Airborne biological, fungal, and bacterial particles inside homes: Sizes, concentrations, and influential factors

Airborne particles of biological origin, when inhaled, may contribute to the development of adverse health effects. To study the concentrations and size distributions of these bioaerosols under real-world conditions, three field campaigns were conducted in northern California. Biochemical assay techniques quantified both viable and nonviable particles: endotoxin was used as a biomarker to track gram-negative bacterial concentrations, (1→3)-beta-D-glucan to evaluate fungal levels, and protein to reflect overall bioaerosol concentrations.; In the first two campaigns, 24-hour filter samples of bioaerosols were collected from 29 office buildings and 9 homes. The highest bioaerosol concentrations were found in occupied rooms of homes. However, unoccupied rooms in homes still had higher bioaerosol concentrations than unoccupied offices.; The third campaign surveyed twenty homes, administering questionnaires and collecting carpet dust samples for biomarker analyses. For ten of these homes, we subsequently collected airborne particles in three size ranges (PM 2.5, PM10, and TSP) over four days and one night (9-12 hrs/sample) spanning a 3.5-week period. The effects of cleaning interventions using both traditional and high efficiency vacuums were assessed. Comparisons were made with simultaneous outdoor samples, culturable bacteria and fungi counts, and PM10 carpet dust samples.; Most of the mass concentration of airborne particles and protein was in the fine fraction (PM2.5), while the mass of airborne endotoxin and (1→3)-beta-D-glucan was mainly in the coarser fractions (PM 2.5-10 and PM10-TSP). No strong correlations were seen between culturable bacteria and fungi counts and the corresponding biomarker levels. House dust was found to be a poor surrogate measure for all fine airborne biomarkers, but showed correlations with coarser airborne protein and endotoxin. Daytime indoor levels of the biomarkers tended to be higher than outdoors, especially for the PM2.5-10 fraction, but only in a few cases were the indoor/outdoor relationships statistically significant. No obvious differences in airborne or fine dust biomarker levels were observed when comparing vacuum cleaning by a variety of household vacuum cleaners with a high-efficiency vacuum cleaner. Certain home and occupant characteristics were found to be associated with biomarkers in air and in dust, including the level of human activity, and the presence of pets.