Second-hand smoke

Passive smoking is the involuntary inhalation of smoke from tobacco products. It occurs when tobacco smoke permeates any environment, causing its inhalation by all people within that environment. Such smoke is called secondhand smoke (SHS) or environmental tobacco smoke (ETS). Scientific evidence shows that exposure to secondhand tobacco smoke causes disease, disability, and death.¹²³⁴

The risks associated with passive smoking are one of the main reasons for smoking bans in workplaces and indoor public places, including restaurants, bars and night clubs.

Long-term effects

Research has generated scientific evidence that secondhand smoke (that is, in the case of cigarettes, a mixture of smoke released from the smoldering end of the cigarette and smoke exhaled by the smoker) causes the same problems as direct smoking, including heart disease,⁵ cardiovascular disease, lung cancer, and lung ailments such as COPD, bronchitis and asthma.⁶ Specifically, meta-analyses have shown lifelong non-smokers with partners who smoke in the home have a 20–30% greater risk of lung cancer, and those exposed to cigarette smoke in the workplace have an increased risk of 16–19%.⁷

A wide array of negative effects are attributed, in whole or in part, to frequent, long term exposure to second hand smoke.⁸⁹¹⁰ Some of these effects include:

Causal mechanisms

A study issued in 2002 by the International Agency for Research on Cancer of the World Health Organization concluded that nonsmokers are exposed to the same carcinogens as active smokers.⁴⁸ Sidestream smoke contains more than 4000 chemicals, including 69 known carcinogens such as formaldehyde, lead, arsenic, benzene, and radioactive polonium 210,⁴⁹ and several well-established carcinogens have been shown by the tobacco companies' own research to be present at higher concentrations in sidestream smoke than in mainstream smoke.⁵⁰

Environmental tobacco smoke (ETS) has been shown to be a much higher source of pollution than an idling ecodiesel engine in regard to particulate matter (PM) emission. In an experiment conducted by the Tobacco Control Unit of the National Cancer Institute, three cigarettes were left smouldering, one after the other, in a 60 m³ garage with a limited air exchange. The cigarettes produced PM indoor pollution exceeding outdoor limits, as well as PM concentrations up to 10-fold that of the idling engine.⁵¹

Tobacco smoke exposure has immediate and substantial effects on blood and blood vessels in a way that increases the risk of a heart attack, particularly in people already at risk.⁵² Exposure to tobacco smoke for 30 minutes significantly reduces coronary flow velocity reserve in healthy nonsmokers.⁵³

Animal experiments have directly shown a wide variety of adverse effects from tobacco smoke exposure including induced pulmonary emphysema [1] and degranulation of mast cells contributing to lung damage [2].

Epidemiological studies of passive smoking

Epidemiological studies show that non-smokers exposed to secondhand smoke are at risk for many of the health problems associated with direct smoking.

In 1992, the Journal of the American Medical Association published a review of the available evidence regarding the relationship between secondhand smoke and heart disease, and estimated that passive smoking was responsible for 35,000 to 40,000 deaths per year in the United States in the early 1980s.⁵⁴ Some studies find that non-smokers living with smokers have about a 25% increase in risk of death from heart attack, are more likely to suffer a stroke, and can sometimes contract genital cancer. Some research, with better measures of secondhand smoke exposure suggests that risks to nonsmokers may be even greater than this estimate. A British study reported that exposure to secondhand smoke increases the risk of heart disease among non-smokers by as much as 60%, similar to light smoking.⁵⁵

Parental smoking can affect children and babies, and is associated with low birth weight, sudden infant death syndrome (SIDS), bronchitis and pneumonia, and middle ear infections.⁵⁶

In 2002, a group of 29 experts from 12 countries convened by the Monographs Programme of the International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) reviewed all significant published evidence related to tobacco smoking and cancer. It concluded:

Subsequent meta-analyses have confirmed these findings,⁵⁸⁵⁹ and additional studies have found that high overall exposure to passive smoke even among people with non-smoking partners is associated with greater risks than partner smoking and is widespread in non-smokers.⁵⁵

The National Asthma Council of Australia cites studies showing that environmental tobacco smoke (ETS) is probably the most important indoor pollutant, especially around young children:⁶⁰

In France passive smoking has been estimated to cause between 3,000⁶¹ and 5,000 premature deaths per year, with the larger figure cited by Prime minister Dominique de Villepin during his announcement of a nationwide smoking ban: "That makes more than 13 deaths a day. It is an unacceptable reality in our country in terms of public health."⁶²

Studies of passive smoking in animals

Experimental studies in which animals are exposed to tobacco smoke have produced results supporting the carcinogenicity of passive smoking. The International Agency for Research on Cancer expert group concluded that:

