Workplace exposure to secondhand smoke and its association with respiratory symptoms—a cross-sectional study among workers in Shanghai
- 1Department of Preventive Medicine, School of Public Health, Fudan University, Shanghai, PR China
- 2Sydney School of Public Health, University of Sydney, New South Wales, Australia
- 3Health Inspection Institute of Changning District, Shanghai, PR China
- Correspondence to Professor Hua Fu, School of Public Health, Fudan University, PO Box 248, 138 Yixueyuan Road, Shanghai 200032, PR China;
Contributors ZZ, WL and JG completed the field work, PZ completed the data analysis and wrote the manuscript, SC contributed a lot of writing and shaping the whole paper; HF supervised the whole study.
- Received 21 March 2010
- Accepted 15 July 2010
- Published Online First 21 October 2010
Objective To describe workplace exposure to secondhand smoke (SHS) among different working populations in Shanghai; to identify any association between respiratory symptoms and SHS exposure in these workplaces.
Design Cross-sectional survey with a standardised questionnaire.
Setting 150 worksites (including restaurants, shopping malls, hotels, hospitals, schools, kindergartens).
Subjects 3530 workers.
Outcome measures Prevalence of workers with workplace exposure to SHS; average time of exposure to SHS per day; proportion of workers reporting any respiratory and sensory symptoms.
Results 13.3% of employees were covered by complete smoke-free policies. Restaurant employees had the highest level of exposure to SHS (67% exposed with 2.95±3.10 h of exposure on average per day) while kindergarten employees had the lowest level (0.5% exposed with 0.01±0.01 h of exposure per day). Compared with employees from kindergartens, non-smoking workers from restaurants and shopping malls reported a higher proportion of respiratory and sensory symptoms and were more likely to suffer from all eight respiratory and sensory symptoms (OR 1.8–8.9). The length of exposure to SHS each day was positively associated with all eight symptoms except runny nose.
Conclusions Workplace exposure to SHS is extensive in Shanghai and the implementation of the current municipal regulation does not provide adequate worker protection. There is an urgent need to establish 100% smoke-free legislation covering all workplaces and public places in Shanghai.
Globally, more than half of all countries, accounting for nearly two thirds of the world's population, still allow smoking in government offices, workplaces and other indoor places, meaning that a majority of workers worldwide are occupationally exposed to secondhand smoke (SHS).1 The WHO has estimated that each year workplace exposure to SHS causes an estimated 200 000 deaths among employees and that one in seven work-related deaths are attributable to chronic exposure to SHS in the workplace.1
Smoking contributes to four of the five leading causes of death in China today2 with the 2007 national tobacco control report declaring that one million deaths per year including 100 000 deaths caused by SHS were attributable to tobacco.3 It is estimated that among the 500 million people exposed to SHS in China, 67% of nonsmokers are exposed in public places such as shopping malls and restaurants and 35% are exposed in workplaces.3 Although the Framework Convention on Tobacco Control (FCTC) has been in force in China since 2006, there is no national law prohibiting tobacco use in indoor public places. Under the encouragement of the central government, some provincial and city governments passed local bans prohibiting smoking in some public places. However, SHS exposure in workplaces needs to be better addressed. Although some research has showed that SHS is a particular occupational health hazard for food-service workers,4 most smoking restrictions in China exclude restaurants and bars. Even in some public places which have been covered by smoking restriction regulations, ineffective strategies such as smoking zones (rooms) still expose employees to SHS.
As an international metropolis in China, Shanghai (population 19.2 million) established a municipal regulation prohibiting smoking in public places as early as 1994 and made some improvements in 1997. However, smoking is only banned in some public places such as cinemas, indoor gymnasia, public transport, waiting rooms, clinical areas and patient rooms in hospitals, indoor areas in schools and kindergartens, and shopping areas larger than 200 m2. As these are regulations rather than laws, they are often poorly enforced and SHS exposure is frequent in public places and workplaces.5 In 2009, the Shanghai government began to draft a new legislation to restrict smoking in the public places.
Most studies examining workplace exposure to SHS and assessing the association between exposure of SHS and common respiratory symptoms have been conducted in western countries and mainly focused on hospitality workers.6–8 A population-based study in Hong Kong did not provide details of exposure to SHS among the specified work groups.9 The objective of this study was to determine and compare the prevalence of workplace exposure to SHS among different working populations as well as identifying any association between reported respiratory symptoms and workplace exposure to SHS. Hopefully, the results of this study can provide useful evidence in evaluating the implementation of the current regulations.
