Wastewater as a medium contains information on both circulating pathogens and drug consumption at the population level. This study combines tracking of respiratory viruses and quantification of pharmaceuticals as untargeted indicators of symptoms related to acute respiratory infections and influenza-like illnesses such as coughing, fever and pain. From January 2021 to June 2024, raw wastewater samples from ten locations covering 23% of the Swiss population were analysed. This encompassed 15 pharmaceuticals and four priority respiratory viruses including severe acute respiratory syndrome coronavirus virus-2 (SARS-CoV-2), respiratory syncytial virus (RSV), influenza A and influenza B viruses. The pharmaceutical compounds dextromethorphan, pheniramine, clarithromycin, acetaminophen and codeine showed a strong correlation with respiratory virus loads in wastewater. This enabled the estimation of pathogen-specific and cumulative symptom treatment in the population. In 2021 and 2024, notable increases in pharmaceutical loads without corresponding increases in viral loads signalled high community symptoms linked to unsurveilled pathogens. This study demonstrates that pharmaceutical surveillance can inform respiratory disease burden and highlights the value of integrated surveillance for assessing emerging public health threats beyond those routinely monitored.

Pollinosis is the most prevalent allergic disorder. Assessing the impact of real-world pollen exposure on symptoms remains challenging due to extensive patient-level efforts required.
This study explores the potential of wastewater-based epidemiology (WBE) to investigate the relationship between airborne pollen concentrations and antihistamine residues in wastewater as an indicator of pollinosis symptom treatment at the population-scale.
In Zurich (Switzerland), 279 wastewater samples were collected during 2021–2023. Each sample represents a 24-h period with excreta from approximately 471,000 individuals. Eleven antihistamine markers were analyzed in the samples using liquid chromatography high-resolution mass spectrometry. The relationship between antihistamine loads in wastewater and airborne pollen concentrations (47 taxa and miscellaneous pollen) was investigated by determining seasonal components of antihistamine loads and exploring pollen-specific contributions using Non-Negative Least Squares (NNLS) optimization.
Four antihistamines were detected in quantifiable amounts in wastewater. The first-generation antihistamine, diphenhydramine, demonstrated rather constant levels. In contrast, the three second-generation antihistamines - bilastine, cetirizine, and fexofenadine - showed pronounced day-to-day variation with strong correlations among each other. For fexofenadine, which was investigated in detail for its correlation with airborne pollen concentrations, approximately 50 % of the annual wastewater loads were associated with acute pollen exposure. Another 20 % related to baseline consumption during the pollen season, while the remaining 30 % seems unrelated to pollen. Birch, grasses, hazel, hornbeam, plane, and plantain explained most of the variance in wastewater loads (R² = 0.82), with grass pollen alone accounting for a quarter of the annual loads. Increased fexofenadine loads during periods without elevated concentrations of common allergenic pollen suggests the presence of additional triggers for allergy symptoms, potentially yew pollen.
Our study demonstrates that WBE can effectively reveal substantial day-to-day variation in antihistamine use related to pollen exposure. Thus, WBE presents an objective and questionnaire-independent method for investigating pollinosis symptom treatment at a population-scale.

Objectives: Illicit drug use presents a significant challenge to global health and public safety, requiring innovative and effective monitoring strategies. This study aimed to evaluate the current landscape of wastewater-based epidemiology (WBE) for monitoring illicit drugs in Europe, focusing on collaboration, current practices, and barriers, while identifying opportunities for improvement. Study design: Cross-sectional survey-based study. Methods: Coordinated by the Sewage Analysis CORe Group Europe (SCORE) and the European Union Drugs Agency (EUDA), two surveys were conducted in 2023 targeting researchers and stakeholders using WBE for illicit drugs. Data were analysed to identify trends, gaps, and opportunities for improving WBE implementation. Results: The findings indicate a robust research infrastructure and diverse analytical methods among European institutions. Two-thirds of the participating countries reported using WBE data to inform policy. However, challenges persist, particularly in securing funding and coordination, as well as generating national estimates from multiple locations and addressing specific local policy needs. Conclusions: WBE has proven to be a valuable tool for monitoring illicit drug trends and informing drug policies. To unlock its full potential, sustained funding, methodological standardization, and enhanced cooperation are essential. This study provides critical insights into the European WBE landscape, offering a roadmap for strengthening the integration of actionable WBE data into public health and policy frameworks.