Secondhand smoke is generally recognized as a risk factor for cancer in pets.⁶⁴ A study conducted by the Tufts University School of Veterinary Medicine and the University of Massachusetts concluded that cats living with a smoker were more likely to get feline lymphoma; the risk increased with the duration of exposure to secondhand smoke and the number of smokers in the household.⁶⁵ A study by Colorado State University researchers, looking at cases of canine lung cancer, was generally inconclusive, though the authors reported a weak relation for lung cancer in dogs exposed to environmental tobacco smoke.⁶⁶

In 1990, a tobacco-industry researcher in Germany proposed a study of the effects on animals of lifetime exposure to secondhand smoke. The proposed study was blocked by Philip Morris,⁶⁷ as described in an internal company report:

Risk level of passive smoking

Most experts believe that moderate, occasional exposure to secondhand smoke presents a small but measurable cancer risk to nonsmokers. The overall risk depends on the effective dose received over time. The risk level is higher if non-smokers spend many hours in an environment where cigarette smoke is widespread, such as a business where many employees or patrons are smoking throughout the day, or a residential care facility where residents smoke freely.⁷⁰

The study estimated that living or working in a place where smoking is permitted increases the non-smokers' risk of developing heart disease by 25–30% and lung cancer by 20–30%. The report also found that passive smoke causes sudden infant death syndrome (SIDS), respiratory problems, ear infections, and asthma attacks in children.⁷¹

Current state of scientific opinion

Currently, there is widespread scientific consensus that exposure to secondhand smoke is harmful.⁷² The link between passive smoking and health risks is accepted by every major medical and scientific organization, including:

While there is scientific agreement regarding the existence of a link between passive smoking and heart disease, the magnitude of the increased risk remains debated by a minority of epidemiologists.⁸⁷ For example, John Bailar of the National Academy of Sciences questioned the proportionality of the passive smoking risk, stating:

One proposed explanation is that secondhand smoke is not simply a diluted version of "mainstream" smoke, but has a different composition with more toxic substances per gram of total particulate matter.⁸⁷ The more toxic makeup of secondhand smoke was first recognized in the tobacco industry's own research, though it never published its findings.⁸⁸ Some scientists believe that the risk of passive smoking, in particular the risk of developing coronary heart diseases, may have been substantially underestimated.⁸⁹

The health benefit to non-smokers of smoking bans has also been disputed by a small number of epidemiologists, who call for a prospective trial to more accurately determine the benefit. These epidemiologists advocate indoor smoking bans, but express a concern that widespread outdoor smoking bans, as implemented by some towns in the U.S., may be unsupported by the evidence available thus far.⁸⁷

Public opinion

Recent major surveys conducted by the U.S. National Cancer Institute and Centers for Disease Control have found widespread public belief that secondhand smoke is harmful. In both 1992 and 2000 surveys, more than 80% of respondents agreed with the statement that secondhand smoke was harmful. A 2001 study found that 95% of adults agreed that secondhand smoke was harmful to children, and 96% considered tobacco-industry claims that secondhand smoke was not harmful to be untruthful. ⁹⁰^{, p. 588}

A 2007 Gallup poll found that 56% of respondents felt that secondhand smoke was "very harmful", a number that has held relatively steady since 1997. Another 29% believe that secondhand smoke is "somewhat harmful"; 10% answered "not too harmful", while 5% said "not at all harmful". Regarding smoking bans, the poll found a majority (54%) in favor of complete smoking bans in restaurants; however, most respondents favored designated smoking areas in hotels, motels and workplaces. In bars, the survey found that 45% prefer smoking areas, 29% support a smoking ban, and 23% want no restrictions on smoking.⁹¹

Controversy over harms of passive smoking

In 1986, the United States Surgeon General issued a report concluding that secondhand smoke was a cause of disease. In the same year, the International Agency for Research on Cancer and the National Research Council also released reports concluding that secondhand smoke was a cause of lung cancer.⁹² Over the subsequent 20 years, the accumulation of scientific evidence has led to a scientific consensus that passive smoking is indeed harmful to non-smokers.⁹³ A U.S. District Court found, in a racketeering case against the tobacco industry, that the industry had internally acknowledged the harmfulness of passive smoking even earlier.⁷²^{, pp. 1523–1525} Nonetheless, the tobacco industry has played a central role in generating and sustaining controversy over the effects of passive smoking.⁹⁴⁹⁵⁹⁶

Critique of individual studies and epidemiology

A number of studies funded by the tobacco industry have yielded results inconsistent with the scientific consensus, or have criticised the epidemiological approach associated with that consensus.

