Airborne Particle Concentrations Research Articles

Particle release and control of worker exposure during laboratory-scale synthesis, handling and simulated spills of manufactured nanomaterials in fume hoods

Fume hoods are one of the most common types of equipment applied to reduce the potential of particle exposure in laboratory environments. A number of previous studies have shown particle release during work with nanomaterials under fume hoods. Here, we assessed laboratory workers’ inhalation exposure during synthesis and handling of CuO, TiO2 and ZnO in a fume hood. In addition, we tested the capacity of a fume hood to prevent particle release to laboratory air during simulated spillage of different powders (silica fume, zirconia TZ-3Y and TiO2). Airborne particle concentrations were measured in near field, far field, and in the breathing zone of the worker. Handling CuO nanoparticles increased the concentration of small particles (< 58 nm) inside the fume hood (up to 1 × 105 cm−3). Synthesis, handling and packaging of ZnO and TiO2 nanoparticles did not result in detectable particle release to the laboratory air. Simulated powder spills showed a systematic increase in the particle concentrations inside the fume hood with increasing amount of material and drop height. Despite powder spills were sometimes observed to eject into the laboratory room, the spill events were rarely associated with notable release of particles from the fume hood. Overall, this study shows that a fume hood generally offers sufficient exposure control during synthesis and handling of nanomaterials. An appropriate fume hood with adequate sash height and face velocity prevents 98.3% of particles release into the surrounding environment. Care should still be made to consider spills and high cleanliness to prevent exposure via resuspension and inadvertent exposure by secondary routes.

Examination of Environmental Factors Influencing the Emission Rates of Semivolatile Organic Compounds

Some types of semivolatile organic compounds (SVOCs) that are emitted from plastics used in building materials and household appliances have been associated with health risks, even at low concentrations. It has been reported that di‐2‐ethylhexyl phthalate (DEHP)—one of the most commonly used plasticizers—causes asthma and allergic symptoms in children at home. The amount of emitted DEHP, which is classified as a SVOC, can be measured using a microchamber by the thermal desorption test chamber method. To accurately measure the SVOC emission rates, the relation between SVOC and environmental factors should be clarified. Herein, we examined the effects of the temperature, relative humidity, concentration of airborne particles, and flow field in the microchamber on SVOC emission rates. The flow fields inside the microchamber were analyzed via computational fluid dynamics (CFD). The emission rate of SVOC released from PVC flooring increased under high temperatures and at high concentrations of airborne particles but did not depend on the relative humidity. From an evaluation performed using an index of air change efficiency, such as the air age and the coefficient of air change performance, we found that a fixed air exchange rate of 1.5 h−1 in the microchamber is desirable.

Fragrances and Aerosol during Office Cleaning

Fragrance compounds emitted during and after the use of cleaning products in an office were monitored. Mopping the floor with a general purpose cleaner and a domestic bleach and cleaning the windows with an aerosol glass cleaner, as well as a combination of these cleaning activities, were carried out. The following compounds were found in detectable amounts: d-limonene, α-pinene, α-terpineol, 2-butoxyethanol, 1,3,5-trimethylbenzene, eucalyptol, tetrahydrolinalool and diphenyl ether. Along with the fragrances, the number concentrations of airborne particles with an aerodynamic diameter range between 0.2 μm and 10 μm were monitored continuously. Cleaning affected the number concentrations of all particle sizes, but particles with an aerodynamic diameter above 0.4 μm were the most affected. The largest increase above background concentrations was observed during mopping the floor with a solution of general purpose cleaner in combination with cleaning the windows with a glass-cleaning spray. In this case, for particles larger than 0.4 μm, indoor number concentrations were 19 times larger than the background concentrations. Conversely, for particles below 0.4 μm, number concentrations increased only 4 times above the background concentrations during the same event. Auxiliary measurements included carbon dioxide (CO_2) concentrations and the indoor micro-climatic conditions (air velocity, light intensity, temperature and relative humidity).

Exposure to airborne particles associated with the handling of graphene nanoplatelets

Background:It is recognized that engineering control measures are needed to reduce occupational exposure to engineered nanomaterials (NMs): of these, fume hoods are among the most widespread collective protection equipment used while handling NMs in occupational settings. It is known that in some circumstances, handling NMs in fume hoods can result in a significant release of NMs.Objective:To assess the effectiveness of fume hoods in reducing exposure while handling graphene nanoplatelets and to define the conditions that result in a lower dispersion of particles and thus less operator exposure.Methods:An experimental protocol was established to monitor the variations of airborne particle concentrations while handling graphene in fume hoods (transferring and pouring). The measurement locations were at the laboratory, inside the hood and at operator’s breathing zone. Handling tasks were performed under different operating conditions: the variable factors included hood face velocity and sash height.Results:Results of this study indicate that the handling of graphene nanoplatelets may pose a potential risk of contamination of the work environment and hence exposure of the involved operators, if adequate control measures are not taken. In fact, when inadequate or not sufficiently cautionary operational conditions were utilized, non-negligible increases in airborne graphene particle concentrations during the nanomaterial manipulation phases were observed.Conclusions:Some operating conditions (e.g., face velocity, sash height) can be adjusted to avoid relevant personal exposure conditions and contamination of the work environment by NMs, thus ensuring safer conditions.

