Smoking facts and evidence

Read the key facts about smoking and cancer risk, and find the supporting evidence from academic research and scientific studies to see why we say what we do.

Experts agree that tobacco is the single biggest avoidable cause of cancer in the world. [1,2] Smoking causes over a quarter (28 per cent) of cancer deaths in the UK and nearly one in five cancer cases. [3,4]

And smoking doesn’t only cause cancer. It also causes tens of thousands of deaths each year in the UK from other conditions, including heart and lung problems. [3] Tobacco was responsible for more than 100 million deaths worldwide in the 20th Century.[5] The World Health Organisation has estimated that, if current trends continue, tobacco could cause a billion deaths in the 21st Century.[5]
 
Up to two thirds of all long-term smokers will be killed by their habit. [6–8] On average smokers lose around a decade of life compared with non-smokers. [1,3,7–9]
 
References
 
1. IARC. Monographs on the Evaluation of Carcinogenic Risks to Humans VOLUME 83 Tobacco Smoke and Involuntary Smoking. 2004;83.
 
2. Swerdlow AJ, Peto R, Doll R. Epidemiology of cancer. In: Oxford Textbook of Medicine. Oxford, UK: Oxford University Press; 2010:299-332.
 
3. Peto R, Lopez AD, Boreham J, Thun MJ. Mortality from smoking in developed countries 1950 - 2005 (or later).
 
4. Parkin DM, Boyd L, Walker LC. The fraction of cancer attributable to lifestyle and environmental factors in the UK in 2010. Br J Cancer. 2011;105 Suppl(S2):S77-S81. doi:10.1038/bjc.2011.489.
 
5. WHO. Tobacco. 2013. http://www.who.int/mediacentre/factsheets/fs339/en/. Accessed January 9, 2014.
 
6. Doll R, Peto R, Wheatley K, Gray R, Sutherland I. Mortality in relation to smoking: 40 years’ observations on male British doctors. BMJ. 1994;309(6959):901-911. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2541142&tool=p....
 
7. Doll R, Peto R, Boreham J, Sutherland I. Mortality in relation to smoking: 50 years’ observations on male British doctors. BMJ. 2004;328(7455):1519. doi:10.1136/bmj.38142.554479.AE.
 
8. Banks E, Joshy G, Weber MF, et al. Tobacco smoking and all-cause mortality in a large Australian cohort study: findings from a mature epidemic with current low smoking prevalence. BMC Med. 2015;13:38. doi:10.1186/s12916-015-0281-z.
 
9. Jha P. Avoidable global cancer deaths and total deaths from smoking. Nat Rev Cancer. 2009;9(9):655-664. doi:10.1038/nrc2703.
Smoking increases the risk of at least 14 cancers, including cancer of the lung, larynx (voice box) oesophagus (gullet), mouth and pharynx (upper throat), bladder, pancreas, kidney, liver, stomach, bowel, cervix, ovary, nose and sinuses, as well as some types of leukaemia [1–3].There is some evidence that smoking could cause breast cancer [3–7]. 
 
Smoking contributes to a greater proportion of lung cancer cases than for other cancer types. The upper aerodigestive tract cancers (mouth, upper throat, voice box and gullet) have the next highest proportions ofcases linked to smoking – with more than six in 10 cases of these cancers caused by smoking [8].
 
References
 
1. Gandini S, Botteri E, Iodice S, et al. Tobacco smoking and cancer: a meta-analysis. Int J Cancer. 2008;122(1):155-164. doi:10.1002/ijc.23033.
 
2. Cogliano VJ, Baan R, Straif K, et al. Preventable exposures associated with human cancers. J Natl Cancer Inst. 2011;103(24):1827-1839. doi:10.1093/jnci/djr483.
 
3. IARC. Personal Habits and Indoor Combustions, Volume 100 E, A Review of Human Carcinogens. 2012;100.
 
4. Manjer J, Tjonneland A, Olsen A, et al. Active and passive cigarette smoking and breast cancer risk : Results from the EPIC cohort. Int J Cancer. 2014;134:1871-1888. doi:10.1002/ijc.28508.
 
5. Boyd NF, Cantor KP, Hammond SK, Johnson KC, Miller AB. Canadian Expert Panel on Tobacco Smoke and Breast Cancer Risk.; 2009.
 
6. Gaudet MM, Gapstur SM, Sun J, Diver WR, Hannan LM, Thun MJ. Active smoking and breast cancer risk: original cohort data and meta-analysis. J Natl Cancer Inst. 2013;105(8):515-525. doi:10.1093/jnci/djt023.
 
7. DeRoo L a, Cummings P, Mueller B a. Smoking before the first pregnancy and the risk of breast cancer: a meta-analysis. Am J Epidemiol. 2011;174(4):390-402. doi:10.1093/aje/kwr090.
 
