Low-Cost Sensor System for Air Purification Process Evaluation.

With the development of civilisation, the awareness of the impact of versatile aerosol particles on human health and the environment is growing. New advanced materials and techniques are needed to purify the air to reduce this impact. This brings the necessity of fast and low-cost devices to evaluate the air quality from particulate and gaseous impurities, especially in a place where gas chromatography (GC) techniques are unavailable. Small portable and low-cost systems may work separately or be incorporated into devices responsible for air-cleaning processes, such as filters, smoke adsorbers, or plasma air cleaners. Given the above, this study proposes utilising a self-assembled low-cost system to evaluate air quality, which can be used in many outdoor and indoor applications. ESP32 boards with the wireless communication protocol ESP-NOW were used as the framework of the system. The concentration of aerosol particles was measured using Alphasense sensors. The concentrations of the following gases were measured: NO2, SO2, O3, CO, CO2, and H2S. The system was used to evaluate the quality of air containing tobacco smoke after passing through an actual DBD plasma reactor where the purification occurred. A high amount of reduction in aerosol particles and a reduction in the SO2 concentration were detected. An increase in the NO2 concentration was seen as an undesirable effect. The aerosol particle measurements were compared with those using a professional device (GRIMM, Hamburg, Germany), which showed the same trends in aerosol particle behaviour. The obtained results are auspicious and are a step towards producing a low-cost, efficient system for evaluating air quality as well as indoor and outdoor conditions.

Effect of Microplastic Particles on the Rheological Properties of Human Saliva and Mucus.

Pollution by plastic microparticles is rising rapidly. One avenue of human exposure to nanoparticles is through inhalation. The main source of microplastics in indoor environments, leading to unintended inhalation, is synthetic fabric used in clothing. Other sources include curtains, carpets, furniture, wall paints, and floor finishes. Occupational exposure is particularly significant in waste management and recycling operations, during exposure to high heat, during high-energy treatment of polymer composites, and during 3D printing. In outdoor environments, exposure can happen through breathing in contaminated aerosols from ocean waves or airborne particles from dried wastewater treatments. Airborne particles affect human health in various ways, including via direct interactions with the epithelium and its mucus layer after deposition in the mouth and respiratory system. Exposure due to the ingestion of microplastics present in various environmental compartments may occur either directly or indirectly via the food chain or drinking water. This study aimed to determine the effects of plastic microparticles on the rheology of mucus and saliva, and, thus, their functioning. The experiments used artificial mucus, saliva, and plastic nanoparticles (namely, PS-polystyrene and PE-polyethylene). The rheological properties of saliva and mucus were determined via the use of an oscillatory rheometer at various temperatures (namely, 36.6 °C and 40 °C, which correspond to healthy and ill humans). The results were compared with those obtained for pure saliva and mucus. An increase in apparent viscosity was observed for saliva, which is behavior typical of for solid particle suspensions in liquids. In contrast, for mucus, the effect was the opposite. The influence of the presence of the particles on the parameters of the constitutive viscosity equations was studied. Plastic micro- and nanoparticles in the saliva and mucus may interfere with their physiological functions.

Fibrous Structures Produced Using the Solution Blow-Spinning Technique for Advanced Air Filtration Process.

This study proposes utilising the solution blow-spinning process (SBS) for manufacturing a biodegradable filtration structure that ensures high efficiency of particle filtration with an acceptable pressure drop. The concept of multi-layer filters was applied during the design of filters. Polylactic acid (PLA) was used to produce various layers, which may be mixed in different sequences, building structures with varying filtration properties. Changing the process parameters, one can create layers with diverse average fibre diameters and thicknesses. It enables the design and creation of optimal filtration materials prepared for aerosol particle filtration. The structures were numerically modelled using the lattice Boltzmann approach to obtain detailed production guidelines using the blow-spinning technique. The advantage of this method is the ability to blow fibres with diameters in the nanoscale, applying relatively simple and cost-effective equipment. For tested PLA solutions, i.e., 6% and 10%, the mean fibre diameter decreases as the concentration decreases. Therefore, the overall filtering efficiency decreases as the concentration of the used solution increases. The produced multi-layer filters have 96% overall filtration efficiency for particles ranging from 0.26 to 16.60 micrometres with a pressure drop of less than 160 Pa. Obtained results are auspicious and are a step in producing efficient, biodegradable air filters.

Modeling of Inhalation Profiles Through Dry Powder Inhaler in Healthy Adults and Asthma Patients As a Prerequisite for Further In Vitro and In Silico Studies.

