A survey of the representativeness and usefulness of wastewater-based surveillance systems in 10 countries across Europe in 2023.

Wastewater-based surveillance (WBS) has become a widespread method to monitor transmission of SARS-CoV-2 and other human pathogens in Europe. We conducted a survey about WBS systems' objectives, approaches, representativeness and usefulness in 10 invited European countries in 2023, i.e. Austria, Belgium, Denmark, Finland, Greece, Hungary, Italy, Luxembourg, the Netherlands and Norway. All countries completed the study questionnaire about their SARS-CoV-2 WBS systems, and shared information about WBS of other pathogens as deemed relevant. SARS-CoV-2 WBS systems primarily monitored national and subnational trends (population coverage: 25-99%), and a majority (8/10) also tracked variant distribution. Nine of 10 countries reported that their SARS-CoV-2 WBS systems were representative of their population and all countries remarked that the findings were valuable for public health decision-making. Results were shared with relevant public health authorities and published via dedicated websites and/or dashboards. WBS systems of other pathogens were mostly in the early stages, with some countries implementing pilots. Notable exceptions were the well-established poliovirus surveillance systems in Finland, Italy and the Netherlands. This study brings understanding the diverse landscape of WBS in Europe, offering insights for future developments and collaborations. Furthermore, it highlights the need for further integration of WBS into other European surveillance systems.

Temperature-driven and discharge-driven variability of organic micropollutants in a large urban river and its implications for risk-based monitoring.

Urban rivers are exposed to an increasing load of organic micropollutants from wastewater effluent posing an ecological as well as public health hazard. One-off surveys can capture a snapshot of the pollution profile but fail to reveal the full scale of spatial and temporal heterogeneity. In the present study, 41 micropollutants (non-steroid anti-inflammatory drugs (NSAID), antihypertensives, antiepileptic, antidiabetic, antibiotics, iodinated contrast media (ICM), corrosion inhibitors, pesticides) were monitored every two weeks for one-year upstream and downstream of the Budapest metropolitan area in Danube River (336 samples total). ICMs, benzotriazoles and metamizole degradation products were detected in highest concentration regularly exceeding 100 ng/L. Median concentration of other pharmaceuticals ranged from <1 to 26 ng/L, while pesticides were typically below 10 ng/L. Variability of micropollutant concentration was primarily temporal, exhibiting two different patterns: (1) inverse correlation to river discharge, observed for corrosion inhibitors and carbamazepine (r = -0.505 to -0.665) or (2) inverse correlation to water temperature, observed primarily for ICMs, antihypertensives and antibiotics, r = -0.654 to -0.904). Temperature dependence was also significant after correcting for river discharge. Relative increase of pharmaceuticals was 2-134% after the metropolitan area, partially explained by emission estimates calculated from retail data and metabolization rates. The concentration of five ICMs (iopamidol in 100, iodixanol in 96, diatrizoate in 22, iomeprol in 21 and iohexol 13% of the samples) and two NSAIDs (ibuprofen and diclofenac (in 31.5 and 23% of the samples) exceeded the predicted no environmental effect concentration, posing a risk to algae (HQ = 1.2-6) and fish (HQ = 1.4-1.9), respectively. Results suggest that risk-based monitoring and risk management efforts should focus on ICMs, NSAIDs and industrial chemicals, taking into account that sampling in cold periods and during low flow provides the worst-case estimates.