A look at second-hand smoking

Background

A person smoking causes bystanders to inhale second-hand smoke (SHS). Also called passive smoke, second-hand smoke is what a smoker produces for those around him/her to inhale themselves: what emanates from the burning tip of the cigarette or cigar or pipe being smoked added to the smokers' actual breathing out of the inhaled substance. The burning cigarette produces side-stream smoke and makes up 85% of passive smoke while what the smoker exhales, mainstream smoke, contributes to second-hand smoke by only 15%. This smoke is a mixture of gases and particles containing thousands of chemicals of which hundred cause disease.

Active smoking was first shown as being statistically linked to lung cancer a century and a year ago, but it wasn't until after 1950 that smoking as causally linked to respiratory and cardiovascular disease was established. Indeed, alongside the publications of two American researchers and a German one, British psychologist and epidemiologist Richard Dole, (together with statistician Austin Bradford Hill), presented the results of a case-control study showing that among lung cancer cases, there were more smokers than among those free of lung cancer. Richard Dole continued his inquiry with the British Doctors Study, where 2/3rd of all British male physicians (40,000) volunteered to answer questionnaires regarding their health and smoking habits. The results of that epidemiological study showed - with a degree of certainty close to that of a randomised controlled study -, that both lung cancer and myocardial infarction occurred more often in smokers than in non-smokers. In 1964, the United States Surgeon General's Report on smoking and Health was published; this led millions of American smokers to quit, the banning of certain advertising, and the requirement of warning labels on tobacco products.

A section of the 1972 Surgeon General's report was devoted to second-hand smoke for the fist time and was the object of full report in 1986 and 2006 thereafter. In Europe, the European Union started issuing laws regarding promotion and advertising of tobacco in 2001. The 2005 WHO Framework convention, the first international treaty under the auspices of the World Health Organization has been ratified by 168 parties - the US is one of the 9 countries such as Cuba and Switzerland that have signed yet have not ratified the treaty). It provides a framework for tobacco measures to be implemented. 

This review summarises the effects of passive smoke and takes a look at smoking ban laws - with a particular view to acute myocardial infarction. 

I - Effect on Health

Passive smoke is one of the most preventable causes of coronary artery disease (CAD), and of acute myocardial infarction (AMI) (1) next to obesity and a sedentary lifestyle.
Toxins produced by SHS directly affect the cardiovascular system through well known multiple mechanisms, such as an increase in platelet activation, endothelial dysfunction, oxidative stress and inflammation, among others (2,3,4). Several studies, have shown the reduction of AMI incidence after implementation of smoking bans in public places in a variety of countries (5,6,7,8,9).

Second hand smoking may induce AMI through such mechanisms as the prothrombotic state, increased myocardial workload, reduced oxygen-carrying capacity of blood caused by carbon monoxide, coronary vasoconstriction, and cathecholamine release. 

Moreover SHS is responsible for accelerating atherosclerosis by lipid profile alteration, endothelial dysfunction and damage, hemodynamic stress, oxidant injury, neutrophil activation, enhanced thrombosis, increased fibrinogen and blood viscosity (3). Even a brief exposure to SHS can cause platelet aggregation and other hemodynamic changes favoring AMI onset and this effects seem to disappear a short time after SHS exposure cessation. There is no safe level of exposure to cigarette smoke. 

Specifically, the effects of SHS on the cardiovascular system are 1) platelet activation 2) endothelial dysfunction and 3) atherosclerosis with low HDL levels, high LDL levels, plaque instability, increased LDL oxidation, increased oxidative stress, decreased energy metabolism, increased insuline resistance, increased infarct size, autonomic dysfunction, decreased heart rate variability and increased arterial stiffness.

A quarter of the excess mortality among smokers is accounted for by lung cancer and chronic obstructive lung disease and another quarter by ischaemic heart disease; most of the rest involves other neoplastic, respiratory, or vascular diseases that could well be made more probable (among the survivors at a given age) by smoking.

II - Recommendations and epidemiology

According to latest figures from the World health Organisation, tobacco kills nearly 6 million people yearly, 600,000 of which are the result of non-smokers being exposed to second-hand smoke. Although the number of smokers is decreasing in certain high-income and upper middle-income countries (typically halving from 40 percent to 20 percent smoking), nearly 80% of the world's one billion smokers live in low- and middle-income countries.

The latest ESC guidelines on cardiovascular disease prevention (2012) hold two messages (10):

1. Smoking cessation is a cornerstone for improving cardiovascular health 
2. Public health measures, including smoking bans, are crucial for the public perception of smoking as an important health hazard.

