Aerosol Science and Technology最新文献

Per- and polyfluoroalkyl substances (PFAS) are manufactured chemicals and ubiquitously present in the environment, including in homes. The two major exposure pathways for PFAS indoors are inhalation and accidental ingestion of house dust; however, the influence of dust particle size on PFAS exposure is not well understood to date. Thus, we are aiming to better understand the relationship between dust particle size and PFAS concentrations. We collected dust from 10 homes in North Carolina and seven homes in New York, sieved the dust into multiple size fractions ranging from <63 μm to <2,000 μm, and used targeted methods to analyze the fractions for PFAS. We found that many neutral PFAS are significantly (p < 0.05) and negatively correlated with dust particle size (mean Pearson correlation coefficient $r=-0.70$ to -0.90), i.e., higher concentrations were found in the smaller size fractions. This suggests that neutral PFAS concentrations in dust are primarily influenced by partitioning to the dust particles from the gas phase. On the other hand, several perfluoroalkyl acids showed no clear or positive correlations between particle size and concentration (mean Pearson $r=-0.45$ to 0.65), suggesting that additional migration pathways contribute preferentially to the larger size fractions, such as abrasion of fibers from upholstery. Dust-air partition coefficients, $K_d^{\text{'}}$ , derived for neutral PFAS for a subset of homes reflect this observation, with higher $\log \left(K_d^{\text{'}}\right)$ values found for smaller dust size fractions compared to larger size fractions. This work highlights the importance of the choice of size fraction when analyzing PFAS in dust and for exposure assessments.

Understanding the seasonality and prevalence of respiratory viruses in indoor environments is essential for protecting public health in the post-pandemic era. This study investigated the presence of airborne SARS-CoV-2 in university indoor spaces where no symptomatic or confirmed positive individuals were supposed to be present. A total of 127 high-efficiency particulate air (HEPA) filter samples were analyzed from air purifiers installed in classrooms, conference rooms, and a community room within a university building across different seasons from Fall 2022 to Summer 2023. Viral RNA was extracted and quantified using RT-qPCR for each sample. SARS-CoV-2 RNA was detected in 21% of the samples, with the positivity rate varying significantly by room type but not by season. Among the 27 positive samples, viral RNA concentrations were significantly higher in fall-winter compared to summer, with no significant differences across room types. Additionally, respiratory syncytial virus (RSV) and influenza A virus (IAV) were detected in far fewer samples (positive rates: 2% and 4%, respectively) and at much lower concentrations than SARS-CoV-2. These findings provide evidence of the potential for airborne SARS-CoV-2 transmission in shared indoor spaces, even in the absence of known infectious individuals. They also suggest that SARS-CoV-2 may circulate in each season, underscoring the continued need for interventions to reduce indoor viral exposure.

Reliable assessment of personal exposure to air pollution remains a challenge due to the limitations of monitoring technology. Recent technology developments, such as reductions in the size and cost of samplers as well as incorporation of continuous sensors for location, activity, and exposure (i.e., global positioning systems [GPS], accelerometers, and low-cost pollutant sensors), have advanced our ability to assess personal exposure to air pollution. This study evaluated the upgraded Ultrasonic Personal Aerosol Sampler (UPAS v2.1 PLUS) as a tool for quantifying time-integrated indoor and personal exposure to particulate matter (PM) and black carbon (BC) among a panel of participants in California's Central Valley and exploring personal exposures in different microenvironments using time/location-resolved PM data. Three field campaigns demonstrated that filter-derived PM₁₀, PM_2.5, PM₁₀ BC, and PM_2.5 BC concentrations measured using the UPAS were linear, unbiased, and precise compared to those measured using conventional personal sampling equipment. Time-resolved PM, GPS, and light intensity data from the UPAS allowed for personal PM_2.5 exposure assessment across microenvironments. The majority of daily PM_2.5 exposure occurred inside the home. Participants with higher out-of-home PM_2.5 exposures received those exposures primarily in agricultural and in-transit environments, in accordance with their self-reported occupational exposures. This study demonstrated the UPAS v2.1 PLUS is a reliable and valid tool for characterizing indoor air pollution and personal exposures in both temporal and spatial dimensions. Its enhanced capabilities should reduce the burden of personal activity logging in the field and enable accurate and precise estimation of exposures for epidemiological and community-based research.

