Risk Factors for Lung Cancer
An overview of the evidence
2014
Risk factors for lung cancer: an overview of the evidence was prepared and produced by:
Cancer Australia
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© Cancer Australia 2014. Published with minor amendments.
ISBN Print: 978-1-74127-269-7 ISBN Online: 978-1-74127-262-8
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Cancer Australia, 2014. Risk factors for lung cancer: an overview of the evidence, Cancer Australia, Surry Hills, NSW.
Risk factors for lung cancer: an overview of the evidence can be downloaded from the Cancer Australia website:
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Foreword
Lung cancer is the fourth most common cancer diagnosed in both men and women in Australia and the leading cause of cancer death.
Risk factors for lung cancer: an overview of the evidence is a comprehensive, evidence-based summary of factors that affect a person's risk of developing lung cancer, based on a systematic review of the international literature commissioned by Cancer Australia.
This overview aims to increase awareness and understanding of the key lifestyle, environmental and occupational factors that affect lung cancer risk, in addition to the role of family history. The overview also highlights factors where the evidence is either limited or inconsistent in relation to risk of lung cancer.
We anticipate the overview will be a valuable resource to support health professionals, policy makers and the community with evidence about exposure to risk factors for lung cancer, to increase understanding of those who may be at greatest risk of lung cancer, and to inform interventions to ultimately reduce the burden of lung cancer.
Helen Zorbas AO
CEO
Cancer Australia
Risk factors for lung cancer | An overview of the evidence 55
Contents
Foreword i
Acknowledgments iv
Project Working Group iv
Cancer Australia iv
Funding iv
Executive Summary v
Tobacco Smoking v
Environmental and Occupational Risk Factors vi
Painting as an Occupation viii
Family History ix
Factors with Limited Evidence of an Association with Lung Cancer x
What does this mean for individuals? x
Summary of relative risks xi
Background 1
What is lung cancer? 1
Lung Cancer in Australia 1
What is a Risk Factor? 2
How do we measure risk? 2
About this Overview 4
What does this overview mean for individuals? 5
Tobacco Smoking 6
Active Smoking 6
Passive Smoking 9
Environmental and Occupational Risk Factors 11
Radon 11
Arsenic 13
Polycyclic Aromatic Hydrocarbons 15
Cadmium 17
Asbestos 19
Silica 22
Iron and Steel Founding 24
Nickel 26
Beryllium 28
Painting as an Occupation 30
Chromium VI 31
Air Pollution 33
Family History 35
What is the Risk? 35
Factors with Limited Evidence of an Association with Lung Cancer 36
Consumption of Red Meat and Processed Meat 36
Alcohol Consumption 37
Dietary and Blood Cholesterol 37
Exposure to Birds 38
Exposure to Wood Dust 39
Physical Activity 39
Glossary 40
Appendix 1 International Agency for Research on Cancer (IARC) 42
References 44
Risk factors for lung cancer | An overview of the evidence 55
Acknowledgments
Cancer Australia gratefully acknowledges the contributions to the development of Risk factors for lung cancer: an overview of the evidence from:
· the Project Working Group, which provided expert guidance and direction to the project
· the Joanna Briggs Institute, University of Adelaide, which was commissioned by Cancer Australia to undertake a systematic review of national and international literature regarding risk factors for lung cancer, which formed the basis of this overview
· Biotext Pty Ltd, which was commissioned by Cancer Australia to summarise the findings of the systematic review and contributed technical editing and design.
Project Working Group
· Mr Andrew Bowen, consumer
· Professor Kwun Fong, Thoracic and Sleep Physician; Professor, School of Medicine, University of Queensland
· Professor Don Iverson, Behavioural Scientist; Executive Dean, Faculty of Science, Medicine and Health, University of Wollongong
· Professor Bernard Stewart, Environmental Cancer Specialist and Head, Cancer Control Program, South East Sydney Local Health District
· Professor David Roder: Cancer Epidemiologist; Chair of Cancer Epidemiology and Population Health, University of South Australia
Cancer Australia
· Ms Sue Sinclair, General Manager, Service Development and Clinical Practice
· Dr Vivienne Milch, Medical Officer
· Ms Liz King, Manager, Lung Cancer
· Ms Kathleen Mahoney, Senior Project Officer, Lung Cancer
· Dr Rona Hiam, Clinical and Primary Care Adviser, Lung Cancer
· Ms Julie Mueller, Project Manager, Lung Cancer
Funding
The development of this overview was funded by the Australian Government through Cancer Australia.
Executive Summary
In Australia, lung cancer is the fourth most common cancer in both men and women, and the fifth most commonly diagnosed cancer overall.1 Lung cancer causes more deaths than any other cancer, accounting for 18.9% of all cancer deaths.2 A person's chance of developing lung cancer may be increased by a number of factors, known as risk factors. Risk factors can include behaviours (such as tobacco smoking), chemical agents in the environment or the workplace (such as asbestos, arsenic or radon) or a family history of cancer. Some risk factors are modifiable, meaning the risk can be altered by changing behaviour or adopting safety measures. Other risk factors, such as age, are regarded as non-modifiable.
This overview summarises the evidence for a range of factors that are associated with a person's risk of developing lung cancer, and is based on a systematic review of published scientific studies.3 The systematic review examined the published research on primary lung cancer up to April 2011 to identify any associations between particular risk factors and lung cancer, and to determine the magnitude of each risk. Pleural mesothelioma, however, is not regarded as a malignant tumour of the lung in the current version of the international coding standards for cancer, and is not considered in this report.
