Efficacy of Grignard Pure to Inactivate Airborne Phage MS2, a Common SARS-CoV-2 Surrogate.

Grignard Pure (GP) is a unique and proprietary blend of triethylene glycol (TEG) and inert ingredients designed for continuous antimicrobial treatment of air. TEG has been designated as a ″Safer Chemical" by the US EPA. GP has already received approval from the US EPA under its Section 18 Public Health Emergency Exemption program for use in seven states. This study characterizes the efficacy of GP for inactivating MS2 bacteriophage─a nonenveloped virus widely used as a surrogate for SARS-CoV-2. Experiments measured the decrease in airborne viable MS2 concentration in the presence of different concentrations of GP from 60 to 90 min, accounting for both natural die-off and settling of MS2. Experiments were conducted both by introducing GP aerosol into air containing MS2 and by introducing airborne MS2 into air containing GP aerosol. GP is consistently able to rapidly reduce viable MS2 bacteriophage concentration by 2-3 logs at GP concentrations of 0.04-0.5 mg/m3 (corresponding to TEG concentrations of 0.025 to 0.287 mg/m3). Related GP efficacy experiments by the US EPA, as well as GP (TEG) safety and toxicology, are also discussed.

Resuspension of particles deposited by nano-enabled consumer sprays: The role of product type, flooring material, and resuspension force.

With the development of nanotechnology, an increasing number of nano-enabled consumer products are introduced into the market. The release, deposition, and resuspension of particles from such products could be an important contributor to indoor air pollution and adverse health effects. Our study tested the spray and resuspension of seven nano-enabled consumer products and investigated how flooring material and resuspension force affected the resuspension of particles from these products. Results show that resuspension rates can range from 10-4 to 5 × 10-1  h-1 , depending on the product, flooring material (e.g., carpet and vinyl), and resuspension force (e.g., a walking adult and a moving child; the latter was simulated by a robotic sampler). The resuspension rate from the carpet was statistically significantly higher than that from vinyl flooring, while the resuspension rate by the adult was statiscally significantly higher than that by the robot. In addition, the interaction of investigated factors also played a role in particle resuspension rate. For a subgroup of products based on copper (Cu), silver (Ag), and zinc (Zn) nanomaterials, the resuspension rate reached as high 5 × 10-1  h-1 , rates higher than those reported in existing studies with house dust or Arizona Road Dust.

Portable air cleaners and residential exposure to SARS-CoV-2 aerosols: A real-world study.

Individuals with COVID-19 who do not require hospitalization are instructed to self-isolate in their residences. Due to high secondary infection rates in household members, there is a need to understand airborne transmission of SARS-CoV-2 within residences. We report the first naturalistic intervention study suggesting a reduction of such transmission risk using portable air cleaners (PACs) with HEPA filters. Seventeen individuals with newly diagnosed COVID-19 infection completed this single-blind, crossover, randomized study. Total and size-fractionated aerosol samples were collected simultaneously in the self-isolation room with the PAC (primary) and another room (secondary) for two consecutive 24-h periods, one period with HEPA filtration and the other with the filter removed (sham). Seven out of sixteen (44%) air samples in primary rooms were positive for SARS-CoV-2 RNA during the sham period. With the PAC operated at its lowest setting (clean air delivery rate [CADR] = 263 cfm) to minimize noise, positive aerosol samples decreased to four out of sixteen residences (25%; p = 0.229). A slight decrease in positive aerosol samples was also observed in the secondary room. As the world confronts both new variants and limited vaccination rates, our study supports this practical intervention to reduce the presence of viral aerosols in a real-world setting.

Passive Bioaerosol Samplers: A Complementary Tool for Bioaerosol Research. A Review.

