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This briefing examines the health effects of exposure to secondhand smoke.
Contents
Glucose intolerance and diabetes
Health effects of SHS on children
Health effects of prenatal exposure to SHS
Protection for nonsmokers: Smokefree laws and public places
Breathing other people's smoke is known as passive, involuntary or secondhand smoking. It can also be called ‘environmental tobacco smoke’. (Note: the term ‘secondhand smoke’ or ‘SHS’ has been used throughout this briefing.)
Smokers and nonsmokers alike inhale SHS. Inhaling tobacco smoke is an unavoidable consequence of being in a smoke-filled environment.1
SHS is a mixture of air-diluted ‘sidestream’ smoke from the burning tip of a cigarette, and the exhaled ‘mainstream’ smoke exhaled by the smoker. While the proportions of sidestream and exhaled mainstream smoke can differ, sidestream smoke is usually the larger constituent of SHS.
Mainstream smoke inhaled by a smoker contains over 4000 chemicals (both particles and gases), including chemical irritants and almost 70 carcinogens (cancer causing substances). Sidestream smoke has a similar composition but the relative quantities of chemicals can differ.
Mainstream and sidestream smoke contain fine particles and thousands of gases made up from the combustion of tobacco, paper and additives in a cigarette. The concentration of these chemicals and particles changes over time and in different environmental conditions. The concentration is dependent on the number of smokers, the rate at which they are smoking and the volume of air that the smoke is distributed into.
Exposure to SHS has immediate health effects. It can reduce lung function; exacerbate respiratory problems; trigger asthma attacks; reduce coronary blood flow; irritate eyes; and cause headaches, coughs, sort throats, dizziness and nausea.
As well as the immediate health effects there are also long-term health effects, especially with continued exposure over time. The US Surgeon General in June 2006 concluded that that there is no risk-free level of exposure to SHS.[1] This conclusion adds to the weight of scientific evidence including a review by the Scientific Committee on Tobacco and Health (SCOTH) in the UK, published in 2004, which stated that “no infant, child or adult should be exposed to secondhand smoke” and that SHS is a substantial health hazard.[2]
The International Agency for Research on Cancer (IARC) and the World Health Organization (WHO) have classified SHS as a known (class A) human carcinogen. Other class A carcinogens include asbestos, arsenic, benzene and radon gas.[3]
Evidence about the health impacts of SHS exposure has built up over decades and has included comprehensive reviews by the US National Research Council, reports by the US Surgeon General, the Californian Environmental Protection Agency, the National Health and Medical Research Council of Australia and the Scientific Committee on Smoking and Health in the UK. The WHO also recognises there is no safe level of exposure to SHS.[4]
Whilst living with a person or people who smoke is a major contributory factor in SHS exposure, people also receive exposure through workplaces and public places (particularly pubs and restaurants).[5] The exposure of the foetus to SHS either through active smoking by the mother or from the mother’s own exposure to SHS is also classed by the US Surgeon General as involuntary exposure.
In 2003 across the United Kingdom an estimated 617 people died from the effects of passive smoking at work, 54 of these were long term employees of the hospitality industry. Another 11,000 deaths were attributable to passive smoking exposure in the home in adults aged 20 to ≥ 65.[6] This accounts for around 2% of the current annual toll from all smoking related deaths in the UK.[7]
Population estimates in the US show the number of annual estimated deaths from SHS exposure as significant. For nonsmokers:
· around 3,400 people die from lung cancer (ranging from 3,423 to 8,866)
· 46,000 die from cardiac-related illness (range of 22,700 to 69,600)
· 430 children die from sudden infant death syndrome (SIDS).
