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Tobacco smoke in an Irish pub before a smoking ban came into effect on March 29, 2004
Passive smoking is the inhalation of smoke, called secondhand smoke (SHS), or environmental tobacco smoke (ETS),
by persons other than the intended "active" smoker. It occurs when
tobacco smoke enters an environment, causing its inhalation by people
within that environment. Exposure to secondhand tobacco smoke causes disease, disability, and death. The health risks of secondhand smoke are a matter of scientific consensus. These risks have been a major motivation for smoke-free laws in workplaces and indoor public places, including restaurants, bars and night clubs, as well as some open public spaces.
Concerns around secondhand smoke have played a central role in
the debate over the harms and regulation of tobacco products. Since the
early 1970s, the tobacco industry has viewed public concern over secondhand smoke as a serious threat to its business interests.
Harm to bystanders was perceived as a motivator for stricter regulation
of tobacco products. Despite the industry's awareness of the harms of
secondhand smoke as early as the 1980s, the tobacco industry coordinated
a scientific controversy with the purpose of stopping regulation of
their products.
Effects
secondhand smoke causes many of the same diseases as direct smoking, including cardiovascular diseases, lung cancer, and respiratory diseases. These diseases include:
- Cancer:
- General: overall increased risk; reviewing the evidence accumulated on a worldwide basis, the International Agency for Research on Cancer concluded in 2004 that "Involuntary smoking (exposure to secondhand or 'environmental' tobacco smoke) is carcinogenic to humans."
- Lung cancer: passive smoking is a risk factor for lung cancer. In the United States passive smoke is estimated to cause more than 7,000 deaths from lung cancer a year among non-smokers.
- Breast cancer: The California Environmental Protection Agency concluded in 2005 that passive smoking increases the risk of breast cancer in younger, primarily premenopausal females by 70% and the US Surgeon General has concluded that the evidence is "suggestive," but still insufficient to assert such a causal relationship. In contrast, the International Agency for Research on Cancer concluded in 2004 that there was "no support for a causal relation between involuntary exposure to tobacco smoke and breast cancer in never-smokers." A 2015 meta-analysis found that the evidence that passive smoking moderately increased the risk of breast cancer had become "more substantial than a few years ago."
- Pancreatic cancer: A 2012 meta-analysis found no evidence that passive smoking was associated with an increased risk of pancreatic cancer.
- Cervical cancer: A 2015 overview of systematic reviews found that exposure to secondhand smoke increased the risk of cervical cancer.
- Bladder cancer: A 2016 systematic review and meta-analysis found that secondhand smoke exposure was associated with a significant increase in the risk of bladder cancer.
- Circulatory system: risk of heart disease, reduced heart rate variability.
- Epidemiological studies have shown that both active and passive cigarette smoking increase the risk of atherosclerosis.
- Passive smoking is strongly associated with an increased risk of stroke, and this increased risk is disproportionately high at low levels of exposure.
- Lung problems:
- Risk of asthma.
- Risk of chronic obstructive pulmonary disease (COPD)
- According to a 2015 review, passive smoking may increase the risk of tuberculosis infection and accelerate the progression of the disease, but the evidence remains weak.
- The majority of studies on the association between secondhand smoke exposure and sinusitis have found a significant association between the two.
- Cognitive impairment and dementia: Exposure to secondhand smoke may increase the risk of cognitive impairment and dementia in adults 50 and over. Children exposed to secondhand smoke show reduced vocabulary and reasoning skills when compared with non-exposed children as well as more general cognitive and intellectual deficits.
- Mental health: Exposure to secondhand smoke is associated with an increased risk of depressive symptoms.
- During pregnancy:
- Low birth weight
- Premature birth (Note that evidence of the causal link is described only as "suggestive" by the US Surgeon General in his 2006 report.) Laws limiting smoking decrease premature births.
- Stillbirth and congenital malformations in children
- Recent studies comparing females exposed to Environmental Tobacco Smoke and non-exposed females, demonstrate that females exposed while pregnant have higher risks of delivering a child with congenital abnormalities, longer lengths, smaller head circumferences, and low birth weight.
