Analyzing long-term trends in cotinine concentrations among smokers and non-smokers under South Korea's tobacco control policies

Following the ratification of the Framework Convention on Tobacco Control (FCTC) in 2003, South Korea has implemented various smoking cessation policies. As a result, both smoking rates and secondhand smoke (SHS) exposure rates in Korea have been steadily declining. However, there is a lack of studies analyzing long-term trends in biomarker-assessed SHS exposure across smoking status groups over time, using cotinine concentration (μg/L) as a biomarker.

This study employed a repeated cross-sectional design, utilizing data from the First (2009–2011) to Fourth (2018–2020) Waves of the Korean National Environmental Health Survey. A total of 19,741 participants were selected after excluding missing data. The urinary cotinine concentrations of the smoking status groups were presented as geometric means. Multiple regression analysis was conducted to identify factors influencing cotinine concentration.

Compared to 2009, cotinine levels decreased by 51.4 % in never smokers (1.40 μg/L in 2009; 0.68 μg/L in 2013), 35.2 % in former smokers (1.93 μg/L in 2009; 1.25 μg/L in 2013), and 28.0 % in current smokers (1302.46 μg/L in 2009; 937.97 μg/L in 2012) in the mid-2010s. However, cotinine levels in never smokers and former smokers have shown a steady increase since then, surpassing pre-policy levels by 2020, at 1.17 μg/L and 1.50 μg/L, respectively.

The rise in cotinine levels among current non-smokers, despite FCTC-based policies, likely stems from the spread of novel nicotine products, misconceptions about e-cigarettes, and stealth usage. As urinary cotinine levels are expected to continue rising in the future, addressing these hidden contributors require enhanced surveillance and targeted interventions to ensure more effective tobacco control measures.