INHALATION OF BENZPYRENE AND CANCER IN MAN

Both cigarette smoke and polluted urban air contain very small amounts of benzo[a]pyrene, or BaP, a substance which is carcinogenic to experimental animals if relatively large amounts are applied in certain ways such as skin painting or subcutaneous injection. This suggested the possibility that the BaP in cigarette smoke might account for the high degree of association between cigarette smoking and lung cancer, and it suggested the possibility that BaP poliution of urban air might perhaps increase the risk of lung cancer. Some years ago Wynder and Hoffman found an average of 2.5 pg of BaP in the smoke from 100 American cigarettes smoked mechanically.' The average amount has dropped considerably in more recent years. Based upon this, it would appear that even during a lifetime of heavy cigarette smoking, the concentration of BaP per square centimeter of bronchial tissue over which it might be spread would be extremely small as compared with the dose required to produce skin cancer in mice. The concentration of BaP in the air of large American cities is reported to vary from about 0.3 to 6.0 pgl1,OOO cubic meters in summer and from 6.0 to as high as 74.0 in winter.* The air of British cities is more heavily contaminated with BaP. In some British cities, in winter it varies from 73.0 to as high as 170.0 pgl1,OOO cubic meters of air.g During the course of a year, nonsmokers living in some of these cities probably inhale far more BaP than do heavy cigarette smokers living in rural areas of America. Even so, the amount is extremely low as compared with the amount required to produce skin cancer in susceptible strains of mice, surface area being taken into consideration, Largely because of interest in the possible effects of small amounts of BaP in cigarette smoke and in urban air, we decided to study mortality from lung cancer and other causes among people with very heavy occupational exposure to BaP in air. Roofers and waterproofers are such a group. Sawicki collected air samples in the vicinity of men working in pitch roofing operations and found 14,000 pg of BaP/ 1,000 cubic meters of air (see TABLE 1 ) . Even higher amounts were found in air samples collected close to where a roofer was attending a kettle of hot pitch. Thus it would appear that roofers working with hot pitch are exposed to far greater amounts of BaP than are heavy cigarette smokers living in urban areas.