Fluorescent Bioaerosol Particles Resulting from Human Occupancy with and Without Respirators

Caijia Xu,Maosheng Yao,Chang-Yu Wu

doi:10.4209/aaqr.2016.09.0400

Abstract

Airborne transmission of pathogenic aerosols via human breath plays a major role in infectious disease outbreaks in indoor environments. Yet, their bioaerosol emission profiles are still not well quantified. Here, we first studied bioaerosol emission rates of human exhaled breath from 12 healthy subjects, and then evaluated the bioaerosol emissions when wearing two different respirators “Doctor masks” and N95 in a controlled environment (27 m3) using a bioaerosol sensor-ultraviolet aerodynamic particle spectrometer (UV-APS). The human bioaerosol contribution was further confirmed through classroom observation. The results showed that there was a peak around 1.5 µm for the fluorescent particles emitted from humans’ breath. For the controlled environment, the presence of 5 people without wearing masks increased bioaerosol concentration by 107% within 30 min at an average emission rate of 8.4 × 105 fluorescent particles person–1 hour–1 resulting from the occupancy. When wearing N95 masks or “Doctor masks”, bioaerosol increases were observed to be 81% or 31% for the controlled environment, respectively, lower compared to those without masks. In-classroom observation also showed a fluorescent particle concentration increase of about 50%. In all experiments, we observed a decline in PM number concentration. Bioaerosol emission from exhaled breath was calculated to account for about 17% of the increase in the controlled environment. The results here suggest the need for re-evaluating microbial aerosol exposure risks for medical sites that demand high levels of hygiene even while wearing a respirator.

Highlights

Human exposure to bioaerosols can cause a variety of adverse health effects including infectious disease, respiratory impairment, and other allergenic reactions
It was shown that most exhaled bacterial aerosol particles were in the range of 0.5–1 μm using scanning electron microscope in conjunction with a new exhaled breath collection device (Xu et al, 2012), and such identical size ranges were observed in another study (Wan et al, 2014)
The results here suggest that human occupancy in the environment can contribute significantly to its bioaerosol levels via breathing (17%; this work), and previously reported skin emission and resuspension

Summary

Introduction

Human exposure to bioaerosols can cause a variety of adverse health effects including infectious disease, respiratory impairment, and other allergenic reactions. There are an increasing number of studies investigating bioaerosols from indoor and occupational environments including impacts from ambient ones (Hsu et al, 2012; Fang et al, 2014; Qian et al, 2014; Galès et al, 2015; Li et al, 2015; Sidra et al, 2015; Yamamoto et al, 2015; Goudarzi et al, 2016; Jahne et al, 2016; Li et al, 2016; Mirhoseini et al, 2016; Smets et al, 2016). A study using the UV-APS has shown that for the particle size range of 2.5–10 μm, there was an average 0.9 ± 0.3 million particles per person-h

Methods

Results

Conclusion