Organic micropollutants in combined sewer overflows (CSOs) pose a potential risk to aquatic ecosystems. Previous studies mainly reported event mean concentrations (EMCs) and often focused on a small number of substances. This study presents realistic exposure scenarios using high-temporal resolution (10-minute) data from 24 events at two CSO sites. We analyzed 49 dissolved organic micropollutants for all events and 198 for four events, including pharmaceuticals, pesticides, and road-related compounds, of which we detected 83 substances at least once. From these, we assessed the mixed chemical risk by applying acute quality criteria and evaluated how the risk assessment outcome changes for two aspects: temporal resolution and selection of substances. Our results reveal that total risk quotients (RQ_tot) can vary greatly within CSO events, with 10-minute data capturing peak concentrations that are missed with EMCs. Using EMCs underestimates the maximum RQ_tot of an event by a median factor of 4.9, up to a maximum factor of 6.9. When comparing a selection of 20 substances from the Swiss Waters Protection Ordinance to a broader list of 49 substances commonly detected at CSOs and a comprehensive list of 198 substances, the estimated RQ_tot increases between 1.1 to 2.3-fold. RQ_tot values exceed the threshold of 1 in 75 % of the events, requiring further dilution in the receiving water body. All three pollutant classes (pharma, pesticide, road) drive the total risk, and no specific phase during overflow events consistently poses higher risk than other phases, which challenges the design of effective mitigation measures. Furthermore, the exposure scenarios presented here offer essential input for future ecotoxicological research as they reveal high short-term fluctuations in RQ_tot whose ecological significance is still largely unknown.

Combined sewer overflows (CSOs) discharge organic micropollutants (MPs) into open water bodies, posing potential environmental threats. Knowledge of the numbers, sources, and dynamics of MPs during CSOs is scarce but crucial for assessing their impact and developing mitigation strategies. To shed light on the dynamics of dissolved organic MPs in CSOs, we conducted high-temporal-resolution sampling (10 min composite samples) followed by liquid chromatography high-resolution mass spectrometry analysis, both target (60 substances) and nontarget, at two CSO sites in a small [17 hectares reduced (ha_red)] and a large (368 ha_red) catchment for over 10 events each. We observe similar patterns among indoor substances in the large catchment and among tire-associated compounds in both catchments, indicating source-specific behavior. Due to high and diverse concentration variability, no temporal correlations were found among indoor substances in the small catchment or among pesticides in either catchment. A random forest classifier was applied to assign nontarget time series to indoor and road sources in the large catchment. The results indicate that CSOs discharge several thousand substances from indoor sources, followed by a few hundred from outdoor sources with continuous leaching. These high numbers substantially surpass the scope of traditional target lists and underscore the importance of broad-spectrum screening methods when assessing MP contamination.

Measles outbreaks remain a significant public health challenge, despite high vaccination coverage in many regions. Wastewater-based surveillance (WBS) offers a noninvasive and community-level approach to monitoring the circulation of pathogens, including the measles virus. Here, we retrospectively applied a duplex digital PCR assay to distinguish between wild-type and vaccine strains of the measles virus in wastewater samples available from an existing national WBS program. Samples originated from the wastewater treatment plant serving the Lausanne city catchment area, where an outbreak occurred before spreading to the broader Canton Vaud region. Despite high vaccination rates, viral loads of the measles wild type were detected during the first transmission event involving 21 cases identified within a week. However, viral loads were no longer detectable after the initial 21 cases, despite an additional 30 cases reported in the following 3 weeks, possibly due to lower incidence rate or location outside the catchment. Measles vaccine strain was not detected during the outbreak. Our results demonstrate the complementarity of WBS with clinical surveillance and suggest its potential as an early warning system for measles and other vaccine-preventable diseases. Further improvements in the assay sensitivity and integration with epidemiological data could enhance the utility of WBS for outbreak detection and control.

