Specific Occupational Cancers and Their Environmental Counterparts

The preceding critical appraisal of the characteristics of occupational respiratory carcinogens has demonstrated definitely that occupational respiratory cancers can be induced by a variety of chemical agents. Occupational respiratory cancers and their industry-related and etiologically identical environmental and medicinal counterparts provide conclusive evidence of the polyetiology of respiratory cancers. The data presented have shown moreover that some of the occupational respiratory carcinogens are widely distributed in the general atmosphere especially in urban and industrialized regions and in some metropolitan communities, such as London and New York, contaminate the air and therefore are inhaled by their residents in amounts considerably higher than those inhaled by the majority of smokers and reached only exceptionally by the most heavy smokers. It has been noted also that the carcinogenic potency of many of the occupational respiratory carcinogens is distinctly higher according to human and experimental evidence than that demonstrable for cigarette smoke even when applied as a tar condensate under most severe experimental conditions. While pluripotential carcinogenic properties of cigarette smoke has been deduced from circumstantial statistical evidence on man, these qualities have been established beyond any doubt in man and animals for various occupational carcinogens. Human experience with the majority of the occupational respiratory carcinogens indicates furthermore that these agents are capable of inducing cancers in different parts of the respiratory tract, including the nasal cavity and nasal sinuses. The latter parts so far have as yet not been incriminated as susceptible to the alleged carcinogenic action of cigarette smoke. There exists also adequate clinical and experimental evidence which demonstrates that cancers of the lung and nasal sinuses follow not only by an inhalatory introduction of respiratory carcinogens but also upon an ingestive and parenteral one. More recent observations on the carcinogenic action of a large series of nitrosamines by Druckrey and associates, and others, have brought out the fact that the chemical structure of these compounds some of which are widely used in industry directs their action toward specific target organs, including the lung and nasal sinuses for some of these substances.