Comparison of tobacco use in a university town and a nearby urban area in China by intensive analysis of wastewater over one year period
Graphical abstract
Introduction
Smoking is a leading risk factor for premature death and disability globally (Forouzanfar et al., 2016; James et al., 2018). More than 7 million people die from direct tobacco use every year worldwide, and 1.2 million deaths are caused by exposure to second-hand smoke (World Health Organisation, 2020). China is the world's largest tobacco producer and consumer, accounting for 45% of global production and 40% of use (U.S.National Cancer Institute and World Health Organization, 2016, Statista, 2019). More than 1 million Chinese people die every year from tobacco-related diseases (CCDC, 2015). Despite being a member to the WHO Framework Convention on Tobacco Control, smoking prevalence remains high in China. There is evidence of a decreasing trend in tobacco use with prevalence among the population aged 15+ declining from 28.1% to 26.6% over the past eight years (CCDC, 2018). This decline in smoking must be accelerated if China is to reach its goal of less than 20% smoking prevalence by 2030 (State Council of the People's Republic of China, 2016). Of great concern are reports that smoking among Chinese men aged 15–24 is heading in the opposite direction, with an increase from 30% in 2010 to 36.5% in 2015 (CCDC, 2015). Previous research also shows an increase in e-cigarette use among adolescents from 2014 to 2016 (Chen et al., 2018). Hence, continued close monitoring of tobacco use in China is needed to determine if current public health strategies are achieving their intended goals and which populations are most responsive.
Traditional surveys and tax statistics are the most common methods to monitor tobacco use. However, population surveys on tobacco use are infrequent in China. National adult smoking statistics were reported for 2010, 2015 and 2018 (CCDC, 2010, 2015, 2018), while surveys of smoking in adolescents were conducted in 2014 and 2019 (CCDC, 2014, 2019). There are surveys via questionnaires at the provincial- or city-wide level reported tobacco use at low spatial resolution (Shen et al., 2019; Zhao et al., 2020) while tobacco use at community level is generally unavailable. In addition, these surveys also do not have a high temporal resolution and mostly are based on sub analysis of national-wide surveys. Tobacco taxation or sales statistics can provide yearly estimates, but due to warehousing (13% in 2017), such estimates may cause an over- or under-estimations as they do not directly measure use. Furthermore, taxation data is not publicly available in China. Therefore, alternative methods of monitoring tobacco use could provide valuable evidence for public health researchers and policymakers.
Wastewater-based epidemiology (WBE) is a useful tool that complements traditional surveys and overcomes some of the limitations of self-report data to monitor the use of substances including tobacco (Chen et al., 2019; Driver et al., 2020; Gracia-Lor et al., 2020; Mackie et al., 2019; Montes et al., 2020). To estimate tobacco use, WBE analyses the tobacco-related biomarkers, cotinine and hydroxycotinine, in wastewater influent as it enters a sewage treatment plant, then back-calculates to estimate the population use level by normalizing the flow rate, catchment population and pharmacological data on the biomarkers (Gao et al., 2020; Lai et al., 2018). Six years ago, a review by Gao et al. (2015) has predicted the potential of WBE applications in China including the monitoring of tobacco use and subsequently we have published estimates of tobacco use in China at the provincial level (Wang et al., 2016; Zheng et al., 2017) and national level (Gao et al., 2020; Shao et al., 2021). However, in those studies, finer temporal trends (weekly) and tobacco use by specific populations in China have not been examined.
In this study, we applied WBE to investigate tobacco use in a general urban population and a university town with a high proportion of university students over one year. The main objectives were: 1) to investigate tobacco use among these two populations; and 2) to assess the temporal trends (weekly, seasonal, annual) in tobacco use in a general population in a Chinese city.
Section snippets
Sample collection
24-hour composite wastewater influent samples were collected by an auto-sampler using time-proportional mode at 30 min intervals with 30 mL of sampling volume from an urban wastewater treatment plant (WWTP), covering about 500,000 residents, located in a city in Southern China. Daily composite samples were collected from November 2017 to October 2018 (n = 279) for analysis. The same sampling method was applied to collect composite sample every Wednesday from a pump station, which serves a
Results and discussion
The two consumption biomarkers of nicotine, cotinine and hydroxycotinine, were detected in all wastewater samples collected from both catchments.. With the low prevalence of use of e-cigarettes (0.5% in 2015 and 0.9% in 2018) and other nicotine replacement therapies in China (CCDC, 2018; Wang et al., 2019), cotinine and hydroxycotinine measured in wastewater in this study can be assumed to be mostly from tobacco use, thus confirming the popularity of tobacco smoking in the monitored populations.
Conclusion
This study reported the patterns of tobacco use in an urban population and a university population in China. The high temporal resolution of WBE provides the measurement of weekly, yearly trends of tobacco use in the population, allowing short-term and medium-term level to be examined. Stable tobacco use throughout the week confirmed that most users are regular smokers. The high temporal resolution samples revealed an overall upward trend of tobacco use in the urban area and a stable trend in
Declaration of Competing Interest
Authors declare no competing interests.
Acknowledgement
The Queensland Alliance for Environmental Health Sciences, The University of Queensland gratefully acknowledges the financial support of Queensland Health. This work was supported by the National Natural Science Foundation of China [Grant No. 41877466]; Natural Science Foundation of Guangdong Province [Grant No. 2019A1515011037]. Qiuda Zheng and Zhe Wang receive UQI scholarships for their PhD. Gary C.K. Chan is funded through the NHMRC Fellowship (APP1176137). The authors express our thanks to
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