8. Parkin DM, Boyd L, Walker LC. The fraction of cancer attributable to lifestyle and environmental factors in the UK in 2010. Br J Cancer. 2011;105 Suppl(S2):S77-S81. doi:10.1038/bjc.2011.489

 

More than 4 in 5 UK lung cancers are caused by smoking [1,2]. Lung cancer is by far the most common cause of cancer death in the UK [1,3]. 

People who smoke were first shown to be more likely to develop lung cancer than non-smokers in 1950 [4]. This study found that people who smoked around 20 cigarettes a day had 26 times the lung cancer risk of non-smokers. And people who smoked around 3 cigarettes a day still had 6 times the lung cancer risk of non-smokers.
 
After these first results came out, UK scientists began a large long-running study of smoking in British doctors, which Cancer Research UK has helped to fund, that has told us a lot about the dangers of smoking [5]. This study has found similarly huge risks associated with smoking. Men who smoked 25 or more cigarettes a day had over 24 times the risk of dying from lung cancer as men who had never smoked [6].
 
There are long time lags between changes in the number of people who smoke and the number of people who develop lung cancer due to smoking [7–9]. So rates of lung cancer in the UK reflect smoking rates decades earlier.
 
We cannot exactly calculate a person’s lung cancer risk based on how many cigarettes they smoke or the number of years they have been a smoker. But research has shown that lung cancer risk is greatest among those who smoke the most cigarettes, over the longest period of time, having started at the youngest age [9,10].
 
Although both have an effect on risk, the number of years someone has spent smoking is more important than the number of cigarettes they smoke a day [11]. This means that overall, smoking 20 cigarettes a day for 20 years is even worse for you than smoking 40 a day for 10 years. 
 
References
 
1. Peto R, Lopez AD, Boreham J, Thun MJ. Mortality from smoking in developed countries 1950 - 2005 (or later).
 
2. Parkin DM, Boyd L, Walker LC. The fraction of cancer attributable to lifestyle and environmental factors in the UK in 2010. Br J Cancer. 2011;105 Suppl(S2):S77-S81. doi:10.1038/bjc.2011.489.
 
3. Cancer Research UK. Lung cancer mortality statistics. August 2014. http://www.cancerresearchuk.org/cancer-info/cancerstats/types/lung/morta.... Accessed January 9, 2014.
 
4. Doll R, Hill AB. Smoking and carcinoma of the lung: Preliminary report. Br Med J. 1950;2(4682):739-748.
 
5. Doll R, Hill AB. The mortality of doctors in relation to their smoking habits: a preliminary report. Br Med J. 1954;1(4877):1451-1455.
 
6. Doll R, Peto R, Boreham J, Sutherland I. Mortality in relation to smoking: 50 years’ observations on male British doctors. BMJ. 2004;328(7455):1519. doi:10.1136/bmj.38142.554479.AE.
 
7. Jha P. Avoidable global cancer deaths and total deaths from smoking. Nat Rev Cancer. 2009;9(9):655-664. doi:10.1038/nrc2703.
 
8. WHO. Global health risks: mortality and burden of disease attributable to selected major risks. 2009.
 
9. IARC. Monographs on the Evaluation of Carcinogenic Risks to Humans VOLUME 83 Tobacco Smoke and Involuntary Smoking. 2004;83.
 
10. IARC. Personal Habits and Indoor Combustions, Volume 100 E, A Review of Human Carcinogens. 2012;100.
 
11. Flanders WD, Lally CA, Zhu B, Henley SJ, Thun MJ. Lung Cancer Mortality in Relation to Age , Duration of Smoking , and Daily Cigarette Consumption : Results from Cancer Prevention Study II Lung Cancer Mortality in Relation to Age , Duration of Smoking , and Daily Cigarette Consumption : Results from Canc. 2003:6556-6562

 

Although the risk of an early death increases the more you smoke, people who think of themselves as light or occasional smokers also have an increased risk compared to people who don’t smoke [1,2]. One study found that people who smoked up to 4 cigarettes a day were about 50 per cent more likely to die prematurely than non-smokers [1]. And the Million Women study found that women who smoked up to 10 cigarettes a day were twice as likely to die prematurely than non-smokers [2].  

Large studies looking at the health risks of smoking, such as the British Doctors Study and the Million Women Study, have found that people smoking between 1 and 14 cigarettes a day are at least 7 times as likely to die from lung cancer compared to people who have never smoked [2–4]. And one study found people who smoked between 5 and 9 cigarettes a day had a higher risk of dying from lung cancer, or any type of cancer [1]. 
 
References
 
1. Bjartveit K, Tverdal A. Health consequences of smoking 1-4 cigarettes per day. Tob Control. 2005;14(5):315-320. doi:10.1136/tc.2005.011932.
 
