found, being the lowest in the lake (4.2 × 10¹ gc (genomic copies)/L) and the highest in the wadi (1.7 × 10⁴ gc/L). <i>Cryptosporidium</i> was not found in any sample. Low levels of adenovirus 40/41 were found in some samples in the river (1.8 × 10¹ gc/L) and lake (7.2 × 10° gc/L), indicating human fecal contamination. <i>Legionella pneumophila</i> was found in the sedimentation pond, with higher concentrations after rain events (1.3 × 10² gc/L). Cyanochlorophyll-a was found in the lake (7.0 × 10^–1 μg/L), the sedimentation pond (1.1 × 10° μg/L), and the pond in the park (2.9 × 10¹ μg/L), where low levels of microcystin were found (2.1 × 10° μg/L). <i>Campylobacter</i> data were used to estimate gastrointestinal risks from recreational exposure. This revealed risks above the annual disease incidence of campylobacteriosis in The Netherlands, being highest in the wadi and river. Measures are proposed to reduce the health risks