Field performance of a novel passive bioaerosol sampler using polarized ferroelectric polymer films

Passive bioaerosol samplers can improve environmental and health protection by enhancing the practicality and cost-effectiveness of air sampling. Here, we present the outdoor field testing of a novel, passive bioaerosol sampler, the Rutgers Electrostatic Passive Sampler (REPS), based on the use of polarized, ferroelectric polymer film (poly(vinylidene fluoride)). Four 10-day-long field campaigns were conducted to compare total (culturable + non-culturable) and culturable bioaerosol collection efficiencies of REPS to passive samplers (PTFE settling filters and agar settling plates). These collection efficiencies were calculated relative to performance of an active, reference Button Sampler. Compared to passive PTFE filters, which exclusively rely on gravitational particle deposition, REPS collected a seven-fold higher total microorganism quantity. Relative to the Button Sampler, REPS collected 25% of the total number of bacteria and fungi and 65% of the culturable bacteria. Furthermore, REPS achieved this performance without any air movers, pumps, batteries, or external power. Since the Button Samplers operated at 4 L/min, REPS was calibrated to have equivalent sampling rates of 2.6 L/min and 1.0 L/min for culturable bacteria and total microorganisms, respectively. These results suggest that REPS can passively collect airborne microorganisms, including culturable bacteria, with high efficiency over long-term sampling durations. REPS can provide better preservation of bacterial culturability because it has no active airflow, which desiccates microbes in active samplers. Since there are limited options available for long-term, unattended bioaerosol sampling, REPS can complement currently available bioaerosol sampling technologies for numerous environmental health applications, such as exposure assessment for epidemiology and monitoring aeroallergen trends.

© 2017 American Association for Aerosol Research     

Assessment of Bioaerosol Generation and Sampling Efficiency Based on Pantoea agglomerans

This study was conducted to evaluate the effect of aerosol generation, relative humidity, and method of sampling on the culturability of the vegetative bacteria Pantoea agglomerans (P. agglomerans) formerly known as Erwinia herbicola. This research has relevance both for the use of this organism as a biowarfare simulant and for bioaerosol exposure assessment and public health. The culturability of P. agglomerans was tested using a test chamber against two generating systems (Collison and Bubble nebulizers), two sampling systems (the all-glass impinger (AGI-30), and the BioSampler), three collection media (water, TSB, and PBS) and across a range of humidities. Results indicated that the Bubble nebulizer was 15% more efficient in generating viable P. agglomerans counts (p ≤ 0.05). No difference was observed in overall efficiency between sampling methods (p > 0.05). However, as a collection media, PBS was observed to yield higher (p ≤ 0.01) viable counts compared to sterile deionized water. Relative humidity was found to strongly influence airborne P. agglomerans culturability. Culturable P. agglomerans was below the limit of detection for RH < 15% and then increased in a log-linear fashion to humidities of 75%. This research will help identify optimal means for evaluation of environmentally sensitive airborne bacteria for purposes of exposure assessment and public health as well as homeland security.     

Design and development of a self-contained personal electrostatic bioaerosol sampler (PEBS) with a wire-to-wire charger

Here, we present a concept of a personal electrostatic bioaerosol sampler (PEBS), which is an open channel collector consisting of a novel wire-to-wire particle charger and a collection section housing a double-sided and removable metal collection plate and two quarter-cylinder ground electrodes. The charger consists of a tungsten wire (25.4 mm long and 0.076 mm in diameter) connected to high voltage and positioned in the center of the charging section (a cylinder 50.8 mm long and 25.4 mm in diameter); a ring of stainless steel wire 0.381 mm in diameter surrounds the hot electrode at its midpoint and is grounded. The newly designed wire-to-wire charger produces lower ozone concentrations compared to traditional wire-to-plate or wire-to-cylinder charger designs. The particles captured on the collection plate are easily eluted using water or other fluids. The sampler was iteratively optimized for optimum charging and collection voltages, and collection electrode geometry. When tested with polystyrene latex particles ranging from 0.026 µm to 3.1 µm in diameter and 10 L/min collection flow rate, the sampler's collection efficiency was approximately 70%–80% at charging and collection voltages of +5.5 kV and ?7 kV, respectively. The PEBS showed this collection efficiency at sampling times ranging from 10 min to 4 h. Preliminary tests with Bacillus atrophaeus bacterial cells and fungal spores of Penicillium chrysogenum showed similar collection efficiency. The use of a unique wire-to-wire charger resulted in ozone production below 10 ppb. Due to low ozone emissions, this sampler will allow maintaining desirable physiological characteristics of the collected bioaerosols, leading to a more accurate sample analysis.