Data from a retrospective study from 192 countries (2011) revealed that SHS represents a considerable problem: 40% of children, 33% of male non-smokers and 35% of female non-smokers were exposed to SHS and SHS exposure caused 379,000 deaths in these countries due to CAD.
Second hand smoking was shown to augment the risk of acute myocardial infarction by 25% in these countries (11).
In Switzerland (8 million inhabitants), each year 9,000 deaths have been attributed to tobacco consumption and 47% of these are imputable to cardiovascular disease. 
In particular, non-smoking women seem to be more affected by SHS negative effects. Notably, the exposure to SHS occurred not only in public places or in workplaces but even at home, especially in the eastern Mediterranean region where SHS exposure is greater in women than in men (12). Eighty per cent of the world's smoking population is thought to be made of men.

In the Interheart study, 39% of people without history of AMI reported a time of exposure to SHS between 1 and 7 hours/week, while the 5.3% referred an exposure time even surpassing 22 hours/week. Bedside current smokers were more exposed to SHS than never and former smokers. Moreover, among individuals with low level of exposure to SHS, the risk of AMI increased by the 24% (OR 1.24) when compared with never smokers or with people who had never been exposed to SHS.
The risk of AMI appears to increase according to the hours per week spent in a SHS environment.
The World Health Organisation estimates that 600,000 patients die to passive smoke every year, of which 1/4th are children.

III- Bans

Smoking bans have existed since the introduction of tobacco to Europe from the New-World but were isolated and tended to originate in a particular leader's views on tobacco such as those of Pope Urban VII's in the 16th century, who announced he would excommunicate anyone who brought tobacco inside a church (14), King James I of England, who considered the habit "beastly" and wrote a treatise against tobacco or Adolf Hitler who had been a heavy smoker himself, later viewed it as "decadent" and outlawed in many public places - find here histories of 1) smoking, 2) bans, and 3) litigation.
South Africa that was the first country to ban smoking in all public places. In North America, states, starting with California, and cities, starting with New York City implemented SB regulations before the introduction in Europe, starting with Ireland, which is (15) is actually due to be totally smoke-free by 2025, hoping to go from 22% of smokers to 5%. Today, close to twenty EU countries have smoking ban laws in all enclosed public places. Countries such as Buthan, Australia, New-Zealand, Singapore, Iceland together with Ireland are working toward a total ban to come into place between 2012 or 2040. Russia, the world's top consumer of tobacco has a smoking ban coming into place on Jan. 1st, 2014. Other tobacco-curbing efforts exist alongside smoking bans such as in New York, where anyone buying cigarettes will need to be 21 and over. Australia has introduced a plain package law, where all packages are brown and contain only small text with brand information and large text and graphic warnings depicting the effects of tobacco on various parts of the body.  
On the European scale, the latest European anti-smoking policy is a directive: it calls for health warnings covering 65% of cigarette packs - indeed, current warning labels cover only 30-40 percent of packages - ban of menthol cigarettes by 2022 (menthol is used to some degree in 90% of all cigarettes currently manufactured) and the sale of cigarettes in packets of ten. Description of the directive can be found here, while the ESC's position paper on the directive project can be found here. Find Philipp Morris' comment on the directive here. Although the directive has been voted on, the legislature still must reach a compromise with the 28 European Union governments on certain points before the rules can actually enter into force, and since it is a directive, states are fee to choose the means to achieve these goals. The European Parliament also voted to ban additives and flavorings like chocolate or vanilla. 

In Switzerland during the years 2001-02, 60% of the population aged between 14 and 65 years, was exposed weekly to SHS for one hour or more. This proportion decreased to 27% in 2009 and to 13% in 2010 (13). This effect was likely due to the implementation of smoking-ban laws in indoor public places in some cantons.

From a cardiovascular disease standpoint, effects of a smoking ban have also shown to be immediate. The community of Helena Montana (USA) for example, introduced a SB in public places from June 2002 until December 2002, at which time it the ban was suspended because of legal challenge. During the ban, a 40% decline in the incidence of AMI was observed, followed by an increase after the ban suspension. This was the first and only study on a public SB to collect data related to the period after a ban suspension (bans usually are not usually suspended).

