Wastewater-Based Epidemiology (WBE): Potential Application for Assessing the Use of Conventional and New Generation Tobacco and Nicotine Products

Wastewater-based epidemiology (WBE) is a recent methodology for assessing the exposure to and (intentional) use of all kinds of chemicals in defined populations (communities) by analysis of suitable biomarkers in wastewater (WW) samples, which are commonly collected at the inlet of wastewater treatment plants (WWTPs) serving this population. WBE has been also applied to determine the use of life-style products containing caffeine, alcohol and nicotine on a global basis. This paper outlines the methodological principles of WBE and presents the outcome of a systematic review on WBE studies that utilize cotinine as biomarker in WW samples to assess tobacco/nicotine product use prevalence. For the latter purpose, 60 studies conducted on four continents (no studies were performed in Africa) could be evaluated. Back-calculated WBE-derived mean nicotine consumptions were found to be in the range of 2000–3000 mg/d/1000 persons, with large variations. WBE-derived nicotine consumption data were mostly in fair agreement with the results of ‘classical’ methods such as surveys, (official) statistics, cigarette sales data and epidemiological studies. As reasons for deviations between WBE and classical methods, most frequently the use of illicit tobacco products, nicotine replacement therapy (NRT) products, electronic cigarettes (ECs), reporting bias or outdated statistics were discussed by the study authors. Hitherto available long-term WBE studies covered time periods of 1–8 years showing mostly constant or decreasing time trends for nicotine consumption, depending on the country and time period investigated. The decrease is mostly interpreted as a consequence of lower smoking rates due to tobacco control activities. In a few studies, the minor tobacco alkaloid anabasine (AB) was measured in WW samples as a specific indicator for tobacco-containing products. The currently available results imply that AB in WW is decreasing faster over time than cotinine in WW does, suggesting that the use of tobacco products (mainly combustible cigarettes, CCs) is gradually replaced by tobacco-free nicotine products such as NRT products, ECs and others.

Taking up this approach, we conducted a Monte Carlo simulation (MCS) by which the time courses over 10 years of cotinine (indicator of the consumption of (any) nicotine product), AB (indicator of the consumption of (any) tobacco-product) and 2-cyanoethyl-mercapturic acid (2CyEMA, indicator of the exposure to the combustion product acrylonitrile, assumed to originate mainly from CC use) concentrations in WW samples collected at the inlet of a (hypothetical) WWTP serving a large city were modelled. The outcome of the MCSs for two simplified, but, in our view, not unrealistic scenarios revealed that time courses, in particular those of the WW concentration ratios AB/cotinine and 2CyEMA/cotinine, can provide useful information on the use habits for conventional (CCs and oral tobacco products) and smokeless nicotine products (ECs, HTPs, oral nicotine pouches, NRT products) in a population over time. These changes are the net result of transitions between user groups of the various nicotine/tobacco products and non-users and thus would allow to deduce the success (or failure) of tobacco harm reduction (THR) measures in a population.

From the presented evidence we conclude that WBE is a potential tool to monitor the progress of THR in populations, provided that suitable biomarkers are measured in WW samples collected over a time period of several years.