Elevated concentrations of fine particulate matter (PM_2.5, particles < 2.5 μm) lead to negative health outcomes in urban areas, such as New York City (NYC). The sources of particles contributing to PM_2.5 in NYC are variable and complex due to the range of primary anthropogenic and biogenic emissions, as well as secondary aerosol formation (i.e., aging) from gaseous precursors. To improve understanding of the contributors to PM_2.5, single particle microspectroscopy uses chemical fingerprints to identify sources and the extent of aging, but few studies have integrated multiple microspectroscopy methods to understand PM_2.5 in NYC. Herein, we focus on a recently-developed form of microspectroscopy that can measure atmospherically-sized particles (>~0.8 μm), optical photothermal infrared (O-PTIR). We compare O-PTIR to existing microspectroscopy methods [Raman, fluorescence, and energy dispersive X-ray (EDX)] to study sources and aging of the complex NYC aerosol based on functional group and elemental information, which we also relate to bulk mass spectrometry methods. Single particle data shows submicron aerosol composition dominated by carbonaceous particles that fluoresce mixed with ammonium and sulfate, with a range of oxidized organic functional groups observed. At larger sizes, more primary sources (salts, dust, and biological) were observed, with nitrate being the dominant secondary anion. Collectively, the results from OPTIR and other instruments across case-study days reveal variations in sources and aging, with greater variability at larger diameters. Demonstrating the potential of O-PTIR when combined with the other methods to provide data that is important for improving air quality in urban megacities.

A "Community Condensation Particle Counter" (cCPC) has been developed to provide an affordable monitor of airborne particle number concentrations. The cCPC is an expansion-type condensation particle counter that incorporates single particle counting to yield a direct measurement of number concentration. Particle number concentrations are derived from the detection of individual droplets exiting the cell during the expansion, combined with the pressure readings and the physical volume of the particle cell. Modeling and experiment confirm detection of particles as small as 4 nm, with >95% detection above 20 nm. For 12 days of ambient sampling two collocated cCPCs exhibit a pooled standard deviation of 3.5%. Comparison to a pair of benchtop instruments (ADI MAGIC CPCs) yields a correlation of R²=0.98 and a regression slope of 1.1. Laboratory studies at concentrations higher than 3×10⁴ cm^-3 for both sulfate and dioctyl sebacate show equally reduced response when compared to a versatile water CPC, but this was not observed in ambient aerosol sampling. Further research will be needed to resolve this discrepancy.

The deposition of inhaled particles is typically highly localized in both the bronchial and alveolar region of the lung displaying spot-like, line-like and other deposition patterns. However, knowledge is very limited on how different deposition patterns may influence downstream cellular responses. In this study, the Dosimetric Aerosol in Vitro Inhalation Device (DAVID) was used for dose-controlled deposition of cupric oxide nanoparticles (CuONPs) in four different patterns (i.e., spot, ring, line and circle) on human alveolar A549 cells cultured at an air-liquid interface (ALI). After CuONP deposition (<15 min) and a 24 h incubation phase, cell viability, apoptotic / necrotic cell count, and gene expressions were measured. At the lowest dose of ~5 μg/cm², the line pattern resulted in the lowest viability of cells (57%), followed by the spot pattern (85%) while the ring and circle patterns exhibited >90% viability, compared to the particle free air control. At the highest dose of ~20 μg/cm², the viability reduced to 44%-60% for all patterns. Also, the gene profile was found to depend on deposition pattern. The results demonstrate that the deposition pattern is a critical parameter influencing cellular response, thus an important parameter to consider in toxicity and drug delivery studies. Furthermore, the ability of DAVID to control the delivery of aerosolized particles in various deposition patterns was demonstrated, which enables implementation of nonhomogeneous particle deposition patterns that mimic real-life human inhalation exposures in future in vitro toxicology studies.

A falling powder can generate a dust cloud from its interaction with the ambient air and from its splash onto a substrate. This article reports the results of a numerical simulation study, which attempts to model this second process. We argue that the dust cloud arises from the aerodynamic resuspension of previously deposited small particles. The agglomerated falling powder is modeled as a falling pellet disk impacting a surface covered with a monolayer of previously deposited particles. The Reynolds number of the air flow in the vicinity of the impacting pellet is Re ~ 1860, so the air flow is modeled as laminar and incompressible. The dust particles are incorporated via a Lagrangian multiphase treatment. The sudden deceleration of the disk sheds an aerodynamic vortex, which suspends particles from the monolayer. Characteristics of the dust cloud (average and maximum height and radius) are tracked; these are conveniently summarized by following the trajectory of the dust cloud centroid. The probability of aerosolization decreases with distance from the impacted pellet. The centroid trajectory is studied as a function of dust particle size. The model is relatively insensitive to disk radius and thickness. More realistic modeling of dust clouds generated by the splash of falling powders will require a statistical analysis of aggregate size and location, as well as the inclusion of interparticle and particle-surface interactions.

