Assay of possible carcinogens related to lung cancer, with special reference to atmospheric pollution

1. From a background of epidemiological, statistical, clinical and biological information, evidence has been adduced for the consideration of carcinogenic aromatic polycyclic hydrocarbons as occupying a key role in the pathogenesis of the human non-adenomatous lung cancers which are relatable to general atmospheric pollution. 2. Assays of particulate air pollutants for the hydrocarbons which are Carcinogenic under laboratory conditions have been made, using the methods of repetittive adsorption chromatography, U.V. absorption spectrophotometry and fluorescence spectrography. The pollutants investigated were samples of Petrol and Diesel engine exhaust soots, and a sample of general atmospheric soot. The relative importance of the former two soots as sources of atmospheric enrichment in carcinogenic hydrocarbons was gauged by comparison with the latter soot. 3. Petrol Exhaust soot was found to be an important source of atmospheric enrichment in 3,4-Benzopyrene. The following carcinogens have also been identified in this soot: 1,2,3,4-Dibenzopyrene, 1,2,4,5-Dibenzopyren and 3,4-Benzofluoranthene. 4. The Diesel Exhaust Soot was not found to be a good source of 3,4-Benzopyrene, in contrast with the Petrol Soot. However, like the latter, it was found to be a source of 1,2,3,4-Dibenzopyrene and 3,4-Benzofluoranthene. Trace quantities of this latter compound, whose strong carcinogenicity for mice has only recently been discovered, have been detected in the sample of general atmospheric soot, and may have had its origin in vehicular exhausts. 5. The biological significance of an associated oil in the case of the exhaust soots as a possible adjuvant factor was discussed. 6. The fluorescence and absorption features of many compounds, not hitherto recorded in the present connection, have been presented. 7. Evidence suggesting that side-stream and exhaled cigarette smoke contribute to the general atmospheric pool of 3,4-Benzopyrene has been obtained. 8. Accepting the validity of the statistical findings which - for men - causal1y relate cigarette smoking with non-adenomatous lung cancer, a special carcinogenic environment for cigarette smokers was postulated. Cigarette smoke mu considered as being carcinogenic per se. A variety of carcinogenic hydrocarbons were demonstrated in cigarette smoke in quantifies less than 2 p.p.m. of whole tar, for those estimated. The carcinogenic hydrocarbons found were, 3,4-Bonzopyrene and 1,2,3,4-Dibenzopyrene as well as the following compounds for which some carcinogenic activity under laboratory conditions ban boon demonstrated. 1,2-Benzanthrene, two 1,2-Benzoanthrene derivatives, 3,4m-Benzophenanthrene, 1,2-Benzopyrone, 1,12-Benzoperylene. Attention was further drawn to three other fractions (one of which contains what is tentatively identified as 1,2,7,8-Dibenzofluorene) which may be carcinogenic. 9. The cigarette smoker is shown to have an exposure to 1,2,3,4-Dibengopyrone at a concentration (1.6 mug per 100 cigarettes smoked) which is not realised by his non-smoking neighbour.10. Doubt remained as to whether the proposed special environment was explicable solely on the bole of the treditional carcinogenic hydrocarbons found, and con-sequently cigarette smoke was investigated for the presence of other factors of possible carcinogenic significance, Such investigations led to the estimation of the reducing or anti-oxidant activity of cigarette smoke by use of the stable free radical. Diphenyl-picrylhydrasyl, and to the detection and estimation of free radicals in cigarette smoke by the Electron Paramagnetic Resonance Method. 11. The Smoke from ope cigarette in Bensene was Found to have a reducing power equivalent to an 0.5 x 10