Accurate measurement of airborne biological particle concentration based on laser-induced fluorescence technique

We develop a biological particle counter based on laser-induced fluorescence for accurate measurement of biological particle concentrations in the air. Pure water, NaCl particles, polystyrene latex spheres, and standard fluorescent particles are used as media to evaluate the performance of the counter. Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa are used as representative biological particles to evaluate the measurement accuracy of the counter. In experiments, the results measured by the counter are consistent with he results obtained with the culture method; For each bacterium, good linear agreement is observed between the two results, and the values of the coefficient R2 are all more than 0.97. Because of particle superposition errors, system error, etc., at low concentrations, the number measured by the counter divided by the number measured by the culture method, η = Ncounter/Nculture, is larger than that at high concentrations. For same type of test sample, although the distribution is different, the η values at same concentrations are similar. Finally, the repeatability of the two methods is tested. The results obtained using the counter are found to be more stable, with a relative standard deviation (RSD) of 8.14%; this is less than the RSD of 15% obtained using the culture method.

Microbiological air contamination in university premises and the evaluation of drug resistance of staphylococci occurring in the form of a bioaerosol

The aim of this research was to evaluate exposure to microbiological aerosol of persons staying in selected office and teaching areas of the university premises. The number and biodiversity of microorganisms constituting the bioaerosol, in particular the Staphylococcus spp., and their drug resistance profile, were determined. Moreover, the influence of temperature, level of airborne particle concentration and the type of ventilation on the number of microorganisms was analysed. The monitoring was carried out using the MAS-100 impactor. The level of airborne particle concentration was measured using the DustTrak II dust meter. The analysis of drug resistance level of staphylococci was carried out using the disk-diffusion method. On the basis of research conducted, the highest microbiological air contamination was found in the biomass lab, due to the research carried out there. On the other hand, no unequivocal link between the concentration of microorganisms present in the air and the type of ventilation used was found. Airborne particles concentrations of PM10 and PM2.5 exceeded the standard limit values – therefore the air was classified as contaminated. In the sampled air, multi-resistant staphylococci were found, which may pose an epidemiological threat to persons staying in the analysed premises.

Impact of Air Quality and Site Selection on Gas Turbine Engine Performance

Air pollution can have detrimental effects on gas turbine performance leading to blade fouling, which reduces power output and requires frequent cleanings. This issue is a fairly well-known phenomenon in the power industry. However, site selection for gas turbine installation on the basis of air quality is rarely part of the decision-making process, mainly due to lack of geographical options especially in an urban environment or perhaps due to a simple assumption that air quality at a local micro-level has no impact on the performance of the engine. In this paper, we perform a computational fluid dynamics (CFD) study on an area surrounding a combined heat and power (CHP) facility to assess the impact of local wind distribution on air quality and the performance of a gas turbine engine. Several aerodynamic properties are suggested as possible indicators of air quality and/or high airborne particulate concentration. These indicators are then compared to data collected at various points in and around the site. The results suggest that through post-processing of a simplified CFD simulation analyzing the adjacent terrain, a continuous map of field variables can be obtained and help designers locate future CHP or gas turbine power plants in regions of lower particulate concentrations. This, in turn, would greatly increase efficiency and cost-effectiveness of the proposed power plant.

A study of parameters affecting the dirtiness on the performance signals of a room air conditioning unit

To maintain a good performance, a room air conditioning unit is generally recommended to be cleaned twice a year, regardless of operating hours or concentration of airborne particles. With less operating hours or under clean ambience, the maintenance cost could be postponed under common energy efficiency. If a cleaning signal could be sent from the unit, itself, to the owner, a proper cleaning schedule could be provided. A dirtiness monitoring factors are aimed to be investigated from this study. Under varied degree of dirtiness simulated on the fan coil unit, system operation behaviors and thermodynamic properties were investigated. An experimental apparatus was installed under the actual indoor and outdoor conditions, in order to follow up related factors on real-time vapor compression cycle.

Size and mineral composition of airborne particles generated by an ultrasonic humidifier.