2. Pirie K, Peto R, Reeves GK, Green J, Beral V. The 21st century hazards of smoking and benefits of stopping: a prospective study of one million women in the UK. Lancet. 2013;381(9861):133-141. doi:10.1016/S0140-6736(12)61720-6.
 
3. Doll R, Peto R, Boreham J, Sutherland I. Mortality in relation to smoking: 50 years’ observations on male British doctors. BMJ. 2004;328(7455):1519. doi:10.1136/bmj.38142.554479.AE.
 
4. Doll R, Peto R, Boreham J, Sutherland I. Mortality from cancer in relation to smoking: 50 years observations on British doctors. Br J Cancer. 2005;92(3):426-429. doi:10.1038/sj.bjc.6602359
A large number of studies have shown that stopping smoking can greatly reduce the risk of smoking-related cancers, compared to continuing to smoke [1,2]. And the earlier you stop, the better [3–5].
 
The latest results from the British Doctors’ Study show that stopping smoking before the age of 30 meant  that life expectancy remained similar to that of a non-smoker [4]. And even people who quit smoking when they were about 60 years old lost fewer years of life to smoking than those who continued [4].
 
References
 
1. IARC. Monographs on the Evaluation of Carcinogenic Risks to Humans VOLUME 83 Tobacco Smoke and Involuntary Smoking. 2004;83.
 
2. IARC. Personal Habits and Indoor Combustions, Volume 100 E, A Review of Human Carcinogens. 2012;100.
 
3. Jha P, Ramasundarahettige C, Landsman V, et al. 21st-century hazards of smoking and benefits of cessation in the United States. N Engl J Med. 2013;368(4):341-350. doi:10.1056/NEJMsa1211128.
 
4. Doll R, Peto R, Boreham J, Sutherland I. Mortality in relation to smoking: 50 years’ observations on male British doctors. BMJ. 2004;328(7455):1519. doi:10.1136/bmj.38142.554479.AE.
 
5. Pirie K, Peto R, Reeves GK, Green J, Beral V. The 21st century hazards of smoking and benefits of stopping: a prospective study of one million women in the UK. Lancet. 2013;381(9861):133-141. doi:10.1016/S0140-6736(12)61720-6
The evidence for the health benefits of cutting down the number of cigarettes you smoke is mixed. Some studies have shown that considerably reducing your cigarette consumption, compared to carrying on smoking the same amount, has benefits for lung cancer risk and overall survival [1–3]. But other studies found benefits only with quitting completely [4,5]. 
 
However if you reduce the amount you smoke you may be more likely to stop smoking in future [6–10]. So although you only experience the full health benefits if you stop smoking altogether, cutting down can be a good first step, if you find it too difficult to quit completely in one go.
 
References
 
1. Gerber Y, Myers V, Goldbourt U. Smoking reduction at midlife and lifetime mortality risk in men: a prospective cohort study. Am J Epidemiol. 2012;175(10):1006-1012. doi:10.1093/aje/kwr466.
 
2. Godtfredsen NS, Prescott E, Osler M. Effect of smoking reduction on lung cancer risk. JAMA. 2005;294(12):1505-1510. doi:10.1001/jama.294.12.1505.
 
3. Song Y-M, Sung J, Cho H-J. Reduction and cessation of cigarette smoking and risk of cancer: a cohort study of Korean men. J Clin Oncol. 2008;26(31):5101-5106. doi:10.1200/JCO.2008.17.0498.
 
4. Tverdal A, Bjartveit K. Health consequences of reduced daily cigarette consumption. Tob Control. 2006;15(6):472-480. doi:10.1136/tc.2006.016246.
 
5. Hart C, Gruer L, Bauld L. Does smoking reduction in midlife reduce mortality risk? Results of 2 long-term prospective cohort studies of men and women in Scotland. Am J Epidemiol. 2013;178(5):770-779. doi:10.1093/aje/kwt038.
 
6. NICE. Tobacco : harm-reduction approaches to smoking. 2013;(July).
 
7. McDermott L, Dobson A, Owen N. Smoking reduction and cessation among young adult women: a 7-year prospective analysis. Nicotine Tob Res. 2008;10(9):1457-1466. doi:10.1080/14622200802323241.
 
8. Broms U, Korhonen T, Kaprio J. Smoking reduction predicts cessation: longitudinal evidence from the Finnish adult twin cohort. Nicotine Tob Res. 2008;10(3):423-427. doi:10.1080/14622200801888988.
 
9. Falba T, Jofre-Bonet M, Busch S, Duchovny N, Sindelar J. Reduction of quantity smoked predicts future cessation among older smokers. Addiction. 2004;99(1):93-102. doi:10.1111/j.1360-0443.2004.00574.x.
 