© 2017 American Association for Aerosol Research     

Investigation of the Efficiencies of Bioaerosol Samplers for Collecting Aerosolized Bacteria Using a Fluorescent Tracer. I: Effects of Non-sampling Processes on Bacterial Culturability

By sampling aerosolized microorganisms, the efficiency of a bioaerosol sampler can be calculated depending on its ability both to collect microorganisms and to preserve their culturability during a sampling process. However, those culturability losses in the non-sampling processes should not be counted toward the sampling efficiency. Prior to the efficiency assessment, this study was designed to investigate the culturability losses in three non-sampling processes: (1) the tracer uranine induced loss; (2) the loss during aerosolization (pre-sampling process); and (3) the bacteria and uranine recovery in air sample handling procedures for the samples of the Andersen 6-stage impactor and the Airport MD8 (post-sampling process). The results indicated that uranine had no significant effect on the culturability of Enterococcus faecalis, Escherichia coli, and Mycoplasma synoviae in suspensions (P > 0.05), but negatively affected the culturability of Campylobacter jejuni (P = 0.01). The culturability of E. faecalis, E. coli, and M. synoviae was not affected by stresses caused by aerosolization (P > 0.05). Only 29% of C. jejuni were still culturable during aerosolization (P = 0.02). In the air sample handling procedures, the four species of bacteria were recovered without significant losses from the samples of the Andersen impactor, but only 33–60% uranine was recovered. E. faecalis, E. coli, and M. synoviae were recovered without significant losses from the samples of the Airport MD8. More C. jejuni was recovered (172%), probably due to multiplication or counting variation. It is suggested that tracer and bacteria should be aerosolized separately when the tracer negatively affects the bacterial culturability. In both pre- and post-sampling processes, losses of bacterial culturability (or multiplication) may occur, which should be taken into account when assessing the efficiencies of bioaerosol samplers.     

Pulsed ultraviolet light decontamination of virus-laden airstreams

Continuous ultraviolet germicidal irradiation (UVGI) has been extensively studied, but research on pulsed UVGI (PUVGI) is lacking and has primarily focused on disinfection of solid surfaces or liquids. This study addressed the gap in knowledge on the effectiveness of pulsed UVGI for disinfecting virus-laden calm air, with relevance to indoor rooms. Φ6 bacteriophage (a surrogate used to study communicable enveloped human respiratory viral pathogens such as influenza virus) was aerosolized by a Collison device into an enclosed test chamber, wherein the bioaerosol was exposed to PUVGI. The spectral content and performance of a pulsed white light lamp with a substantial UVC component were defined. Pulsed UV exposure of 10 to 30 s resulted in a two-log reduction in viable recovered virus from filter membranes and cyclone-based samplers. The small differences in Φ6 survival, after 10 to 30 s of exposure, emphasized the difficulty of complete eradication. However, exposure to 10 s of PUVGI resulted in significant reduction of virus viability. The dose–response displayed clear regimes of fast and slow exponential decay. Susceptibility factor for the fast-decay regime of aerosolized Φ6 (Z = 0.24 m²/J) was similar to those reported for influenza A virus aerosols at similar relative humidity. Our study demonstrated the potency of PUVGI against a viral bioaerosol. This has potential implications for the control of infectious bioaerosols in the healthcare setting.

© 2017 American Association for Aerosol Research     

Optimization of Propidium Monoazide Quantitative PCR for Evaluating Performances of Bioaerosol Samplers for Sampling Airborne Staphylococcus aureus