Bioaerosols consist of airborne particles of biological origin. They play an important role in our environment and may cause negative health effects. The presence of biological aerosol is typically determined using active samplers. While passive bioaerosol samplers are used much less frequently in bioaerosol investigations, they offer certain advantages, such as simple design, low cost, and long sampling duration. This review discusses different types of passive bioaerosol samplers, including their collection mechanisms, advantages and disadvantages, applicability in different sampling environments, and available sample elution and analysis methods. Most passive samplers are based on gravitational settling and electrostatic capture mechanism or their combination. We discuss the agar settle plate, dustfall collector, Personal Aeroallergen Sampler (PAAS), and settling filters among the gravity-based samplers. The described electrostatics-based samplers include electrostatic dust cloths (EDC) and Rutgers Electrostatic Passive Sampler (REPS). In addition, the review also discusses passive opportunity samplers using preexisting airflow, such as filters in HVAC systems. Overall, passive bioaerosol sampling technologies are inexpensive, easy to operate, and can continuously sample for days and even weeks which is not easily accomplished by active sampling devices. Although passive sampling devices are usually treated as qualitative tools, they still provide information about bioaerosol presence and diversity, especially over longer time scales. Overall, this review suggests that the use of passive bioaerosol samplers alongside active collection devices can aid researchers in developing a more comprehensive understanding of biological presence and dynamics, especially over extended time scales and multiple locations.

Estimating Lung Deposition of Fungal Spores Using Actual Airborne Spore Concentrations and Physiological Data.

Exposure to bioaerosols has been implicated in adverse respiratory symptoms, infectious diseases, and bioterrorism. Although these particles have been measured within residential and occupational settings in multiple studies, the deposition of bioaerosol particles within the human respiratory system has been only minimally explored. This paper uses real-world environmental measurement data of total fungal spores using Air-o-Cell cassettes in 16 different apartments and residents' physiological data in those apartments to predict respiratory deposition of the spores. The airborne spore concentrations were measured during the spring, summer, and fall. The respiratory deposition of five most prevalent spore genera-Ascospores, Aspergillus, Basidiospores, Cladosporium, and Myxomycetes-was predicted using three empirical models: the Multiple Path Particle Dosimetry model, using both the Yeh and age-specific versions, and the Bioaerosol Adaptation of the International Committee on Radiological Protection's Lung deposition model. The predicted total deposited number of spores was highest for Ascospores and Cladosporium. While the majority of spores deposit were in the extrathoracic region, there is a significant deposition for both Aspergillus and Cladosporium in the alveolar region, potentially leading to the development of aspergillosis or allergic asthma. Although the dose-response relationship is unknown, the estimate of the actual spore deposition could be the first step in determining such a relationship.

Residential indoor air quality interventions through a social-ecological systems lens: A systematic review.

Indoor air quality (IAQ) is an important consideration for health and well-being as people spend most of their time indoors. Multi-disciplinary interest in IAQ is growing, resulting in more empirical research, especially in affordable housing settings, given disproportionate impacts on vulnerable populations. Conceptually, there is little coherency among these case studies; they traverse diverse spatial scales, indoor and outdoor environments, and populations, making it difficult to implement research findings in any given setting. We employ a social-ecological systems (SES) framework to review and categorize existing interventions and other literature findings to elucidate relationships among spatially and otherwise diverse IAQ factors. This perspective is highly attentive to the role of agency, highlighting individual, household, and organizational behaviors and constraints in managing IAQ. When combined with scientific knowledge about the effectiveness of IAQ interventions, this approach favors actionable strategies for reducing the presence of indoor pollutants and personal exposures.

Presence and variability of culturable bioaerosols in three multi-family apartment buildings with different ventilation systems in the Northeastern US.

Bioaerosol concentrations in residential buildings located in the Northeastern US have not been widely studied. Here, in 2011-2015, we studied the presence and seasonal variability of culturable fungi and bacteria in three multi-family apartment buildings and correlated the bioaerosol concentrations with building ventilation system types and environmental parameters. A total of 409 indoor and 86 outdoor samples were taken. Eighty-five percent of investigated apartments had indoor-outdoor (I/O) ratios of culturable fungi below 1, suggesting minimal indoor sources of fungi. In contrast, 56% of the apartments had I/O ratios for culturable bacteria above 1, indicating the prominence of indoor sources of bacteria. Culturable fungi I/O ratios in apartments serviced by central heating, ventilation, and air-conditioning (HVAC) system were lower than those in apartments with window AC. The type of ventilation system did not have a significant effect on the presence of indoor culturable bacteria. A significant positive association was determined between indoor dew point (DP) levels and indoor culturable fungi (P < .001) and bacteria (P < .001), regardless of ventilation type. Also, residents in apartments with central HVAC did not experience extreme DP values. We conclude that building ventilation systems, seasonality, and indoor sources are major factors affecting indoor bioaerosol levels in residential buildings.

