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Secondhand smoke (SHS) poses serious harms to human health. Currently, there are 316 million smokers in China, and about 740 million non-smokers are exposed to SHS (1). The number of deaths caused by SHS is more than 100,000 every year (2). The Regulation on Smoking Control in Public Places of Shanghai was implemented on March 1, 2010. To further strengthening the tobacco control, Amendment of the Regulation on Smoking Control of Shanghai was formally implemented on March 1, 2017, restricting smoking in all indoor public places. It is of great significance to understand the level and status of SHS exposure for the formulation of tobacco control policies and intervention strategies (3).
The data of this study was from the Shanghai Adult Tobacco Survey in 2018, which was conducted among the population aged 15 years and older. Multi-stage, geographically clustered sampling was used and covered 100 monitor points from 16 districts. A total of 3,250 families were sampled, and one individual was randomly selected from each family to complete the survey. The Global Adult Tobacco Survey (GATS) standard questionnaire was used and face-to-face survey was conducted, 3,112 individuals completed the survey (95.8%), and this study analyzes SHS exposure data. SHS exposure of non-smokers refers to exposure to tobacco smoke at least 1 day per week; SHS exposure at home and in public places refers to the proportion of participants, including smokers and non-smokers, who saw someone smoking, smelled smoke, or saw cigarette butts when visiting specific places in the past 30 days (1-3). The data was weighted according to the sampling method and analyzed using SAS software (version 9.3; SAS Institute, Inc. Cary, NC, USA) complex survey design.
The survey included 1,465 males and 1,647 females, and after weighted adjustment, male respondents accounted for 51.6% and female respondents 48.4%. For different age groups, the proportion of participants aged 25 to 44 years was the highest (41.4%), followed by those aged 45 to 64 years (32.3%), and the proportions of different genders and age groups in this study were similar to that of Shanghai overall (4), which indicated good representativeness of the sample data. In terms of education levels, participants with college degree or above accounted for the highest proportion at 40.8%. The highest proportion in terms of occupation was enterprise, business, and service personnel at 44.7%.
According to the survey, the SHS exposure rate of non-smokers among the age of 15 years and above in Shanghai was 46.7% (95% CI: 40.4%–53.0%) in 2018 and was higher in males (52.6%) than in females (42.8%). However, the proportion of women exposed daily was higher than men (p<0.001). Among different occupational groups, the exposure rate in enterprises, businesses, and service personnel was the highest (51.2%), followed by farmers (51.0%), and the unemployed (50.9%), all of which were above 50%; while medical personnel (38%) and teachers (16.2%) had a relatively lower exposure (p=0.026). The proportion of SHS exposure at home in the last 30 days was 23.5%, higher in males than in females (p<0.001); however, in the subgroup of non-smokers, the rate was a little higher in females than in males. Based on different age groups, the group aged 15–24 years had the highest exposure rate at 25.6%, followed by the group aged over 65 years at 21.2% (p<0.001). The differences were also significant among different educational levels with education level being inversely related to exposure rate from 24.5% to 8.8% (p<0.001) (Table 1).
