Public support for smoke-free policies in outdoor areas and (semi-)private places: a systematic review and meta-analysis

Introduction

Exposure to second-hand smoke (SHS) poses a major burden to population health globally. Each year, 1.2 million deaths and 36.3 million disability-adjusted life years (DALYs) are attributed to SHS exposure.¹ Compelling evidence indicates that comprehensive legislation to protect non-smokers from tobacco smoke exposure in all indoor public places and workplaces is a powerful tool to reduce the adverse effects of tobacco smoke, including among children.1, 2, 3 In an attempt to further improve population health, an increasing number of jurisdictions have expanded smoke-free policies to encompass outdoor places (e.g., public parks, pedestrian plazas and beaches),⁴ semi-private places (e.g., public housing units),⁵ and private places (e.g., cars).⁶ Emerging evidence shows that such “novel” policies can indeed be effective in further reducing the burden of SHS exposure in children.^7,8

Public support is important for policymakers to consider implementing novel smoke-free policies and to maximise compliance.⁹ The World Health Organization (WHO) stated in their 2009 report on the global tobacco epidemic that ‘involving civil society is central to achieving effective legislation’.¹⁰ Previous literature has shown large differences in public support between various smoke-free places and within populations. For example, in the USA and Canada playgrounds generally received a higher degree of support compared to sidewalks, and smokers are generally less in favour of smoke-free policies than non-smokers.¹¹ To inform policy-making regarding extending smoke-free policies, it is thus important to derive insights into the levels and determinants of public support for smoke-free policies that cover outdoor areas and (semi-)private places.

Therefore, the primary objective of this study was to systematically review evidence on the levels and determinants of public support for smoke-free policies covering outdoor places or (semi-)private places, henceforth referred to as ‘novel smoke-free policies’. To our knowledge this is the first comprehensive overview of support for novel smoke-free policies that is not limited to a specific smoke-free place or geographic region. Our secondary objective was to identify which personal and country-level characteristics are associated with public support for these policies.

Methods

Results

14,749 records were identified from the databases. Duplicates and reports published before 2004 were omitted, resulting in 6229 unique records to screen. Full-text records were assessed for 348 records and 107 reports were included (Fig. 1).22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120, 121, 122, 123, 124, 125, 126, 127, 128 The included reports presented estimates of public support for novel smoke-free places from 33 different countries. Appendix II reports the geographic location, the smoke-free place, measure of support, sample size, and the reported support per study.

Most reports (n = 67) assessed support for hypothetical scenarios, i.e., support for smoke-free places not yet in place without referring to concrete plans for implementation or actual implementation (see Appendix III).22, 23, 24, 25, 26, 27^{,29,30,33,34,39,42,43,}47, 48, 49, 50, 51^,56, 57, 58^,60,61,63, 64, 65, 66, 67, 68^{,71,72,74,75,}77, 78, 79^,81,83,85, 86, 87^,89, 90, 91, 92, 93^,95,99,100,102, 103, 104, 105, 106^{,108,110,112,115,116,119,120,}123, 124, 125, 126^,128,129 Four reports assessed support for smoke-free policies that were likely to be implemented,¹⁰⁷ or for possible extensions of—or additions to—existing policies.^54,105,118 Thirty-six reports assessed public support for policies that were already implemented (Appendix IV), among which five were introduced at the national level: smoke-free cars with children or pregnant women in Italy⁸²; a smoke-free prison policy in Scotland^37,114; and a smoke-free public housing act in the USA.^88,121 In the remaining thirty-one studies support for local smoke-free policies was assessed regarding university or college campuses,^{31,35,38,41,52,76,84,97,109,127} school grounds,^40,113 hospital grounds,^{40,59,80,117,122} playgrounds,^45,113 parks and beaches,^{28,54,73,94,107,111,118} multi-unit housing,^44,46,70 and outdoor gathering places such as streets.^28,32,98

Discussion

This systematic review and meta-analysis including data from almost 900,000 unique participants from 33 different countries indicates high levels of support for smoke-free policies in the majority of outdoor areas and (semi-)private places. Support was particularly high for smoke-free places where children are commonly exposed to tobacco smoke, such as cars carrying children, playgrounds, and school grounds. Except for outdoor private areas, support was 50% or higher for all places evaluated. Non-smokers and ex-smokers were more in favour of smoke-free policies than smokers.

