IARC Monographs (Vol 83) Tobacco Smoke and Involuntary Smoking (June 2002): Summary of data reported and evaluation
A scientific working group of 29 experts from 12 countries convened by the Monographs Programme of the International Agency for Research on Cancer (IARC) of the World Health Organization, Lyon, France, has reviewed all significant published evidence related to tobacco smoking and cancer, both active and involuntary. While its conclusions unsurprisingly confirmed the cancer-causing effects of active smoking, which an earlier working group had considered back in 1986, it now concluded its evaluation of the carcinogenic risks associated with involuntary smoking, with second-hand smoke also classified as carcinogenic to humans.
Disease burden very high
In brief, the tobacco epidemic is big one-half of all persistent cigarette smokers are eventually killed by a tobacco-caused disease. Half of these deaths occur in middle age (35-69 years), when those killed by tobacco lose on average 20-25 years of nonsmoker life expectancy. There is an emerging epidemic in females and in developing countries. While annually tobacco accounts for millions of cancer deaths worldwide, it causes an even greater number of premature deaths from cardiovascular and lung diseases and from stroke than from cancer. Nonetheless, tobacco use is the largest cause of preventable cancers around the world.
Unfortunately, as we continue to examine the cancer risk caused by smoking we are learning that it is even greater than previously thought and more cancer sites are affected.
New cancer sites affected
In this monograph, the Working Group added additional cancer sites to the already very long list of cancers caused by smoking. Some of these are among the most common kinds of cancer around the world, including cancers of the stomach, liver, uterine cervix, and kidney (renal cell carcinoma) and myeloid leukemia. In addition, the cancer risks of tobacco smoking are greatly enhanced for some cancer sites when combined with exposure to other known carcinogens.
Not only cigarettes
Apart from cigarette smoking, other widely used forms of tobacco smoking, such as cigars, pipes and bidis (common in South Asia and growing in popularity in the United States), also increase cancer risks for cancer of the lung, cancer of the head and neck, and other cancers.
The younger one starts, the more significant the risk
Risks to smokers are increased greatly the longer they smoke. The tendency of youth around the world to start smoking at younger and younger ages will predispose them to substantial risks in later life.
Dont start smoking, or if you smoke, stop!
While it is best never to start smoking, within the next several decades the greatest reduction in the number of cancer deaths will be due to the reduction in risk for those who stop. Smoking cessation, along with never starting to smoke, will remain the best ways to prevent cancer around the world in the 21st century. Any possible public health gains from changes in cigarette composition would be minimal in comparison.
Fortunately, the scientific evidence continues to mount on the benefits of cessation at any age. Most of the harmful effect is avoided if smoking is stopped in the early 30s, but reduction in risk is obtained even when smoking is stopped later in life. Stopping smoking works.
Men and women equal
The lung cancer risks of smoking are similar in women and men when it has been continued equally long and in similar ways. In the United States and the United Kingdom (where many women have smoked cigarettes throughout adult life), roughly 90% of lung cancers in both men and women are attributable to cigarette smoking.
Some cancer risks unaffected
Tobacco smoking does not cause all cancers. There is now clear evidence that smoking causes little or no risk of breast cancer or of endometrial cancer. Prostate cancer does not seem to be caused by tobacco smoking either.
Second-hand smoke causes lung cancer
Nonsmokers are exposed to the same carcinogens as active smokers. Even the typical levels of passive exposure have been shown to cause lung cancer among never smokers. Second-hand tobacco smoke IS carcinogenic to humans.
Concern that breast cancer or any other cancer not caused by active smoking might be caused by involuntary smoking is unjustified by the evidence.
Uncertainty as to risk to children exposed
The evidence for increased cancer risks in later life among children exposed to parental and other passive exposures is uncertain at this time.
The IARC Monographs
The IARC Monographs series publishes authoritative independent assessments by international experts of the carcinogenic risks posed to humans by a variety of agents, mixtures and exposures. Since its inception in 1972, the series has reviewed more than 880 agents, and IARC Monographs have become well-known for their thoroughness, accuracy and integrity.