Real-time sensing of bioaerosols: Review and current perspectives

Figures & data

Table 1. List of PBAP classes applied to RT detection.

		Application information				Particle information			Detection information
	Particle category	Application classes	Application examples	Scientific communities represented	End-point for written results	Bioparticle classes	Physiological state	Example(s)	Taxonomic specificity required	Temporal window necessary	Selected detection challenges
1	Human pathogens	Indoor pathogen monitoring	Hospitals, public transport, schools, homes, workplace	Public health, medical professionals, national security	Trade-specific publ.; peer-reviewed journals	Viral, bacterial, fungal	Viable	Mycobacterium tuberculosis (bacteria), influenza virus, Measles morbillivirus	High (species)	Fast (minutes)	RT detection of viruses; Rapid identification of bacterial pathogens at low cost
2	Human pathogens	Outdoor pathogen monitoring	Water and waste treatment, municipal composting and trash, urban areas	Public health, national security	Trade-specific publ.; peer-reviewed journals	Viral, bacterial, fungal	Viable	Aspergillus fumigatus, coccidioides	High (genus or species)	Slow (hours to days)	RT detection of viruses; Rapid identification of bacterial pathogens at low cost
3	Human pathogens	National, military, homeland security	Airports, military bases, dense public areas	Public health, national security	Governmental reports; peer-reviewed journals	Viral, bacterial, fungal	Viable	Bacillus anthracis, Pasteurella pestis, Francisella tularensis	High (species)	Fast (minutes)	RT detection of viruses; Rapid identification of bacterial pathogens at low cost
4	Allergens	Indoor allergen monitoring	Residential, workplace monitoring	Indoor air research, built environment engineering	Peer-reviewed journals; Trade-specific publ.	Fungal, pollen, insect fragments/feces, pet dander	Any	Alternaria alternata, Blomai tropicalis, Dermatophagoides sp. (house dust mites)	Medium-high (species or allergenic groups)	Slow (hours to days)	Sufficient taxonomic differentiation autonomously at low cost
5	Allergens	Outdoor allergen monitoring	Municipal monitoring and forecasting, pollination spread (invasives or with climate)	Allergen dispersal monitoring, biodiversity, climate research	Transmitted directly to public; peer-reviewed journals	Pollen, fungal	Any	Ambrosia artemisiifolia pollen (ragweed pollen), Alternaria alternata spores (mold)	Medium-high (species or allergenic groups)	Slow (hours)	RT identification of fungal spores
6	PBAP reproductive units	Outdoor PBAP ecology	Biodiversity, biogeography, organism dispersal range, climate changes	Biodiversity, ecology, climate research	Peer-reviewed journals	Pollen, fungal, bacterial, viral (viable)	Viable or dormant	Any from bioparticle classes	Medium to high (species or groups; viable)	Very slow (days or longer)	RT identification of fungal allergens
7	Plant pathogens	Crop and agriculture monitoring	Dispersal, movement of crop disease	Agricultural engineering, farmers	Proprietary info.; trade-specific publ.; peer-reviewed journals	Fungal, bacterial	Viable	Puccinia graminis (rust); Phytopthora infestans (potatoe blight)	High (species)	Slow (hours to days)	Sufficient taxonomic differentiation autonomously at low cost
8	Animal pathogens	Livestock, domestic animal care	Monitoring of airborne disease vectors, indoor and outdoor livestock facilities	Agricultural engineering, farmers, ranchers	Proprietary info.; trade-specific publ.	Viral, bacterial, fungal	Viable	Foot-and-mouth disease virus	High (species)	Medium (minutes to hours)	RT detection of viruses
9	All PBAP	Industrial monitoring	Pharmaceutical production	Manufacturing, industrial hygiene	Proprietary info.; trade-specific publ.	Bacterial, fungal	Any	Any contaminant	Low (general)	Fast (minutes)	RT detection and rapid identification of fungal and bacterial particles
10	All PBAP	Industrial monitoring	Cleanroom manufacturing, e.g., computer chip assembly	Manufacturing, industrial hygiene	Proprietary info.; trade-specific publ.	Bacterial, fungal	Any	Any contaminant	Low (general)	Fast (minutes)	RT detection and rapid identification of fungal and bacterial particles
11	All PBAP	Aerosol-cloud- precipitation- climate interactions	Hygroscopic or ice-nucleation active PBAP	Atmospheric and climate scientists	Peer-reviewed journals	Bacteria, fungal, pollen, fragments	Any	Pseudomonas syringae (bacterial); Mortierella alpina (fungal)	Low in some cases, high in others. Often unknown.	Fast (minutes)	Rapid measurement of INA-relevant properties, diversity of PBAP, low concentrations at high altitude
12	All PBAP	Atmospheric chemistry	Atm. aging, surface or aqueous reaction, organic aerosol surface coating	Atmospheric and climate scientists	Peer-reviewed journals	Bacterial, fungal, pollen, fragments, any other PBAP surfaces	Any	Any PBAP	Low (general classes) to High	Very fast (seconds/ minutes) to slow (hours to days)	PBAP identification after atmospheric processing
13	Metabolic PBAP	Airborne cell metabolism	Active cell metabolism or reproduction in cloud droplets, dry aerosol	Atmospheric and climate scientists, cell biologists, diverse discipline	Peer-reviewed journals	Bacteria	Metabolically active	Pseudomonas syringae, Pseudomonas graminis	Medium (groups or species)	Fast (minutes)	Measuring airborne reproduction, cell metabolism conditions, metabolic state, biochemical cycling