- General:
- Worsening of asthma, allergies, and other conditions. A 2014 systematic review and meta-analysis found that passive smoking was associated with a slightly increased risk of allergic diseases among children and adolescents; the evidence for an association was weaker for adults.
- Type 2 diabetes. It remains unclear whether the association between passive smoking and diabetes is causal.
- Risk of carrying Neisseria meningitidis or Streptococcus pneumoniae.
- A possible increased risk of periodontitis.
- Overall increased risk of death in both adults, where it is estimated to kill 53,000 nonsmokers per year, making it the 3rd leading cause of preventable death in the U.S, and in children. The World Health Organization states that passive smoking causes about 600,000 deaths a year, and about 1% of the global burden of disease. As of 2017, passive smoking causes about 900,000 deaths a year, which is about 1/8 of all deaths caused by smoking.
- Skin conditions: A 2016 systematic review and meta-analysis found that passive smoking was associated with a higher rate of atopic dermatitis.
Risk to children
- Sudden infant death syndrome (SIDS). In his 2006 report, the US Surgeon General concludes: "The evidence is sufficient to infer a causal relationship between exposure to secondhand smoke and sudden infant death syndrome." Secondhand smoking has been estimated to be associated with 430 SIDS deaths in the United States annually.
- Asthma. Secondhand smoke exposure is also associated with an almost doubled risk of hospitalization for asthma exacerbation among children with asthma.
- Lung infections, also including more severe illness with bronchiolitis and bronchitis, and worse outcome, as well as increased risk of developing tuberculosis if exposed to a carrier. In the United States, it is estimated that secondhand smoke has been associated with between 150,000 and 300,000 lower respiratory tract infections in infants and children under 18 months of age, resulting in between 7,500 and 15,000 hospitalizations each year.
- Impaired respiratory function and slowed lung growth
- Allergies
- Maternal passive smoking increases the risk of non-syndromic orofacial clefts by 50% among their children.
- Prenatal and childhood passive smoke exposure does not appear to increase the risk of inflammatory bowel disease.
- Learning difficulties, developmental delays, executive function problems, and neurobehavioral effects. Animal models suggest a role for nicotine and carbon monoxide in neurocognitive problems.
- An increase in tooth decay (as well as related salivary biomarkers) has been associated with passive smoking in children.
- Increased risk of middle ear infections.
- Invasive meningococcal disease.
- Maternal exposure to secondhand smoke exposure during pregnancy is associated with an increased risk of neural tube defects.
- Miscarriage: a 2014 meta-analysis found that maternal secondhand smoke exposure increased the risk of miscarriage by 11%.
- Anesthesia complications and some negative surgical outcomes.
- Sleep disordered breathing: Most studies have found a significant association between passive smoking and sleep disordered breathing in children, but further studies are needed to determine whether this association is causal.
- Adverse effects on the cardiovascular system of children.
Evidence
Exposure to secondhand smoke by age, race, and poverty level in the US.
Epidemiological
studies show that non-smokers exposed to secondhand smoke are at risk
for many of the health problems associated with direct smoking. Most of
the research has come from studies of nonsmokers who are married to a
smoker. Those conclusions are also backed up by further studies of
workplace exposure to smoke.
In 1992, a review estimated that secondhand smoke exposure was responsible for 35,000 to 40,000 deaths per year in the United States in the early 1980s. The absolute risk increase of heart disease due to ETS was 2.2%, while the attributable risk percent was 23%. A 1997 meta-analysis found that secondhand smoke exposure increased the risk of heart disease by a quarter, and two 1999 meta-analyses reached similar conclusions.
Evidence shows that inhaled sidestream smoke, the main component
of secondhand smoke, is about four times more toxic than mainstream
smoke. This fact has been known to the tobacco industry since the 1980s,
though it kept its findings secret. Some scientists believe that the risk of passive smoking, in particular the risk of developing coronary heart diseases, may have been substantially underestimated.
In 1997, a meta-analysis on the relationship between secondhand
smoke exposure and lung cancer concluded that such exposure caused lung
cancer. The increase in risk was estimated to be 24% among non-smokers
who lived with a smoker.
