Real-time sensing of bioaerosols: Review and current perspectives

Abstract

Detection of bioaerosols, or primary biological aerosol particles (PBAPs), has become increasingly important for a wide variety of research communities and scientific questions. In particular, real-time (RT) techniques for autonomous, online detection and characterization of PBAP properties in both outdoor and indoor environments are becoming more commonplace and have opened avenues of research. With advances in technology, however, come challenges to standardize practices so that results are both reliable and comparable across technologies and users. Here, we present a critical review of major RT instrument classes that have been applied to PBAP research, especially with respect to environmental science, allergy monitoring, agriculture, public health, and national security. Eight major classes of RT techniques are covered, including the following: (i) fluorescence spectroscopy, (ii) elastic scattering, microscopy, and holography, liii: Raman spectroscopy, (iv) mass spectrometry, (v) breakdown spectroscopy, (vi) remote sensing, (vli) microtiuidic techniques, and iViiil paired aqueous techniques. For each class of technology we present technical limitations, misconceptions, and pitfalls, and also summarize best practices for operation, analysis, and reporting. The final section of the ankle presents pressing scientific questions and grand challenges for RT sensing of PBAP as well as recommendations for future work to encourage high-quality results and Increased cross-community collaboration.

The investigation of atmospheric aerosols of biological origin arose in the mid-nineteenth century due to speculations on the origin of diseases afflicting humans and crops (Carnelley, Haldane. and Anderson 1887; Pasteur 1862; Vallery-Radot and Hamilton 1885). Many other applications of aerobiology followed within the first half of the twentieth century, including population biology, aero-allergology, and the detection of biowarfare agents (Gregory 1961; Stackman et al. 1942). Today, research regarding the sources, properties, concentrations, and diversity of bioaerosol is motivated by increasingly diverse The investigation of atmospheric aerosols of biological origin arose in the mid-nineteenth century due to speculations on the origin of diseases afflicting humans and crops (Carnelley, Haldane. and Anderson 1887; Pasteur 1862; Vallery-Radot and Hamilton 1885). Many other applications of aerobiology followed within the first half of the twentieth century, including population biology, aero-allergology, and the detection of biowarfare agents (Gregory 1961; Stackman et al. 1942). Today, research regarding the sources, properties, concentrations, and diversity of bioaerosol is motivated by increasingly diverse Research: Methods, Challenges, and Perspectives" is to provide broad recommendations to these diverse communities.

Discussion is complicated by the use of variable nomenclature across research communities. Here, we use the terms bioaerosol and PBAP interchangeably, defined as in Despres et al. (2012), to describe "solid airborne particles derived from biological organisms, including microorganisms and fragments of biological materials such as plant debris and animal dander."

Identification of PBAP, e.g.. to the genus and species level for many infectious microorganisms, or the genus level for some allergenic fungi and bacteria, is required for many applications (Tabic I). Thus, many measurement methods involve collection of particles followed, e.g., by visual identification of cultured microbes or of individual particles under a microscope (Mandrioli et al. 1998), antigen/antibody assay, or polymerase chain reaction. Such manual analysis can be subjective, costly, and time-intensive, which causes delays in data availability, limits the breadth of application, and can result in poor subsampling of measurements. As a result, samplers capable of autonomous and continuous real-time (RT) or near-RT analysis have become increasingly common. The terms online and offline are also used here to refer to RT and manual methods, respectively. In some cases, a distinction is necessary` between true direct-reading RT sensors that sample particles and then collect, analyze, and report interpreted data without requiring human input, and sensors that autonomously sample particles and then collect and analyze data in RT, but which require some level of manual human interpretation and analysis at a later stage. The timescale of automatic analysis and reporting leads to further distinction between sensors. In some cases, sampling, analysis, and reporting can be achieved within seconds or minutes, and in other cases, this requires integration times of several hours.