Demographic characteristics Overall of non-smokers* (Rate [%] [95% CI]) Home† (Rate [%] [95% CI]) One day or above/per week Nearly everyday Overall Non-smokers Gender Male 52.6(44.8−60.4) 12.2(7.6−16.8) 28.4(23.6−33.3) 14.1(9.7, 18.6) Female 42.8(36.7−48.8) 15.1(11.7−18.6) 18.2(13.9−22.4) 17.8(13.6, 22.0) χ2 13.869 20.583 32.488 3.782 p value <0.0001 <0.0001 <0.0001 0.052 Age group 15–24 years 48.0(35.6−60.4) 13.5(5.6−21.5) 31.9(20.4−43.4) 25.6(15.4, 35.7) 25–44 years 48.5(42.1−55.0) 12.9(8.8−17.0) 17.5(13.4−21.6) 12.6(8.5, 16.6) 45–64 years 46.3(38.1−54.4) 15.7(11.4−20.0) 25.6(19.8−31.5) 14.9(9.8, 20.1) ≥65 years 40.8(34.4−47.2) 14.1(10.1−18.0) 28.3(23.5−33.2) 21.2(16.4, 26.0) χ2 3.123 0.541 18.864 18.315 p value 0.373 0.910 <0.0001 <0.0001 Educational level§ Primary school and below 42.1(35.0−49.3) 19.7(14.1−25.3) 34.3(27.0−41.7) 24.5(18.6, 30.5) Junior high school 53.2(45.7−60.7) 19.2(14.6−23.8) 29.5(24.1−34.8) 20.5(15.4, 25.5) Senior high school 47.4(37.3−57.5) 16.8(10.8−22.9) 24.8(19.1−30.5) 15.2(9.5, 20.8) College and above 43.8(36.6−51.1) 8.4(4.5−12.3) 12.6(9.5−15.7) 8.8(5.5, 12.0) χ2 7.393 18.290 117.126 50.076 p value 0.060 <0.0001 <0.0001 <0.0001 Occupation Farmer 51.0(34.5−67.6) 20.1(7.2−32.9) 36.7(22.9−50.5) 25.7(12.0, 39.5) Government/public institution personnel 49.5(36.2−62.8) 13.7(4.7−22.7) 18.2(7.3−29.1) 17.2(5.1, 29.3) Enterprise, commercial, service personnel 51.2(43.2−59.2) 12.4(7.6−17.2) 22.7(17.7−27.6) 13.1(9.1, 17.2) Teacher 16.2(3.2−29.2) − 5.6(0.0−14.1) 6.1(0.0, 15.5) Medical worker 38.0(19.5−56.5) 12.3(0.0−26.2) 13.2(2.2−24.3) 14.3(0.6, 27.9) Unemployed 50.9(34.5−67.3) 24.9(11.2−38.7) 28.9(16.1−41.8) 25.5(12.9, 38.1) Others 42.3(34.5−50.1) 14.8(10.2−19.5) 24.3(19.4−29.2) 18.4(13.0, 23.7) χ2 14.332 7.227¶ 14.425 11.739 p value 0.026 0.204 0.025 0.068 Total 46.7(40.4−53.0) 14.0(10.4−17.6) 23.5(19.2−27.7) 16.3(12.4, 20.3) * Refers to the frequency of non-smokers’ exposure to secondhand smoke per week.
† People who report that someone smokes in their home on a daily/weekly/monthly basis.
§ The educational level of respondents over 25 years old was only reported.
¶ The category that does not show results is eliminated, when doing Chi-square test.Table 1. Estimation of exposure of second-hand smoke overall and at home.
The proportion of SHS exposure in major public places were, from highest to lowest, 28.1% for restaurants, 17.3% for indoor workplaces, 12.1% for universities, 10.0% for government buildings, 7.7% for primary and secondary schools, 4.2% for medical institutions, and 1.8% for public transports. The proportions of SHS exposure of females in indoor workplaces, restaurants, public transport, and primary and secondary schools were lower than that of men (p<0.01). Different age groups, educational levels, and occupations were contributing factors that influenced the proportion of SHS exposure of indoor workplaces (Table 2).
