Influence of environmental factors on the respiratory tract summary and perspectives

An overview is presented of toxic environmental factors (carcinogens, toxic metals, asbestos, silica and coal dust); pulmonary defense mechanisms (particle deposition, components of the alveoli, bronchial clearance, pulmonary lymph nodules, bronchial phagocytes, pulmonary lymphatic system, sites of bronchogenic cancer); macrophages and their functions; respiratory infections; allergic pulmonary reactions, and synergism among toxic environmental agents (cigarette smoke). Toxic environmental agents directly injure the lung or injure it due to the immunologic (allergic) response developed by the host. Carcinogenic agents can be inactivated by host metabolism or created by host metabolism (or both). Radiation, alkylating chemicals and oxidants (producing peroxides and free radicals) may alter DNA, causing genetic defects and cancer; and individuals may be born with a genetic constitution that makes them more susceptible to cancer, pulmonary fibrosis, emphysema or immunologic (allergic) diseases. Pharmaceutical agents can be used to treat infection, allergic disease and cancer and yet these same agents may cause severe adverse reactions in certain people (e.g., penicillin allergy or immunosuppression). Prevention of injury from toxic and carcinogenic agents in the environment is best accomplished by eliminating the offending agent or reducing its concentration. The multitude of toxic environmental agents that we all encounter have not been proven to cause a high incidence of overt disease. Human beings, in fact all animals and plants, often detoxify or adapt to ambient concentrations of such agents. On the other hand, many of these agents may have unrecognized effects, at least in some people. They may lower one's susceptibility to viral and bacterial agents or contribute to the onset of cancers appearing many years after exposure. Living in an industrial society entails risks and annoyances different from those in a less complex society. We must accept some of these liabilities along with the multitude of assets that our society provides to enhance the comforts and the variety in life. (91 references)