Background: The severity of airway obstruction may affect patient's ability to perform an effective drug inhalation from a dry powder inhaler (DPI). Also, an incorrect inhalation technique may negatively affect the efficacy of asthma treatment. The aims of the study were (1) to analyze and compare inhalation profiles recorded with the use of different inhalation techniques, and thus, (2) to establish model inhalation profiles representative for healthy subjects and subjects with mild and moderate-to-severe asthma. Methods: This study was performed in healthy volunteers, patients with mild and moderate-to-severe asthma. A modified flow-volume test to define two different expiratory levels (to residual volume and half-way to residual volume) was performed. Inspiratory flow parameters were extracted: peak inspiratory flow rate (PIFinh), time at which peak inspiratory flow rate occurs (tPIFinh), total inhalation time (T), and inhaled volume (V). Test of frequency for tPIFinh100% and tPIFinh50% by asthma severity was performed, to provide information about initial flow accelerations. The impact of two different expiratory levels preceding inhalation (with severity of asthma as a categorical factor) on inspiratory flow parameters was examined. Results: PIFinh was dependent upon asthma severity (p = 0.046). Type of exhalation before inhalation had no effect on PIFinh values. V value was significantly affected both by asthma severity (p = 0.024) and type of exhalation before inhalation (p < 0.0001). Mean T value was influenced by type of exhalation before inhalation (p = 0.0003), but not by asthma severity. Mean tPIFinh value was affected by the type of exhalation before inhalation only in healthy subjects (p = 0.01). Conclusions: Both asthma severity and type of exhalation before inhalation have little impact on the dynamics of inhalation through a DPI. An alternative form of equation describing inhalation profiles demonstrating a relationship between lung mechanics and dynamics of inspiratory profile has been proposed.

Inhalation Profiles Through a Dry Powder Inhaler: Relation Between Inhalation Technique and Spirometric Measures.

Background: The understanding of the real flow profiles through a dry powder inhaler (DPI), generated by asthma patients, is a prerequisite for satisfactory drug delivery to the lungs. The aims of the study were to assess the relationship between spirometric measures and inhalation profiles through a low-resistance DPI, and to compare parameters of those profiles between optimal and suboptimal inhalation technique type. Methods: Both healthy adult volunteers and patients with asthma were included in the study. Spirometry was conducted along with modified flow-volume test to detect expiratory levels (maximum "100%" exhalation to residual volume [RV] and halfway "50%" to RV). These were the reference levels of the depth of exhalation for each patient to simulate the effect of incomplete exhalation. Individual inhalation profiles were recorded using spirometry in-house software as the volumetric airflow through the inhaler versus time. Inspiratory flow parameters were extracted: time to peak inspiratory flow through inhaler (PIFinh), time at which peak inspiratory flow occurs (tPIFinh), total inhalation time (T), and inhaled volume during maneuver (V). Results and Conclusions: There are significant relationships between spirometric indices and parameters of inhalation through a low-resistance, cyclohaler-type DPI (assessed by single-factor analysis of Spearman's rank correlation coefficient). Multiple regression models were constructed, predicting inspiratory flow parameters (including spirometric indices, demographic parameters, and inhaler's usage history as determinants). The exhalation halfway to RV before inhalation did not affect significantly PIFinh and tPIFinh (and, thus, initial flow dynamics) in asthma patients. T and V parameters were then significantly decreased, but seemed sufficient for successful DPI performance. Both exhalation to RV and incomplete exhalation halfway to RV preceding inhalation allow for effective usage of low-resistance DPI.

The effect of desert dust particles on rheological properties of saliva and mucus.

Transported desert dust particles (TDDP) are soil particles suspended in the air. Being spread all over the globe by the winds, TDDP affect animals, including humans, plants and other organisms not only in the areas of their emission. In humans, TDDP are responsible for diseases of the respiratory (e.g. asthma) and circulatory (e.g. heart failure) systems and they also act directly on the epithelium and its mucus layer after deposition in the mouth and respiratory system. The aim of the study was to determine the influence of TDDP on the rheology of mucus and saliva, and thus on their functioning. The artificial mucus and saliva, as well as Arizona TDDP, were used in experiments. The rheological properties of TDDP were determined with the use of an oscillatory rheometer, at various temperatures and in the presence of different amount of TDDP. Moreover, the diffusion time of the marker (rhodamine B) throughout mucus with desert dust particles was examined. The obtained results demonstrate that the presence of TDDP in the saliva and mucus model increases their apparent viscosity. The concentration of particles is positively correlated with the increase of viscosity. However, it has not been demonstrated that the presence of TDDP in mucus significantly influenced the diffusion of a fluorescent marker throughout the mucus. The presence of TDDP in the saliva and mucus may interfere with their moisturising function, and cause difficulties in swallowing by increasing the viscosity of mucus and saliva. Moreover, increased viscosity of mucus may cause problems with its ability to pass to the upper respiratory tracts, which may lead to a general discomfort or local inflammation.