Airborne Staphylococcus aureus causes a significant proportion of nosocomial infections. The purpose of this study was to combine real-time quantitative polymerase chain reaction with the DNA-binding agent propidium monoazide (PMA-qPCR) to assess exposures to airborne S. aureus. In this work, we generated a S. aureus aerosol and used our assay to detect viable, airborne S. aureus in a study chamber. The biological collection efficiencies of three samplers (the AGI-30 impinger, BioSampler, and Nuclepore filter sampler) were evaluated using the S. aureus aerosols. The effects of storage in collection fluid on S. aureus sampled by the AGI-30 impinger and BioSampler were evaluated. Furthermore, air samples from an intensive care unit (ICU) and a gymnasium (GYM) were subsequently used to test the performance of a BioSampler combined with our PMA-qPCR technique. The BioSampler was more effective than the AGI-30 and Nuclepore filter samplers for preserving the culturability and viability of S. aureus aerosol samples. After sampling by impingement, the loss of viable S. aureus was minimized by treating the cells with PMA prior to storage at ?20°C and analyzing the samples by qPCR within 3 weeks. In field applications, we noted that traditional culture assays tended to underestimate the viable concentrations of S. aureus by approximately one order of magnitude. Overall, combining qPCR with and without PMA staining may be useful for assessing exposure to airborne S. aureus. However, a complex set of parameters that may affect the efficiency of PMA-qPCR must be taken into account before applying PMA-qPCR to bioaerosol detection.

Copyright 2014 American Association for Aerosol Research     

Field Evaluation of Sampling Bias with Plastic Petri Dishes for Size-Fractionated Bioaerosol Sampling

Reusable glass dishes are recommended for use with the six-stage viable impactor for size-fractionated bioaerosol sampling. However, it is not convenient to use glass dishes because they are fragile and heavy, not to mention the time-consuming preparation process prior to bioaerosol sampling. On the other hand, disposable plastic dishes have been widely used in microbiology laboratories. However, plastic materials can retain electrostatic charges and may lead to sampling bias. The objective of this study was to evaluate the sampling bias with the use of plastic dishes when a multistage viable impactor is used for airborne fungi and bacteria sampling for field sampling. Two six-stage viable impactors were placed side-by-side 1 m apart in a 147-m³ room. One was used with plastic dishes and the other with glass dishes. Compared with the concentration data obtained with glass dishes, those collected with the plastic dishes demonstrated a significant difference for both fungi and bacteria. However, there was a strong correlation between the data obtained using glass and plastic dishes, which can be estimated by C_plastic = 0.88 C_glass for airborne fungi and C_plastic = 0.86 C_glass for airborne bacteria. When using plastic dishes fungi and bacteria counts were underestimated by 12% and 14%, respectively.

Copyright 2015 American Association for Aerosol Research     

Investigation of the Efficiencies of Bioaerosol Samplers for Collecting Aerosolized Bacteria Using a Fluorescent Tracer. II: Sampling Efficiency and Half-Life Time

Using uranine as a physical tracer, this study assessed the sampling efficiencies of four bioaerosol samplers (Andersen 6-stage impactor, all glass impinger “AGI-30,” OMNI-3000, and Airport MD8 with gelatin filter) for collecting Gram-positive bacteria (Enterococcus faecalis), Gram-negative bacteria (Escherichia coli and Campylobacter jejuni), and bacteria without cell wall (Mycoplasma synoviae) which were aerosolized in a HEPA isolator. In addition, the half-life times of these bacteria in aerosols were estimated. The uranine concentrations collected by the samplers were used for calculating the physical efficiencies, and the bacteria/uranine ratios were used for calculating the biological efficiencies. The results show the Airport MD8 had the highest physical efficiency. Compared with the Airport MD8, the physical efficiencies of the AGI-30 and the OMNI-3000 were 74% and 49%, respectively. A low physical efficiency of the Andersen impactor (18%) was obtained, but it was mainly caused by the incomplete recovery of uranine when handling the air samples, so could not be ascribed to the sampler efficiency. Both the Andersen impactor and the AGI-30 showed high biological efficiencies for all four bacterial species. The biological efficiencies of the OMNI-3000 for C. jejuni (1%) and of the Airport MD8 for E. coli (38%) and C. jejuni (2%) were significantly lower than 100%, indicating that their sampling stresses inactivated the bacterial culturability. The half-life times at 21–23°C temperature and 80–85% relative humidity were 43.3 min for E. faecalis, 26.7 min for M. synoviae, 21.2 min for E. coli, and 4.0 min for C. jejuni in the air.     

