Uncertainties in estimating alcohol and tobacco consumption by wastewater-based epidemiology

The accuracy of wastewater-based epidemiology (WBE) to assess consumption of substances relies on several factors. This review considered uncertainties specific to ethanol and tobacco biomarkers used in WBE. Although sampling and analysis were relatively minor sources of uncertainty (<11%), the excretion rate contributed to additional uncertainties of 25% and 15% for cotinine and ethanol, respectively. Cotinine, a common biomarker of tobacco consumption, increased the uncertainty in regions with high uptake of nicotine replacement therapies and e-cigarettes. The excretion rates and in-sewer stability of the alternative tobacco biomarkers are yet to be determined. The content of nicotine and ethanol in products also contribute considerable uncertainty if results were expressed as standardized units. We provide suggestions for future research to minimise uncertainties relating to estimates of alcohol and tobacco consumption by WBE.