A cross-sectional study was conducted from March to August in 2009. Five districts were randomly selected among the 19 districts in Shanghai (Changning, Huangbu, Qingan, Xuhui, Minhang). In each district, 2 hospitals, 2 schools (one primary school and one junior high school), 2 kindergartens and 15–20 restaurants were selected to present areas where people frequently visit or were popular among local residents. Hotels (four star and above) and shopping malls (larger than 200 m2) were randomly selected from the three downtown districts (Changning, Huangbu, Qingan) due to the wide range of hotels and shopping malls in Shanghai (population 19.2 million). Altogether, 9 hospitals, 9 schools (4 primary schools and 5 junior high schools), 10 kindergartens, 11 shopping malls, 91 restaurants and 20 hotels were involved in the study.
The eligibility criteria for employees included: (1) being 18 years or older, (2) being employed for a minimum of 24 h per week, (3) being employed in the current workplace for at least 30 days and (4) working indoors at least 5 h per day. In restaurants, chefs and outdoor waiters were excluded from the survey. In hotels, only employees working in lobbies were involved in the survey. Approval for this study was obtained from the Ethics Committee of the School of Public Health, Fudan University.
In each of the selected establishments, we asked the manager to provide a list of staff meeting the above criteria. All employees on the list were approached by us to participate in the survey. Once their permission had been obtained, the investigators conducted face-to-face interviews using standardised questionnaires. In total, 3925 workers were targeted and 3530 agreed to participate (89.9% response rate).
The sample size was calculated by estimating the prevalence of SHS exposure among the working population. The previous study in China estimated a SHS exposure prevalence of 35% in the workplace among nonsmokers.3 It was estimated that 87 subjects were needed for each group in order to obtain an α level of 5% with statistical power of 90%. However, considering the proportion of nonsmokers in the whole study population as well as the variation of prevalence of SHS exposure among the different work groups, we enlarged the sample size to 200 for each work group.
Participating employees provided information on demographics, sources and hours of SHS exposure, and respiratory symptoms. SHS exposure was assessed by asking ‘In a typical working day, how many hours are you exposed to other people's tobacco smoke indoors at work?’ Respondents who self-reported 0 h of exposure were classified as not exposed, while the others were classified as exposed. To measure SHS exposure at home, participants were asked ‘Do you live with a smoker?’ Exposure to SHS other than at work or home was measured by asking ‘How do you assess your exposure to SHS in settings other than home and work? (1) often, (2) sometimes, (3) seldom, (4) never’.
Survey participants were asked to identify the workplace smoking policy that was most similar to theirs: (1) smoking is not allowed anywhere in the workplaces, (2) smoking is allowed only in designated areas, (3) smoking is allowed in most areas. The item selected by most workers was defined as the policy type in each worksite.
Compliance with the smoking policy was assessed by asking ‘If there is some restriction on smoking in your workplaces, how do you assess the enforcement of the policy? (1) enforced most of the time, (2) enforced sometimes, (3) seldom enforced’. The worksite was recorded as being compliant only if over 60% of respondents reported that the policy could be enforced most of the time.
The International Union against Tuberculosis and Lung Disease's Bronchial Symptoms Questionnaire was used to assess the adverse health effects of SHS exposure.10 Five upper respiratory symptoms were surveyed, including wheezing, dyspnoea, morning cough, cough during the rest of the day or night, as well as phlegm production. Three sensory symptoms were surveyed including red or irritated eyes; runny nose, sneezing, or nasal mucus; and sore throat. Respondents were asked if they had experienced any of the above symptoms in the previous 4 weeks. To assess the presence of other conditions, including those that could potentially account for these symptoms, participants were also asked whether they had experienced a cold in the preceding 4 weeks, had doctor confirmed asthma or any other health conditions that caused respiratory problems.
We categorised employees into two groups: current smokers and nonsmokers. Being a current smoker meant any smoker who had ever smoked more than 100 cigarettes in his/her life and had smoked in the past 30 days. Nonsmokers were identified as those who had smoked less than 100 cigarettes in their life time, or those who had not smoked (even a puff) in the past 30 days.
To evaluate the impact of the municipal regulation, we recorded the working population in one of two groups. Group 1: workers in worksites covered by the municipal regulation such as shopping malls, schools, hospitals and kindergartens. Group 2: workers in worksites not covered by the municipal regulation including restaurants and hotels.
Fisher's exact test or the χ2 test was used to examine group differences for categorical variables, and the Student ttest was used to examine differences between groups for continuous data. Logistic regression models were used to investigate predictors of respiratory symptoms after adjusting for possible confounding factors. The control variables included in the analyses were presence of cold, asthma, respiratory conditions, home SHS exposure and other exposure to SHS, age, gender and education.
All subjects were included in estimating workplace exposure to SHS. However, only nonsmokers were included when assessing the proportion of subjects suffering from respiratory symptoms and evaluating the relationship between the workplace SHS exposure and respiratory symptoms.