Current wastewater-based epidemiology (WBE) studies are predominantly focused on the analysis of urinary biomarkers present in the liquid phase of influent wastewater (IWW). This approach systematically underestimates less polar metabolites, such as cannabis biomarkers. These biomarkers can potentially sorb to and desorb from suspended particulate matter (SPM) present in IWW. This study investigates the bidirectional partitioning of THC[sbnd]COOH between the liquid phase and SPM of IWW by performing multiple sorption experiments using THC[sbnd]COOH-D₉ as a surrogate due to the unavailability of blank SPM and blank IWW. In addition, this study involves the analysis of IWW collected from eight wastewater treatment plants (WWTP) (n = 56) across four European countries, where raw IWW, the liquid phase and SPM were separately analysed to identify potential trends in the fraction of THC[sbnd]COOH in the SPM between and withing the examined locations. Based on the performed sorption experiments, bidirectional partitioning of THC[sbnd]COOH between the liquid phase and SPM was noted, showing partition between both phases when only one of the two phases was spiked. It was illustrated that the concentration of SPM had a notable influence on the THC[sbnd]COOH partitioning between both phases. In addition to the inter location variability (average THC[sbnd]COOH present in the SPM ranged 31–59 %), a substantial intra location variation was also observed, e.g., in one location ranged 17–58 %. While the determination of a correction factor for the amount of THC[sbnd]COOH present in SPM would be ideal, this is challenging, since the amount of SPM is not fixed in all IWW samples. Although SPM has influence on the THC[sbnd]COOH partition, no correlation (p value Spearman correlation = 0.3160) was observed between the SPM concentration and the fraction of THC[sbnd]COOH in the solid phase. Moreover, the collection of homogenized samples is difficult, and the time required to reach an equilibration in partitioning of THC[sbnd]COOH between both IWW phases remains unclear. Due to i) the large inter-and intra-location variation of THC[sbnd]COOH present in the SPM, ii) the variability in SPM concentration in IWW samples, and iii) the time required to reach a partitioning equilibration, an analytical procedure based on liquid-liquid extraction (LLE) that considers both the liquid phase and SPM of IWW is recommended to reduce the overall uncertainty for THC[sbnd]COOH measurement in IWW. It was illustrated that this extraction method is capable to recover the total concentration of THC[sbnd]COOH in both phases.

Combined sewer overflows (CSOs) are an important pathway of organic micropollutants from urban areas to open water bodies. Understanding the temporal dynamics of these micropollutants during overflow events is crucial for applying appropriate sampling methods and implementing effective management strategies. Yet, little is known about the dynamics of micropollutants in CSOs, because most studies report concentrations from single grab samples or event mean concentrations (EMCs). With unique high temporal resolution measurements (3 min), we show the real dynamics of polar organic micropollutants in CSOs of one small (2,700 people: P) and one large (159,000 P) urban catchment, for two micropollutant categories: (i) 33 micropollutants in municipal wastewater and (ii) 13 micropollutants from urban surface runoff. The concentration dynamics depend on the substance source and the catchment size. Indoor substances such as pharmaceuticals show high temporal dynamics with changes of 1 to 2 orders of magnitude within 9 min in the CSO of the small catchment. In contrast, outdoor substances at the small catchment and all substances at the large catchment display considerably lower variation. We tested various time-proportional sampling strategies to assess the range of error when estimating EMCs. We recommend an interval of 3 min to capture the dynamics of indoor substances in CSOs from small catchments. The results highlight that both future monitoring campaigns and the planning and management of urban wet-weather treatment systems will benefit from high temporal sampling resolutions, not only to understand dynamics but also to minimize errors of estimated EMCs.

Wastewater-based epidemiology (WBE) has emerged as an effective tool for monitoring SARS-CoV-2 dynamics during the COVID-19 pandemic. Here, we add a spatial component to WBE and use it to investigate SARS-CoV-2 spread in the canton of Ticino during the onset of the pandemic in Switzerland (end of February 2020 to beginning of March 2020). Ticino is located at the border to Northern Italy, where a large COVID-19 outbreak occurred in February 2020. Not surprisingly, Ticino was the site of the first clinically confirmed COVID-19 case in Switzerland. We retrospectively analyzed daily influent samples from nine wastewater treatment plants in Ticino that jointly cover an area of 20 km × 60 km and 351,000 people (>99% of the population). Our result is a fine-grained view of the spatiotemporal evolution of the COVID-19 pandemic in this canton. The wastewater analysis revealed that by February 29, 2020, SARS-CoV-2 had already spread to all catchments. At the same time, only four individual cases had been clinically confirmed across the region served by the treatment plants investigated. Our results demonstrate that WBE could serve as a versatile tool to monitor the introduction and spread of an infectious agent on a regional scale. To fully exploit its utility, WBE should be implemented in real time and become an integral part of future disease surveillance efforts.

