MODULATION OF HOST DEFENSES BY EXPOSURE TO OXIDANT AIR-POLLUTANTS

This report reviews the literature on modulation of host defenses by o xidant air pollution, and possible links with increased susceptibility to respiratory infections. The notion of increased susceptibility to respiratory infections is primarily based on available animal data. Si nce the basic biological mechanisms of action of the human and the ani mal pulmonary defenses are similar, it is reasonable to extrapolate th ese biologic responses in experimental animals to human exposures. How ever, no firm conclusions on a relationship of exposure to oxidant air pollutants and defense to infections can yet be drawn from epidemiolo gic data. At this point it is not possible to answer questions such as the relative importance of duration and concentration of exposure, an d reversibility and adaptation phenomena, although these issues are of the utmost importance for population risk assessment. Research at var ious levels is required to fill the scientific gaps. Experimental inha lation toxicologic research using human volunteers and laboratory anim als should focus on dose and time-course dependence, mechanisms of eff ects of exposure to oxidant gases, and the extent of reversibility of the effects. Epidemiologic studies on prevalence and nature of respira tory infections and possible association with exposure to air pollutan ts are also needed.