Size-Resolved Concentrations of Particulate Matter and Bioaerosols Inside versus Outside of Homes

Size-resolved airborne particulate matter samples (PM2.5, PM10, and TSP) collected inside ten northern California homes over four days and one night (9-12 h/sample, spanning a 3.5 week period) were analyzed for protein, endotoxin, and (1 3)--D-glucan concentrations. Some simultaneous size-resolved outdoor samples were also collected. The associations of residential characteristics and occupant behavior with the indoor airborne levels were investigated. In addition, the relation between these chemical biomarkers and the more traditional culturing approaches was studied. Most of the indoor mass concentration of airborne particles and protein was in the fine fraction (PM2.5), while the mass of airborne endotoxin and (1 3)--D-glucan was mainly in the coarser fractions (PM10-2.5 and PMTSP-10). No strong correlations were seen between short-term (3-6 min) culturable bacteria and fungi counts and the corresponding longer-term (9-12 h) biomarker levels. Daytime indoor levels of the biomarkers tended to be higher than outdoors, especially for the PM10-2.5 fraction, but only in a few cases were the indoor/outdoor relationships statistically significant. Indoor pets were associated with elevated airborne PM and bioaerosols inside homes. Two other factors, wall-to-wall carpet and older houses, also appear to be associated with some elevations in indoor levels.