AIRBORNE POLLUTANTS AND THE IMMUNE-SYSTEM

The effects of airborne pollutants on the immune system have been most widely studied in the respiratory tract, Entry may occur as a volatil e gas (ozone, benzene), as liquid droplets (sulfuric acid, nitrogen di oxide), or as particulate matter (diesel exhaust, aromatic hydrocarbon s), The subsequent interaction with the immune system may result in lo cal and systemic responses, and studies have shown examples of disease occurring from both overactive immune responses and immunosuppression . For the most part, airborne pollutants (small molecular weight chemi cals) have to be coupled with other substances (proteins or conjugates ) before they can be recognized by the immune system and exert their e ffects. Fortunately, this encounter rarely causes immunologically medi ated human disorders, The following briefly reviews some of the disord ers that may occur, Immunologically nonspecific inflammation of the lu ng can occur after inhalation of ozone in anyone given sufficient dose and time of exposure, Immunologically specific cell-mediated (T lymph ocyte) reactions appear to predominate in chronic beryllium disease, w hich results in a granulomatous form of lung disease, Beryllium alone does not appear to be antigenic but requires chemical linkage with a l arger molecule, Mercury-induced autoimmune disease (immune system atta cks self-antigens) affecting kidneys and lungs has been demonstrated i n animal models (changes similar to those seen in people with Goodpast ure's syndrome), Immunosuppression can be demonstrated after exposure to polycyclic aromatic hydrocarbons (2,3,7,8-tetrachlorodibenzo-p-diox in). Hypersensitivity (or allergic) reactions can occur after exposure to toluene diisocyanate (occupational asthma). In summary, airborne p ollutants may cause a wide spectrum of immunologically mediated disord ers, There is clearly an underlying genetic basis for the susceptibili ty to immunologic disease resulting from exposure to pollutants, but k nowledge in this area is rudimentary at present. Studies have been imp eded by lack of appropriate in vitro models, as well as difficulties i n identifying the biologically active substance.