Tobacco smoke is one of the most common asthma triggers. Asthma may be caused by smoking, and childhood exposure to secondhand smoke (SHS) increases the risk for asthma exacerbations [
]. Chronic obstructive pulmonary disease (COPD) accounts for 73% of smoking-related conditions among current cigarette smokers and 50% among former smokers [
]. Cigarette smoking is the most important risk factor in the development of COPD, as well as the most important modifiable risk factor in reducing the progression and severity of COPD [
]. Reduction in cigarette smoke exposure can reduce the incidence of new cases and exacerbations of COPD and asthma [
Protecting the public from exposure to tobacco smoke is a key component of the World Health Organization (WHO) Framework Convention on Tobacco Control [
]. After four decades, worldwide smoke-free policies and laws are still works in progress [
]. Partial or comprehensive smoke-free workplace laws are in place in 36 of the 50 United States (US) as well as 92 nations worldwide [
]. Nearly 50% of the US population is covered by comprehensive smoke-free regulations and over 80% are covered by partial smoke-free policies. Smoke-free policies and laws have been associated with reduced exposure to SHS and reductions in smoking prevalence [
]. The effects of smoke-free policies and laws among populations are difficult to accurately measure due to the number of potential environmental confounders. Despite this limitation of epidemiologic studies, the association between the smoke-free policies and the reduction of SHS exposure has been unequivocally demonstrated [
]. Studies have shown a 72% drop in environmental measures of SHS within one year of smoke-free workplace law implementation and a median decrease of 6% in self-reported exposure to SHS [
]. In 2009, there were approximately 2.1 million asthma-related emergency department (ED) visits in the US, which translated to 69.7 asthma-related visits per 10,000 [
]. In 2010 the rate for COPD-related ED visits was 1.5 million, which translated to 72 ED visits per 10,000 [
]. In this study, we evaluated the impact of the implementation of a state-wide clean indoor air law in 2007 (i.e., Freedom to Breathe Act) on the frequency of ED visits for asthma and COPD [
] within Olmsted County, Minnesota (MN).
In this study, we observed a reduction in asthma-related ED visits for both adults and children following the enactment of the smoke-free workplace law. Other investigations have evaluated the association between smoke-free laws and asthma incidence, symptoms, hospitalizations, and asthma-related ED visits [
] with similar findings. Our findings are in keeping with a number of studies demonstrating the health benefits of smoke-free indoor air laws, particularly with regard to asthma. Investigators in Kentucky evaluated ED visits for asthma from four different hospitals, comparing rates before and after implementation of a smoke-free law. A 22% reduction in asthma-related ED visits after implementation of the smoke free law was observed [
]. The percentage reduction in asthma-related ED visits is similar to our results. In slight contrast, a study in England evaluating the impact of smoke-free laws on emergency room admissions observed only a 4.9% reduction in asthma-related ED visits after implementation of the smoke-free laws [
]. In a multi-state study, hospital discharge rates for asthma were compared between 12 states with strong smoke-free laws and 5 with weak or no smoke-free laws. A significant reduction in hospital discharges for asthma was observed in states with strong smoke-free laws [
]. Additionally, a recent review of 45 studies focusing on 33 smoke-free laws found a 24% reduction in overall respiratory disease hospitalizations and deaths [
]. This study, with a median follow-up of two years after smoke-free law implementation, observed that the risk of hospitalization and death from tobacco-caused disease does not change with longer follow-up, suggesting that risk reductions will likely be sustained over time [
]. An Arizona study comparing hospital admissions between counties with and without smoke-free policies for the four major tobacco-related diseases (acute myocardial infarction, angina, stroke, and asthma) found a reduction in hospital admissions for these diseases among those counties with a smoke-free policy; notably, asthma admissions were reduced by 22% [
When a smoke free policy has been enacted in a stepwise fashion, an association with asthma incidence has not always been found to be consistent between steps. Two studies evaluated more than two periods during smoke-free policy enactment and found little to no association. Investigators in Toronto, Canada who reviewed multiple periods during smoke-free policy enactment and implementation found a large decrease in respiratory conditions overall when the smoke-free law was implemented for restaurant settings, but found no subsequent change when the law was extended to other indoor settings [
]. A study conducted in Geneva looked at hospital admissions in one hospital during four differing time periods in the smoke-free law enactment and implementation process; and although a similar analysis (adjusted Poisson Regression) was used, they found the reverse of our findings. In their study, they found a reduction in COPD hospital admissions but not in asthma admissions [
Data concerning the impact of the smoke-free policy upon ED visits by asthmatic youth are more robust. A study in Ireland evaluating the impact of the nationwide smoke-free policy showed a larger reduction in asthma-related ED visits (RR = 0.60) for the younger age group compared to overall asthma-related ED visits (RR = 0.85) [
]. This is consistent with our study findings of a larger reduction in asthma-related ED visits in children (RR = 0.75), compared to overall asthma-related ED visits (RR = 0.81). In another study in England smoke-free policies were temporally-related to a 12.3% reduction in childhood asthma-related ED visits [
]. A study in the US, which reviewed data among youth from the National Health and Nutrition Examination Survey (NHNES) between 1999 and 2006, observed a significant reduction (OR = 0.66) in asthmatic symptoms related to the implementation of smoke-free laws [
]. In Scotland, a trend for increasing childhood asthma-related ED visits (+5.2% per year) was observed prior to smoke-free law implementation, but a significant decrease in childhood asthma-related ED visits (-18.2% per year) was found after the law was implemented, yielding a net reduction of 13% per year following the smoke-free policy implementation [
]. Among children in our current study, we found that an upward trend in ED visit rates (+1.1% per month) for asthma prior to the passage of the smoke-free law was reversed, resulting in a downward trend (-0.4% per month) following the implementation of the law.
