Lung Cancer and Bronchitis in Relation to Cigarette Smoking and Fuel Consumption in Twenty Countries

Abstract

In their report on Smoking and Health, the Royal College of Physicians (1962) concluded that cigarette smoking was a cause of lung cancer but that smoking was not the only cause of this disease. The report on the same subject by the Surgeon General's Advisory Committee of the United States Public Health Service (1964) concluded that: Cigarette smoking is causally related to lung cancer in men; the magnitude of the effect of cigar ette smoking all other factors. The phrase far outweighs has been wrongly taken by some to imply that the other factors are of little consequence in their total effect but, when dealing with a disease responsible for some 30,000 deaths a year in the United Kingdom, a fraction of only one-fifth due to other factors would account for 6,000 deaths and such a number could hardly be regarded as unimportant. The first tentative esti mates of one-fifth were derived from very small numbers of non-smokers, and studies of more adequate data have shown that in some large urban areas the contribution of other causes to the total deaths must be a good deal higher. For example, it was estimated in 1955 that about half the deaths of men from lung cancer in Liverpool arose from cigarette smoking and about three-eighths must have been due to factors only slightly present in neighbouring rural areas (Stocks and Campbell, 1955). In classical studies of lung cancer mortality related to histories of past residence and smoking of men and women in the United States, Haenszel and his co-workers (Haenszel, Loveland, and Sirken, 1962; Haenszel and Taeuber, 1964) have analysed in great detail the periods of life-time spent, by those who died of the disease, in towns of different population size and in rural and farm areas. Standardized mortality ratios based on 100 for all white males, and adjusted both for their age and smoking history, were, for all durations of residence combined, 65 in farm areas increasing by stages according to the size of town lived in to 123 in cities of half a million population or over; and for white females the mortality ratios increased from 69 in the farm areas to 132 in the large cities. When durations of residence between 10 and 40 years only were considered, the corresponding mortalities were 77 and 122 for males, 70 and 149 for females. This disposes of the idea that the urban excess of lung cancer could be explained away by more cigarette smoking in town than country. Another study of male mortality in Canada according to smoking history, comparing those who had lived for 5 years or more in cities with those who had not, showed an overall ratio of 1-50 for lung cancer contrasted with 1 12 for all causes of death (Department of Health and Welfare, Canada, 1966). A recent evaluation of the urban excess for lung and stomach cancer and bronchitis in English conurba tions compared with surrounding areas, during periods from 1921-30 to 1951-60, has shown that the excess, which continues to be large, cannot be explained either by smoking differences or by the social factors affecting the three diseases, and must be attributed to air pollution in the case of lung cancer and bronchitis for lack of any other conceiv able explanation (Stocks, 1966). Comparisons between lung cancer death rates in whole countries with good standards of diagnosis and cause certification have become possible in recent years, and Nielsen and Clemmesen (1954) demonstrated a rough correspondence between the crude rates in eight countries about the year 1950 and the annual consumption of tobacco per inhabitant 20 years previously. Improvement in reliability of death rates and in availability of trade figures of cigarette consumption made possible a study of death rates at different ages in 1958-9 in 181