Tobacco and tobacco smoke contain many substances that are known to cause cancer (the term used is ‘carcinogens’) in laboratory animals and humans. Some carcinogens are natural parts of the tobacco plant itself, and some are formed when tobacco is burned or during processing, curing, ageing, or storing, such as benzene, formaldehyde and tobacco-specific nitrosamines, to mention few. The number and quantity of carcinogens can vary between tobacco products within and across countries. Certain types of smokeless tobacco can be produced with a reduced concentration of tobacco-specific nitrosamines – one of the main carcinogens in tobacco products. Continued tobacco use, and hence continued exposure to cancer-causing substances, can lead to the development of cancer.

Some of the chemicals found in tobacco and tobacco smoke have been classified as human carcinogens by the International Agency for Research on Cancer (IARC), part of the World Health Organization (WHO) (Table 2). Figure 3 highlights some of the many substances present in tobacco smoke that cause cancer in laboratory animals and in humans.

Figure 3: Some cancer-causing substances in tobacco smoke

Source: IARC