Impact of physicochemical parameters on nicotine metabolites and Bisphenol A in municipal wastewater: A pilot study in a German metropolitan area

Wastewater-based epidemiology (WBE) is a promising approach for assessing population-level exposures to toxicants and lifestyle factors. Our pilot investigated the spatial variability of biomarkers indicating exposure to nicotine and endocrine disrupting chemicals in municipal wastewater, taking into account important covariates, i.e. physicochemical wastewater parameters and sewershed characteristics. We also tested normalization by an endogenous population marker. Twenty-four-hour composite samples (n = 24) were collected in a volume-proportional manner using automated samplers from four wastewater treatment plants in Essen, Germany, over three weeks in late 2023. Substances of public health concern, previously already quantified in wastewater and expected to be present in high concentrations, were analyzed using SPE-LC-HRMS. Concentrations were normalized to the reported population (de jure) and the daily mass load of the catecholamine metabolite vanillylmandelic acid (VMA) as a proxy for the de facto population. Spatial variations were analyzed using multiple linear regression. Nicotine metabolites (cotinine, hydroxycotinine) and the industrial chemical Bisphenol A (BPA) were quantifiable in all wastewater samples. The population-normalized daily mass load of nicotine metabolites (median range: 0.6-1.6 g/d/1000 inh) and BPA (2.5-4.0 g/d/1000 inh) varied between the WWTPs, but the observed variation disappeared when adjusting for wastewater temperature (nicotine) and wastewater pH (BPA). Normalization to the VMA daily mass load resulted in different spatial patterns and increased the variance considerably. Our findings highlight the importance of adjusting for physicochemical characteristics when analyzing community-wide differences in exposure to toxicants and lifestyle factors via wastewater, to ensure accurate interpretations of the underlying drivers of these differences.