A two-year study of microbiological indoor air quality in a new apartment

Concentrations and types of bacteria and fungi in the air and on surfaces were measured in a new, one-bedroom apartment before occupancy and at 3-mo intervals thereafter for 2 y. Air samples were collected with a single-stage impactor at two locations in the kitchen, living room, bedroom, bathroom, and outdoors. Even though damp surfaces supported large populations of bacteria and yeasts, the air concentrations in the kitchen and bathroom were similar to those in other rooms. No changes in concentrations or types of microbiological contamination were observed between the first and second years of occupancy, but elevated outdoor humidity, lower air temperature, and winds from the northeast were associated with higher bacterial and fungal air concentrations. The median air concentrations of bacteria were 98 cfu/m3 (95% confidence interval 26-372 cfu/m3) indoors and 101 cfu/m3 (28-364 cfu/m3) outdoors. The median air concentrations of fungi were 198 cfu/m3 (58-673 cfu/m3) indoors and 362 cfu/m3 (113-1158 cfu/m3) outdoors. This information established useful baseline data against which measurements in neighboring complaint residences could be compared.