Improving Wastewater-Based Tobacco Use Estimates Using Anabasine.

In wastewater-based epidemiology (WBE), nicotine metabolites have been used as biomarkers for monitoring tobacco use. Recently, the minor tobacco alkaloids anabasine and anatabine have been suggested as more specific biomarkers for tobacco use since nicotine use can be from both tobacco and non-tobacco sources. This study aimed to provide an in-depth evaluation of the suitability of anabasine and anatabine as WBE biomarkers of tobacco and subsequently estimate their excretion factors for WBE applications. Pooled urine (n = 64) and wastewater samples (n = 277), collected between 2009 and 2019 in Queensland, Australia, were analyzed for nicotine and its metabolites (cotinine and hydroxycotinine), as well as anabasine and anatabine. Anabasine performed as the better biomarker, showing a similar per capita load in pooled urine (2.2 ± 0.3 µg/day/person) and wastewater samples (2.3 ± 0.3 µg/day/person), while the per capita load of anatabine in wastewater was 50% higher than its load in urine. It is estimated that 0.9 µg of anabasine was excreted per cigarette smoked. Triangulation of tobacco sales data and tobacco use estimated from either anabasine or cotinine showed that anabasine-based estimates were 5% higher than sales data, while cotinine-based estimates were between 2 and 28% higher. Our results provided concrete evidence to confirm the suitability of anabasine as a specific biomarker for monitoring tobacco use by WBE.

Considerations for assessing stability of wastewater-based epidemiology biomarkers using biofilm-free and sewer reactor tests.

Wastewater-based epidemiology is an increasingly popular method for analysing drugs or metabolites excreted by populations. The in-sewer transformation of biomarkers is important but often receives little consideration in published studies. Many studies publish stability under biofilm-free conditions only, which do not represent actual sewer conditions. This study aims to fill a gap in the field by comparing the wastewater stability of 33 licit drug and pharmaceutical biomarkers in biofilm-free (BFF) conditions to stability in sewer biofilm reactors. All but one biomarker was stable under BFF conditions, whereas most transformed in sewer biofilm reactors. Sewer reactor results tended to overestimate the degradation in pilot and actual sewers, whereas BFF stability had no clear relationship to stability in pilot and actual sewers. Our results provide additional basis for more informed interpretation of biofilm-free and sewer reactor stability results for past and future WBE studies.

Impact of in-Sewer Degradation of Pharmaceutical and Personal Care Products (PPCPs) Population Markers on a Population Model.

A key uncertainty of wastewater-based epidemiology is the size of the population which contributed to a given wastewater sample. We previously developed and validated a Bayesian inference model to estimate population size based on 14 population markers which: (1) are easily measured and (2) have mass loads which correlate with population size. However, the potential uncertainty of the model prediction due to in-sewer degradation of these markers was not evaluated. In this study, we addressed this gap by testing their stability under sewer conditions and assessed whether degradation impacts the model estimates. Five markers, which formed the core of our model, were stable in the sewers while the others were not. Our evaluation showed that the presence of unstable population markers in the model did not decrease the precision of the population estimates providing that stable markers such as acesulfame remained in the model. However, to achieve the minimum uncertainty in population estimates, we propose that the core markers to be included in population models for other sites should meet two additional criteria: (3) negligible degradation in wastewater to ensure the stability of chemicals during collection; and (4) < 10% in-sewer degradation could occur during the mean residence time of the sewer network.