Another 24,500 babies are born with low birth weight and 71,900 born prematurely. There are around 202,300 episodes of childhood asthma (new cases and exacerbations) and 787,700 cases of middle ear infection in children due to SHS exposure.[8]
Since the 1950’s it has been established that long-term cigarette smoking is a major cause of lung cancer.3 Studies over the past twenty five years have pointed to the causal effect of exposure to SHS and the risk of developing lung cancer.2
In 2004 the International Agency for Research on Cancer (IARC) concluded that a nonsmoker living with a smoker or smoker has a significantly increased risk of lung cancer, by approximately 24% for women and 37% for men.2
Studies of nonsmokers exposed to SHS in their workplace show an increased risk of lung cancer of the order of 16% to 19% compared to people not exposed.3
The IARC states that the evidence is clear: adult nonsmokers exposed to SHS have a higher risk of lung cancer than those not exposed. There is also strong evidence of a dose-response relationship between lung cancer risk and the duration of exposure to SHS. The three main sources of SHS exposure are the home, the workplace and the social environment.[9]
The IARC research has found an exposure-response relationship from living with a smoking spouse and the development of lung cancer. The risk of developing lung cancer in the non-smoking spouse increases with the years spent living with the smoker, the number of cigarettes the smoker smokes and the number of years the person smokes.3
Studies have consistently shown that exposure to SHS increases the risk of coronary heart disease (CHD) in nonsmokers. In the 1990’s heart disease caused by passive smoking was estimated to have been the third leading cause of preventable death in the United Sates, ranking just behind active smoking and alcohol use.[10]
Exposure to SHS increases blood platelet activity, causing the blood to thicken and become more likely to clot. The tobacco smoke also affects cells lining the coronary arteries, contributing towards the narrowing of the arteries. This reduction in blood flow may lead to a heart attack. A small study in 2001 concluded that even half an hour of exposure to SHS can reduce coronary blood flow.[11]
It is estimated that SHS exposure increases the risk of an acute coronary heart disease event by 25-35%.3
A review by Law, Morris & Wald in 1997 found that nonsmokers had an overall 23% increased risk of heart disease when living with a smoker, even after adjusting for cofounders such as diet, in comparison to those people who were not exposed to SHS.[12] A British study (published in 2004) suggests that CHD in nonsmokers is widespread and that the effects of passive smoking in earlier studies have been underestimated.5
A study in Helena, Montana, USA, reported in 2004, found in the six months following the introduction of a public smoking ban there was a reduction in hospital admissions due to heart attacks.[13] During the six months the law was enforced the number of heart attack admissions fell from 40 admissions during the year prior to the law to 24 after the law was enacted. The ordinance was subsequently overturned and the number of acute heart attack admissions returned to previous levels, around 40 per year.
The limitation of the Helena study is that it was small in size and in an isolated community. Therefore the results of the study should not be extrapolated to the general population. However, the study demonstrates the significant health improvements as a result of the smoking ban.
From this study the researchers stressed that even a brief exposure to environmental smoke increases the tendency of blood to clot, restricting blood flow to the heart, and can produce a serious and even lethal effect on patients with heart disease. They recommend that people who are at risk of heart disease should avoid all places that allow smoking indoors.[14]
The most common effect of SHS exposure is that of sensory irritation of the eyes, nose and throat, including red eyes, sore throat, coughing or wheezing and hoarseness.
The chemical constituents of SHS that are thought to be responsible for this sensory irritation include organic acids (acetic and propionic acid), aldehydes (formaldehyde and acrolein), nicotine, ammonia, pyridine, toluene, sulphur dioxide and nitrogen oxides. Nonsmokers also typically find the odour from tobacco smoke annoying. 3
Many studies have shown that people with allergies and/or asthma experience more nasal symptoms, headaches, cough, wheezing, sore throat, hoarseness, eye irritation and aggravation of asthma symptoms due to exposure to SHS.3
Exposure to SHS can also be a trigger for an asthma attack.