A further study was performed In Europe (Scotland), where direct and indirect measurements were used to quantify SHS exposure. There, a ban was introduced in March 2006 in all enclosed public places. From June 2005 to March 2006, 3,235 patients with acute coronary syndrome were hospitalised. In the first 10 months after the ban, investigators observed a 17% decrease in the number of acute coronary syndromes. Hospital admissions for acute coronary syndromes decreased by 14% in smokers, 19% in former smokers and 21% in never smokers. The reduction of SHS exposure decreased from 43% to 22% in non-smokers (9). Similar results were observed in other two Italian retrospective studies (6,8) and in Switzerland as well. Indeed, a significant reduction of ST-Elevation Myocardial Infarctions was observed in the two Swiss cantons (Canton Ticino and Canton Graubunden) which firstly introduced (2007 and 2008) SB laws in all indoor public places (16,17).
In all, an unequivocal relationship exists between SHS or passive smoking and heart diseases. Second hand smoking causes an increase in AMI by 25% to 31%. Conversely, smoking ban laws in indoor public places and workplaces are associated with a reduction of about 17% in the incidence of AMI. Non-smokers seem to benefit most from smoking ban laws on the incidence of AMI and women especially, as shown also in the latest results published from the Tromso study (2013), in a 11-year follow-up of 11,763 men and 13,206 women in which passive smoking was an independent risk factor for myocardial infarction (18).

Added to the effect on smokers health, the SB law introduction also affects smoker habits. In Italy a 5.7% reduction in cigarette sales and a significant increase in nicotine replacement therapy sales were reported after the enforcement of a ban (19). It is conceivable that such observations may contribute to explain in part the results observed in the above-mentioned studies. Indeed, there may be an initial reaction, where people stop to go to the places where they use to be able to smoke. However, habits change and people start to appreciate the smoke-free environment, including smokers who may smoke less themselves or try to quit.
All may also enjoy the newly contaminated-free odorless surfaces of furniture, clothing and objects that remain after the second-hand smoke has cleared (see third hand smoking here).

IV - Role of industry (tobacco)

It is in the tobacco industry's interest to sell cigarettes and in particular, to get people to start smoking, preferably at an early age. Indeed, the World Health Organisation states irreconcilable differences between the tobacco industry's interests and Public Health's interests such that it has issued legislation in order to effectively deny its claim to be a partner in tobacco control.  
To habitual smokers, cigarettes do not provide a feeling of elation, only relief in response to a craving being satisfied. The key for the industry is to get people started. For example, cigarettes were distributed to soldiers during the war, and this practice only ceased officially in 1975. During the Marshal Plan, for every dollar sent in food to Europe, 1 dollar was sent in cigarettes. In movies, some scenes involving cigarette smoking were carefully orchestrated. There was candy shaped as cigarettes. 'Buy one get one free' promotional items, and menthol and fruit flavors, helped people, and youth particularly, to get started. Slim cigarettes or colored cases, targeted part of the market to women. When controversy arose surrounding the risk to health, low tar filtered cigarettes showed. They were marketed as safer - however it has been shown that smokers take more frequent, deep breaths and in the US, light cigarettes have been outlawed in 2009 when the FDA acquired the right to regulate tobacco products. "Life contains risks" stated one early campaign: "Choose your risks". Today lobbies argue for the freedom of individuals and businesses and that tobacco is vital to a country's fiscal health (find a look at what would happen in America if everyone were to stop smoking here).
For a particular individual, it is difficult to definitively prove a direct causal link between exposure to a tobacco smoke and the cancer that follows; such statements can only be made at the aggregate population level. Tobacco companies exploited the doubts of clinicians, who consider only individual cases.
As a result of the Minnesota settlement, and others, the tobacco industry was forced to disclose 35 million pages of tobacco industry documents. Some of these documentsaddress how the industry manipulated the chemicals in their products, marketed these products, and concealed the serious health effects of smoking.
Robert Proctor, a Stanford teacher in the history of Medicine takes full advantage of the research made public as a result of this litigation in his book, The Golden Holocaust. "For those interested in the role of science in forming public policy", writes the Editor of the International Journal of Epidemiology, Dr. Proctor provides a masters level seminar on how the cigarette manufacturers used science to subvert public policy". Read regarding Philipp Morris' research here.

Conclusions

Epidemiological data are clear. Second hand smoking represents a huge problem worldwide and SHS has been a major motivation for smoke-free laws. Smoking bans are a simple intervention that can help in the prevention of cardiovascular diseases which currently represent the major cause of death worldwide. The physician needs to make sure that patients coming to consultation know about the dangers of smoking and second-hand smoking, especially in terms of the less known risk of AMI and also as bans do not concern private homes. Electronic cigarettes, that for now are yet the object of no jurisdiction, are now a new concern for their nicotine habit-forming effect.