Use of gelatin filter and BioSampler in detecting airborne H5N1 nucleotides,bacteria and allergens

In this study, the pure influenza A virus (H5N1) nucleotides, dermatophagoides allergens (Der f 1 and Der p 1), and Bacillus subtilis vegetative cells were aerosolized and collected by a Button Aerosol Sampler equipped with gelatin filter and a BioSampler, which were operated at 4 and 12.5 L/min, respectively, for 1–5 min. The collected air samples were analyzed by quantitative polymerase chain reaction (qPCR) and enzyme-linked immuosorbent assay (ELISA). In addition, the performances of the samplers when quantifying total outdoor bacteria were also studied.The cycle threshold (Ct) value for 0.1 fg/μl RNA positive control was observed around 26, and the Ct value for the negative control was about 30. Gelatin filters were shown to report 1-2 times higher nucleotides and B. subtilis concentrations than those obtained by the BioSampler. When sampling outdoor bacteria, both samplers however obtained similar concentration levels (p-value=0.36). In contrast, the BioSampler reported substantially higher dust mite allergen concentration levels, especially for Der f 1 than the gelatin filters in this study. The sampling time up to 5 min was shown not to have a statistically significant effect on the performance of qPCR when the gelatin filter was used. Such finding was also observed with the performance of ELISA for the sampling time up to 15 min.This study suggests that the bioaerosol sampler, collection medium and analysis methods such as qPCR and ELISA would play overall roles in characterizing airborne biological materials.     

A novel laminar-flow-based bioaerosol test system to determine biological sampling efficiencies of bioaerosol samplers

In this work, we describe a novel type of bioaerosol test system based on a laminar airflow chamber that provides a homogenous aerosol of microbial cells with known concentrations and defined culturability to bioaerosol samplers positioned in the chamber. In the system, three control and monitoring points (CMPs) are implemented in which the number and culturability of microbes can be determined by combining optical particle counting with microscopic and culture-based microbiological analyses. This lineup is designed to quantify the biological sampling efficiency (BSE) of a bioaerosol sampling device. Seven bioaerosol samplers were tested with four fungal and one bacterial species and their BSEs have been determined under optimized standard operating conditions. After executing tests with the appropriate statistical power, this new laminar-flow platform demonstrated the sensitivity necessary to determine significant differences in the recovery efficiency of viable fungal spores and bacterial cells in modern samplers. Under these test conditions, the samplers showed considerable differences in BSEs for the individual fungal and bacterial species. Our data demonstrate that a large number of experimental repetitions and measurements under tightly controlled and monitored conditions are necessary to quantify the BSE of a given sampler and to compare them to each other. Employing this system improves biological evaluation of samplers because natural environments are not suitable for this task due to their high variabilities in homogeneity and distribution of cells as well as fluctuations in culturability ratios.

© 2019 American Association for Aerosol Research     

Design and evaluation of an aerodynamic focusing micro-well aerosol collector

Aerosol sampling and identification is vital for the assessment and control of particulate matter pollution, airborne pathogens, allergens, and toxins and their effect on air quality, human health, and climate change. In situ analysis of chemical and biological airborne components of aerosols on a conventional filter is challenging due to dilute samples in a large collection region. We present the design and evaluation of a micro-well (µ-well) aerosol collector for the assessment of airborne particulate matter (PM) in the 0.5–3 µm size range. The design minimizes particle collection areas allowing for in situ optical analysis and provides an increased limit of detection for liquid-based assays due to the high concentrations of analytes in the elution/analysis volume. The design of the collector is guided by computational fluid dynamics (CFD) modeling; it combines an aerodynamic concentrator inlet that focuses the aspirated aerosol into a narrow beam and a µ-well collector that limits the particle collection area to the µ-well volume. The optimization of the collector geometry and the operational conditions result in high concentrations of collected PM in the submillimeter region inside the µ-well. Collection efficiency experiments are performed in the aerosol chamber using fluorescent polystyrene microspheres to determine the performance of the collector as a function of particle size and sampling flow rate. The collector has the maximum collection efficiency of about 75% for 1 µm particles for the flow rate of 1 slpm. Particles bigger than 1 µm have lower collection efficiencies because of particle bounce and particle loss in the aerodynamic focusing inlet. Collected samples can be eluted from the device using standard pipettes, with an elution volume of 10–20 µL. The transparent collection substrate and the distinct collection region, independent of particle size, allows for in situ optical analysis of the collected PM.