In the UK 5.2 million people live with asthma, of these 2.1 million suffer from severe asthma. A survey conducted in 2003 of people with severe asthma found that 44% said their social life was restricted because they could not go to pubs or restaurants due to smoky atmospheres. One in five of those interviewed said their asthma was life-threatening.[15]
The 2001 Health Survey for England found that being exposed to other people’s tobacco smoke for six or more hours a week significantly increased the risk of wheezing in the previous 12 months.[16]
The IARC research shows that the strongest causal effect of SHS exposure is chronic respiratory symptoms in adults.3
A large European prospective study (EPIC) found that exposure to SHS increased the risk of respiratory diseases including Chronic Obstructive Pulmonary Disease (COPD) among former smokers (having stopped for at least 10 years) compared to never smokers, which could indicate a greater susceptibility of mutations in former smokers (the association was limited to exposure related to work).[17]
Irish hospitality workers experienced significant reductions in both air nicotine levels (80% drop) and saliva cotinine concentrations (70% decrease) during the first six weeks of the Irish smoking ban. Cotinine is produced by the body to break down nicotine and can be used to show recent passive smoking exposure. Before the law came into effect, 68% of workers reported having over 21 hours of SHS exposure per week. After the introduction of the ban this changed to 70% of workers reporting no exposure to SHS per week.[18]
New York State implemented the Clean Indoor Air Act in 2003. After the ban there was a marked reduction in reported exposure by hospitality employees to SHS. Study subjects reported an 89% decrease in exposure to SHS at work; this was confirmed by urinary cotinine tests of the workers.[19]
Few epidemiological studies have examined the effects of SHS on stroke and aortic aneurysms. The SCOTH report found insufficient evidence of an association between SHS exposure and stroke.2
Previous research in New Zealand, in 1999, found SHS exposure increased the risk of stroke in nonsmokers by 82%.[20] Recent research in China has found that non-smoking women living with partners who smoke have an elevated prevalence of stroke. The prevalence increased with intensity of smoking (number of cigarettes smoked) and duration of the partners’ smoking.[21] The US Surgeon General has concluded that the risk of stroke and SHS exposure warrants further study.1
Recent research released in 2006 has showed an increased risk of glucose intolerance (a precursor to diabetes) from SHS exposure over a 15 year time period. The incidence of glucose intolerance amongst young adults was 17% among nonsmokers exposed to SHS compared to 12% not exposed to SHS. The link between exposure to SHS and diabetes needs further research before being conclusive.[22]
As carcinogens have no known safe threshold, it is reasonable to assume that if active smoking is a cause of a specific cancer then passive smoking will impose some degree of increased risk.
SHS exposure has been associated with increased risk of developing cervical tumours (cervical neoplasia). In particular women who have lived with smokers have a 40% increased risk of developing cervical cancer compared to women living with nonsmokers.[23]
Other cancers such as leukaemia, nasal and breast may be associated with increased risk from SHS exposure. However, the epidemiological studies of these cancers and SHS exposure are sparse.[24]
Children’s exposure to tobacco smoke generally takes place in their home with the main source of exposure being from their parents and in particular maternal smoking. Smoking has a significant impact on the health of the child both in childhood and in later life.
A child exposed to SHS has an increased risk of cancer; increased risk of developing and/or exacerbating asthma; reduced respiratory function (cough, wheezes); risk of bronchitis; middle ear infection; pneumonia; meningococcal or meningitis infection and sudden infant death syndrome (SIDs).24
In 1997 the Canadian Institute of Child Health found that children are especially vulnerable to SHS as they breathe more rapidly and they inhale more pollutants per pound of body weight (a higher relative ventilation rate) than adults.[25]
In the UK around 5 million children are exposed regularly to SHS and close to half of all children still live in households with at least one smoker.2,[26]
Children’s exposure to SHS can be affected by:
· the number of smokers at home
· the number of cigarettes being smoked
· the level of parents education
· where the parents or others smoke in the house.[27]
Children are more likely to commence smoking if they grow up in households where those around them smoke and are more likely to smoke if one or both of their parents do.24
A study in Sweden released in 2006 has shown that parents who smoke are greatly increasing their child’s risk of developing several types of cancer. Similar risks for exposure by mothers and fathers smoking were found for lung cancer (71%), and upper aerodigestive cancer (45%). There was an 8-fold increased risk of developing nasal cancer (nasal adenoid cystic carcinoma) by exposure to SHS from either parent during childhood.[28]
Children who are exposed to SHS on a daily basis grow up with more than triple the risk of lung cancer later in life compared to those who grow up in smokefree environments.17
Asthma is the most common chronic disease of childhood. In particular SHS exposure can trigger the development of asthma and exacerbate symptoms.[29]
Three potential modifiable causes of asthma have been identified by researchers, these include: exposure to SHS, lack of dietary fruit intake (fruit intake is related to increased lung function) and the proximity of the home to a main road. A UK study found no association between living close to a main road and asthma, a moderate increased risk for children who consume no fruit, and an exposure-response relation between smoking and asthma. Parental smoking was a causal factor of asthma in children and the prevalence of asthma increased with number of smokers in the home. The authors found that of the three preventable risk factors, SHS exposure was the independent determinant of the disease.[30]
Children who suffer from asthma and whose parents smoke are at least twice as likely to suffer asthma symptoms all year round compared to the children of non-smokers. Wheeze and physician-diagnosed asthma was more common in children who lived with a smoker and the prevalence of asthma increases with the number of smokers living in the home.29
An effective means of preventing asthma is to reduce the person’s exposure to SHS.29,30
More information
Further information on effects on children of SHS can be found in ASH’s ‘Passive smoking: Impact on children’ briefing. http://www.ash.org.uk/html/passive/html/kidsbrief.html
The largest source of SHS exposure for children is from maternal smoking. This can be a cumulative effect of exposure during pregnancy and the close proximity of the child to the mother during early life.