There were 3530 workers from 150 worksites (classified into six workgroups) who completed the survey. Of these, 18 (12.0%) of worksites had a total smoking ban, which covered 13.3% employees. Even among the 39 worksites covered by municipal regulation, only 14 (35.8%) banned smoking with 92.9% being compliant. There were 63 (42.0%) worksites which had designated smoking areas and 39 (61.9%) were compliant. Regardless of whether worksites were covered by the municipal regulation, the proportion of compliance among the worksites with smoking ban was higher than that of worksites only with designated smoking area (94.4% vs 61.9%) (table 1).
Although there were some worksites covered by the municipal regulation, total bans were not common with most (except kindergartens) adopting designated smoking areas. Table 2 shows exposure to SHS among different working populations. Municipal regulation was best enforced among kindergartens where only 0.5% employees reported exposure to SHS at work with an average 0.01 h of exposure per day. The low level of SHS exposure in kindergartens may be due to the high proportion of females in these worksites who rarely smoke. With the least protection from municipal regulations and worksite smoking policies, restaurant workers were exposed most to SHS with the highest proportion (67%) and longest average exposure time per day (2.95 h). In spite of being excluded by the municipal regulation, most hotel lobbies have a designated smoking area (usually bars or cafes). In all, workers in group 1 (covered by municipal regulations) had significantly lower levels of exposure to SHS (exposed: 30.7%, shift exposure: 0.90±1.75 h) than those in group 2 (not covered by municipal regulations) (60.9%, 2.31±2.84 h, respectively).
Although not covered by municipal regulations, some restaurants had established their own smoking policy (most were chain restaurants such as McDonalds). Table 3 compares exposure to SHS among the restaurant workers under different smoking policies. Workers in the smoke-free restaurants had lowest prevalence of current smoking and exposure to SHS. However, even in the smoke-free restaurants, there were still 24% employees who reported being exposed to SHS at work. In spite of this, workers' estimates about compliance in the smoke-free restaurants were still significantly higher than those in restaurants with smoking and non-smoking sections (81.1% vs 69.9%).
Logistic regression analysis showed that, after adjusting for other sources of SHS exposure and other potential confounders, compared with working in kindergartens working in shopping malls and restaurants was significantly associated with an increasing likelihood of having all the eight symptoms. Hotels workers were also significantly more likely than kindergarten workers to report the above symptoms except wheezing and morning cough. No increasing likelihood of respiratory symptoms was found among employees in hospitals and schools. Compared to kindergarten employees, workers in restaurants, shopping malls and hotels were more likely to report any respiratory symptoms (OR=7.5, OR=4.8, OR=3.1, respectively) (table 4).
The same logistic regression analysis method was applied to compare those working at sites covered by municipal smoke-free regulation and those not covered. The results showed that workers in worksites not subject to the municipal regulation were more likely to suffer from six respiratory and sensory symptoms compared with those covered by the regulation (table 5).
Logistic regression was also used to examine association between hours of workplace exposure to SHS per day and each respiratory symptom. The potential confounders we adjusted for were the same as those in tables 4 and 5. The results showed that the average hours of exposure to SHS per day at work was positively associated with all symptoms we evaluated, except runny nose. The risk of suffering from any symptom increased by 1.11 times with one more hour of exposure to SHS at work per day (figure 1).
China, as the nation with the world's largest population, is the most important country in the global tobacco control effort.5 To the best of our knowledge, this is the first study to estimate the workplace SHS exposure as well as the prevalence of sensory and respiratory irritation symptoms among large working populations on the mainland of China. Just as most international studies have focused on SHS exposure in hospitality venues such as bars, pubs and casino workers,6–8 11 12 this study provides a comprehensive map of data on SHS among several different working populations in China, including the hospitality industry. The study also provides important evidence in evaluating the enforcement of the current municipal regulation which has been implemented since 1994.
The highest level of exposure to SHS among the different worksites was among restaurant employees. This is almost certainly a reflection of the lowest implementation of smoke-free policy in these settings. Although restaurant workers were the worker group who experienced most symptoms from SHS, they remain excluded from smoke-free legislation. The results of our study support the need of a comprehensive smoke-free legislation, covering all workplaces, including restaurants and hotels.
Because of the weakness of the municipal regulation, protection of the working population provided by the current regulation is quite limited. In the 39 worksites covered by the municipal laws in this study, only 14 banned smoking in all indoor areas. It is not surprising that workers in shopping malls covered by the regulation were still mostly (64%) exposed to SHS for an average of 1.79 h per day. The high level of exposure to SHS was also associated with high reports of respiratory and sensory symptoms among workers in shopping malls. Our site visiting found that in these malls some smokers (including the employees) smoked in restrooms and employees' cafes. The regulation only prohibits smoking in the shopping areas, not in these other areas.
