TOXICOLOGICAL EVIDENCE FOR HEALTH-EFFECTS FROM INHALED PARTICULATE POLLUTION - DOES IT SUPPORT THE HUMAN-EXPERIENCE

The fine size mode of ambient particulates, designated as PM-10, is a heterogeneous mixture that can vary in particle size and chemical comp osition, depending on geographical location, meteorology, and source e missions. While epidemiological studies indicate an association betwee n ambient particulate air pollution exposure and increased human morta lity and morbidity, the question remains as to biological plausibility . individual components of PM-10 have been shown, in experimental stud ies, to produce what may be considered to be adverse health effects si milar to those observed in humans. For example, diesel exhaust particl es are associated with lung tumors, and acid sulfates are associated w ith airway hyperresponsiveness and alterations in mucociliary clearanc e. However, in most cases, exposure levels are well above those found in ambient air, and the relationship between results oi toxicological assessments and human exposure scenarios is not always clear. Furtherm ore, in some cases, the chemical species resulting in adverse response s in toxicological studies are not always the same as those associated with effects in human population studies. Thus, while toxicological e vidence clearly indicates the ability of certain ambient particles to induce increased morbidity in laboratory studies, the responsible chem ical species have not been definitively delineated.