A person's risk of developing lung cancer can be presented as either absolute risk or relative risk. Absolute risk is a person's chance of developing lung cancer over a specified time period, while relative risk describes how many times more likely a person exposed to the risk factor is of developing lung cancer than a person who is not exposed to the risk factor. Relative risk also allows comparison of the effects of different risk factors on a person's likelihood of developing the disease.
Relative risk can be expressed in several different ways. All of the following expressions have the same meaning:
· The relative risk is 1.5.
· The risk is 1.5 times higher.
· There is a 50% greater risk.
Similarly, if the relative risk is 9.0, this means that the risk is 9 times higher in people exposed to the risk factor.
In the case of most risk factors for human diseases, an increase in risk depends on intensity, frequency and duration of exposure, as well as other contextual factors. The interaction of these risk and contextual factors can affect the risk estimate; therefore, relative risk should be considered as indicative of a comparative risk that may vary to some extent from place to place.
Tobacco Smoking
Active Smoking
Active smoking refers to smoking tobacco in any form, but does not include exposure to other people's tobacco smoke (passive smoking). There is clear evidence that active smoking significantly increases a person's risk of developing lung cancer.4 Overall, current smokers are approximately 9 times more likely to develop lung cancer than people who have never smoked (relative risk 9.0).5 Former smokers are almost 4 times more likely to develop lung cancer than people who have never smoked (relative risk 3.9).5 The length of time since quitting smoking varied among studies of 'former smokers, but was at least one year in the studies that specified a timeframe.5 The more a person smokes, the greater their risk of developing lung cancer. For example, men who smoke more than 20 cigarettes per day are almost 14 times more likely to develop lung cancer than people who do not smoke (relative risk 13.7)5 while those who smoke fewer than 10 cigarettes per day are 1.4 times more likely to develop lung cancer than non-smokers.5 Smoking can also interact with other lung cancer risk factors to further compound a person's risk.
Passive Smoking
Passive smoking occurs when tobacco smoke is inhaled by people other than through active smoking (i.e. exposure to other people's tobacco smoke). It is most common in indoor settings, where smoke may not be as easily dispersed as it is outdoors. Passive smoking does not present as pronounced a risk as active smoking, although the risk can still be considerable. Evidence suggests that people who are exposed to passive smoking in their workplace are up to twice as likely to develop lung cancer as people who are not exposed (relative risk 1.2-2.0).6 Exposure to passive smoking at home is also associated with an increase in risk of lung cancer. Women who have never smoked, but have partners who smoke, are 1.3 times more likely to develop lung cancer than women who live with a non-smoking partner.7 The effect on men from the smoking habits of their partners is similar, although not statistically significant—most likely due to the small number of studies that are available.8 There is also emerging evidence to suggest that people exposed to passive smoking as children may be at increased risk of developing lung cancer as adults.4
Environmental and Occupational Risk Factors
Radon
Radon is a naturally occurring radioactive gas. Occupational exposure to radon is most common in uranium miners, who have been found to be 1.6-3.8 times more likely to develop lung cancer than people who are not exposed to high levels of radon.9,10 This risk increases with increasing exposure,11 and also with smoking.12 There is evidence that exposure to moderate amounts of radon in the home can also increase the risk of lung cancer, although not to the same extent as occupational exposure (relative risk 1.3).13
Arsenic
Occupational exposure to arsenic most commonly occurs in the mining and manufacturing industries through inhalation of particles that contain arsenic. Evidence suggests that occupational exposure to arsenic compounds in smelter workers, miners (particularly tin and gold miners) and production workers increases the risk of lung cancer.14 Generally, a person's risk increases with increasing levels and duration of exposure. Smoking appears to further increase the risk of lung cancer in people who are exposed to arsenic in their workplace.15,16 There is also evidence that high levels of arsenic in drinking water in some populations are associated with an increased risk of lung cancer;14,17 however, these findings are not generalisable to developed countries such as Australia, where concentrations of arsenic in drinking water fall well within the World Health Organization's prescribed safe levels. Studies suggest that smoking further increases the risk of lung cancer after exposure to arsenic in drinking water, particularly at high concentrations of arsenic.14
Polycyclic Aromatic Hydrocarbons
Polycyclic aromatic hydrocarbons (PAHs) are byproducts of burning organic material, such as coal, crude oil, natural gas, garbage and tobacco. Sources of PAHs include urban and industrial air pollution, tobacco smoke and diet. People working in particular occupations and industries may be exposed to high levels of PAHs. Industries associated with a higher risk of lung cancer from PAH exposure include coal gasification, coke production and carbon black production (relative risk for workers in these industries is approximately 1.2-2.0).18 It is not clear whether the length of time that a person is exposed to PAHs affects their risk.
Cadmium
Cadmium is a metal that occurs naturally in the Earth's crust and in sea water, and is used in a range of industrial applications. Evidence suggests there is a modest increase in risk of lung cancer associated with cadmium exposure; however, the high level of variability in studies makes it difficult to measure the overall risk. It is also difficult to define the risk of occupational cadmium exposure, although it appears that exposure to cadmium fumes or mist is associated with a greater risk than exposure to cadmium dust (relative risk 2.1 compared with 0.7-1.0 for cadmium dust).19 Cadmium can also accumulate in soil, particularly in areas near industrial sources of cadmium. One study suggests that people who are highly exposed to cadmium in their homes (as a result of proximity to zinc smelters) have a higher risk of developing lung cancer than people who live in unexposed areas.20