Screening-Level Microbial Risk Assessment of Urban Water Locations: A Tool for Prioritization

People in urban areas are exposed to microbial hazards in urban waters. In this study, various hazards, diseases, and water systems, where different recreation activities take place, are compared in an integrated quantitative microbial risk assessment (QMRA). The event and annual probability of gastrointestinal illness (GI) and Legionnaires’disease (LD) were analyzed in QMRA models using selected literature data. Highest mean event probabilities of GI were found for playing in pluvial flood from a combined sewer overflow (34%), swimming (18%), and rowing (13%) in the river, swimming (8.7%) and rowing (4.5%) in the lake, and playing in a water playground (3.7%) and in the pluvial flood from stormwater sewers (4.7%). At these locations, the GI probability was above the EU Bathing Water Directive threshold for excellent water quality (3%). All the annual risk medians were below the national incidence of legionellosis of 0.002%. The illness probability was most sensitive to the pathogens concentration (particularly <i>Campylobacter</i>, Norovirus, and <i>Legionella</i>) and exposure frequency. Therefore, site-specific pathogen data collection is the best next step to strengthen the certainty of the risk estimates. This study created an evidence-base that was used by water authorities to understand the health risks and set priorities for risk management

Screening-Level Risk Assessment of <i>Coxiella burnetii</i> (Q Fever) Transmission via Aeration of Drinking Water

A screening-level risk assessment of Q fever transmission through drinking water produced from groundwater in the vicinity of infected goat barnyards that employed aeration of the water was performed. Quantitative data from scientific literature were collected and a Quantitative Microbial Risk Assessment approach was followed. An exposure model was developed to calculate the dose to which consumers of aerated groundwater are exposed through aerosols inhalation during showering. The exposure assessment and hazard characterization were integrated in a screening-level risk characterization using a dose–response model for inhalation to determine the risk of Q fever through tap water. A nominal range sensitivity analysis was performed. The estimated risk of disease was lower than 10^–4 per person per year (pppy), hence the risk of transmission of <i>C. burnetii</i> through inhalation of drinking water aerosols is very low. The sensitivity analysis shows that the most uncertain parameters are the aeration process, the transport of <i>C. burnetii</i> in bioaerosols via the air, the aerosolization of <i>C. burnetii</i> in the shower, and the air filtration efficiency. The risk was compared to direct airborne exposure of persons in the vicinity of infected goat farms; the relative risk of exposure through inhalation of drinking water aerosols was 0.002%

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