Overview of cancer time-trend studies in relation to changes in cigarette manufacture.

The chief purpose of the present chapter is not to review lung cancer trends in general, but merely to consider the extent to which trends in national lung cancer rates can help assess any differences between the carcinogenic effects of different types of cigarette. For this limited purpose, the British data are uniquely informative, for British male lung cancer rates were already high but stable before the cigarette tar levels were halved, and British male cigarette consumption remained stable for some years thereafter. Against this apparently stable background, an otherwise unexplained decrease of about one-half in British male lung cancer mortality in early middle age has followed the decrease in cigarette tar deliveries, which is consistent with Stellman's conclusion (this volume), based on review of the case-control and prospective studies, that cigarette-induced lung cancer risks are approximately proportional to machine-measured tar deliveries. Lung cancer trends are also reviewed for males from the USA (where cigarette tar deliveries have been greatly reduced) and from the USSR (where they have not).