Table 2. List of RT bioaerosol technique classes discussed in the text. Values listed are approximate and instrument properties are listed as general attributes. Text sections and individual research manuscripts should be consulted for more detail.

RT Measurement Type	Example Instrument(s)	Detection Principle	Measured Parameters	Particle size range (μm)	Discrimination level (example of best case published)
LIF (1–3 channel)	WIBS, UV-APS, BioScout	Fluorescence and elastic scattering	Particle size, fluorescence intensity (1–3 channel spectral resolution)	∼0.5 to 10–50	Biological vs non-biological particles
LIF (multichannel)	Rapid-E, MBS, SIBS, DPFS	Fluorescence (and elastic scattering for some instruments)	Particle size, fluorescence intensity (8–32 channel spectral resolution)	∼0.5 to 10–100	Rapid-E: different pollen morphotypes (mostly at the genus level) DPFS: Bacillus subtilis spores
LIF (multichannel ) + holography	Poleno	Fluorescence + elastic scattering + holography	Particle size, fluorescence in multiple channels, holographic images	∼0.5 to 100	Different pollen morphotypes (mostly at the genus level)
LIF (multi-channel) + LIBS + elastic scattering	RAAD Biodetector	Fluorescence + LIBS + polarized elastic scattering	Particle size, fluorescence intensity, elemental composition, and absorption	∼0.5 to 10	Broad classification among biological materials, e.g., spores vs. vegetative cells
Optical microscopy	BAA500, PollenSense	Optical microscopy or high-definition photography	Microscope images	>5	BAA500: different pollen morphotypes (mostly at the genus level)
Elastic scattering	KH-3000	Elastic scattering	Forward and side scattering	>10	Select pollen morphotypes
Raman spectroscopy	REBS	Raman scattering (+ background fluorescence)	Images from which Raman spectra are extracted	<10	Bacillus spores.
Mass spectroscopy	SPMS, AMS, SPAMS, PALMS, ATOFMS, ALABAMA	Mass spectrometry	Mass spectra of fragment ions from single or ensembles of particles	∼0.05 to 5	PBAP by certain marker ions (PO^3–, CN^–, CNO^–, K^+)
Breakdown spectroscopy	LIBS	Atomic spectroscopy	Atomic spectra	1 to 100	Limited as a stand-alone technique