In 2000, Copas and Shi reported that there was clear evidence of
publication bias in the studies included in this meta-analysis. They
further concluded that after correcting for publication bias, and
assuming that 40% of all studies are unpublished, this increased risk
decreased from 24% to 15%. This conclusion has been challenged on the basis that the assumption that 40% of all studies are unpublished was "extreme".
In 2006, Takagi et al. reanalyzed the data from this meta-analysis to
account for publication bias and estimated that the relative risk of
lung cancer among those exposed to secondhand smoke was 1.19, slightly
lower than the original estimate. A 2000 meta-analysis found a relative risk of 1.48 for lung cancer among men exposed to secondhand smoke, and a relative risk of 1.16 among those exposed to it at work.
Another meta-analysis confirmed the finding of an increased risk of
lung cancer among women with spousal exposure to secondhand smoke the
following year. It found a relative risk of lung cancer of 1.29 for
women exposed to secondhand smoke from their spouses.
A 2014 meta-analysis noted that "the association between exposure to
secondhand smoke and lung cancer risk is well established."
A minority of epidemiologists have found it hard to understand
how secondhand smoke, which is more diluted than actively inhaled smoke,
could have an effect that is such a large fraction of the added risk of
coronary heart disease among active smokers.
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.
Passive smoking appears to be capable of precipitating the acute
manifestations of cardio-vascular diseases (atherothrombosis) and may
also have a negative impact on the outcome of patients who suffer acute
coronary syndromes.
In 2004, 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:
These meta-analyses show that there is a statistically significant and consistent association between lung cancer risk in spouses of smokers and exposure to second-hand tobacco smoke from the spouse who smokes. The excess risk is of the order of 20% for women and 30% for men and remains after controlling for some potential sources of bias and confounding.
Subsequent meta-analyses have confirmed these findings.
The National Asthma Council of Australia cites studies showing
that secondhand smoke is probably the most important indoor pollutant,
especially around young children:
- Smoking by either parent, particularly by the mother, increases the risk of asthma in children.
- The outlook for early childhood asthma is less favourable in smoking households.
- Children with asthma who are exposed to smoking in the home generally have more severe disease.
- Many adults with asthma identify ETS as a trigger for their symptoms.
- Doctor-diagnosed asthma is more common among non-smoking adults exposed to ETS than those not exposed. Among people with asthma, higher ETS exposure is associated with a greater risk of severe attacks.
In France, exposure to secondhand smoke has been estimated to cause between 3,000 and 5,000 premature deaths per year, with the larger figure cited by Prime Minister Dominique de Villepin
during his announcement of a nationwide smoke-free law: "That makes
more than 13 deaths a day. It is an unacceptable reality in our country
in terms of public health."
There is good observational evidence that smoke-free legislation reduces the number of hospital admissions for heart disease.
Risk level
The International Agency for Research on Cancer of the World Health Organization concluded in 2004 that there was sufficient evidence that secondhand smoke caused cancer in humans.
Those who work in environments where smoke is not regulated are at
higher risk. Workers particularly at risk of exposure include those in
installation repair and maintenance, construction and extraction, and
transportation.
The US Surgeon General,
in his 2006 report, 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%.
In the U.S., smokers that have not quit successfully have a risk of
lung cancer about 20 times higher than that of never smokers.
Biomarkers
Breath
CO monitor displaying carbon monoxide concentration of an exhaled
breath sample (in ppm) with corresponding percent concentration of
carboxyhemoglobin displayed below.
Environmental tobacco smoke can be evaluated either by directly
measuring tobacco smoke pollutants found in the air or by using
biomarkers, an indirect measure of exposure. Carbon monoxide monitored through breath, nicotine, cotinine, thiocyanates, and proteins are the most specific biological markers of tobacco smoke exposure.
Biochemical tests are a much more reliable biomarker of secondhand
smoke exposure than surveys. Certain groups of people are reluctant to
disclose their smoking status and exposure to tobacco smoke, especially
pregnant women and parents of young children. This is due to their
smoking being socially unacceptable. Also, it may be difficult for
individuals to recall their exposure to tobacco smoke.
A 2007 study in the Addictive Behaviors
journal found a positive correlation between secondhand tobacco smoke
exposure and concentrations of nicotine and/or biomarkers of nicotine in
the body. Significant biological levels of nicotine from secondhand
smoke exposure were equivalent to nicotine levels from active smoking
and levels that are associated with behaviour changes due to nicotine
consumption.