The findings that asthma-related ED visits were significantly reduced after the smoke-free law implementation, but the COPD-related visits were not significantly reduced, is not surprising. The lack of findings with COPD-related visits confirms findings from a recent meta-analysis [
]. Typically COPD is associated with irreversible or minimally reversible airway obstruction, unlike the bronchospasms in asthma, which can be severe but may be completely reversible. Exposure to triggers such as SHS may precipitate acute bronchospasms in asthmatics and is more likely to increase respiratory symptoms but not acute bronchospasms in people with COPD. Acute exacerbations of asthma often require emergency treatment or hospitalization to reverse. In communities with strong smoke-free laws, the changes in COPD-related hospital and ED admissions may be seen 12 months or more after implementation of the law [
]. This likely reflects the slower improvement seen in COPD symptoms and exacerbations as SHS smoke exposure declines. This may also explain the variable effects that are noted in studies of smoke-free laws on COPD adverse events. Investigators in Ireland, using time series analysis, evaluated the impact of the nationwide smoke-free law and found an effect only for COPD mortality only among females [
]. An ecological analysis of hospital discharge rates in Texas found a reduction for COPD hospital discharges only for white patients after implementation of the smoke-free law [
]. The greatest impact of smoke-free laws on COPD may be the effect they have on encouraging smokers to quit smoking, thus reducing the risk of COPD progression. This impact would be seen over the longer term and may be variable among the affected populations, consistent with the empirical data from population-based studies.
Our finding of decreased asthma-related ED visits following implementation of a statewide smoke-free law is biologically plausible and consistent with the known causal relationship between cigarette smoke exposure and exacerbation of pulmonary disease symptoms [
] as well as with previous observations of the relationship between smoke-free policies and reductions in SHS exposure and respiratory symptoms. The WHO estimated that smoke-free policies are associated with 40% (widespread) to 80%-90% (in high exposure setting) reductions in SHS exposure [
]. This report has been supported by a systematic review of over 50 studies addressing the role of the smoke-free policies on exposure to SHS [
]. In this systematic review, the studies addressing the role of SHS exposure consistently found a reduction of SHS in public places (workplace, restaurants, and bars) of about 72% within one year of a smoke-free law implementation [
]. This review also reported reductions in both reported respiratory and sensory irritation symptoms after smoke-free law implementation in 10 studies [
]. These sensory symptoms included wheezing or whistling in chest; shortness of breath; cough; phlegm; red, teary, or irritated eyes; runny nose or sneezing; and sore or scratchy throat. An additional study, not included in the prior referenced review, is a cross-sectional telephone survey of 382 nonsmokers in the workplace, which showed a positive dose–response relationship between exposure to SHS and increased reports of respiratory ailments [
]. Another study, which evaluated the impact of workplace and pub smoke-free laws in Ireland, collected air samples and conducted pulmonary function tests among 81 employees of 42 pubs before, and 1 year after, the law was implemented [
]. Using particulate matter, benzene concentration, expired air carbon monoxide, and salivary cotinine, the researchers found a 90% reduction to SHS exposure (i.e., 83% reduction in particulate matter 2.5 μm or smaller, an 80% reduction in benzene concentration, a 79% reduction in expired air carbon monoxide, and an 81% reduction in salivary cotinine), a significant improvement in respiratory function, and a decrease in other respiratory symptoms in nonsmokers after implementation of the law [
Our study has several limitations. First, we did not measure actual SHS exposure in different environments around the community. Second, our study data was limited only to ED visits which were for the most part, ambulatory and did not include hospital admissions for the local hospitals. Third, other tobacco control efforts were occurring during the study period, which could have contributed to the decrease in smoking prevalence and to reductions in SHS exposure. For example, from 1999 through 2010, the per capita cigarette sales in MN declined by 40% and smoke-free homes increased from 64.5% (1999) to 87.2% (2010) [
]. Other activities included a marketing campaign for the state tobacco quitline and local clinic tobacco treatment services and a 2004–2007 mass media campaign focused on the hazards of SHS. Despite these limitations, the data presented does parallel the 22% postban reduction of respiratory ED visits associated with the smoke-free law of other geographic locations [
JOE – Dr. Ebbert reports personal fees from GlaxoSmithKline, grants from Pfizer, Inc, and grants from Orexigen, outside of the submitted work.
JTH – Dr. Hays reports grants from Pfizer, Inc, outside of the submitted work.
RDH – Dr. Hurt reports an education grant from Pfizer Medical Education Group, outside of the submitted work.
ITC, DRS, AMC, VLR. The authors declare that they have no competing interests.
ITC – Participated in the study design and coordination and provided administrative, technical, and material support. Had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Drafted the manuscript and participated in critical revision of the manuscript for important intellectual content. JOE – Participated in the study concept and design and in critical revision of the manuscript for important intellectual content. JTH – Had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis, and participated in critical revision of the manuscript for important intellectual content. DRS – Participated in the study design. Had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis, and participated in critical revision of the manuscript for important intellectual content. AMC – Performed statistical analysis and participated in critical revision of the manuscript for important intellectual content. VLR – Conceived the study concept and design; helped to obtain funding and provided administrative, technical, and material support. Had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis, and participated in critical revision of the manuscript for important intellectual content. RDH – Conceived the study concept and design; obtained funding and provided administrative, technical, and material support. Had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis, and participated in critical revision of the manuscript for important intellectual content. All authors read and approved the final manuscript.