The continuing emergence of SARS-CoV-2 variants of concern and variants of interest emphasizes the need for early detection and epidemiological surveillance of novel variants. We used genomic sequencing of 122 wastewater samples from three locations in Switzerland to monitor the local spread of B.1.1.7 (Alpha), B.1.351 (Beta) and P.1 (Gamma) variants of SARS-CoV-2 at a population level. We devised a bioinformatics method named COJAC (Co-Occurrence adJusted Analysis and Calling) that uses read pairs carrying multiple variant-specific signature mutations as a robust indicator of low-frequency variants. Application of COJAC revealed that a local outbreak of the Alpha variant in two Swiss cities was observable in wastewater up to 13 d before being first reported in clinical samples. We further confirmed the ability of COJAC to detect emerging variants early for the Delta variant by analysing an additional 1,339 wastewater samples. While sequencing data of single wastewater samples provide limited precision for the quantification of relative prevalence of a variant, we show that replicate and close-meshed longitudinal sequencing allow for robust estimation not only of the local prevalence but also of the transmission fitness advantage of any variant. We conclude that genomic sequencing and our computational analysis can provide population-level estimates of prevalence and fitness of emerging variants from wastewater samples earlier and on the basis of substantially fewer samples than from clinical samples. Our framework is being routinely used in large national projects in Switzerland and the UK.

Tracking the occurrence of a broad variety of chemicals in the aquatic environment at a high temporal resolution over extended time periods is challenging. Here, we present a transportable platform integrating sample preparation, liquid chromatography-high-resolution mass spectrometry measurement, automated data processing, and remote control and surveillance. The system is capable of quantifying pollutants at 20 min intervals with high sensitivity (limit of quantification down to 10 ng/L) and operated stably on-site over prolonged periods (<3 ppm mass drift over two weeks, <0.3 min retention time drift over six weeks). Field campaigns under different conditions demonstrated unprecedented insights into pollutant dynamics. Time-resolved measurements in a small creek revealed concentration peaks with up to 10-fold exceedances of environmental quality standards. The quantification of illicit drugs and their metabolites in raw wastewater distinguished fractions of consumed and discarded cocaine. Frequency analyses and data mining showed clusters of diurnal, episodic, and possibly industry-related pollutants, including newly identified substances. With this enabling technology the potential for researching and managing chemicals in natural and technical environments can be significantly expanded beyond our current capabilities, for example, real-time control in process engineering and sewer operation (water management and environmental toxicology), industrial surveillance, and wastewater-based epidemiology.

Wastewater-based epidemiology (WBE) applies advanced analytical methods to quantify drug residues in wastewater with the aim to estimate illicit drug use at the population level. Transformation processes during transport in sewers (chemical and biological reactors) and storage of wastewater samples before analysis are expected to change concentrations of different drugs to varying degrees. Ignoring transformation for drugs with low to medium stability will lead to an unknown degree of systematic under- or overestimation of drug use, which should be avoided. This review aims to summarize the current knowledge related to the stability of commonly investigated drugs and, furthermore, suggest a more effective approach to future experiments. From over 100 WBE studies, around 50 mentioned the importance of stability and 24 included tests in wastewater. Most focused on in-sample stability (i.e., sample preparation, preservation and storage) and some extrapolated to in-sewer stability (i.e., during transport in real sewers). While consistent results were reported for rather stable compounds (e.g., MDMA and methamphetamine), a varying range of stability under different or similar conditions was observed for other compounds (e.g., cocaine, amphetamine and morphine). Wastewater composition can vary considerably over time, and different conditions prevail in different sewer systems. In summary, this indicates that more systematic studies are needed to: i) cover the range of possible conditions in sewers and ii) compare results more objectively. To facilitate the latter, we propose a set of parameters that should be reported for in-sewer stability experiments. Finally, a best practice of sample collection, preservation, and preparation before analysis is suggested in order to minimize transformation during these steps.

Aims. To perform wastewater analyses to assess spatial differences and temporal changes of illicit drug use in a large European population.
Design. Analyses of raw wastewater over a 1-week period in 2012 and 2013.
Setting and Participants. Catchment areas of wastewater treatment plants (WWTPs) across Europe, as follows: 2012: 25 WWTPs in 11 countries (23 cities, total population 11.50 million); 2013: 47 WWTPs in 21 countries (42 cities, total population 24.74 million).
Measurements. Excretion products of five illicit drugs (cocaine, amphetamine, ecstasy, methamphetamine, cannabis) were quantified in wastewater samples using methods based on liquid chromatography coupled to mass spectrometry.
Findings. Spatial differences were assessed and confirmed to vary greatly across European metropolitan areas. In general, results were in agreement with traditional surveillance data, where available. While temporal changes were substantial in individual cities and years (P ranging from insignificant to <10⁻³), overall means were relatively stable. The overall mean of methamphetamine was an exception (apparent decline in 2012), as it was influenced mainly by four cities.
Conclusions. Wastewater analysis performed across Europe provides complementary evidence on illicit drug consumption and generally concurs with traditional surveillance data. Wastewater analysis can measure total illicit drug use more quickly and regularly than is the current norm for national surveys, and creates estimates where such data does not exist.