Aerosolized albuterol sulfate delivery under neonatal ventilatory conditions: in vitro evaluation of a novel ventilator circuit patient interface connector.

BACKGROUND: Aerosolized medications that have been used in infants receiving ventilatory support have not been shown to be effective clinically among the smallest patients. The aim of this study was to characterize the delivery of aerosolized albuterol sulfate in vitro under simulated neonatal ventilatory conditions using a novel ventilator circuit/patient interface connector. METHODS: A Babylog(®) ventilator (VN500(®); Draeger), a novel ventilator circuit/patient interface (VC) connector (Afectair(®); Discovery Laboratories, Inc.), a TwinStar(®) HME (Draeger) low-volume filter, and either a test lung (Draeger) or lung simulator ASL 5000(®) (IngmarMed) were used. Intermittent mandatory ventilation conditions were set to replicate the most typical ventilation conditions for premature infants. Continuous positive airway pressure was also used to measure aerosol delivery with active respiratory drive from the patient. Albuterol sulfate (0.5 mg/mL) was loaded into the drug reservoir of a Misty Finity(®) nebulizer (Airlife(®); Cardinal Health) and connected to the ventilator circuit either via a "T" connector as described by the manufacturer [standard of care (SoC)] or via the VC connector. Albuterol extracted from the filters was analyzed using qualified high-performance liquid chromatography. In addition, a laser diffraction spectrometry (Spraytec(®); Malvern) and white-light spectrometry (Welas model 2100; Palas GmbH) were used to determine particle size distribution (PSD). RESULTS: Compared with SoC, the amount of albuterol delivered using the VC connector was significantly greater (p<0.001) under simulated neonatal ventilatory conditions. Additionally, the PSD profile of albuterol sulfate delivered using the VC connector was more representative of the PSD profile directly from the nebulizer. CONCLUSIONS: The use of the VC connector increased the delivery of albuterol sulfate and resulted in a PSD profile at the patient interface that is more consistent with the PSD profile of the selected nebulizer when compared with SoC. This VC connector may be a useful, new approach for the delivery of aerosolized medications to neonates requiring positive pressure ventilatory support.

Penetration of diesel exhaust particles through commercially available dust half masks.

Half masks are certified by the competent, national institutions--National Institute for Occupational Safety and Health (NIOSH) in the USA and the respective European national institutions applying common European regulations. However, certification testing is conducted with particles of NaCl, paraffin oil, or dioctyl phthalate (DOP) and at the constant flow rate, whereas particles commonly found in workplaces may differ in size, shape, and morphology from these particles. Therefore, the aim of this study was to investigate filtration efficiency of commercially available filtering facepiece half masks under the condition of exposure to diesel fumes. In this study, we focused on the particulate phase [diesel exhaust particles (DEP)] of three (petroleum diesel, ecodiesel, and biodiesel) diesel fuel combustion types. Two types of European standard-certified half masks, FFP2 and FFP - Filtering Facepiece, and three types of popular diesel fuels were tested. The study showed that the filtration efficiencies for each examined half mask and for each of diesel exhaust fumes were lower than the minimum filtration efficiency required for the standard test aerosols by the European standards. For FFP2 and FFP3 particulate half masks, standard minimum filtration efficiency is 94 and 99%, respectively, whereas 84-89% of mass of DEP from various fuels were filtered by the tested FFP2 and only 75-86% by the FFP3. The study indicated that DEP is more penetrating for these filters than the standard salt or paraffin oil test aerosols. The study also showed that the most penetrating DEP are probably in the 30- to 300-nm size range, regardless of the fuel type and the half-mask model. Finally, the pressure drops across both half masks during the 80-min tests remained below an acceptable maximum of breathing resistance-regardless of the fuel types. The respiratory system, during 40-min test exposures, may be exposed to 12-16mg of DEP if a FFP2 or FFP3 particulate half mask is used. To conclude, commercially available half masks may not ensure a sufficient level of protection of the respiratory tract against diesel exhaust fumes.

Study of an axial flow cyclone to remove nanoparticles in vacuum.

An axial flow cyclone for removing nanoparticles was tested for collection efficiency. Data were validated numerically in vacuum conditions of several Torrs, with flow rates of 0.35-0.57 slpm. The experimental cutoff aerodynamic diameter of the cyclone ranged from 21.7 to 49.8 nm. A 3-D numerical simulation was conducted first to calculate detailed flow and pressure fields, then a Brownian Dynamics simulation was done to determine the collection efficiency of nanoparticles. Both centrifugal force and Brownian diffusion were taken into account. The simulated results for both pressure drop and cutoff aerodynamic diameter are in good agreement with the experimental data. In comparison, previous theories using simplified tangential flow field assumption are not able to predict collection efficiencies accurately. The numerical model developed in this study can facilitate cyclone design to classify valuable nanopowders below a certain diameter, or to remove toxic nanoparticles from the vacuum exhaust of process chambers commonly used in high-tech industries.