© 2017 American Association for Aerosol Research     

Use of an Andersen Bioaerosol Sampler to Simultaneously Provide Culturable Particle and Culturable Organism Size Distributions

A method is provided for estimating size distributions in terms of both culturable particles (CP) and culturable organisms (CO) from a single sample collected with an Andersen bioaerosol impactor. Half of the agar surface of each Petri dish is covered with a polycarbonate filter substrate through which liquid from the agar can wick and thereby form a flat wetted collection surface, and the other half of the agar surface is uncovered. Quantification of CO distribution results involves washing the collected particles from the filter surfaces and plating suitable dilutions of de-agglomerated particles, followed by incubating the organisms, and counting the resulting colonies; whereas, quantification of CP results is based on direct culturing of the agar media. Experiments were conducted with near-monodisperse clusters of Bacillus atrophaeus (aka BG) aerosols covering APS-determined geometric number mean sizes from 1.83 to 8.7 μm aerodynamic diameter (AD). There is little difference between the Andersen-determined median sizes of the CO and CP distributions of the near-monodisperse clusters, which supports the utility of the CO method. The method was applied to sampling bioaerosol in a previously occupied classroom and the results showed median sizes of 1.7 and 3.1 μm AD for the CP and CO distributions, respectively. Total bioaerosol concentrations were 0.53 and 3.4 CO/L, respectively, so the average CP contained 6.4 CO.

Copyright 2012 American Association for Aerosol Research     

Design and Performance of a Low-Cost Micro-Channel Aerosol Collector

Aerosol sampling and identification is vital for assessment and control of particulate matter pollution, airborne pathogens, allergens and toxins, and their effect on air quality, human health, and climate change. Assays capable of accurate identification and quantification of chemical and biological airborne components of aerosol provide very limited sampling time resolution and relatively dilute samples. A low-cost micro-channel collector (μCC) which offers fine temporal and spatial resolution, high collection efficiency, and delivers highly concentrated samples in very small liquid volumes was developed and tested. The design and optimization of this μCC was guided by computational fluid dynamics (CFD) modeling. Collection efficiency tests of the sampler were performed in a well-mixed aerosol chamber using aerosolized fluorescent microspheres in the 0.5–6 μm diameter range. Samples were collected in the μCC and eluted into 100 μL liquid aliquots; bulk fluorescence measurements were used to determine the performance of the collector. Typical collection efficiencies were above 50% for 0.5 μm particles and 90% for particles larger than 1 μm. The experimental results agreed with the CFD modeling for particles larger than 2 μm, but smaller particles were captured more efficiently than predicted by the CFD modeling. Nondimensional analysis of capture efficiencies showed good agreement for a specific geometry but suggested that the effect of channel curvature needs to be further investigated.

Copyright 2014 American Association for Aerosol Research     

Assessment of Bioaerosol Sampling Techniques for Viable Legionella pneumophila by Ethidium Monoazide Quantitative PCR

Legionella pneumophila causes severe pneumonia and Pontiac fever in humans. Rapid and sensitive bioaerosol monitoring techniques for viable L. pneumophila are unavailable. Coupled with a newly developed viable assay called ethidium monoazide with quantitative PCR (EMA-qPCR), this study applies EMA-qPCR to aerobiology for the first time to evaluate the effects of the method of sampling (all-glass impinger (AGI-30), BioSampler, and MAS-100 sampler) and sampling time (3, 30, 60 min) on the collection of viable L. pneumophila. The effects of the collection fluid (deionized water (DW) and Tween mixture) and the replenishment of DW every 15 min during 60-min sampling were also assessed. Escherichia coli, as a model microorganism in bioaerosol research, was also tested. Using the Tween mixture (DW containing 1% peptone, 0.01% Tween 80, and 0.005% antifoam), the AGI-30 and BioSampler performed significantly better than the MAS-100 sampler for collecting viable L. pneumophila and viable E. coli (P < 0.05). An increase in sampling time adversely affected the quantification of both bacterial species (P < 0.05). The collection with DW yielded greater recovery of viable L. pneumophila than the Tween mixture in both AGI-30 and BioSampler, regardless of sampling time, by a factor of 1.4–6.9 (P < 0.05). The replenishment of DW every 15 min further improved the collection of viable L. pneumophila. This study demonstrates that viable L. pneumophila can be efficiently sampled by the AGI-30 and BioSampler and successfully quantified by EMA-qPCR.     