The impact of suspended particles on health, climate, and industrial applications is highly size-dependent. Thus, regulations are typically based on particles with diameters below a specific size, such as particulate matter less than 2.5 μm (PM_2.5). For over a century, cyclones have been employed to isolate particles below a certain diameter by removing large particles from a gas stream, but cyclones are typically relatively large, heavy, and expensive to fabricate compared to objects made with low-cost 3-dimensional (3D) printers. Herein, we present one-piece 3D-printed micro-cyclones (PM_2.5 and PM₁) to isolate particles smaller than a specific diameter. The collection efficiencies and 50% cut-off diameters (d₅₀) of multiple cyclones were evaluated with both monodisperse and polydisperse standards ranging from 0.1 to 3 μm, as well as ambient aerosol. By altering the inlet orientation relative to the micro-cyclone centerline (orthogonal, 50% offset, and fully offset), we show that shifting the inlet radially outward increased the steepness of the transmission curve resulting in a sharper cut-point. The d₅₀ also decreased below the designed for diameter, (PM₁ = 1.4, 1.0, and 0.9 μm; PM_2.5 = 3.2, 2.0, 1.9 μm), which was attributed to imperfect models, internal surface roughness, and print errors versus machining. These single piece, 3D-printed cyclones provide a cheaper (< $1), faster, and more accessible approach to manufacture micro-cyclones for use in a range of aerosol applications.

This study investigates the effectiveness of electrospun nanofibrous filters in capturing polydisperse virus-containing aerosols and the subsequent release of viruses, in comparison with standard commercial filters used in respirators, military gas masks, and devices for airborne virus sampling. We assessed the performance of these filters in capturing and releasing polydisperse aerosols containing MS2 bacteriophage, as well as in their ability to filter monodisperse dioctyl phthalate aerosols measuring 0.185 μm and 0.3 μm in diameter. Our findings indicate that nanofibrous filters provide superior filtration efficiency for monodisperse aerosols, achieving a reduction in the concentration of penetrating aerosols by 2-3 orders of magnitude compared to their commercial counterparts. However, this enhanced efficiency is accompanied by a higher pressure drop and a lower quality factor, underscoring the need for further improvements. Additionally, our research confirms the feasibility of producing aligned nanofibers via multiple-jet needleless electrospinning, though alignment did not significantly impact filtration efficiency. Nanofibrous filters demonstrated filtration efficiency for aerosolized virus-containing particles that was comparable to or better than that of commercial filters. Notably, certain nanofibrous filters exhibited exceptionally low rates of viral aerosol capture and release, indicating a potential for virus neutralization. Moreover, filters made from water-soluble electrospun polyvinylpyrrolidone significantly outperformed those made from gelatin in terms of viral particle release, underscoring the potential of water-soluble electrospun materials in improving viral particle collection. Overall, our study highlights the significant promise of electrospun nanofibers in public health, especially in enhancing defenses against the transmission of viral aerosols.

Exposure to airborne respiratory viruses can be a health hazard in occupational settings. In this study, air sampling was conducted from January to March 2023 in two outpatient medical clinics-one primary care clinic and one clinic dedicated to the diagnosis and treatment of respiratory illnesses-for the purpose of assessing airborne respiratory virus presence. Work involved the operation of a BioSpot-VIVAS^™ as a stationary air sampler and deployment of NIOSH BC-251 bioaerosol samplers as either stationary devices or personal air samplers worn by staff members. Results were correlated with deidentified clinical data from patient testing. Samples from seven days were analyzed for SARS-CoV-2, influenza A H1N1 and H3N2 viruses, and influenza B Victoria- and Yamagata-lineage viruses, with an overall 17.5% (17/97) positivity rate. Airborne viruses predominated in particles of aerodynamic diameters from 1-4 μm and were recovered in similar quantities from both clinics. BC-251 samplers (17.4%, 15/86) and VIVAS (18.2%, 2/11) collected detectable viruses at similar rates, but more numerous BC-251 samplers provided greater insight into virus presence across clinical spaces and job categories. 60% of samples from reception areas contained detectable virus, and exposure to significantly more virus (p = 0.0028) occurred at reception desks as compared to the "mobile" job categories of medical providers and nurses. Overall, this study provides valuable insights into the impacts of hazard mitigation controls tailored to reducing respiratory virus exposure and highlights the need for continued diligence toward exposure risk mitigation in outpatient medical clinics.