Tobacco

Tobacco is the greatest preventable cause of cancer.²,³ The estimated percentage of cancer cases attributable to tobacco ranges from 15.5–24% using European estimates¹⁶ to 29-33% in the United States.²,³ WHO identifies tobacco use as the single greatest avoidable risk factor for cancer mortality worldwide, and estimates tobacco use to cause up to 1.5 million cancer deaths each year.¹

Tobacco in Australia

In Australia, the percentage of daily smokers has been steadily declining, from 22.4% of adults in 2001 to 16.1% in 2011–12.³² This equates to 2.8 million adults who were daily smokers in 2011–12.³²

Tobacco smoking has been estimated to be the greatest contributor to the health burden of Indigenous people, at 12% of the total Indigenous health burden.³³ While the proportion of current smokers amongst Indigenous people has decreased from 51% in 2002 to 47% in 2008,³⁴ Indigenous Australians were 2.2 times as likely to smoke tobacco compared to non-Indigenous Australians.¹⁹

Tobacco and cancer

The IARC has identified tobacco consumption as the single largest cause of cancer in the world and tobacco smoking as the single largest cause of lung cancer.⁵ About 90% of lung cancer in Australian men and 65% of lung cancer in Australian women is estimated to be a result of tobacco smoking.³⁵ A 2012 IARC Monograph on tobacco smoking reviewed the evidence and classified tobacco smoking as a Group 1 carcinogen (see Appendix 1 for explanation of IARC classifications).⁵ The IARC identified that tobacco smoking also causes cancers of the oral cavity, pharynx, nasal cavity and accessory sinuses, larynx, oesophagus, stomach, pancreas, colorectum, liver, kidney (body and pelvis), ureter, urinary bladder, uterine cervix and ovary (mucinous), and myeloid leukaemia.⁵ A positive association between tobacco smoking and female breast cancer was also reported by the IARC⁵ and was supported by a recent meta-analysis of nearly 32,000 breast cancer cases.³⁶

The IARC Monograph identified that both the duration of smoking and total tobacco consumption increase the risk of lung and many other cancers.⁵ Alcohol consumption also interacts synergistically with tobacco smoking to increase the incidence of cancers of the upper aero-digestive tract (i.e. oral cavity, pharyngeal, laryngeal and oesophageal cancers) beyond the single additive effects of tobacco smoking or alcohol (See Appendix 2 for explanation).⁵

Second-hand smoke and cancer

Tobacco smoke has an effect on the wider population beyond smokers, through exposure to second-hand tobacco smoke or the chemicals in tobacco smoke (also known as passive smoking and environmental smoke). The IARC Monograph classified second-hand smoke as a Group 1 carcinogen, which causes lung cancer and is associated with pharyngeal and laryngeal cancers.⁵

Reducing individual risk of cancer and staying healthy

Quitting smoking reduces the risk of lung and other major cancers.³⁷,³⁸ Five years after quitting smoking, risk of mouth, throat, oesophageal and bladder cancers are halved, and the risk for dying from lung cancer drops by half after 10 years.³⁹ Quitting smoking can also contribute to both short and long-term improvements in health,^40-42 including: a dramatic drop in blood levels of carbon monoxide, a drop in heart rate and blood pressure, improved circulation and lung function, decreased coughing and shortness of breath, and reduced risk of coronary heart disease and stroke.⁴³ WHO reports that people of all ages can still benefit from quitting, including those who have already developed smoking-related health problems.⁴³

The Australian National Tobacco Campaign encourages individuals to stop smoking and provides support through the Quitline.

Cancer Australia recommendations for individuals

Cancer Australia recommends not smoking and avoiding exposure to second-hand smoke to reduce cancer risk.

Table 1: Summary of evidence for tobacco and cancer sites

Risk factor	Source	Evidence	Cancer site
Tobacco smoking	IARC 20125	Sufficient evidence (highest IARC classification for carcinogenicity)	Lung, oral cavity, pharynx, nasal cavity and accessory sinuses, larynx, oesophagus, stomach, pancreas, colorectum, liver, kidney (body and pelvis), ureter, urinary bladder, uterine cervix and ovary (mucinous), myeloid leukaemia
		Limited evidence  (positive association)	Female breast
Second-hand smoke	IARC 20125	Sufficient evidence (highest IARC classification for carcinogenicity)	Lung
		Limited evidence  (positive association)	Pharynx, larynx

See Appendix 1 for explanation of evidence.