Strengths of the study include the comprehensive search in six databases, and the absence of any language restriction. With 107 reports included covering data from 33 different countries, the body of existing literature describing support was substantial. Data from 99 studies were pooled for 15 different areas of smoke-free policies, and we accounted for potential clustering at country-level by applying a three-level meta-analysis. Hence, we accounted for variance at participant, study, and country level. In addition to the meta-analysis we conducted subgroup analyses, meta-regression, and sensitivity analyses, providing additional insight in the patterning of public support for novel smoke-free policies. Sensitivity analyses generally showed no meaningful differences in support between lower and higher risk-of-bias studies, suggesting that the evidence is robust.

A limitation of this study is that generalisability to other countries from which no surveys were available may be limited. Although there was no indication for publication bias, countries included might be subject to bias, as it is likely that countries planning for novel ways to reduce negative harms of tobacco among the population are more likely to survey support for such policies. This is reflected by the large number of studies from the USA where traditional smoke-free policies are already commonplace, and the low proportion of studies from LMICs, where governmental actions regarding tobacco are commonly more limited. Thirteen reports with 69 estimates in our systematic review were from 11 LMICs. The majority of estimates included in the meta-analysis (33%) however, were from one country (i.e., republic of Georgia). Other limitations of this study concern the different ways in which support was assessed. We did take into consideration the type of answer categories, and did not find large differences when participants were asked if they supported smoke-free policies with a yes-no question or on a Likert scale. Some papers reported proportion not in favour of a policy and outcome estimates were reversed. Although for one study this led to the reported outcome including neutral and positive answers, potentially overestimating support, any bias resulting from this will be very limited. Negative or positive framing of a question might also influence the response.¹³² These aspects may have contributed to the substantial heterogeneity observed across studies, in addition to existing cultural and contextual differences. Finally, the minimum sample size requirement of 400 participants might have caused an underrepresentation of locations with smaller populations, such as subsidised housing or inpatient facilities. For a complete overview of excluded full reports see Appendix XI.

Previous studies have shown strong increases in support for novel smoke-free policies over time,¹¹ which was not confirmed in our study. Since support was generally high, it is possible that support already reached a plateau, after which little change is observed. Policy makers might be concerned that actual implementation can backfire support. Our review indicates that this concern is not backed by previous literature, with 6 out of 12 studies that assessed support before and after implementation showing an increase in support.^{31,45,59,76,122,127} Among the remaining studies support was often already high, indicating a plateau in support.^52,70,76,114 An additional worry could be that support is theoretical and might change when it regards actual implementation. However, our study showed no differences in support between implemented policies and hypothetical scenarios. For outdoor non-hospitality places, the group with most estimates, no significant differences were found, indicating support is equally high for hypothetical questions as for implemented policies. Another consideration for policy makers could be that a high level of support may not necessarily ensure adequate compliance with smoke-free policies, especially in places where enforcement is challenging. Additional research is needed to investigate optimal approaches to enforcement, including self-enforcement in places where formal regulation is lacking.

Public support is an essential element facilitating policy implementation. We identified highest levels of support for places where children are frequently exposed to tobacco smoke. For example, support for smoke-free cars when driving with children was much higher (86%) compared to a generic policy making cars smoke-free (57%). Similarly, support for smoke-free playgrounds (80%) was higher compared to support for smoke-free parks and beaches (53%). On average, support was highest for indoor private places; this was primarily driven by the high level of support for smoke-free cars carrying children. Apart from that, support was generally higher for semi-private places compared to private places. For example, support for smoke-free regulations in multi-unit housing (76%) was higher compared to private housing (59%).