Cotinine
Cotinine,
the metabolite of nicotine, is a biomarker of secondhand smoke
exposure. Typically, cotinine is measured in the blood, saliva, and
urine. Hair analysis has recently become a new, noninvasive measurement
technique. Cotinine accumulates in hair during hair growth, which
results in a measure of long-term, cumulative exposure to tobacco smoke.
Urinary cotinine levels have been a reliable biomarker of tobacco
exposure and have been used as a reference in many epidemiological
studies. However, cotinine levels found in the urine reflect exposure
only over the preceding 48 hours. Cotinine levels of the skin, such as
the hair and nails, reflect tobacco exposure over the previous three
months and are a more reliable biomarker.
Carbon monoxide (CO)
Carbon monoxide monitored via breath
is also a reliable biomarker of secondhand smoke exposure as well as
tobacco use. With high sensitivity and specificity, it not only
provides an accurate measure, but the test is also non-invasive, highly
reproducible, and low in cost. Breath CO monitoring measures the
concentration of CO in an exhalation in parts per million, and this can be directly correlated to the blood CO concentration (carboxyhemoglobin). Breath CO monitors can also be used by emergency services to identify patients who are suspected of having CO poisoning.
Pathophysiology
A 2004 study by the International Agency for Research on Cancer of the World Health Organization concluded that non-smokers are exposed to the same carcinogens as active smokers. Sidestream smoke contains more than 4,000 chemicals, including 69 known carcinogens. Of special concern are polynuclear aromatic hydrocarbons, tobacco-specific N-nitrosamines, and aromatic amines, such as 4-aminobiphenyl,
all known to be highly carcinogenic. Mainstream smoke, sidestream
smoke, and secondhand smoke contain largely the same components, however
the concentration varies depending on type of smoke. 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.
secondhand smoke has been shown to produce more particulate-matter (PM) pollution than an idling low-emission diesel engine. In an experiment conducted by the Italian National Cancer Institute, three cigarettes were left smoldering,
one after the other, in a 60 m³ garage with a limited air exchange. The
cigarettes produced PM pollution exceeding outdoor limits, as well as
PM concentrations up to 10-fold that of the idling engine.
secondhand 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. Exposure to tobacco smoke for 30 minutes significantly reduces coronary flow velocity reserve in healthy nonsmokers. secondhand smoke is also associated with impaired vasodilation among adult nonsmokers. secondhand smoke exposure also affects platelet function, vascular endothelium, and myocardial exercise tolerance at levels commonly found in the workplace.
Pulmonary emphysema can be induced in rats through acute exposure
to sidestream tobacco smoke (30 cigarettes per day) over a period of 45
days. Degranulation of mast cells contributing to lung damage has also been observed.
The term "third-hand smoke"
was recently coined to identify the residual tobacco smoke
contamination that remains after the cigarette is extinguished and
secondhand smoke has cleared from the air. Preliminary research suggests that by-products of third-hand smoke may pose a health risk,
though the magnitude of risk, if any, remains unknown. In October 2011,
it was reported that Christus St. Frances Cabrini Hospital in Alexandria, Louisiana
would seek to eliminate third-hand smoke beginning in July 2012, and
that employees whose clothing smelled of smoke would not be allowed to
work. This prohibition was enacted because third-hand smoke poses a
special danger for the developing brains of infants and small children.
In 2008, there were more than 161,000 deaths attributed to lung
cancer in the United States. Of these deaths, an estimated 10% to 15%
were caused by factors other than first-hand smoking; equivalent to
16,000 to 24,000 deaths annually. Slightly more than half of the lung
cancer deaths caused by factors other than first-hand smoking were found
in nonsmokers. Lung cancer in non-smokers may well be considered one of
the most common cancer mortalities in the United States. Clinical
epidemiology of lung cancer has linked the primary factors closely tied
to lung cancer in non-smokers as exposure to secondhand tobacco smoke,
carcinogens including radon, and other indoor air pollutants.