Prenatal exposure to tobacco smoke has adverse impacts on the health of the foetus including low birth weight, premature birth, spontaneous abortion and still birth.
Babies born to women who smoke weigh around 200 grams less than nonsmokers. There is a small adverse effect on the baby’s weight of non-smoking mothers who themselves have been exposed to SHS during their pregnancy.3 Smoking also impacts on IVF and fertility rates. It has been found that exposure to SHS is as damaging as smoking itself in terms of successful pregnancy outcomes for people using IVF.[31]
Prenatal exposure can have adverse impacts on the learning and behavioural development of a child. Maternal prenatal smoking is associated with both antisocial behaviour and attention deficit hyperactivity disorder (ADHD) in children and adolescents.
This association remains after controlling for confounders such as socio-economic status, maternal age, birth weight and maternal psychopathology.33
Exposure to SHS after birth is well established as a cause of sudden infant death syndrome (SIDS or cot death).[32] Therefore smoking during pregnancy and around children should be avoided.[33]
While there is a high degree of overall awareness about the health risks of SHS amongst UK adults, around 80% believe that a nonsmoker’s risk of lung cancer, bronchitis and asthma is increased by SHS exposure. However, only 57% of heavy smokers (20 or more cigarettes a day) believe that SHS increases the risk of heart disease.26,[34]
Younger people (ie aged under 35) and those who have never smoked are more likely to know about the health effects of passive smoking on adults and children.26
Around 60% of nonsmokers dislike people smoking around them. People do not like the smell of cigarettes (61%); are concerned about the health effects of SHS (45%) and dislike the smell of smoke on clothes (42%). A large number of people also reported adverse health reactions due to SHS including that: it affects their breathing; makes them cough; gets in their eyes and makes them feel sick.34
Education about the dangers of SHS exposure can have an impact on health. In Norway the proportion of smoking parents has only minimally reduced from 1995 to 2001, but there was a significant reduction in children’s SHS exposure and a significant change in the health-risk awareness of passive smoking during this time.[35] For example 85% of all households now impose rules to limit people to smoking outside and the prevalence of children’s exposure has fallen from 32% in 1995 to 18% in 2001.35
Many people are exposed to SHS at their workplace or in social situations. A law to ban smoking in virtually all workplaces in England (separate measures apply to Wales and Northern Ireland) and will be implemented in 2007. Scotland has already enacted legislation from March 2006.
There is high level of public support for restrictions on smoking in public places. A poll conducted by BMRB* (commissioned by the British Heart Foundation and ASH) found 70% of the English public supported all workplaces, including pubs and clubs being smokefree.[36]
This evidence adds to an earlier poll conducted by You Gov in December 2005 (commissioned by Cancer Research UK and ASH) which, when given a list of specific places, 66% of people (in England) agreed that all pubs and bars should be smokefree by law. This figure was up from 51% in spring 2004.[37]
The detrimental health impact of people’s exposure to SHS will be significantly reduced as a result of the smokefree legislation.