10. Hyland A, Levy DT, Rezaishiraz H, et al. Reduction in amount smoked predicts future cessation. Psychol Addict Behav. 2005;19(2):221-225. doi:10.1037/0893-164X.19.2.221.
Scientists have identified over 5,300 different chemicals in tobacco smoke [1]. The International Agency for Research into Cancer (IARC), the gold standard for establishing the causes of cancer, state that there are more than 70 chemicals in tobacco smoke that have been found to cause cancer in studies involving people or in the laboratory [1]. And many of the other thousands of chemicals are toxic and harmful to your health, including carbon monoxide, hydrogen cyanide and ammonia [2,3].
In 1994 tobacco companies in the US released a list of 599 different cigarette additives, which included chocolate, vanilla, sugar and liquorice as well as common herbs and spices [4]. Although these don’t make cigarettes any more toxic, they are meant to make cigarettes taste nicer and ensure that smokers want to continue smoking. Flavoured tobacco, such as menthol or chocolate-flavoured cigarettes, has been banned in Europe under the Tobacco Products Directive, [5] this will be introduced by 2020. Although additives necessary for manufacturing tobacco can continue to be used, including sugar lost during the curing process, tobacco companies will have to do more research into additives with the possibility that those found to be more harmful or addictive could be banned from use [5].
 
References
 
1. IARC. Personal Habits and Indoor Combustions, Volume 100 E, A Review of Human Carcinogens. 2012;100.
 
2. Hoffmann D, Hoffmann I. The changing cigarette: chemical studies and bioassays. Smok Tob Control Monogr No 13. 2001:159-191.
 
3. IARC. Monographs on the Evaluation of Carcinogenic Risks to Humans VOLUME 83 Tobacco Smoke and Involuntary Smoking. 2004;83.
 
4. Doull J, Frawley JP, George WJ, Loomis T, Squire RA, Taylor SL. List of ingredients added to tobacco in the manufacture of cigarettes by 6 major American cigarette companies. 1994.
 
5. The European Commission. Commission Directive 2014/39/EU.; 2014.
Chemicals found in tobacco smoke can damage DNA [1–3]. For example, studies have shown that benzo(a)pyrene damages a gene called p53 that normally protects our cells from cancer [1,4]. While polonium-210 becomes concentrated in hotspots in smokers’ airways, subjecting them to very high doses of high-energy alpha-radiation that damages the DNA of nearby cells [5].
 
The cocktail of chemicals in tobacco smoke is even more dangerous as a mix. Toxic metals found in tobacco smoke, like cadmium, arsenic, and lead, stop our cells from repairing DNA damage [6]. This worsens the effects of chemicals like benzo(a)pyrene that damage DNA and makes it even more likely that damaged cells will eventually turn cancerous.
 
Many tobacco poisons disable the cleaning system that our bodies use to remove toxins. Some substances including formaldehyde and acrolein kill cilia, tiny hairs in our airways that help to clear away toxins [1].
 
References
 
1. U.S. Surgeon General. How Tobacco Smoke Causes Disease : The Biology and Behavioral Basis for Smoking-Attributable Disease.; 2010.
 
2. IARC. Personal Habits and Indoor Combustions, Volume 100 E, A Review of Human Carcinogens. 2012;100.
 
3. IARC. Monographs on the Evaluation of Carcinogenic Risks to Humans VOLUME 83 Tobacco Smoke and Involuntary Smoking. 2004;83.
 
4. Denissenko MF, Pao A, Tang M, Pfeifer GP. Preferential formation of Benzo(a)pyrene adducts at lung cancer mutational hotspots in p53. Science (80- ). 1996;274:430-432.
 
5. Zagà V, Lygidakis C, Chaouachi K, Gattavecchia E. Polonium and lung cancer. J Oncol. 2011;2011:860103. doi:10.1155/2011/860103.
 
6. Koedrith P, Seo YR. Advances in carcinogenic metal toxicity and potential molecular markers. Int J Mol Sci. 2011;12(12):9576-9595. doi:10.3390/ijms12129576.
Most smokers do not smoke out of choice, but because they are addicted to nicotine [1,2]. This was highlighted in a report by The Royal College of Physicians into the effects of nicotine [1]. They also compared nicotine to other supposedly ‘harder’ drugs such as heroin and cocaine. They looked at many things including how these drugs cause addiction, how difficult it is to stop using them and how many deaths they caused. The report concluded that nicotine is a highly addictive substance, particularly when people are exposed to it through using tobacco, and that tobacco dependence is at least as serious as addiction to ‘harder’ drugs [1].
 
