Seasonal Variations of Indoor Microbial Exposures and Their Relation to Temperature, Relative Humidity, and Air Exchange Rate

Abstract

. Concentrations of fungi were predominately higher outdoors than indoors, whereas bacteria, endotoxin, and inhalable dust concentrations were highest indoors. Bacteria and endotoxin correlated with the mass of inhalable dust and number of particles. Temperature and air exchange rates were positively associated with fungi and N-acetyl-beta-D-glucosaminidase and negatively with bacteria and the total inflammatory potential. Although temperature, relative humidity, and air exchange rates were significantly associated with several indoor microbial exposures, they could not fully explain the observed seasonal variations when tested in a mixed statistical model. In conclusion, the season significantly affects indoor microbial exposures, which are influenced by temperature, relative humidity, and air exchange rates.

Assessment of Airborne Microflora in the Indoor Micro-Environments of Residential Houses of Lahore, Pakistan

“…Frankel et al (2012) also observed a distinct seasonal variation in bioaerosol levels. In our study, since the sampling was carried out during different seasons, a one way ANOVA was applied to determine the impact of season upon bacterial and fungal levels in indoor environments.…”

Why Does Rain Increase the Concentrations of Environmental Bioaerosols during Monsoon?

“…In the same period, PM10 concentrations strongly decreased during rain events. To explain this phenomenon, several hypotheses were proposed: 1) raindrops carried the microorganisms from higher altitude environments to ground-level environments; 2) the rainclouds decreased UV irradiation, which prevented the inactivation of culturable bioaerosols; 3) the splashing effects of raindrops propelled microorganisms on the ground into the surrounding air environment; and 4) the increased relative humidity during rain enhanced the sampling efficiency of the biosampler for culturable bioaerosols and might have generated adequate environments for the growth of microorganisms (Pasanen et al, 1991;Frankel et al, 2012;Heo et al, 2014). In the current study, we tried to test and evaluate each hypothesis by measuring bioaerosols in various environmental conditions.…”

Main Environmental Factors Affecting Concentrations of Culturable Airborne Bacteria in Indoor Laboratories Over a Period of One Year

“…In previous studies of indoor air quality conducted in Chicago homes, culturable bacteria were highest in summer and fall (Moschandreas et al, 2003), whereas in Finland, only a slight yet significant difference was observed between summer and winter bacterial levels (Reponen et al, 1992). However, other studies in homes have shown a large decline from spring to summer, an increase in fall, followed by a decrease toward winter (Frankel et al, 2012). These discrepancies might be caused by other factors, which can influence CAB concentrations, rather than by seasonal changes themselves.…”