INTERACTION OF GASEOUS AND PARTICULATE POLLUTANTS IN THE RESPIRATORY-TRACT - MECHANISMS AND MODULATORS

Human contact with air pollution usually involves exposure to more tha n one chemical, and biological responses to the inhalation of polluted atmospheres likely depend upon the interplay between individual mater ials. Thus, characterizing effects from exposures to mixtures of air p ollutants is necessary for adequate quantitation of health risks. Expo sure to gas/particle mixtures may result in respiratory tract response s which are additive, or reflect synergistic or antagonistic interacti ons. The occurrence and type of interaction depends upon numerous fact ors, including the biological endpoint being examined and the specific exposure conditions, such as concentration, duration, and the physico chemical characteristics of the exposure atmosphere. It is, therefore, not always possible to predict solely from the presence of certain po llutants in a complex atmosphere exactly whether there will be an inte raction and, if so, what type it will be. This complicates attempts to relate responses observed in laboratory studies of mixtures to those which may occur under ambient patterns of exposure, an extrapolation n eeded for human risk assessment.