Factors affecting personal exposure to thoracic and fine particles and their components

Central monitoring site (CMS) concentrations have been used to represent population-based personal exposures to particulate matter (PM) of ambient origin. We investigated the associations of the concentrations of PM2.5 and PM10 and their elemental components for elderly clinic patients with chronic obstructive pulmonary disease in two cities with different PM compositions, that is, New York City (NYC) and Seattle. Daily measurements of CMS, outdoor residential, and indoor PM10 and PM2.5 concentrations, as well as personal PM10, were made concurrently for 12-consecutive winter days at 9 NYC and 15 Seattle residences, as well for 9 NYC residences in summer. Filters were analyzed for elemental components using X-ray fluorescence (XRF), and for black carbon (BC) by light reflectance, and outdoor-indoor-personal relationships of PM components were examined using mixed-effect models. Using sulfur (S) as a tracer of PM of ambient origin, the mean contributions of outdoor PM2.5 was 55.2% of the indoor concentrations in NYC, and 80.0% in Seattle, and outdoor PM2.5 in NYC and Seattle were 19.7 and 18.5% of personal PM2.5 concentration. S was distributed homogeneously in both cities (R-2 = 0.65), whereas nickel (R-2 = 0.23) was much more spatially heterogeneous. Thus, CMS measurements can adequately reflect personal exposures for spatially uniform components, such as sulfate, but they are not adequate for components from more local sources.