People associate smoking with feeling less stressed and anxious, but the evidence suggests this is only because it temporarily relieves the unpleasant symptoms of nicotine withdrawal [1,2]. If anything, current smokers seem to feel more stressed and anxious than ex-smokers or people who have never smoked [1]. 
Smokers can also make mental associations with abstract things like the smell of cigarettes, objects related to smoking like ashtrays and lighters, and situations in which they usually smoke. These can all act to reinforce the addiction to smoking [2].
 
References
 
1. Tobacco Advisory Group of The Royal College of Physicians. Nicotine Addiction in Britain. 2000.
 
2. U.S. Surgeon General. How Tobacco Smoke Causes Disease : The Biology and Behavioral Basis for Smoking-Attributable Disease.; 2010
Current smokers have a higher risk of lung cancer than former smokers or never smokers, whatever type of cigarettes they smoke [1,2]. People who smoke cigarettes ‘rated’ as low and very low in tar actually have a similar risk as those who smoke products classed as ‘medium tar’ [3]. But smoking unfiltered high tar varieties makes the risk even higher [1–3].
 
The amounts of tar or nicotine associated with a particular variety of cigarette are based on machine measurements of smoking. But the measurements don’t accurately reflect the amounts actually received by a smoker [1,4–6]. Research that measured markers of nicotine and certain cancer-causing chemicals in smokers found that they took in the same amounts whatever the tar rating of the cigarettes they smoked [7]. Smokers change the way they smoke – such as taking bigger or more frequent puffs, blocking filter holes or smoking more cigarettes in total – in order to satisfy their nicotine cravings [1,2,4,6].
 
In 2003 EU legislation came into force banning tobacco companies from using phrases like ‘light’, ‘mild’ or ‘low-tar’ to describe their products because these could mislead people into believing such products were safer or healthier [8].
 
References
 
1. IARC. Monographs on the Evaluation of Carcinogenic Risks to Humans VOLUME 83 Tobacco Smoke and Involuntary Smoking. 2004;83.
 
2. IARC. Personal Habits and Indoor Combustions, Volume 100 E, A Review of Human Carcinogens. 2012;100.
 
3. Harris JE, Thun MJ, Mondul AM, Calle EE. Cigarette tar yields in relation to mortality from lung cancer in the cancer prevention study II prospective cohort, 1982-8. BMJ. 2004;328(7431):72. doi:10.1136/bmj.37936.585382.44.
 
4. Thun MJ, Burns DM. Health impact of “reduced yield” cigarettes: a critical assessment of the epidemiological evidence. Tob Control. 2001;10 Suppl 1(Suppl I):i4-i11.
 
5. Hoffmann D, Hoffmann I. The changing cigarette: chemical studies and bioassays. Smok Tob Control Monogr No 13. 2001:159-191.
 
6. U.S. Surgeon General. How Tobacco Smoke Causes Disease : The Biology and Behavioral Basis for Smoking-Attributable Disease.; 2010.
 
7. Hecht SS, Murphy SE, Carmella SG, et al. Similar Uptake of Lung Carcinogens by Smokers of Regular , Light , and Ultralight Cigarettes Similar Uptake of Lung Carcinogens by Smokers of Regular ,. Cancer Epidemiol Biomarkers Prev. 2005;14(3):693-698.
 
8. The European Parliament and the Council of the European Union. Directive 2001/37/EC.; 2001.
Alcohol has also been shown to be a cause of mouth, oesophageal and liver cancers, among others [1]. And scientists have found that together, the effects of alcohol and tobacco are much worse than for either one of them by itself [1–5].
 
References
 
1. IARC. Personal Habits and Indoor Combustions, Volume 100 E, A Review of Human Carcinogens. 2012;100.
 
2. Kuper H, Tzonou  a, Kaklamani E, et al. Tobacco smoking, alcohol consumption and their interaction in the causation of hepatocellular carcinoma. Int J Cancer. 2000;85(4):498-502.
 
3. Boyle P. European Code Against Cancer and scientific justification: third version (2003). Ann Oncol. 2003;14(7):973-1005. doi:10.1093/annonc/mdg305.
 
4. Hashibe M, Brennan P, Chuang S-C, et al. Interaction between tobacco and alcohol use and the risk of head and neck cancer: pooled analysis in the International Head and Neck Cancer Epidemiology Consortium. Cancer Epidemiol biomarkers Prev. 2009;18(2):541-550. doi:10.1158/1055-9965.EPI-08-0347.
 
5. Turati F, Garavello W, Tramacere I, et al. A Meta-analysis of Alcohol Drinking and Oral and Pharyngeal Cancers: Results from Subgroup Analyses. Alcohol Alcohol. 2012;0(0):1-12. doi:10.1093/alcalc/ags100.
There is clear evidence that breathing in other people’s smoke causes cancer in non-smokers [1–4]. Second-hand smoke, also known as environmental tobacco smoke or passive smoking, exposes people to cancer-causing chemicals [3].
 
