Contributions of Foot Traffic and Outdoor Concentrations to Indoor AirborneAspergillus

Abstract

Aspergillus is a mold genus that can cause allergies, asthma, and pulmonary infections in sensitive people; its particles are common in indoor air. Two potential contributors to indoor Aspergillus particles were examined in this field study: human activity (walking over carpet), and outdoor Aspergillus concentrations. Filtered air samples were collected outdoors and inside two carpeted hallways in public buildings, while measuring indoor foot traffic. Aspergillus concentrations were analyzed using quantitative Polymerase Chain Reaction (qPCR). A bivariate model was used to predict indoor Aspergillus concentrations based on foot traffic and outdoor Aspergillus concentrations. For 3 of 4 scenarios, most of the variation in indoor Aspergillus could be explained by the combined effect of outdoor Aspergillus concentrations and foot traffic, with particularly strong correlations during peak traffic times. In addition, indoor Aspergillus was significantly associated with outdoor Aspergillus in 2 of 4 scenarios, and with foot traffic in 2 of 4 scenarios. For 2 of 3 sampling campaigns, Aspergillus did not have a significant association either with gravimetric particulate matter ≤5 µm (PM 5 ), or with optically measured PM of 0.75-1 µm, 1-2 µm, 2-3.5 µm, or 3.5-5 µm. Controlled experiments, examining whether the foot traffic contribution was due to resuspension from carpeting or to shedding from clothing and/or human bodies, saw a significant increase in Aspergillus levels from resuspension. Although an increase was also seen for clothing over Tyvek suits, it was not statistically significant.

Next-generation DNA sequencing reveals that low fungal diversity in house dust is associated with childhood asthma development

“…While multiple mechanisms may be important, here we found similar fungal taxa in asthma case and control homes, with no detrimental and one potentially protective species. Similarities in fungal taxa in house dust may be due to contributions from common sources, such as outdoor air (Adams et al., ; Goebes et al., ) and human shedding (Park et al., ). Although abundance of no fungal taxon was identified as an asthma risk factor, reduced diversity within Cryptococcus was associated with increased asthma risk.…”

Indoor Exposure to Mould Allergens

“…In contrast to the traditional methods, molecular and immunological tests may detect all types of mould particles (60). Molecular methods (rDNA and qPCR) do not rely on the viability of organisms and can detect very small quantities of genetic material, which is especially valuable in assessing Aspergillus levels in hospitals (60-62).…”

A Risk Assessment Scheme of Infection Transmission Indoors Incorporating the Impact of Resuspension

“…(9)(10)(11) Once these deposited pathogens are resuspended from surfaces and become airborne again, they may be inhaled by occupants and impose a secondary infection risk. Previous studies (12)(13)(14)(15) suggested that pathogen resuspension can be a potential route for infection transmission. For example, Goebes et al (15) found that walking over carpet could significantly increase the airborne concentration of Aspergillus and potentially result in invasive aspergillosis that could be fatal for immunocompromised people.…”

“…Once these deposited pathogens are resuspended from surfaces and become airborne again, they may be inhaled by occupants and impose a secondary infection risk. Previous studies suggested that pathogen resuspension can be a potential route for infection transmission. For example, Goebes et al .…”

“…Previous studies suggested that pathogen resuspension can be a potential route for infection transmission. For example, Goebes et al . found that walking over carpet could significantly increase the airborne concentration of Aspergillus and potentially result in invasive aspergillosis that could be fatal for immunocompromised people.…”