Particulate matter components, sources, and health: Systematic approaches to testing effects

摘要

Exposure to particulate matter (PM) is associated with adverse health outcomes. There has long been a question as to whether some components of the PM mixture are of greater public health concern than others so that the sources that emit the more toxic components could be controlled. In this paper, we describe the National Particle Component Toxicity (NPACT) initiative, a comprehensive research program that combined epidemiologic and toxicologic approaches to evaluate this critical question, partly relying on information from a national network of air quality monitors that provided data on speciated PM_(2.5) (PM with an aerodynamic diameter＜2.5 μm) starting in 2000. We also consider the results of the NPACT program in the context of selected research on PM components and health in order to assess the current state of the field. Overall, the ambitious NPACT research program found associations of secondary sulfate and, to a somewhat lesser extent, traffic sources with health effects. Although this and other research has linked a variety of health effects to multiple groups of PM components and sources ofPM, the collective evidence has not yet isolated factors or sources that would be closely and unequivocally more strongly related to specific health outcomes. If greater success is to be achieved in isolating the effects of pollutants from mobile and other major sources, either as individual components or as a mixture, more advanced approaches and additional measurements will be needed so that exposure at the individual or population level can be assessed more accurately. Enhanced understanding of exposure and health effects is needed before it can be concluded that regulations targeting specific sources or components of PM_(2.5) will protect public health more effectively than continuing to follow the current practices of targeting PM_(2.5) mass as a whole.