Discharge of silver nanoparticles (Ag-NP) from textiles and cosmetics, todays major application areas for metallic Ag-NP, into wastewater is inevitable. Transformation and removal processes in sewers and wastewater treatment plants (WWTP) will determine the impact of Ag-NP on aquatic and terrestrial environments, via the effluents of the WWTP and via the use of digested sludge as fertilizer. We thus conducted experiments addressing the behavior of Ag-NP in sewers and in WWTP.
We spiked Ag-NP to a 5 km long main trunk sewer and collected 40 wastewater samples after 500 m, 2400 m and 5000 m each according to the expected travel times of the Ag-NP. Excellent mass closure of the Ag derived by multiplying the measured Ag concentrations times the volumetric flow rates indicate an efficient transport of the Ag-NP without substantial losses to the sewer biofilm. Ag-NP reacted with raw wastewater in batch experiments were sulfidized to roughly 15% after 5 h reaction time as revealed by X-ray absorption spectroscopy (XAS). However, acid volatile sulfide (AVS) concentrations were substantially higher in the sewer channel (100 μM) compared to the batch experiments (3 μM; still sufficient to sulfidize spiked 2 μM Ag) possibly resulting in a higher degree of sulfidation in the sewer channel. We further investigated the removal efficiency of 10 nm and 100 nm Ag- and gold (Au)-NP coated with citrate or polyvinylpyrrolidone in activated sludge batch experiments. We obtained very high removal efficiencies (∼99%) irrespective of size and coating for Ag- and Au-NP, the latter confirming that the particle type was of minor importance with respect to the degree of NP removal. We observed a strong size dependence of the sulfidation kinetics. We conclude that Ag-NP discharged to the wastewater stream will become sulfidized to various degrees in the sewer system and are efficiently transported to the WWTP. The sulfidation of the Ag-NP will continue in the WWTP, but primarily depending on the size the Ag-NP, may not be complete. Very high removal efficiencies in the WWTP will divert most of the Ag-NP mass flow to the digester and only a small fraction of the Ag will be released to surface waters.

The analysis of 87 peer-reviewed journal articles reveals that sampling for pharmaceuticals and personal care products (PPCPs) and illicit drugs in sewers and sewage treatment plant influents is mostly carried out according to existing tradition or standard laboratory protocols. Less than 5% of all studies explicitly consider internationally acknowledged guidelines or methods for the experimental design of monitoring campaigns. In the absence of a proper analysis of the system under investigation, the importance of short-term pollutant variations was typically not addressed. Therefore, due to relatively long sampling intervals, potentially inadequate sampling modes, or insufficient documentation, it remains unclear for the majority of reviewed studies whether observed variations can be attributed to “real” variations or if they simply reflect sampling artifacts. Based on results from previous and current work, the present paper demonstrates that sampling errors can lead to overinterpretation of measured data and ultimately, wrong conclusions. Depending on catchment size, sewer type, sampling setup, substance of interest, and accuracy of analytical method, avoidable sampling artifacts can range from “not significant” to “100% or more” for different compounds even within the same study. However, in most situations sampling errors can be reduced greatly, and sampling biases can be eliminated completely, by choosing an appropriate sampling mode and frequency. This is crucial, because proper sampling will help to maximize the value of measured data for the experimental assessment of the fate of PPCPs as well as for the formulation and validation of mathematical models. The trend from reporting presence or absence of a compound in “clean” water samples toward the quantification of PPCPs in raw wastewater requires not only sophisticated analytical methods but also adapted sampling methods. With increasing accuracy of chemical analyses, inappropriate sampling increasingly represents the major source of inaccuracy. A condensed step-by-step Sampling Guide is proposed as a starting point for future studies.

A model based on graph theory was developed to efficiently evaluate the impact of the effluent from 742 wastewater treatment plants (WWTPs) on micropollutant loading throughout all river catchments in Switzerland. Model results agree well with measured loads for 12 compounds in river water samples, revealing mean predictive accuracy factors between 0.8 and 3.4. Subsequently, pollutant concentrations were predicted for river sections downstream from 543 WWTPs where hydrological information was available, and compared with recent recommendations for water quality criteria. At base flow conditions, carbamazepine concentrations (parent compound only) are ubiquitously below a water quality criterion of 0.5 μg L⁻¹. In contrast, the sum of diclofenac and its metabolites is expected to exceed the corresponding water quality criterion of 0.1 μg L⁻¹ in 224 river sections. If diclofenac cannot be eliminated at the source, the model suggests a directed upgrade of 173 WWTPs to meet the condition that concentrations are never to exceed this water quality criterion.