More information
For further information on smokefree legislation and workplace smoking bans see www.smokefreeaction.org.uk
Exposure to SHS is a major public health issue and a serious health risk. The 2006 US Surgeon General report shows social norms regarding SHS exposure have changed dramatically since the Royal College of Physicians report* on smoking in 1962 and that this is leading towards a society free from SHS exposure.
The health risks from SHS exposure are now well documented and there is no risk-free level of exposure to SHS.
The 2006 US Surgeon General report found six major conclusions:
*
Note exact wording of the question was “A Government Bill in parliament will make enclosed
workplaces smokefree, with exemptions for pubs not serving food, and private
members clubs. The Chair of the Health Committee supported by committee members
from all parties has tabled an amendment to make ALL enclosed workplaces,
including all pubs and clubs smokefree. How strongly would you support or
oppose this amendment to make ALL enclosed workplaces smokefree?”
70% supported, with 18% opposed and the remainder undecided or don’t know
(n=831).
* Royal College of Physicians. Smoking and Health. A Report of the Royal College of Physicians on Smoking in Relation to Cancer of the Lung and Other Diseases. Pitman Medical Publishing Company 1962
[1] US Department of Health and Human Services. The health consequences of involuntary exposure to tobacco smoke: a report of the Surgeon General – Executive summary. US Department of Health and Human Services, Centers for Disease Control and Prevention, Coordinating Center for Health Promotion, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, Pittsburgh USA. 2006. Viewed 3 Aug. 06: link
[2] Scientific Committee on Tobacco and Health (SCOTH). Secondhand smoke: review of evidence since 1998. Update of evidence on health effects of secondhand smoke. 2004. Department of Health, London pg 6.
[3] International Agency for Research on Cancer (IARC). IARC Monographs on the evaluation of carcinogenic risks to humans Volume 83 Tobacco smoke and involuntary smoking. IARC. France 2004.
[4] Framework Convention Alliance for Tobacco Control. Secondhand smoke factsheet no 3. Framework Convention Alliance for Tobacco Control, Geneva 2005. Viewed 2 Aug. 06 link http://fctc.org/factsheets/3.pdf
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[7] Britton J. Passive smoking and asthma exacerbation. Thorax 2005 Vol. 60 pp. 794-795. Viewed 3 Aug. 06 link
[8] California Environmental Protection Agency. Proposed identification of environmental tobacco smoke as a toxic air contaminant: executive summary. Californian Environmental Protection Agency, Office of Environmental Health Hazard Assessment, California 2005. . Viewed 3 Aug. 06 link
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[16] Department of Health. Health Survey for England 2001. Department of Health, London Viewed 3 Aug. 06 link
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[19] Abrams S. Mahoney M. Hyland A. Cummings M. Davis W and Song L. Early evidence of the effectiveness of Clean Indoor Air Legislation in New York State. American Journal of Public Health 2006 Vol 96. No. 2. pp. 296-298. Viewed 3 Aug 06 link
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[24] Royal College of Physicians Tobacco Advisory Group. Going smokefree: the medical case for clean air in the home, at work and in public places. Royal College of Physicians, London 2005.
[25] Canadian Institute on Child Health. Environmental hazards: protecting children. Canadian Institute of Child Health, Ottawa. Viewed 3 Aug. 06 link
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[29] Cabana M. Birk N. Slish K. Yoon E. Pace K. Nan B and Clark N. Exposure to tobacco smoke and chronic asthma symptoms. Pediatric Asthma Allergy and Immunology 2005 Vol 18. No 4, pp. 180-188.
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[31] Neal M. Hughes E. Holloway A and Foster W. Sidestream smoking is equally as damaging as mainstream smoking on IVF outcomes. Human Reproduction 2005 Vol. 20 No: 9 pp. 2531-2535 link
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[33] Button T. Thapar A and McGuffin P. Relationship between antisocial behaviour, attention-deficit hyperactivity disorder and maternal prenatal smoking. British Journal of Psychiatry 2005 Vol. 187, pp. 155-160
[34] Lader D and Goddard E. Smoking-related behaviour and attitudes 2004. Office for National Statistics, London. 2005
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