Smoking and Cancer

Abstract

The idea that cigarette smoke causes lung cancer makes a strong intuitive appeal. We can readily envisage airborne carcinogens passing through the mouth, past the larynx and pharynx, down the trachea to the bronchi and lodging in the lungs. Animal experiments reveal chemical carcinogens in the condensate of cigarette smoke and no great imaginative feat is needed to connect such carcinogens with the initiation of cancers of the respiratory and gastrointestinal tracts. Positive associations between smoking and various types of tumour, but conspicuously cancers of the pharynx, larynx, bronchus and lung, have been observed in many surveys. It is less immediately obvious how ‘cigarette-associated’ cancers of the kidney, bladder and prostate might arise, although in principle, a general systemic effect due to circulating carcinogens can be invoked.