Indoor bioaerosol dynamics

Nazaroff, William W

An important point is that human occupancy and activities are major factors influencing indoor microbiology. Humans are important primary sources of certain bacteria and viruses. Even for fungi, for which humans do not appear to be a major primary source, human activities play an important role, for example, in shedding particulate matter from our clothing or in suspending settled dust that can contain materials of fungal origin. Figure 4 illustrates this point using samples collected in the same ten houses as discussed in connection with Figure 3 . In this case, only indoor air samples are considered. The ten houses are divided into two equal-sized groups, sorted according to degree of occupancy (Chen and Hildemann, 2009b) . Occupancy is used here as a surrogate measure of the intensity of human activity. Across all measures displayed in the figure-that is, airborne concentrations of particulate matter, protein, endotoxin, and glucans -the geometric mean level in the high activity homes was considerably higher than in the low activity homes.