Opinion of public health authorities
There is widespread scientific consensus that exposure to secondhand smoke is harmful.[3] The link between passive smoking and health risks is accepted by every major medical and scientific organisation, including:
- World Health Organization
- U.S. National Institutes of Health
- Centers for Disease Control
- United States Surgeon General
- U.S. National Cancer Institute
- United States Environmental Protection Agency
- California Environmental Protection Agency
- American Heart Association, American Lung Association, and American Cancer Society
- American Medical Association
- American Academy of Pediatrics
- Australian National Health and Medical Research Council
- United Kingdom Scientific Committee on Tobacco and Health
Public opinion
Recent major surveys conducted by the U.S. National Cancer Institute and Centers for Disease Control
have found widespread public awareness 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.
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".
Controversy over harm
As part of its attempt to prevent or delay tighter regulation of
smoking, the tobacco industry funded a number of scientific studies and,
where the results cast doubt on the risks associated with secondhand
smoke, sought wide publicity for those results. The industry also funded
libertarian and conservative think tanks, such as the Cato Institute in the United States and the Institute of Public Affairs in Australia which criticised both scientific research on passive smoking and policy proposals to restrict smoking. New Scientist and the European Journal of Public Health have identified these industry-wide coordinated activities as one of the earliest expressions of corporate denialism. Further, they state that the disinformation spread by the tobacco industry has created a tobacco denialism movement, sharing many characteristics of other forms of denialism, such as HIV-AIDS denialism.
Industry-funded studies and critiques
Enstrom and Kabat
A 2003 study by James Enstrom and Geoffrey Kabat, published in the British Medical Journal, argued that the harms of passive smoking had been overstated.
Their analysis reported no statistically significant relationship
between passive smoking and lung cancer, coronary heart disease (CHD),
or chronic obstructive pulmonary disease, though the accompanying editorial noted that "they may overemphasise the negative nature of their findings." This paper was widely promoted by the tobacco industry as evidence that the harms of passive smoking were unproven. 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. Notably, the study had failed to identify a comparison group of "unexposed" persons.
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." In a US racketeering lawsuit against tobacco companies,
the Enstrom and Kabat paper was cited by the US District Court as "a
prime example of how nine tobacco companies engaged in criminal
racketeering and fraud to hide the dangers of tobacco smoke." The Court found that the study had been funded and managed by the Center for Indoor Air Research, a tobacco industry front group
tasked with "offsetting" damaging studies on passive smoking, as well
as by Philip Morris who stated that Enstrom's work was "clearly
litigation-oriented." A 2005 paper in Tobacco Control
argued that the disclosure section in the Enstrom and Kabat BMJ paper,
although it met the journal's requirements, "does not reveal the full
extent of the relationship the authors had with the tobacco industry."
In 2006, Enstrom and Kabat published a meta-analysis
of studies regarding passive smoking and coronary heart disease in
which they reported a very weak association between passive smoking and
heart disease mortality.
They concluded that exposure to secondhand smoke increased the risk of
death from CHD by only 5%, although this analysis has been criticized
for including two previous industry-funded studies that suffered from
widespread exposure misclassification.
Gori
Gio Batta Gori, a tobacco industry spokesman and consultant and an expert on risk utility and scientific research, wrote in the libertarian Cato Institute's magazine Regulation
that "...of the 75 published studies of ETS and lung cancer, some 70%
did not report statistically significant differences of risk and are
moot. Roughly 17% claim an increased risk and 13% imply a reduction of
risk."
Milloy
Steven Milloy, the "junk science" commentator for Fox News and a former Philip Morris consultant,
claimed that "of the 19 studies" on passive smoking "only 8— slightly
more than 42%— reported statistically significant increases in heart
disease incidence.."
Another component of criticism cited by Milloy focused on relative risk
and epidemiological practices in studies of passive smoking. Milloy,
who has a master's degree from the Johns Hopkins School of Hygiene and
Public Health, 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:
A major component of the industry attack was the mounting of a campaign to establish a "bar" for "sound science" that could not be fully met by most individual investigations, leaving studies that did not meet the criteria to be dismissed as "junk science."
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".
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.
Levois and Layard
In 1995, Levois and Layard, both tobacco industry consultants, published two analyses in the journal Regulatory Toxicology and Pharmacology
regarding the association between spousal exposure to secondhand smoke
and heart disease. Both of these papers reported no association between
secondhand smoke and heart disease.