Impact of sampling and storage stress on the recovery of airborne SARS-CoV-2 virus surrogate captured by filtration.

Environmental air sampling of the SARS-CoV-2 virus in occupational and community settings is pertinent to reduce and monitor the spread of the COVID pandemic. However, there is a general lack of standardized procedures for airborne virus sampling and limited knowledge of how sampling and storage stress impact the recovery of captured airborne viruses. Since filtration is one of the commonly used methods to capture airborne viruses, this study analyzed the effect of sampling and storage stress on SARS-CoV-2 surrogate virus (human coronavirus OC43, or HCoV-OC43) captured by filters. HCoV-OC43, a simulant of the SARS-CoV-2, was aerosolized and captured by PTFE-laminated filters. The impact of sampling stress was evaluated by comparing the RNA yields recovered when sampled at 3 L/min and 10 L/min and for 10 min and 60 min; in one set of experiments, additional stress was added by passing clean air through filters with the virus for 1, 5, and 15 hr. The impact of storage stress was designed to examine RNA recovery from filters at room temperature (25 °C) and refrigerated conditions (4 °C) for up to 1 week of storage. To our knowledge, this is the first report on using HCoV-OC43 aerosol in air sampling experiments, and the mode diameter of the virus aerosolized from the growth medium was 40-60 nm as determined by SMPS + CPC system (TSI Inc.) and MiniWRAS (Grimm Inc.) measurements. No significant difference was found in virus recovery between the two sampling flow rates and different sampling times (p > 0.05). However, storage at room temperature (25 °C) yielded ∼2x less RNA than immediate processing and storage at refrigerated conditions (4 °C). Therefore, it is recommended to store filter samples with viruses at 4 °C up to 1 week if the immediate analysis is not feasible. Although the laminated PTFE filter used in this work purposefully does not include a non-PTFE backing, the general recommendations for handling and storing filter samples with viral particles are likely to apply to other filter types.

Investigating E-Cigarette Particle Emissions and Human Airway Depositions under Various E-Cigarette-Use Conditions.

E-cigarette use is dramatically increasing, particularly with adolescents. While the chemical composition of e-liquids and e-vapor is well characterized, the particle size distribution and the human airways deposition patterns of e-cigarette particles are understudied and poorly understood despite their likely contribution to adverse health effects from e-cigarette usage. In this study, we examined the impacts of e-cigarette device power, e-liquid composition, and vaping topography on e-cigarette particle sizes and their deposition in human airways. In addition, we observed that particle measurement conditions (dilution ratio, temperature, and humidity) significantly affect measured e-cigarette particle sizes. E-cigarette power output significantly increased particle count median diameters (CMD) from 174 ± 13 (particles generated under 6.4 W) to 236 ± 14 nm (particles generated under 31.1 W). E-cigarette particles generated from propylene glycol-based e-liquids (CMD = 145 ± 8 nm and mass median diameter [MMD] = 3.06 ± 0.17 µm) were smaller than those generated from vegetable glycerin-based e-liquids (CMD = 182 ± 9 nm and MMD = 3.37 ± 0.21 µm). Puff volume also impacted vapor particle size: CMD and MMD were 154 ± 11 nm and 3.50 ± 0.27 µm, 163 ± 6 nm and 3.35 ± 0.24 µm, and 146 ± 12 nm and 2.95 ± 0.14 µm, respectively, for 35, 90, and 170 mL puffs. Estimated e-cigarette particle mass deposition fractions in tracheobronchial and bronchoalveolar regions were 0.504-0.541 and 0.073-0.306, respectively. Interestingly, e-cigarette particles are smaller than the particles generated from cigarette smoking but have similar human airway deposition patterns.