Long-Term Sampling of Viable Airborne Viruses

A novel bioaerosol sampling technique, which utilizes the bubbling process in the collection fluid, has recently been developed and found feasible for a long-term personal sampling of airborne bacteria and fungal spores as it maintained high physical collection efficiency and high microbial recovery rate for robust and stress-sensitive microorganisms. Further tests have shown that the new technique also has potential to collect viable airborne viruses, particularly when utilized for a short-term sampling of robust strains. As the short-term sampling has a limited application for assessing personal exposure in bioaerosol-contaminated environments, the present study was undertaken to investigate the feasibility of the “bubbler” for a long-term monitoring of viable airborne viruses. Liquid droplets containing Vaccinia virions (that simulate Variola, a causative agent of smallpox) were aerosolized with a Collison nebulizer into a 400-liter test chamber, from which the droplets were collected by three identical prototype personal samplers in the liquid medium during different time periods ranging from 1 to 6 hours. The viral content was measured in the collection fluid of the sampler and in the initial suspension of the nebulizer using the fluorescence-based method and by enumerating plaque-forming units per milliliter of the fluids. The relative recovery of viruses after the sampling act was determined. The results show that the “bubbling” technique has consistent collection efficiency over time and is capable of maintaining the viability of Vaccinia, for at least 6 hours, with a loss in recovery rate of about 10%. The data demonstrate a good potential of the new technique for measuring personal exposure to robust airborne viruses over a long period.     

Experimental Study of Electrostatic Aerosol Filtration at Moderate Filter Face Velocity

Aerosol collection efficiency was studied for electrostatically charged fibrous filters (3M Filtrete?, BMF-20F). In this study, collection efficiencies at moderate filter face velocities (0.5–2.5 m/s) representative of some high volume sampling applications was characterized. Experimental data and analytical theories of filter performance are less common in this flow regime since the viscous flow field assumption may not be representative of actual flow through the filter mat. Additionally, electrostatic fiber charge density is difficult to quantify, and measurements of aerosol collection efficiency are often used to calculate this fundamental parameter. The purpose of this study was to assess the relative influence of diffusion, inertial impaction, interception, and electrostatic filtration on overall filter performance. The effects of fiber charge density were quantified by comparing efficiency data for charged and uncharged filter media, where an isopropanol bath was used to eliminate electrostatic charge. The effects of particle charge were also quantified by test aerosols brought into the equilibrium Boltzmann charge distribution, and then using an electrostatic precipitator to separate out only those test particles with a charge of zero. Electrostatically charged filter media had collection efficiencies as high as 70–85% at 30 nm. Filter performance was reduced significantly (40–50% collection efficiency) when the electrostatic filtration component was eliminated. Experiments performed with zero charged NaCl particles showed that a significant increase in filter performance is attributable to an induction effect, where electrostatic fiber charge polarizes aerosol particles without charge. As filter face velocity increased the electrostatic filtration efficiency decreased since aerosol particles had less time to drift toward electrostatically charged fibers. Finally, experimental data at 0.5 m/s were compared to theoretical predictions and good agreement was found for both electrostatic and nonelectrostatic effects.

© 2013 American Association for Aerosol Research     

Analysis of Bioaerosols from Chicken Houses by Culture and Non-Culture Method

In livestock breeding, high bioaerosol concentrations in environments such as chicken houses are an occupational health concern. Two sampling methods (impinger and filter) and three non-culture methods [epifluoresence microscopy with fluorochrome (EFM/FL), flow cytometry with the fluorochrome (FCM/FL), and fluorescent in situ hybridization (FISH)] were used to monitor the total concentration, viability, and culturability of bioaerosols in chicken houses. These results were compared to the commonly used culture method. Total microbial cell concentrations measured by the non-culture methods averaged about 5 × 10 ⁷ cells/m ³ . However, culture method underestimated bioaerosol concentrations by a factor of 10. For sampler comparison, viability determined following impinger collection was higher than that following filter method. In conclusion, impinger was considered an appropriate sampler, and EFM/FL, FCM/FL, and FISH approaches could adequately assess total microbial cell concentration and viability of bioaerosols in environmental samples.     