These analyses have been criticized for failing to distinguish between
current and former smokers, despite the fact that former smokers, unlike
current ones, are not at a significantly increased risk of heart
disease.
World Health Organization controversy
A 1998 study 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."
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 Telegraph and The Economist, among other sources,
alleged that the WHO withheld from publication of 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. The study was published in the Journal of the National Cancer Institute
in October of the same year, and concluded the authors found "no
association between childhood exposure to ETS and lung cancer risk" but
"did find weak evidence of a dose–response relationship between risk of
lung cancer and exposure to spousal and workplace ETS." An accompanying editorial summarized:
When all the evidence, including the important new data reported in this issue of the Journal, is assessed, the inescapable scientific conclusion is that ETS is a low-level lung carcinogen.
With the release of formerly classified tobacco industry documents through the Tobacco Master Settlement Agreement, it was found (by Elisa Ong and Stanton Glantz) 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.
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.
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.
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.
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.
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."
Tobacco-industry funding of research
The tobacco industry's role in funding scientific research on secondhand smoke has been controversial.
A review of published studies found that tobacco-industry affiliation
was strongly correlated with findings exonerating secondhand smoke;
researchers affiliated with the tobacco industry were 88 times more
likely than independent researchers to conclude that secondhand smoke
was not harmful.
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. The 2006 U.S. Surgeon General's report criticized the tobacco industry's role in the scientific debate:
The industry has funded or carried out research that has been judged to be biased, supported scientists to generate letters to editors that criticized research publications, attempted to undermine the findings of key studies, assisted in establishing a scientific society with a journal, and attempted to sustain controversy even as the scientific community reached consensus.
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." All scientific research was subject to oversight and "filtering" by tobacco-industry lawyers:
Philip Morris then expect the group of scientists to operate within the confines of decisions taken by PM scientists to determine the general direction of research, which apparently would then be 'filtered' by lawyers to eliminate areas of sensitivity.
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."
Tobacco industry response
Measures to tackle secondhand smoke pose a serious economic threat to
the tobacco industry, having broadened the definition of smoking beyond
a personal habit to something with a social impact. In a confidential
1978 report, the tobacco industry described increasing public concerns
about secondhand smoke as "the most dangerous development to the
viability of the tobacco industry that has yet occurred." 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."
Accordingly, the tobacco industry have developed several strategies to minimise the impact on their business:
- The industry has sought to position the secondhand smoke debate as essentially concerned with civil liberties and smokers' rights rather than with health, by funding groups such as FOREST.
- Funding bias in research; in all reviews of the effects of secondhand smoke on health published between 1980 and 1995, the only factor associated with concluding that secondhand smoke is not harmful was whether an author was affiliated with the tobacco industry. However, not all studies that failed to find evidence of harm were by industry-affiliated authors.
- Delaying and discrediting legitimate research (see for an example of how the industry attempted to discredit Takeshi Hirayama's landmark study, and for an example of how it attempted to delay and discredit a major Australian report on passive smoking)
- Promoting "good epidemiology" and attacking so-called junk science (a term popularised by industry lobbyist Steven Milloy): attacking the methodology behind research showing health risks as flawed and attempting to promote sound science. Ong & Glantz (2001) cite an internal Phillip Morris memo giving evidence of this as company policy.
- Creation of outlets for favourable research. In 1989, the tobacco industry established the International Society of the Built Environment, which published the peer-reviewed journal Indoor and Built Environment. This journal did not require conflict-of-interest disclosures from its authors. With documents made available through the Master Settlement, it was found that the executive board of the society and the editorial board of the journal were dominated by paid tobacco-industry consultants. The journal published a large amount of material on passive smoking, much of which was "industry-positive".
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." 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."
Position of major tobacco companies
The positions of major tobacco companies on the issue of secondhand
smoke is somewhat varied. In general, tobacco companies have continued
to focus on questioning the methodology of studies showing that
secondhand smoke is harmful. Some (such as British American Tobacco and Philip Morris)
acknowledge the medical consensus that secondhand smoke carries health
risks, while others continue to assert that the evidence is
inconclusive. Several tobacco companies advocate the creation of
smoke-free areas within public buildings as an alternative to
comprehensive smoke-free laws.