A 2003 study by Enstrom and Kabat, published in the British Medical Journal, argued that the harms of passive smoking had been overstated.⁹⁷ Their analysis reported no statistically significant relationship between passive smoking and lung cancer, though the accompanying editorial noted that "they may overemphasise the negative nature of their findings."⁹⁸ This paper was widely promoted by the tobacco industry as evidence that the harms of passive smoking were unproven.⁹⁶⁷²^{, p. 1383} The American Cancer Society (ACS), whose database Enstrom and Kabat used to compile their data, criticized the paper as "neither reliable nor independent", stating that scientists at the ACS had repeatedly pointed out serious flaws in Enstrom and Kabat' s methodology prior to publication.⁹⁹ Enstrom's ties to the tobacco industry also drew scrutiny; in a 1997 letter to Philip Morris, Enstrom requested a "substantial research commitment... in order for me to effectively compete against the large mountain of epidemiologic data and opinions that already exist regarding the health effects of ETS and active smoking."¹⁰⁰ The study was funded and managed by the Center for Indoor Air Research, a tobacco industry front group described in confidential Philip Morris documents as "responsible for producing studies to offset the IARC study" on passive smoking,¹⁰¹ and Enstrom's work was viewed by Philip Morris as "clearly litigation-oriented."⁷²^{, pp. 1380–1383} Enstrom himself has defended the accuracy of his study against what he terms "illegitimate criticism by those who have attempted to suppress and discredit it."¹⁰²

Gio Batta Gori, a tobacco industry consultant and spokeperson,¹⁰³ wrote in the libertarian Cato Institute's journal Regulation that "...of the 75 published studies of ETS and lung cancer, some 70 percent did not report statistically significant differences of risk and are moot. Roughly 17 percent claim an increased risk and 13 percent imply a reduction of risk."¹⁰⁴ Steven Milloy, the "junk science" commentator for Fox News and a former Philip Morris consultant,¹⁰⁵¹⁰⁶ claimed that "...of the 37 studies [on passive smoking], only 7 – less than 19 percent – reported statistically significant increases in lung cancer incidence."¹⁰⁷

Another component of criticism promoted by Milloy focused on relative risk and epidemiological practices in studies of passive smoking. Milloy argued that studies yielding relative risks of less than 2 were meaningless junk science. This approach to epidemiological analysis was criticized in the American Journal of Public Health:

The tobacco industry and affiliated scientists also put forward a set of "Good Epidemiology Practices" which would have the practical effect of obscuring the link between secondhand smoke and lung cancer; the privately-stated goal of these standards was to "impede adverse legislation".¹⁰⁹ However, this effort was largely abandoned when it became clear that no independent epidemiological organization would agree to the standards proposed by Philip Morris et al.¹¹⁰

World Health Organization controversy

A 1998 report by the International Agency for Research on Cancer (IARC) on environmental tobacco smoke (ETS) found "weak evidence of a dose-response relationship between risk of lung cancer and exposure to spousal and workplace ETS."¹¹¹ In March 1998, before the study was published, reports appeared in the media alleging that the IARC and the World Health Organization (WHO) were suppressing information. The reports, appearing in the British Sunday Telegraph¹¹² and The Economist,¹¹³ among other sources,¹¹⁴¹¹⁵¹¹⁶ alleged that the WHO withheld from publication its own report that supposedly failed to prove an association between passive smoking and a number of other diseases (lung cancer in particular).

In response, the WHO issued a press release stating that the results of the study had been "completely misrepresented" in the popular press and were in fact very much in line with similar studies demonstrating the harms of passive smoking.¹¹⁷ The study was published in the Journal of the National Cancer Institute in October of the same year. An accompanying editorial summarized:

With the release of formerly classified tobacco industry documents through the Tobacco Master Settlement Agreement, it was found that the controversy over the WHO's alleged suppression of data had been engineered by Philip Morris, British American Tobacco, and other tobacco companies in an effort to discredit scientific findings which would harm their business interests.¹¹⁹ A WHO inquiry, conducted after the release of the tobacco-industry documents, found that this controversy was generated by the tobacco industry as part of its larger campaign to cut the WHO's budget, distort the results of scientific studies on passive smoking, and discredit the WHO as an institution. This campaign was carried out using a network of ostensibly independent front organizations and international and scientific experts with hidden financial ties to the industry.¹²⁰

EPA lawsuit

In 1993, the United States Environmental Protection Agency (EPA) issued a report estimating that 3,000 lung cancer related deaths in the United States were caused by passive smoking annually.¹⁵ Philip Morris, R.J. Reynolds Tobacco Company, and groups representing growers, distributors and marketers of tobacco took legal action, claiming that the EPA had manipulated this study and ignored accepted scientific and statistical practices.

