Seasonal and Diurnal Variability in Airborne Mold from an Indoor Residential Environment in Northern New York

Abstract

It is well known that characterization of airborne bioaerosols in indoor environments is a challenge because of inherent irregularity in concentrations, which are influenced by many environmental factors. The primary aim of this study was to quantify the day-to-day variability of airborne fungal levels in a single residential environment over multiple seasons. Indoor air quality practitioners must recognize the inherent variability in airborne bioaerosol measurements during data analysis of mold investigations. Changes in airborne fungi due to varying season and day is important to recognize when considering health impacts of these contaminants and when establishing effective controls. Using an Andersen N6 impactor, indoor and outdoor bioaerosol samples were collected on malt extract agar plates for 18 weekdays and 19 weekdays in winter and summer, respectively. Interday and intraday variability for the bioaerosols were determined for each sampler. Average fungal concentrations were 26 times higher during the summer months. Day-to-day fungal samples showed a relatively high inconsistency suggesting airborne fungal levels are very episodic and are influenced by several environmental factors. Summer bioaerosol variability ranged from 7 to 36% and winter variability from 24 to 212%; these should be incorporated into results of indoor mold investigations. The second objective was to observe the relationship between biological and nonbiological particulate matter (PM). No correlation was observed between biological and nonbiological PM. Six side-by-side particulate samplers collected coarse PM (PM 10 ) and fine PM (PM 2.5 ) levels in both seasons. PM 2.5 particulate concentrations were found to be statistically higher during summer months. Interday variability observed during this study suggests that indoor air quality practitioners must adjust their exposure assessment strategies to reflect the temporal variability in bioaerosol concentrations.

Contributions of Foot Traffic and Outdoor Concentrations to Indoor AirborneAspergillus

“…However, the gravimetric PM 5 measurements were very well correlated with the OPC measurements for the hospital hallway (R 2 ≥ 0.89 for all OPC sizes). The lack of a consistent correlation between Aspergillus and PM is consistent with the findings of LeBouf et al (2008). In that study, no correlation was observed between culturebased measurements of fungal levels inside residences and indoor PM 2.5 (and PM 10 ) measurements.…”

Seasonal Impacts on Indoor Fungal Concentrations After Mold Remediation

“…This same phenomenon was alluded to previously by other researchers (LeBouf, et al 2008). In this study that pattern held true for months March through November, but when the December through February data was analyzed a new pattern arises.…”

Multiple comparisons of organic, microbial, and fine particulate pollutants in typical indoor environments: Diurnal and seasonal variations

“…Diurnal variations of mold counts were not significant, probably due to the relatively lower RH levels observed in this study. Interday variability of mold count for both seasons was found to be associated with rapidly growing mold sources and varying environmental conditions (LeBouf et al, 2008). Diurnal variations of both bacteria and fungi were found for morning and afternoon periods of a day in university rooms, and both bacterial and fungal levels were found to be lower in the morning than in the afternoon (Stryjakowska-Sekulska et al, 2007).…”

“…However, levels and compositions of bioaerosols can be affected by the sampling time, sampling day, and season. Nevertheless, only a few research pointed out the importance of diurnal and/or daily variations of bioaerosols (Law et al, 2001;LeBouf et al, 2008;Stryjakowska-Sekulska et al, 2007;Zhu et al, 2003).…”