US racketeering lawsuit against tobacco companies
On September 22, 1999, the U.S. Department of Justice filed a racketeering lawsuit against Philip Morris and other major cigarette manufacturers.
Almost 7 years later, on August 17, 2006 U.S. District Court Judge
Gladys Kessler found that the Government had proven its case and that
the tobacco company defendants had violated the Racketeer Influenced Corrupt Organizations Act (RICO). In particular, Judge Kessler found that PM and other tobacco companies had:
- conspired to minimize, distort and confuse the public about the health hazards of smoking;
- publicly denied, while internally acknowledging, that secondhand tobacco smoke is harmful to nonsmokers, and
- destroyed documents relevant to litigation.
The ruling found that tobacco companies undertook joint efforts to
undermine and discredit the scientific consensus that secondhand smoke
causes disease, notably by controlling research findings via paid
consultants. The ruling also concluded that tobacco companies were
fraudulently continuing to deny the health effects of ETS exposure.
On May 22, 2009, a three-judge panel of the U.S. Court of Appeals
for the District of Columbia Circuit unanimously upheld the lower
court's 2006 ruling.
Smoke-free laws
As a consequence of the health risks associated with secondhand smoke, smoke-free regulations in indoor public places, including restaurants, cafés, and nightclubs have been introduced in a number of jurisdictions, at national or local level, as well as some outdoor open areas. Ireland
was the first country in the world to institute a comprehensive
national smoke-free law on smoking in all indoor workplaces on 29 March
2004. Since then, many others have followed suit. The countries which
have ratified the WHO Framework Convention on Tobacco Control (FCTC) have a legal obligation to implement effective
legislation "for protection from exposure to tobacco smoke in indoor
workplaces, public transport, indoor public places and, as appropriate,
other public places." (Article 8 of the FCTC) The parties to the FCTC have further adopted Guidelines on the Protection from Exposure to secondhand Smoke
which state that "effective measures to provide protection from
exposure to tobacco smoke ... require the total elimination of smoking
and tobacco smoke in a particular space or environment in order to
create a 100% smoke-free environment."
Opinion polls have shown considerable support for smoke-free
laws. In June 2007, a survey of 15 countries found 80% approval for
smoke-free laws. A survey in France, reputedly a nation of smokers, showed 70% support.
Effects
Smoking bans by governments result in decreased harm from second hand smoke including decrease cardiovascular disease. In the first 18 months after the town of Pueblo, Colorado
enacted a smoke-free law in 2003, hospital admissions for heart attacks
dropped 27%. Admissions in neighbouring towns without smoke-free laws
showed no change, and the decline in heart attacks in Pueblo was
attributed to the resulting reduction in secondhand smoke exposure. A 2004 smoking ban instituted in Massachusetts workplaces decreased workers' secondhand smoke exposure from 8% of workers in 2003 to 5.4% of workers in 2010. A 2016 review also found benefits of decrease exposure to smoke from specific location policies.
In 2001, a systematic review for the Guide to Community
Preventative Services acknowledged strong evidence of the effectiveness
of smoke-free policies and restrictions in reducing expose to secondhand
smoke. A follow up to this review, identified the evidence on which the
effectiveness of smoking bans reduced the prevalence of tobacco use.
Articles published until 2005, were examined to further support this
evidence. The examined studies provided sufficient evidence that
smoke-free policies reduce tobacco use among workers when implemented in
worksites or by communities.
While a number of studies funded by the tobacco industry have
claimed a negative economic impact from smoke-free laws, no
independently funded research has shown any such impact. A 2003 review
reported that independently funded, methodologically sound research
consistently found either no economic impact or a positive impact from
smoke-free laws.
Air nicotine levels were measured in Guatemalan bars and
restaurants before and after an implemented smoke-free law in 2009.
Nicotine concentrations significantly decreased in both the bars and
restaurants measured. Also, the employees support for a smoke-free
workplace substantially increased in the post-implementation survey
compared to pre-implementation survey. The result of this smoke-free law
provides a considerably more healthy work environment for the staff.