Hydroxyl Radicals in E-Cigarette Vapor and E-Vapor Oxidative Potentials under Different Vaping Patterns.

Available studies, while limited in number, suggest that e-cigarette vaping induces oxidative stress, with one potential mechanism being the direct formation of reactive oxygen species (ROS) in e-vapor. In the present studies, we measured the formation of hydroxyl radical (•OH), the most destructive ROS, in e-vapor under a range of vaping patterns (i.e., power settings, solvent concentrations, flavorings). Study results show that increased power output and puff volume correspond with the formation of significantly higher amounts of •OH in e-vapor because of elevated coil temperature and oxygen supply. Vegetable glycerin (VG) e-liquids generated higher •OH levels than propylene glycol (PG) e-liquids, as did flavored e-liquids relative to nonflavored e-liquids. E-vapor in combination with ascorbic acid, which is an abundant biological molecule in human epithelial lining fluid, can also induce •OH formation. The dose of radical per puff associated with e-cigarette vaping was 10-1000 times lower than the reported dose generated by cigarette smoking. However, the daily average •OH dose can be comparable to that from cigarette smoking depending on vaping patterns. Overall, e-cigarette users who use VG-based flavored e-cigarettes at higher power output settings may be at increased risk for •OH exposures and related health consequences such as asthma and chronic obstructive pulmonary disease.

Evaluation of E-Vapor Nicotine and Nicotyrine Concentrations under Various E-Liquid Compositions, Device Settings, and Vaping Topographies.

Nicotine is one of the major components of electronic cigarette (e-cigarette) emissions. Nicotyrine is a product of nicotine dehydrogenation in e-vapor and is a known inhibitor of human cytochrome P450 enzyme, which mediates nicotine metabolism. However, the emission of nicotine and especially nicotyrine from e-cigarettes has not been studied under real-world vaping patterns. This study examined the impact of e-liquid composition, e-cigarette device power output, and vaping topography on nicotine and nicotyrine concentrations under real-world vaping patterns. The amount of nicotine emitted from e-cigarettes vaped at high e-liquid nicotine levels, high device power, and large puff volumes ranged from 0.365 µg/puff to 236 µg/puff and was comparable to the amount of nicotine emitted from regular cigarettes. E-cigarette coil temperatures (200-300 °C) favored the formation of nicotyrine: E-cigarette vaping generated 2- to 63-fold more nicotyrine per unit nicotine emission than conventional cigarette smoking. High nicotyrine emission from e-cigarettes indicates that nicotine metabolism could be potentially interrupted, which could lead to reduced e-cigarette usage, and result in lower exposures to toxic chemicals (e.g., formaldehyde and acetaldehyde). However, higher serum nicotine levels might increase cancer risks by stimulating nicotinic acetylcholine receptors (nAchRs).

Design and Development of an Electrostatic Screen Battery for Emission Control (ESBEC).

Current diesel particulate filters (DPFs) can effectively capture the exhaust particles, but they add to engine backpressure and accumulate particles during their operation, which results in the need to regenerate the DPFs by burning off the collected particles periodically. This regeneration results in aerosol emissions, especially in the 10-30 nanometer size range and contributes to ultrafine particle pollution. In this research, we designed and developed a prototype of a novel diesel exhaust control device: the Electrostatic Screen Battery for Emissions Control (ESBEC). The device features high particle collection efficiency without adding to the exhaust backpressure and without the need for thermal regeneration of the collected particles. The ESBEC consists of a series of metal mesh screens coated with a superhydrophobic substance and an integrated carbon fiber ionizer to charge the incoming particles. Multiple pairs of screens (e.g., 5 pairs) are arranged in a battery, in which one screen of each pair is supplied with high voltage, and the other is grounded, producing electrostatic field produced across the screens. The application of a superhydrophobic coating onto the screens allows easy removal of the collected particles using liquid without the need for thermal regeneration. The current prototypes of the device were tested with fluorescent polystyrene latex (PSL) particles of 0.2 and 1.2 µm in size and at 25 and 105 L/min sampling flow rates. The average collection efficiency was ~87% for 0.2 µm and ~95% for 1.2 µm PSL particles. In addition, the ESBEC was tested with actual diesel exhaust particles; here its performance was verified by visually inspecting deposition of particles on an after-filter with the device ON and OFF. In the next stages of this work, the ESBEC will be challenged with diesel exhaust at different mass concentrations and for different collection time periods.