Mechanims of aerosol particle deposition in the Oro-pharynx under non-steady airflow.

Comparison of experimental and computational results of aerosol deposition in the oro-pharyngeal cast of human published recently (Sosnowski TR, Moskal A, Gradon L. (2006) Inhal Toxicol; 18: 773-780) demonstrated the applicability and relevance of considering realistic breathing patterns in analysis of aerosol flow and deposition within the human head airways. This issue is extended in the current paper, focused on a detailed analysis of spatial and temporal distribution of particle deposition in the oro-pharynx during inspiration. CFD modeling was used to determine both the 3D airflow structure and the local particle deposition fluxes at two different inspiratory patterns. Behavior of aerosol (particle size: 0.3-10 micro m, material density: 2200 kg m(-3)) was analyzed applying Lagrangian approach and considering Brownian effects for submicron particles. Results indicate that particles of different sizes are deposited in different parts of the oro-pharynx, depending on the point in the inspiration cycle. Larger particles (3-10 micro m) are separated efficiently in the naso-pharyngeal bend due to inertia, which predominate in the middle phase of inspiration. Submicron particles are deposited more uniformly in the oro-pharyngeal space, and their separation from the air is enhanced in a short transition period between inspiration and expiration. It suggests the importance of mixing of inspired and expired air streams for particle deposition pattern. Comparison of our computational results of deposition to the approximation derived from the in vivo data (Stahlhofen W, Rudolf G, James AC. (1989) J Aerosol Med; 2: 285-308) shows a good agreement for particles, for which the inertia is a predominant mechanism of deposition. The results of this work lead to a more detailed description of the dynamics of oro-pharyngeal aerosol deposition during inspiratory part of the breathing cycle. The recognition of that problem is essential for prediction of toxic or pharmacological local effects of inhaled aerosols.

Deposition of fractal-like aerosol aggregates in a model of human nasal cavity.

Toxicity of diesel exhaust is related to the inhalation of nano-sized fractal-like aerosol aggregates. Their complex behavior (in comparison to spherical particles) should be taken into account in deposition modeling. The deposition of aerosol fractal-like aggregates in the model of a human nose was studied numerically for the flow rate corresponding to breathing conditions. The simplified geometry of the human nasal replica was implemented in the computational fluid dynamics (CFD) code (FLUENT) used for calculation of the three-dimensional airflow structure. A Brownian dynamic (BD) algorithm was applied for determination of the aggregates deposition in the nasal cavity during inhalation. These calculations were carried out for several populations of aggregates. The values of parameters used in the BD simulations for characterization of fractal-like aggregates, that is, fractal dimension (Df) and the radius of gyration (Rg), were in the range of 1.7-2.1 and 0.24-0.36 microm, respectively. These are the representative values for soot aggregates emitted from diesel engines. The results of computation show approximately 20% penetration of submicrometer aggregates through the nose and a weak dependence of deposition efficiency on Df and Rg values. The proposed methodology may lead to a more realistic description of deposition of nonspherical aerosol particles in the respiratory system. A more sophisticated approach for description of fractal-like aggregates dynamics is suggested for future studies.

Dynamics of oropharyngeal aerosol transport and deposition with the realistic flow pattern.

Aerosol flow and deposition in the model of human oropharynx was studied theoretically and experimentally for two realistic inspiratory patterns. The three-dimensional (3D) airflow structure in the sample geometry was solved with the computational fluid dynamics (CFD) code (Fluent), used to calculate dynamic distribution of particle deposition (0.3-10 mum). Experiments were done for the same flow conditions using the silicone-rubber cast with the matching geometry. Nonsteady breathing flows were reproduced with the computer-controlled artificial lung apparatus. Results of computations show that particles smaller than 3 mum easily pass the oropharynx during inspiration, while particles with a size close to 10 mum are substantially deposited, preferentially in the region of the naso-pharyngeal bend. For particles in the submicrometer size range, the spatial and temporal deposition pattern is more complicated, and strongly depends on breathing dynamics. The experiments confirmed that the mass median diameter (MMD) of the aerosol that penetrates the oropharynx and flows to the tracheobronchial tree is reduced. Measured total mass efficiency of deposition of the tested aerosol was in the range of 35-60%, depending on the breathing pattern. These findings are consistent with the CFD results. The methods and the preliminary results enable a more realistic analysis of dynamic effects during the flow of inhaled particles through the complex geometry of the oropharynx. Such analysis is needed for estimation of toxic potential of aerosols, related to their local deposition in different parts of the respiratory tract.