Public opinion
Recent surveys taken by the Society for Research on Nicotine and Tobacco
demonstrates supportive attitudes of the public, towards smoke-free
policies in outdoor areas. A vast majority of the public supports
restricting smoking in various outdoor settings. The respondents reasons
for supporting the policies were for varying reasons such as, litter
control, establishing positive smoke-free role models for youth,
reducing youth opportunities to smoke, and avoiding exposure to
secondhand smoke.
Alternative forms
Alternatives to smoke-free laws have also been proposed as a means of harm reduction,
particularly in bars and restaurants. For example, critics of
smoke-free laws cite studies suggesting ventilation as a means of
reducing tobacco smoke pollutants and improving air quality.
Ventilation has also been heavily promoted by the tobacco industry as
an alternative to outright bans, via a network of ostensibly independent
experts with often undisclosed ties to the industry. However, not all critics have connections to the industry.
The American Society of Heating, Refrigerating and Air-Conditioning Engineers
(ASHRAE) officially concluded in 2005 that while completely isolated
smoking rooms do eliminate the risk to nearby non-smoking areas, smoking
bans are the only means of completely eliminating health risks
associated with indoor exposure. They further concluded that no system
of dilution or cleaning was effective at eliminating risk. The U.S. Surgeon General and the European Commission Joint Research Centre have reached similar conclusions. The implementation guidelines for the WHO Framework Convention on Tobacco Control states that engineering approaches, such as ventilation, are ineffective and do not protect against secondhand smoke exposure. However, this does not
necessarily mean that such measures are useless in reducing harm, only
that they fall short of the goal of reducing exposure completely to
zero.
Others have suggested a system of tradable smoking pollution permits, similar to the cap-and-trade pollution permits systems used by the Environmental Protection Agency in recent decades to curb other types of pollution.
This would guarantee that a portion of bars/restaurants in a
jurisdiction will be smoke-free, while leaving the decision to the
market.
In animals
Multiple studies have been conducted to determine the carcinogenicity
of environmental tobacco smoke to animals. These studies typically fall
under the categories of simulated environmental tobacco smoke,
administering condensates of sidestream smoke, or observational studies of cancer among pets.
To simulate environmental tobacco smoke, scientists expose
animals to sidestream smoke, that which emanates from the cigarette's
burning cone and through its paper, or a combination of mainstream and
sidestream smoke.
The IARC monographs conclude that mice with prolonged exposure to
simulated environmental tobacco smoke, that is 6hrs a day, 5 days a
week, for five months with a subsequent 4 month interval before
dissection, will have significantly higher incidence and multiplicity of
lung tumors than with control groups.
The IARC monographs concluded that sidestream smoke condensates
had a significantly higher carcinogenic effect on mice than did
mainstream smoke condensates.
Observational studies
Secondhand smoke is popularly recognised as a risk factor for cancer in pets. A study conducted by the Tufts University School of Veterinary Medicine and the University of Massachusetts Amherst linked the occurrence of feline oral cancer to exposure to environmental tobacco smoke through an overexpression of the p53 gene. Another study conducted at the same universities 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. 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. The number of
smokers within the home, the number of packs smoked in the home per day,
and the amount of time that the dog spent within the home had no effect
on the dog's risk for lung cancer.
Terminology
As of 2003, "secondhand smoke" was the term most used to refer to other people's smoke in the English-language media.
Other terms used include "environmental tobacco smoke", while
"involuntary smoking" and "passive smoking" are used to refer to
exposure to secondhand smoke. The term "environmental tobacco smoke" can be traced back to a 1974 industry-sponsored meeting held in Bermuda, while the term "passive smoking" was first used in the title of a scientific paper in 1970. The Surgeon General of the United States
prefers to use the phrase "secondhand smoke" rather than "environmental
tobacco smoke", stating that "The descriptor "secondhand" captures the
involuntary nature of the exposure, while "environmental" does not." Most researchers consider the term "passive smoking" to be synonymous with "secondhand smoke". In contrast, a 2011 commentary in Environmental Health Perspectives
argued that research into "thirdhand smoke" renders it inappropriate to
refer to passive smoking with the term "secondhand smoke", which the
authors stated constitutes a pars pro toto.
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