People who have never smoked have their risk of lung cancer increased by around a quarter if they have a spouse who smokes [1,5]. The risk increases the more second-hand smoke they’re exposed to, people exposed to the highest levels can have their risk of lung cancer doubled [5,6].
 
Second-hand smoke can reach high levels in enclosed spaces such as within the home or inside a car [7–11]. Studies have shown that even with open windows, levels can be dangerously high [7,9,11,12].
 
Second-hand smoke also causes other health problems in non-smokers including heart disease and respiratory diseases including asthma in children [1,4,13]. And it may increase the risk of pharyngeal and laryngeal cancers [3,14].
 
References
 
1. Scientific Committee on Tobacco and Health (SCOTH). Secondhand Smoke: Review of evidence since 1998. 2004.
 
2. IARC. Monographs on the Evaluation of Carcinogenic Risks to Humans VOLUME 83 Tobacco Smoke and Involuntary Smoking. 2004;83.
 
3. IARC. Personal Habits and Indoor Combustions, Volume 100 E, A Review of Human Carcinogens. 2012;100.
 
4. U.S. Surgeon General. How Tobacco Smoke Causes Disease : The Biology and Behavioral Basis for Smoking-Attributable Disease.; 2010.
 
5. Taylor R, Najafi F, Dobson A. Meta-analysis of studies of passive smoking and lung cancer: effects of study type and continent. Int J Epidemiol. 2007;36(5):1048-1059. doi:10.1093/ije/dym158.
 
6. Stayner L, Bena J, Sasco AJ, et al. Lung cancer risk and workplace exposure to environmental tobacco smoke. Am J Public Health. 2007;97(3):545-551. doi:10.2105/AJPH.2004.061275.
 
7. Blackburn C, Spencer N, Bonas S, Coe C, Dolan A, Moy R. Effect of strategies to reduce exposure of infants to environmental tobacco smoke in the home: cross sectional survey. BMJ. 2003;327(7409):257. doi:10.1136/bmj.327.7409.257.
 
8. Lofroth G. Environmental Tobacco Smoke: Multicomponent Analysis and Room-to-room Distribution in Homes. Tob Control. 1993;2:222-225.
 
9. Wakefield M, Banham D, Martin J, Ruffin R, McCaul K, Badcock N. Restrictions on smoking at home and urinary cotinine levels among children with asthma. Am J Prev Med. 2000;19(3):188-192. http://www.ncbi.nlm.nih.gov/pubmed/11020596.
 
10. ASH Scotland. Smoking in vehicles : An evidence review. 2013;(April).
 
11. Semple S, Apsley A, Galea KS, MacCalman L, Friel B, Snelgrove V. Secondhand smoke in cars: assessing children’s potential exposure during typical journey conditions. Tob Control. 2012;21(6):578-583. doi:10.1136/tobaccocontrol-2011-050197.
 
12. Sendzik T, Fong GT, Travers MJ, Hyland A. An experimental investigation of tobacco smoke pollution in cars. Nicotine Tob Res. 2009;11(6):627-634. doi:10.1093/ntr/ntp019.
 
13. Tobacco Advisory Group of The Royal College of Physicians. Passive Smoking and Children.; 2010.
 
14. Cogliano VJ, Baan R, Straif K, et al. Preventable exposures associated with human cancers. J Natl Cancer Inst. 2011;103(24):1827-1839. doi:10.1093/jnci/djr483.
It’s not just cigarettes which increase the risk of cancer – other ways of smoking tobacco including pipes, cigars, bidis and shisha are also linked with the disease [1–3,4]. Reviews of the evidence by the International Agency for Research on Cancer have concluded that smoking cigars, pipes or bidis increases the risk of lung, mouth, upper throat, voice box, gullet (oesophagus) and stomach cancers [2,3]. And cigar smoking has also been linked with bladder and pancreatic cancer [1,2,5]. Shisha smoking has been less well studied but the evidence suggests it is linked to lung cancer and possibly other cancers [6 7–9].
 
Because they think it is healthier, some cigarette smokers switch to smoking a cigar or pipe. But aside from the health risks associated with pipes and cigars, research has also shown that because these people are more likely to inhale the smoke than people who have only ever smoked a cigar or pipe, the switch makes little difference to their chance of dying as a result of smoking [1].
 
References
 
1. O’Connor RJ. Non-cigarette tobacco products: what have we learnt and where are we headed? Tob Control. 2012;21(2):181-190. doi:10.1136/tobaccocontrol-2011-050281.Non-cigarette.
 
2. IARC. Monographs on the Evaluation of Carcinogenic Risks to Humans VOLUME 83 Tobacco Smoke and Involuntary Smoking. 2004;83.
 