Demographic characteristics Rate (%) (95% CI) Workplace Government buildings Healthcare facilities Restaurants Public transport Universities Primary and secondary schools† Gender Male 22.4(16.2−28.5) 10.9(5.2−16.6) 3.3(2.1−4.6) 32.7(27.1−38.2) 2.7(1.1−4.3) 17.1(5.4−28.7) 10.1(4.3−15.9) Female 11.5(8.3−14.8) 8.9(3.0−14.8) 5.0(3.0−6.9) 22.6(17.3−27.8) 0.8(0.3−1.4) 6.1(0.0−14.3) 5.2(1.8−8.5) χ2 24.067 0.345 2.272 10.997 8.387 2.285 4.214 p value <.0001 0.557 0.132 0.0009 0.004 0.131 0.040 Age group 15–24 years 16.5(6.1−27.0) − 4.5(0.0−13.4) 32.1(19.2−45.1) 1.6(0.0−3.9) 15.7(0.0−31.6) 13.8(0.0−28.0) 25–44 years 14.9(10.6−19.3) 12.5(6.0−19.1) 2.7(0.7−4.6) 27.5(21.5−33.5) 2.5(0.7−4.3) 10.1(1.5−18.6) 5.5(1.7−9.2) 45–64 years 25.5(18.3−32.8) 5.6(0.0−11.3) 4.4(2.6−6.2) 26.2(20.6−31.8) 1.1(0.4−1.9) 7.8(0.0−19.8) 7.0(2.2−11.8) ≥65 years 33.8(11.2−56.4) 7.4(0.0−16.3) 6.4(3.8−9.0) 29.6(22.9−36.3) 1.3(0.4−2.2) 16.8(0.6−33.0) 12.4(2.8−22.0) χ2 9.510 3.788 3.003 1.360 2.874 1.315 5.207 p value 0.023 0.151 0.391 0.715 0.411 0.726 0.157 Educational level§ Primary schools and below 38.7(23.4−54.1) 1.8(0.0−5.6) 6.7(3.7−9.7) 27.9(15.7−40.1) 5.0(0.0−10.8) − 3.2(0.0−7.9) Junior high
school29.8(20.6−39) 8.8(0.0−18.3) 4.8(2.4−7.2) 34.7(26.8−42.6) 0.9(0.0−1.7) 16.2(0.0−39.8) 10.0(2.5−17.6) Senior high school 20.5(12.2−28.9) 8.0(0.0−20.0) 3.0(1.3−4.7) 25.3(18.5−32.1) 1.0(0.2−1.7) 4.5(0.0−11.7) 6.3(0.3−12.2) College and above 12.7(8.6−16.7) 11.9(6.1−17.8) 3.6(1.3−5.8) 25.4(19.6−31.2) 2.2(0.4−3.9) 10.6(1.6−19.6) 5.1(1.2−9.0) χ2 35.508 1.327 4.517 6.173 7.577 1.901 3.162 p value <0.0001 0.723 0.211 0.104 0.056 0.387 0.367 Occupation Farmer 50.7(23.2−78.2) 5.1(0.0−15.0) 8.4(3.6−13.2) 29.4(8.2−50.6) 7.4(0.0−17.8) − 20.6(0.0−47.5) Government/public institution personnel 8.3(2.6−14.0) 15.2(4.4−25.9) 3.9(0.0−9.6) 21.9(10.7−33.1) 3.3(0.0−9.8) 7.9(0.0−23.8) 8.0(0.0−23.4) Enterprise, commercial, service personnel 20.1(14.7−25.5) 8.6(3.5−13.8) 2.4(0.8−4.1) 29.2(22.8−35.5) 1.7(0.4−3.0) 12.2(0.0−25.6) 5.2(1.4−9.0) Teacher 0.7(0.0−2.3) 25(0.0−72.6) 13.5(0.0−39.5) 27.2(0.0−57.8) − − − Medical worker − − 4.5(0.0−13.5) 18.0(1.9−34.0) − − − Unemployed 39.7(0.0−100.0) 24.6(0.0−69.7) 0.3(0.0−0.9) 28.8(9.7−48.0) − − 16.3(0.0−38.2) Others 14.8(8.4−21.3) 7.5(0.4−14.6) 5.0(3.1−6.9) 28.6(23.2−34.1) 1.4(0.3−2.5) 14.2(2.5−25.9) 10.5(3.1−17.9) χ2 23.246 4.951 8.620 2.569 4.736 0.226 4.030 p value 0.0003 0.422 0.196 0.861 0.192 0.893 0.402 Total 17.3(13.1−21.9) 10.0(5.4−14.7) 4.2(3.0−5.4) 28.1(23.5−32.6) 1.8(0.9−2.6) 12.1(4.4−19.8) 7.7(3.8−11.6) Note: Unweighted sample size less than 25, no results are shown. The category that does not show results is eliminated, when doing Chi-square test,
* People who have been to this kind of place in the past 30 days.
† Including primary school, middle school, high school, technical secondary school, vocational high school, etc.
§ The educational level of respondents over 25 years old was only reported.
Abbreviation: CI=confidence intervals.Table 2. Estimation of exposure to second-hand smoke in various indoor public places*.
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