Introduction

Tobacco, particularly cigarette smoking, accounts for more cancer deaths than all other known factors. Cancers caused by smoking include those of the lung, oral cavity, pharynx, larynx, esophagus, urinary bladder, renal pelvis and pancreas (IARC, 1986). The most important of these is lung cancer. Whether any excess cancers of the stomach, liver, kidney and cervix are attributable to smoking is still uncertain. As the cigarette habit expands, especially in developing countries, tobaccoassociated cancer deaths are increasing. Consumption of smokeless tobacco is also growing in several parts of the world, often on the assumption that it is not dangerous. Several studies suggest that sidestream tobacco smoke, which exposes bystanders to other people's tobacco smoke (passive smoking) may constitute a cancer risk (IARC, 1986; O'Neill et al., 1987).

The literature on tobacco cancer issues has been extensively reviewed (IARC, 1985; 1986; 1987; Zaridze & Peto, 1986; O'Neill et al., 1987). The object of the present chapter is to provide a brief introduction to certain general issues, the role of tobacco usage being described in more detail under specific cancer sites.

History

Although tobacco smoking was quickly regarded as a vice following its introduction in Europe, the carcinogenic properties of tobacco tar were first demonstrated experimentally by Roffo in the late 1920s. However, it was not until the early 1940s that epidemiological evidence appeared from Germany (Müller, 1939) indicating that smoking was a lung carcinogen.