3. IARC. Personal Habits and Indoor Combustions, Volume 100 E, A Review of Human Carcinogens. 2012;100.
 
4. Akl E a, Gaddam S, Gunukula SK, Honeine R, Jaoude PA, Irani J. The effects of waterpipe tobacco smoking on health outcomes: a systematic review. Int J Epidemiol. 2010;39(3):834-857. doi:10.1093/ije/dyq002.
 
5. Bertuccio P, La Vecchia C, Silverman DT, et al. Cigar and pipe smoking, smokeless tobacco use and pancreatic cancer: an analysis from the International Pancreatic Cancer Case-Control Consortium (PanC4). Ann Oncol. 2011;22(6):1420-1426. doi:10.1093/annonc/mdq613.
 
6. Dar N a, Bhat G a, Shah I a, et al. Hookah smoking, nass chewing, and oesophageal squamous cell carcinoma in Kashmir, India. Br J Cancer. 2012;107(9):1618-1623. doi:10.1038/bjc.2012.449.
 
7. Sadjadi A, Derakhshan MH, Yazdanbod A, et al. Neglected role of hookah and opium in gastric carcinogenesis: A cohort study on risk factors and attributable fractions. Int J Cancer. 2013;00:1-8. doi:10.1002/ijc.28344.
 
8. Waziry R, Jawad M, Ballout R, Al Akel M, Akl E. The effects of waterpipe tobacco smoking on health outcomes: an updated systematic review and meta-analysis. Int J Epidemiol. 2016.
 
9. Montazeri Z, Nyiraneza C, El-Katerji H, Little J. Waterpipe smoking and cancer: systematic review and meta-analysis. Tob Control. 2016:1-6. doi:10.1136/tobaccocontrol-2015-052758.
There are a wide variety of smokeless tobacco products used around the world [1,2]. In the UK chewing tobacco, which may be used as part of betel quid, paan or zarda, is popular with South Asian communities. Tobacco can also be chewed or sucked by itself, or taken as snuff.
 
Smokeless tobacco has been shown to cause mouth, gullet (oesophageal) and pancreatic cancers [2,3]. Chewing betel quid with tobacco has also been shown to cause cancer of the mouth, upper throat and gullet (oesophagus) [2]. The size of the cancer risks associated with using smokeless tobacco are likely to vary depending on the type of product and the way it’s used [1].
 
It has been suggested that smokeless tobacco could be used to help people stop using smoking tobacco, and that falling smoking rates in Sweden have been linked to people switching to a type of smokeless tobacco called ‘snus’. But a review of the evidence by the IARC in 2007 concluded that the available evidence does not support these claims [3].
 
There are many cancer-causing chemicals present in smokeless tobacco, including in ‘snus’ [1–3]. Studies have shown that these harmful chemicals, such as tobacco-specific nitrosamines (TSNAs), are taken up by people using these products [1].
 
Smokeless tobacco also contains nicotine, and is therefore addictive [1–3].
 
References
 
1. Boffetta P, Hecht S, Gray N, Gupta P, Straif K. Smokeless tobacco and cancer. 2008;9(July):667-675.
 
2. IARC. Personal Habits and Indoor Combustions, Volume 100 E, A Review of Human Carcinogens. 2012;100.
 
3. IARC. Smokeless Tobacco and Some Tobacco-specific N -Nitrosamines. IARC Monogr Eval Carcinog Risks to Humans. 2007;89.
Evidence so far suggests e-cigarettes are far safer than smoking tobacco [1–4]. Some potentially dangerous chemicals have been found in e-cigarettes but usually at levels far lower than in tobacco cigarettes [1–3]. Cancer Research UK have agreed a consensus statement on e-cigarettes with other leading public health organisations.
 
E-cigarettes may help some smokers quit [5–11] but further trials are needed to explore how best to use them and to see how they compare to other methods of quitting [12]. A Cochrane review of the experimental studies showed e-cigarettes were more effective than placebo in supporting a quit attempt however this was based on limited evidence [11]. Real-world studies comparing how successful quit attempts in England were using different devices showed that those using e-cigarettes were significantly more likely to quit successfully than those using no aid, but prescription medication and behavioural support was by far the best way to stop smoking [10,13]. Initial indications suggest that success rates are high for e-cigarettes used alongside the specialist support from the Stop Smoking Services [14,15].
 
References
 
1. Burstyn I. Peering through the mist: systematic review of what the chemistry of contaminants in electronic cigarettes tells us about health risks. BMC Public Health. 2014;14(1):18. doi:10.1186/1471-2458-14-18.
 
2. Goniewicz M, Knysak J, Gawron M, et al. Levels of selected carcinogens and toxicants in vapour from electronic cigarettes. Tob Control. 2013.
 