Development and Evaluation of a High-Volume Aerosol-into-Liquid Collector for Fine and Ultrafine Particulate Matter

This study presents a novel high-volume aerosol-into-liquid collector, developed to provide concentrated slurries of fine and/or ultrafine particulate matter (PM) to be used for unattended, in situ measurements of PM chemistry and toxicity. This system operates at 200 liters per minute (L/min) flow and utilizes the saturation–condensation, particle-to-droplet growth component of the versatile aerosol concentration enrichment system (VACES), growing fine or ultrafine PM to 3–4-μm droplets, in conjunction with a newly designed impactor, in which grown particles are collected gradually forming highly concentrated slurries. Laboratory evaluation results indicated an excellent overall system collection efficiency (over 90%) for both monodisperse and polydisperse particles in the range of 0.01 to 2 μm. Field evaluations illustrated that overall a very good agreement was obtained for most PM_2.5 species between the new aerosol collection system and the VACES/BioSampler tandem as well as filter samplers operating in parallel. Very good agreement between the new system and the VACES/BioSampler was also observed for reactive oxygen species (ROS) in ambient PM_2.5 samples, whereas lower ROS values were obtained from the water extracts of the filter, likely due to incomplete extraction of water insoluble redox active species collected on the filter substrate. Moreover, the field tests indicated that the new aerosol collection system could achieve continuous and unattended collection of concentrated suspensions for at least 2 to 3 days without any obvious shortcomings in its operation. Both laboratory and field evaluations of the high-volume aerosol-into-liquid collector suggest that this system is an effective technology for collection and characterization of ambient aerosols.

Copyright 2013 American Association for Aerosol Research     

Treatment of Air Filters Using the Antimicrobial Natural Products Propolis and Grapefruit Seed Extract for Deactivation of Bioaerosols

Two natural products; i.e., grapefruit seed extract (GSE) and propolis, were investigated for use in antimicrobial air filters. Staphylococcus aureus was investigated as a test bioaerosol, and was deposited on the antimicrobial filters, which were treated by spraying with various areal densities of GSE and propolis. The pressure drop and particle penetration were investigated to assess the filtration performance of the bioaerosol, and the bacterial-inactivation performance of the filters was evaluated by quantifying S. aureus. There was little change in the pressure drop as a function of the areal density of GSE up to 185.9 μg/cm²; however, a significant change in the pressure drop was found for the air filter coated with propolis at an areal density of 98.4 μg/cm². The penetration levels of bioaerosols in both filters were uniform and in the range 1.4–2.0% (based on particle number), regardless of the areal density of the deposited GSE or propolis. The inactivation rates of the filters with identical deposition masses of GSE and propolis were similar in the ranges of 92.1–100%, 75.2–89.1%, and 54.4–75.5% at the control filters with colony numbers of 10³, 10⁴, and 10⁵ CFU/mL, respectively. The bacterial inactivation rate could be described by an exponential function of the areal density of GSE/propolis per number of colonies.

Copyright 2015 American Association for Aerosol Research     

Bench-Scale Aerosol Filtration Test System and Evaluation of an Acoustic Bioaerosol Removal Device for Indoor Air Streams

It is important to have well-defined, reproducible methods to evaluate and compare newly developed air filtration equipment. To facilitate accurate assessment of air purification devices at the bench scale, an experimental system was designed, built, and documented to evaluate particulate removal efficiency (PRE) of air filtration devices based on principles used in ASHRAE standards. The system was then carefully characterized and used to evaluate PRE and total energy consumption of a novel acoustically enhanced impaction (AEI) air purification device. The AEI device demonstrated 99.998% PRE of 0.5–1.5 μm diameter KCl particles while causing a 120 Pa pressure drop and requiring a total of 3.0 W/l of air treated at indoor ambient conditions. A single element of the AEI device operated in a biological safety level 2 facility was then used to evaluate PRE of bioaerosol consisting of Bacillus cereus (BC) spores. PRE of BC was 99.86 ± 0.05% at indoor ambient temperature and pressure. This research describes the use of the Bench-scale Air Purification Testing and Evaluation Chamber (BAP-TEC) to experimentally evaluate and compare PRE and total energy requirements of novel air purification devices at the bench scale (280–1400 alpm). Further, an AEI device containing a fibrous filter media and high intensity sound field in the same control volume is evaluated using the BAP-TEC. Temporally resolved PRE of a bioaerosol by the AEI is also presented.

Copyright 2013 American Association for Aerosol Research