As expected, compared to workers in restaurants with smoking zones or without any restrictions, workers in smoke-free restaurants were better protected from exposure to SHS, having the lowest proportion of exposed workers and shortest duration of exposure per shift. Workers in restaurants with smoking zones had a similar level of exposure to SHS of workers who worked in restaurants without any smoking restriction. This finding is consistent with conclusions from other studies that spatial separation does not prevent exposure to SHS.13
The failure of voluntary smoke-free policies to protect workers from exposure suggests that such voluntary policies are unlikely to provide satisfactory protection. This study shows that workers' estimates about compliance were higher in smoke-free restaurants than those working in restaurants with separate smoking sections. This may imply that total bans may be easier to implement. However, the 24% who were exposed to SHS with these voluntary smoke-free policies still indicate that such voluntary policies are difficult to implement completely. Therefore, making all indoor workplaces smoke free is the only effective and feasible method to protect the health of the working populations and customers who visit those workplaces. Although there were some anecdotes that smoke-free restaurants may have a negative impact on business, many international studies have shown that cafes and restaurants do not experience any negative economic effects and may even experience some positive effects after the introduction of smoke-free laws.14 Another study in Shanghai also indicated that smoke-free policy may even increase the intent to eat out among restaurant customers.15
Seven respiratory and sensory symptoms were increased with increasing level of workplace exposure to SHS, when measured as reported hours exposed per day. Workers in restaurants and shopping malls who had high levels of exposure to SHS at work experienced a significantly increased risk of respiratory symptoms after adjusting for demographic factors, SHS exposure outside work and other confounding factors. The study adds to evidence from previous studies that higher exposure to SHS is associated to a poorer respiratory and sensory symptom profile.7 9 12 The dose–response relationship showed in this study provides powerful evidence to support the establishment of smoke-free policy in workplaces. Because respiratory and sensory symptoms are reversible,12 a smoking ban in workplaces can decrease these occupational symptoms and prevent more severe diseases such as COPD, coronary heart disease and lung cancer.
There are some potential limitations in this study. First, as a cross-sectional study, there is uncertainty of temporal sequence between exposure and outcome variables. It is unclear whether workers experiencing exposure to SHS were more likely to report symptoms, or if the workers with respiratory symptoms would intend to attribute their symptoms to exposure to SHS. Several prospective studies have confirmed the casual association of workplace exposure to SHS and the frequency of respiratory symptoms.9 16 All these findings strongly support the importance of smoke-free policies to improve the occupational health.
Second, the exposure to SHS in this study was self-reported, which may lead to some recall bias. However, other studies have confirmed that self-reported exposure is a valid measure with self-reported levels being consistent with biological markers such as urinary and salivary cotinine.6 7 In this study, we found a very high consistency between smoking policy and exposure to SHS among the restaurant workers, suggesting that the measure we used in this study was reliable. However, we recommend that, where research resources permit, objective measures like continine should be used to evaluate exposure to SHS.
Finally, the ‘healthy worker effect’ may operate in this study. The most susceptible workers or those who suffer most from SHS may change their work to avoid this exposure which may lead to an underestimation of the relationship between exposure and symptoms.
Although the FCTC has been in force since 2006, tobacco control efforts in China still meet some obstacles due to the large smoking population and the role of tobacco industry in the economy. Recently, the Shanghai government has instituted new legislation on smoking restrictions in public places. However, although considerable achievements have been made in creating a smoke-free environment, there is still a big gap between the legislation and the standards set out in the FCTC. For example, although it is well known that hospitality workers suffer most from SHS and either ventilation or smoking separation cannot provide complete protection,17 18 smoking zones (rooms) are still permitted in some public places including restaurants. The global plan of action on workers' health (2008–2017) emphasises the elimination of SHS from all indoor workplaces to protect and promote health at workplace.19 We hope the evidence of this study will support further steps towards the introduction of 100% smoke-free workplaces.
What this paper adds
Workplace exposure to SHS in China is widespread and has not been well addressed. This study provides a comprehensive map of workplace SHS exposure among several different working populations in Shanghai and indicates its association with respiratory symptoms. Workplace smoking bans are urgently needed in China to improve occupational health.
Funding This work was supported by the Bloomberg Initiative to Reduce Tobacco Use Grants Program (China 2-29).
Competing interests None.
Patient consent Obtained.
Ethics approval This study was conducted with the approval of the Approval for this study was obtained from the Ethics Committee of the School of Public Health, Fudan University.
Provenance and peer review Not commissioned; externally peer reviewed.
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