3. McNeill A, Brose L, Calder R, Hitchman S, Hajek P, McRobbie H. E-Cigarettes : An Evidence Update. Comissioned by Public Health England.; 2015. https://www.gov.uk/government/publications/e-cigarettes-an-evidence-update.
 
4. Tobacco Advisory Group of The Royal College of Physicians. Nicotine without Smoke.; 2016.
 
5. Barbeau AM, Burda J, Siegel M. Perceived efficacy of e-cigarettes versus nicotine replacement therapy among successful e-cigarette users: a qualitative approach. Addict Sci Clin Pract. 2013;8(1):5. doi:10.1186/1940-0640-8-5.
 
6. Etter J-F, Bullen C. Electronic cigarette: users profile, utilization, satisfaction and perceived efficacy. Addiction. 2011;106(11):2017-2028. doi:10.1111/j.1360-0443.2011.03505.x.
 
7. Etter J-F. Electronic cigarettes: a survey of users. BMC Public Health. 2010;10:231. doi:10.1186/1471-2458-10-231.
 
8. Bullen C, Howe C, Laugesen M, et al. Electronic cigarettes for smoking cessation : a randomised controlled trial. Lancet. 2013;6736(13):1-9.
 
9. Caponnetto P, Campagna D, Cibella F, et al. EffiCiency and Safety of an eLectronic cigAreTte (ECLAT) as tobacco cigarettes substitute: a prospective 12-month randomized control design study. PLoS One. 2013;8(6):e66317. doi:10.1371/journal.pone.0066317.
 
10. Brown J, Beard E, Kotz D, Michie S, West R. Real-world effectiveness of e-cigarettes when used to aid smoking cessation: a cross-sectional population study. Addiction. May 2014. doi:10.1111/add.12623.
 
11. Mcrobbie H, Bullen C, Hajek P. Electronic cigarettes for smoking cessation and reduction ( Review ). Cochrane Database Syst Rev. 2014;(12).
 
12. MHRA Working Group on NCPs. Quality, safety and efficay of unlicensed NCPs. 2013.
 
13. Kotz D, Brown J, West R. “Real-world” effectiveness of smoking cessation treatments: a population study. Addiciton. 2013.
 
14. Hiscock R, Bauld L, Arnott D, Dockrell M, Ross L, McEwen A. Views from the coalface: What do english stop smoking service personnel think about E-cigarettes? Int J Environ Res Public Health. 2015;12(12):16157-16167. doi:10.3390/ijerph121215048.
 
15. Health and Social Care Information Centre. Statistics on NHS Stop Smoking Services 2014-15.; 2015. http://www.hscic.gov.uk/catalogue/PUB18002.
Evidence shows that using prescription medication and specialist support, for example from the free local Stop Smoking Services, gives you the best chance of quitting successfully [1,2].
 
Prescription medication could be either nicotine replacement therapy (NRT) or non-nicotine stop smoking medications – varenicline (Champix) or bupropion (Zyban) [2]. The Stop Smoking Services can also help you if you chose to use e-cigarettes or go cold turkey and we know the behavioural support is what makes the biggest difference [2–4].
 
Using NRT with no other support has been shown to work5 but it’s important to use enough for it to be of benefit [6,7].
 
References
 
1. Kotz D, Brown J, West R. Prospective cohort study of the effectiveness of smoking cessation treatments used in the “real world”. Mayo Clin Proc. 2014;89(10):1360-1367. doi:10.1016/j.mayocp.2014.07.004.
 
2. National Institute for Health and Care Excellence. Stop Smoking Services.; 2008. https://www.nice.org.uk/guidance/ph10?unlid=10621085462016427172824.
 
3. National Centre for Smoking Cessation and Training. Electronic Cigarettes: A Briefing for Stop Smoking Services.; 2016. http://www.ncsct.co.uk/usr/pub/Electronic_cigarettes._A_briefing_for_sto....
 
4. Hiscock R, Bauld L, Arnott D, Dockrell M, Ross L, McEwen A. Views from the coalface: What do english stop smoking service personnel think about E-cigarettes? Int J Environ Res Public Health. 2015;12(12):16157-16167. doi:10.3390/ijerph121215048.
 
5. Stead L, Perera R, Bullen C, Mant D, Lancaster T. Nicotine replacement therapy for smoking cessation ( Review ). Cochrane Database Syst Rev. 2008;(3).
 
6. Kotz D, Brown J, West R. “Real-world” effectiveness of smoking cessation treatments: a population study. 2013.
 
7. Beard E, Bruguera C, McNeill A, Brown J, West R. Association of amount and duration of NRT use in smokers with cigarette consumption and motivation to stop smoking: A national survey of smokers in England. Addict Behav. 2014;40C:33-38. doi:10.1016/j.addbeh.2014.08.008.

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