Inactivation of foodborne microorganisms using engineered water nanostructures (EWNS).

Foodborne diseases caused by the consumption of food contaminated with pathogenic microorganisms or their toxins have very serious economic and public health consequences. Here, we explored the effectiveness of a recently developed intervention method for inactivation of microorganisms on fresh produce, and food production surfaces. This method utilizes Engineered Water Nanostructures (EWNS) produced by electrospraying of water vapor. EWNS possess unique properties; they are 25 nm in diameter, remain airborne in indoor conditions for hours, contain Reactive Oxygen Species (ROS) and have very strong surface charge (on average 10 e/structure). Here, their efficacy in inactivating representative foodborne bacteria such as Escherichia coli, Salmonella enterica, and Listeria innocua, on stainless steel surfaces and on organic tomatoes, was assessed. The inactivation was facilitated using two different exposure approaches in order to optimize the delivery of EWNS to bacteria: (1) EWNS were delivered on the surfaces by diffusion and (2) a "draw through" Electrostatic Precipitator Exposure System (EPES) was developed and characterized for EWNS delivery to surfaces. Using the diffusion approach and an EWNS concentration of 24,000 #/cm3, the bacterial concentrations on the surfaces were reduced, depending on the bacterium and the surface type, by values ranging between 0.7 to 1.8 logs. Using the EPES approach and for an aerosol concentration of 50,000 #/cm3 at 90 min of exposure, results show a 1.4 log reduction for E. coli on organic tomato surfaces, as compared to the control (same conditions in regards to temperature and Relative Humidity). Furthermore, for L. innocua, the dose-response relationship was demonstrated and found to be a 0.7 and 1.2 logs removal at 12,000 and 23,000 #/cm3, respectively. The results presented here indicate that this novel, chemical-free, and environmentally friendly intervention method holds potential for development and application in the food industry, as a "green" alternative to existing disinfection methods.

Application of ATP-based bioluminescence for bioaerosol quantification: effect of sampling method.

An adenosine triphosphate (ATP)-based bioluminescence has potential to offer a quick and affordable method for quantifying bioaerosol samples. Here we report on our investigation into how different bioaerosol aerosolization parameters and sampling methods affect bioluminescence output per bacterium, and implications of that effect for bioaerosol research. Bacillus atrophaeus and Pseudomonas fluorescens bacteria were aerosolized by using a Collison nebulizer (BGI Inc., Waltham, MA) with a glass or polycarbonate jar and then collected for 15 and 60 min with: (1) Button Aerosol Sampler (SKC Inc., Eighty Four, PA) with polycarbonate, PTFE, and cellulose nitrate filters, (2) BioSampler (SKC Inc.) with 5 and 20 mL of collection liquid, and (3) our newly developed Electrostatic Precipitator with Superhydrophobic Surface (EPSS). For all aerosolization and sampling parameters we compared the ATP bioluminescence output per bacterium relative to that before aerosolization and sampling. In addition, we also determined the ATP reagent storage and preparation conditions that that do not affect the bioluminescence signal intensity. Our results show that aerosolization by a Collison nebulizer with a polycarbonate jar yields higher bioluminescence output per bacterium compared to the glass jar. Interestingly enough, the bioluminescence output by P. fluorescens increased substantially after its aerosolization compared to the fresh liquid suspension. For both test microorganisms, the bioluminescence intensity per bacterium after sampling was significantly lower than that before sampling suggesting negative effect of sampling stress on bioluminescence output. The decrease in bioluminescence intensity was more pronounces for longer sampling times and significantly and substantially depended on the sampling method. Among the investigated method, the EPSS was the least injurious for both microorganisms and sampling times. While the ATP-based bioluminescence offers a quick bioaerosol sample analysis method, this works demonstrates that the method output depends on bioaerosol generation and sampling methods, as well as reagent storage.

