Trends in nicotine consumption between 2010 and 2017 in an Australian city using the wastewater-based epidemiology approach

Monitoring smoking prevalence is key to assessing responses to tobacco control measures, and evaluating associated health and economic costs. Estimates of tobacco consumed in Australia are based on various data sources - tax excise clearances, sales, and self-report surveys. There are limitations with each of these data sources which makes triangulation of cigarette use estimates by multiple methods important. Wastewater-based epidemiology, the systematic sampling and analysis of wastewater, is now a routine method to measure and monitor human exposure to a range of chemicals. This study provides a high frequency long-term temporal assessment of exposure to nicotine, the main addictive component of tobacco, using this approach. 291 archived wastewater samples collected from a regional city catchment from 2010 to 2017 were analysed for human-specific nicotine metabolites (cotinine and trans-3'-hydroxycotinine), to estimate per capita nicotine use. Temporal trends in nicotine use determined by wastewater-based epidemiology were compared with national sales and survey data. Wastewater analysis showed a 25% reduction in the mean number of cigarette equivalents consumed from 2010 to 2017, representing a 3% annual decline. These findings are in good agreement with estimates based on surveys and sales data, indicating annual declines of 5% and 4%, respectively. Findings of this study demonstrate WBE to be a relatively cost-effective and objective approach to reporting long-term data on nicotine consumption. When combined with alternative data sources, and valuable sociodemographic information of surveys, wastewater-based epidemiology helps to refine our estimates and understanding of the total impacts of smoking.