Of all places evaluated in our study, the highest level of support was found for smoke-free cars: eight out of ten participants were in favour of cleaning the air in cars when children are present. This is in agreement with a previous brief review of support for smoke-free cars, which included studies up to 2008.¹³³ Our report, including studies up to 2022, similarly shows consistently high levels of support for smoke-free cars with children. This is important given the established impact of smoke-free car policies, which have been shown to reduce exposure to second-hand smoke by 31%,^7,134 and reduced paediatric hospital admissions for asthma in Scotland.¹³⁵

A similarity between the places with highest support was their link with children, suggesting the effectiveness of approaching tobacco control as a child health issue.¹³⁶ In addition to protecting children from tobacco smoke exposure, smoke-free policies in these places also protect children through role-modelling, i.e., being less exposed to smoking imagery which decreases their risk of becoming a smoker.^137,138 This perspective is especially important to justify smoke-free policies in outdoor areas that are well ventilated but have many underage visitors, such as beaches. Another argument for banning smoking in such areas is its impact on reducing littering from cigarette butts, which contain microplastics and other toxic substances that pollute the environment.^139,140 Such aspects may be used to inform the public of why smoke-free policies are important, other than directly protecting individuals from being exposed to other people’s tobacco smoke.

The large number of reports included enabled us to evaluate differences in support between population subgroups. Perhaps unsurprisingly, higher levels of support were found among non-smokers and former smokers compared to current smokers.^11,141 Furthermore, subgroup analyses identified a small difference in support among men and women, with higher levels of support among women. This may be because women generally perceive SHS as more harmful compared to men,¹⁴² and see smoking as less socially acceptable.¹⁴³ As voluntary smoke-free rules are already often applied by parents in places such as private homes and cars,144, 145, 146 we anticipated that levels of support would be higher among parents. However, no significant differences were found between parents and non-parents. This pattern more widely applied to smoke-free places involving children, which may indicate that child health is not solely a matter of parents, but regarded important by society at large.

The results presented in this paper indicate that the majority of the surveyed population is in favour of smoke-free environments beyond places currently being legislated. The consistent high level of support for smoke-free policies in cars carrying children in particular, indicates momentum for increased implementation of regulation in this area. Support was consistently high not only for cars carrying children but for all places where children often go. Framing smoke-free policies as a children’s rights or child health issue as part of a broader smoke-free or tobacco-free generation initiative can provide a good starting point for implementing novel smoke-free policies.^147,148 Furthermore, smoke-free policies that go beyond enclosed public places and the workplace should be part of a comprehensive tobacco control programme, including other measures such as tax increases, reducing the number points of sale and banning tobacco display. How support for one measure affects other measures could be assessed in future research.

Support for novel smoke-free policies is generally high across countries, especially for policies in places where children are present. This indicates that there is substantial momentum for policy-makers to take the next step in protecting the public, and children in particular, from the harmful effects of tobacco smoke exposure by expanding smoke-free policies.

Contributors

JVB secured funding for this work. NWB, FJMM, AzS, AB, FJvL and JVB designed the study and wrote the protocol paper. NWB, AsS and EL contributed to the search, study selection, data extraction and risk of bias assessment. NWB conducted the data analyses and created the figures. JVB supervised the review process. NWB, FJMM and JVB verified the underlying data. NWB, FJMM and JVB drafted the manuscript, AzS, AB and FJvL provided feedback. All authors interpreted the analyses, read and approved the final manuscript, had full access to all the data in the study and had final responsibility for the decision to submit for publication.

Data sharing statement

All datasets generated and analyses are available in the article and the appendix.

Declaration of interests

NWB was funded by the Smarter Choices for Better Health Programme from Erasmus University. JVB is PI of a research project to tailor a National Smoking Cessation Programme for (future) parents funded by the Erasmus Initiatives Smarter Choices for Better Health Programme and the Dutch Ministry of Health, Welfare and Sports payed to Erasmus MC. JVB is member of the National Taskforce Smokefree Start, a collaboration of professional organisations involved in the care of pregnant couples, parents, and children aimed at supporting a smoke-free start. This Taskforce is supported by the Trimbos Institute and the Dutch Ministry of Health, Welfare and Sports. Fees for participation in the Taskforce are paid to Erasmus MC. JVB chairs the Taskforce Smokefree Erasmus MC which aims to support a smoke-free hospital environment and optimise smoking cessation support for patients and employees. JVB is a committee member for the national multidisciplinary guideline on tobacco addiction treatment and smoking cessation support.

Appendix A. Supplementary data