Evaluation of particle resuspension in young children's breathing zone using stationary and robotic (PIPER) aerosol samplers.

Development of asthma in young children may be associated with high exposure to particulate matter (PM). However, typical stationary samplers may not represent the personal exposure of children ages 3 and younger since they may not detect particles resuspended from the floor as children play, thus reducing our ability to correlate exposure and disease etiology. To address this, an autonomous robot, the Pretoddler Inhalable Particulate Environmental Robotic (PIPER) sampler, was developed to simulate the movements of children as they play on the floor. PIPER and a stationary sampler took simultaneous measurements of particle number concentration in six size channels using an optical particle counter and inhalable PM on filters in 65 homes in New Jersey, USA. To study particle resuspension, for each sampler we calculated the ratio of particle concentration measured while PIPER was moving to the average concentration of particles measured during a reference period when PIPER remained still. For all investigated particle sizes, higher particle resuspension was observed by PIPER compared to the stationary sampler. In 71% of carpeted homes a more significant (at the α = 0.05 level) resuspension of particles larger than 2.5 µm was observed by PIPER compared to the stationary sampler. Typically, particles larger than 2.5 µm were resuspended more efficiently than smaller particles, over both carpeted and bare floors. Additionally, in carpeted homes estimations of PM10 mass from the particle number concentrations measured on PIPER while it was moving were on average a factor of 1.54 higher compared to reference period when PIPER was not moving. For comparison, the stationary sampler measured an increase of PM2.5 mass by a factor of only 1.08 when PIPER was moving compared to a reference period. This demonstrates that PIPER is able to resuspend particles through movement, and provide a better characterization of the resuspended particles than stationary samplers. Accurate measurement of resuspended PM will improve estimates of children's total PM exposure.

Indoor air quality in green buildings: A case-study in a residential high-rise building in the northeastern United States.

Improved indoor air quality (IAQ) is one of the critical components of green building design. Green building tax credit (e.g., New York State Green Building Tax Credit (GBTC)) and certification programs (e.g., Leadership in Energy & Environmental Design (LEED)) require indoor air quality measures and compliance with allowable maximum concentrations of common indoor air pollutants. It is not yet entirely clear whether compliance with these programs results in improved IAQ and ultimately human health. As a case in point, annual indoor air quality measurements were conducted in a residential green high-rise building for five consecutive years by an industrial hygiene contractor to comply with the building's GBTC requirements. The implementation of green design measures resulted in better IAQ compared to data in references of conventional homes for some parameters, but could not be confirmed for others. Relative humidity and carbon dioxide were satisfactory according to existing standards. Formaldehyde levels during four out of five years were below the most recent proposed exposure limits found in the literature. To some degree, particulate matter (PM) levels were lower than that in studies from conventional residential buildings. Concentrations of Volatile Organic Compounds (VOCs) with known permissible exposure limits were below levels known to cause chronic health effects, but their concentrations were inconclusive regarding cancer health effects due to relatively high detection limits. Although measured indoor air parameters met all IAQ maximum allowable concentrations in GBTC and applicable LEED requirements at the time of sampling, we argue that these measurements were not sufficient to assess IAQ comprehensively because more sensitive sampling/analytical methods for PM and VOCs are needed; in addition, there is a need for a formal process to ensure rigor and adequacy of sampling and analysis methods. Also, we suggest that a comprehensive IAQ assessment should include mixed mode thermal comfort models, semi-volatile organic compounds, assessment of new chemicals, and permissible exposure levels of many known indoor VOCs and bioaerosols. Plus, the relationship between energy consumption and IAQ, and tenant education on health effects of indoor pollutants and their sources may need more attention in IAQ investigations in green buildings.

Potential exposure of adults and children to particles from resuspended nano-enabled consumer sprays.

