This study was conducted between November to December 2020, consisting of six representative cities, Beijing, Shanghai, Shenzhen (with comprehensive smoke-free legislation), and Changsha, Chongqing, Shenyang (without comprehensive smoke-free legislation), 678 subjects were enrolled eventually, the mean age of the 678 subjects was (35.61±12.91)years old. Subjects from cities with comprehensive smoke-free legislation accounted for 49.71% of the total; male subjects accounted for 19.47%; meanwhile subjects from large, medium, and small restaurants accounted for 13.57% (92), 37.32% (253) and 49.11% (333) respectively. The analysis results indicate that the positive rate of restaurants staff of cotinine and 3′-hydroxynicotinine was lower in cities with comprehensive smoke-free legislation(34.12% vs 68.04%, χ2=78.01, P<0.001; 16.32% vs 41.94%, χ2=53.79, P<0.001), with staff from cities with comprehensive smoke-free legislation have lower concentrations of cotinine and 3′-hydroxynicotinine than their counterparts from cities without comprehensive smoke-free legislation(0.250 ng/ml vs 0.742 ng/ml, P<0.001; 0.250 ng/ml vs 0.250 ng/ml, P<0.001). No statistically significant difference in the concentration of cotinine and 3′-hydroxynicotinine in saliva between staff from restaurants of different sizes was detected ( P>0.05).

This study was conducted between November to December 2020, consisting of six representative cities, Beijing, Shanghai, Shenzhen (with comprehensive smoke-free legislation), and Changsha, Chongqing, Shenyang (without comprehensive smoke-free legislation), 678 subjects were enrolled eventually, the mean age of the 678 subjects was (35.61±12.91)years old. Subjects from cities with comprehensive smoke-free legislation accounted for 49.71% of the total; male subjects accounted for 19.47%; meanwhile subjects from large, medium, and small restaurants accounted for 13.57% (92), 37.32% (253) and 49.11% (333) respectively. The analysis results indicate that the positive rate of restaurants staff of cotinine and 3′-hydroxynicotinine was lower in cities with comprehensive smoke-free legislation(34.12% vs 68.04%, χ2=78.01, P<0.001; 16.32% vs 41.94%, χ2=53.79, P<0.001), with staff from cities with comprehensive smoke-free legislation have lower concentrations of cotinine and 3′-hydroxynicotinine than their counterparts from cities without comprehensive smoke-free legislation(0.250 ng/ml vs 0.742 ng/ml, P<0.001; 0.250 ng/ml vs 0.250 ng/ml, P<0.001). No statistically significant difference in the concentration of cotinine and 3′-hydroxynicotinine in saliva between staff from restaurants of different sizes was detected ( P>0.05).