The United States District Court for the Middle District of North Carolina ruled in favor of the tobacco industry in 1998, finding that the EPA had failed to follow proper scientific and epidemiologic practices and had "cherry picked" evidence to support conclusions which they had committed to in advance.¹²¹ The court stated in part, "“EPA publicly committed to a conclusion before research had begun…adjusted established procedure and scientific norms to validate the Agency's public conclusion... In conducting the ETS Risk Assessment, disregarded information and made findings on selective information; did not disseminate significant epidemiologic information; deviated from its Risk Assessment Guidelines; failed to disclose important findings and reasoning…"

In 2002, the EPA successfully appealed this decision to the United States Court of Appeals for the Fourth Circuit. The EPA's appeal was upheld on the preliminary grounds that their report had no regulatory weight, and the earlier finding was vacated.¹²² In 1998 the U.S. Department of Health and Human Services, through the publication by its National Toxicology Program of the 9th Report on Carcinogens, listed environmental tobacco smoke among the known carcinogens, observing of the EPA assessment that "The individual studies were carefully summarized and evaluated."¹²³^{p. 24}

Tobacco-industry funding of research

The tobacco industry's role in funding scientific research on passive smoking has been controversial.¹²⁴ A review of published studies found that tobacco-industry affilation was strongly correlated with findings exonerating passive smoking; researchers affiliated with the tobacco industry were 88 times more likely than independent researchers to conclude that passive smoking was not harmful.¹²⁵ In a specific example which came to light with the release of tobacco-industry documents, Philip Morris executives successfully encouraged an author to revise his industry-funded review article to downplay the role of secondhand smoke in sudden infant death syndrome.¹²⁶ The 2006 U.S. Surgeon General's report criticized the tobacco industry's role in the scientific debate:

This strategy was outlined at an international meeting of tobacco companies in 1988, at which Philip Morris proposed to set up a team of scientists, organized by company lawyers, to "carry out work on ETS to keep the controversy alive."⁹⁵ All scientific research was subject to oversight and "filtering" by tobacco-industry lawyers:

Philip Morris reported that it was putting "...vast amounts of funding into these projects... in attempting to coordinate and pay so many scientists on an international basis to keep the ETS controversy alive."⁹⁵

Tobacco industry response

The passive smoking issue poses a serious economic threat to the tobacco industry. It has broadened the definition of smoking beyond a personal habit to something with a social impact, it has been the cause of successful litigation against employers by workers with a history of exposure to smoke, and it has resulted in various types of smoking restrictions. In a confidential 1978 report, the tobacco industry described increasing public concerns about passive smoking as "the most dangerous development to the viability of the tobacco industry that has yet occurred."¹²⁸ In United States of America v. Philip Morris et al., the District Court for the District of Columbia found that the tobacco industry "... recognized from the mid-1970s forward that the health effects of passive smoking posed a profound threat to industry viability and cigarette profits," and that the industry responded with "efforts to undermine and discredit the scientific consensus that ETS causes disease."⁷²

Accordingly, the tobacco industry have developed several strategies to minimize its impact on their business:

Citing the tobacco industry's production of biased research and efforts to undermine scientific findings, the 2006 U.S. Surgeon General's report concluded that the industry had "attempted to sustain controversy even as the scientific community reached consensus... industry documents indicate that the tobacco industry has engaged in widespread activities... that have gone beyond the bounds of accepted scientific practice."¹³¹ The U.S. District Court, in U.S.A. v. Philip Morris et al., found that "...despite their internal acknowledgment of the hazards of secondhand smoke, Defendants have fraudulently denied that ETS causes disease."⁷²^{, p. 1523}

Position of major tobacco companies

Smoking bans

These initial bans have grown in scope, with countries (such as Ireland, the UK, Australia), jurisdictions (like New York State, Washington State, Ohio, Pennsylvania, and Arkansas in the U.S.) now prohibiting smoking in public buildings as well as establishments such as restaurants and clubs. Many office buildings contain specially ventilated smoking areas; some are required by law to provide them.

The state of Hawaii recently passed a bill making it illegal to smoke in any public place or within 20 feet of an entrance or ventilation shaft intake of a building.

Some regions and local governments have banned smoking in all workplaces, in taxicabs, and in ventilated smoking rooms or enclosed smoking shelters such as those found in front of hospitals.

Even in countries traditionally seen as nations of smokers^who?, opinion polls have shown support for bans, with 70% of those in France supporting a ban.⁶²

In the first 18 months after the town of Pueblo, Colorado enacted a smoking ban in 2003, hospital admissions for heart attacks dropped 27%. Admissions in neighboring towns without smoking bans showed no change. Raymond Gibbons, M.D., American Heart Association president said, "The decline in the number of heart attack hospitalizations within the first year and a half after the non-smoking ban that was observed in this study is most likely due to a decrease in the effect of secondhand smoke as a triggering factor for heart attacks."¹³²

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