The increasing application of nanotechnology has resulted in a growing number of nano-enabled consumer products, and they could be important contributors to indoor particulate matter, with potential adverse health effects. This study investigated the exposure of adults and children to the released and resuspended manufactured particles from seven nano-enabled consumer sprays. Sedimentation and resuspension of released particles were investigated in a newly constructed 2.8 × 1.6 × 2.4 m3 chamber. The resuspension of deposited particles was investigated as a function of product type, flooring material (e.g., carpet and vinyl), resuspension force (e.g., walking by an adult and motion of a robotic sampler that simulated a child), and measurement height. The concentration of released and resuspended particles in the air was determined using Button Aerosol Samplers (SKC Inc.) with 25-mm 2 µm-pore PTFE filters. Samplers were positioned in the experimenter's breathing zone (e.g., 1.5 m for adults and 0.3 m for a child-simulating robot) and at fixed stations of 0.3 m and 1.1 m heights. Resuspended particle mass concentrations ranged from 28 to 905 µg/m3, and the resuspension rates of deposited spray particles for the same variable combinations varied from 10-4 to 10-1 h-1, depending on product type, flooring material, sampling height, and resuspension force. Particle resuspension rates from carpet were up to 320 % higher than resuspension rates from vinyl flooring, resuspension rates measured at 0.3 m were up to 195 % higher than the rates measured with a 1.1 m stationary sampler, and resuspension rates due to a walking adult were up to 243 % higher than resuspension rates caused to a moving robot that simulated a child. Overall, these data on the resuspension of particles from nano-enabled consumer sprays could help us understand the resulting exposures and support future studies on human exposure reduction.

Real-World Effectiveness of Portable Air Cleaners in Reducing Home Particulate Matter Concentrations.

Portable air cleaners (PACs) equipped with HEPA filters are gaining attention as cost-effective means of decreasing indoor particulate matter (PM) air pollutants and airborne viruses. However, the performance of PACs in naturalistic settings and spaces beyond the room containing the PAC is not well characterized. We conducted a single-blinded randomized cross-over interventional study between November 2020 and May 2021 in the homes of adults who tested positive for COVID-19. The intervention was air filtration with PAC operated with the HEPA filter set installed ("filter" condition) versus removed ("sham" condition, i.e., control). Sampling was performed in 29 homes for two consecutive 24-hour periods in the primary room (containing the PAC) and a secondary room. PAC effectiveness, calculated as reductions in overall mean PM2.5 and PM10 concentrations during the filter condition, were for the primary rooms 78.8% and 63.9% (n = 23), respectively, and for the secondary rooms 57.9% and 60.4% (n = 22), respectively. When a central air handler (CAH) was reported to be in use, filter-associated reductions of PM were statistically significant during the day (06:00-22:00) and night (22:01-05:59) in the primary rooms but only during the day in the secondary rooms. Our study adds to the literature evaluating the real-world effects of PACs on a secondary room and considering the impact of central air systems on PAC performance.

Release of free DNA by membrane-impaired bacterial aerosols due to aerosolization and air sampling.

We report here that stress experienced by bacteria due to aerosolization and air sampling can result in severe membrane impairment, leading to the release of DNA as free molecules. Escherichia coli and Bacillus atrophaeus bacteria were aerosolized and then either collected directly into liquid or collected using other collection media and then transferred into liquid. The amount of DNA released was quantified as the cell membrane damage index (ID), i.e., the number of 16S rRNA gene copies in the supernatant liquid relative to the total number in the bioaerosol sample. During aerosolization by a Collison nebulizer, the ID of E. coli and B. atrophaeus in the nebulizer suspension gradually increased during 60 min of continuous aerosolization. We found that the ID of bacteria during aerosolization was statistically significantly affected by the material of the Collison jar (glass > polycarbonate; P < 0.001) and by the bacterial species (E. coli > B. atrophaeus; P < 0.001). When E. coli was collected for 5 min by filtration, impaction, and impingement, its ID values were within the following ranges: 0.051 to 0.085, 0.16 to 0.37, and 0.068 to 0.23, respectively; when it was collected by electrostatic precipitation, the ID values (0.011 to 0.034) were significantly lower (P < 0.05) than those with other sampling methods. Air samples collected inside an equine facility for 2 h by filtration and impingement exhibited ID values in the range of 0.30 to 0.54. The data indicate that the amount of cell damage during bioaerosol sampling and the resulting release of DNA can be substantial and that this should be taken into account when analyzing bioaerosol samples.