This study describes the size distribution and concentration of particles expelled by a portable, 3-L ultrasonic humidifier. The ultrasonic humidifier was filled with waters of varying mineral content and hardness. Aerosol size distributions were measured during 8hours of humidifier operation in a typical bedroom. Humidifiers produced approximately 1.22×1010 -2.50×1010 airborne particles per milliliter of water consumed, resulting in airborne particle concentrations of 3.01-5.91×104 #/cm3 , with modes ranging between 109 and 322nm in diameter. The emission rate of particles varied by water type from 1.02×109 to 2.27×109 #/s. Lower mineral waters produced fewer, smaller particles when compared to higher mineral waters. Chemical analyses of particles collected with a cascade impactor indicated that the minerals in emitted particles had the same relative mineral concentrations as the fill water. Our results demonstrate that ultrasonic humidifiers should be considered a source of inhalation exposure to minerals dissolved in water, and that the magnitude of exposure to inhalable particles will vary with water quality.

Bacterial abundance and viability in rainwater associated with cyclones, stationary fronts and typhoons in southwestern Japan

The abundance and viability of bacterial cells in rainwater at a suburban site in southwestern Japan between October 2014 and September 2015 were measured and their distinctiveness, according to synoptic weather systems, i.e., cyclones (cold fronts), stationary fronts (including Meiyu and non-Meiyu fronts) and typhoons, was examined. On average, the cell concentration of bacteria in the rainwater was 2.3 ± 1.5 × 104 cells mL−1, and bacterial viability, the ratio of viable cells to total cells, was 80 ± 10%. In the rainwater of cyclones when clouds were induced by the intrusion of continental air, the bacterial concentration was higher (3.5 ± 1.6 × 104 cells mL−1) and the viability was lower (75 ± 8%) than in the rainwater of other types. In the rainwater of Meiyu fronts and typhoons when clouds were significantly influenced by marine air, bacterial concentrations were 1.5 ± 0.5 × 104 and 1.2 ± 0.3 × 104 cells mL−1, and bacterial viabilities were 84 ± 7% and 85 ± 7%, respectively. In the rainwater of non-Meiyu stationary fronts, the bacterial concentration was 2.4 ± 1.6 × 104 cells mL−1, and the viability was 78 ± 14%. Abundant bacteria were associated with ions nss-SO42−, nss-Ca2+, and NO3− in rainwater, but bacterial concentrations did not correlate with the ratios of airborne particle concentrations to the precipitation amounts. Further investigations with correlation and principal component analysis combining bacteria and ion species revealed that bacteria in the rainwater were likely enclosed in clouds at the stage of cloud formation in addition to below-cloud removal, and bacteria involved in the rainwater did not show confirmable growth.

Particle and bioaerosol characteristics in a paediatric intensive care unit

The paediatric intensive care unit (PICU) provides care to critically ill neonates, infants and children. These patients are vulnerable and susceptible to the environment surrounding them, yet there is little information available on indoor air quality and factors affecting it within a PICU. To address this gap in knowledge we conducted continuous indoor and outdoor airborne particle concentration measurements over a two-week period at the Royal Children's Hospital PICU in Brisbane, Australia, and we also collected 82 bioaerosol samples to test for the presence of bacterial and viral pathogens. Our results showed that both 24-hour average indoor particle mass (PM10) (0.6–2.2μgm−3, median: 0.9μgm−3) and submicrometer particle number (PN) (0.1–2.8×103pcm−3, median: 0.67×103pcm−3) concentrations were significantly lower (p<0.01) than the outdoor concentrations (6.7–10.2μgm−3, median: 8.0μgm−3 for PM10 and 12.1–22.2×103pcm−3, median: 16.4×103pcm−3 for PN). In general, we found that indoor particle concentrations in the PICU were mainly affected by indoor particle sources, with outdoor particles providing a negligible background. We identified strong indoor particle sources in the PICU, which occasionally increased indoor PN and PM10 concentrations from 0.1×103 to 100×103pcm−3, and from 2μgm−3 to 70μgm−3, respectively. The most substantial indoor particle sources were nebulization therapy, tracheal suction and cleaning activities. The average PM10 and PN emission rates of nebulization therapy ranged from 1.29 to 7.41mgmin−1 and from 1.20 to 3.96pmin−1×1011, respectively. Based on multipoint measurement data, it was found that particles generated at each location could be quickly transported to other locations, even when originating from isolated single-bed rooms. The most commonly isolated bacterial genera from both primary and broth cultures were skin commensals while viruses were rarely identified. Based on the findings from the study, we developed a set of practical recommendations for PICU design, as well as for medical and cleaning staff to mitigate aerosol generation and transmission to minimize infection risk to PICU patients.

Contribution of bacteria-like particles to PM2.5 aerosol in urban and rural environments

We report highly time-resolved estimates of airborne bacteria-like particle concentrations in ambient aerosol using an Aerodyne aerosol mass spectrometer (AMS). AMS measurements with a newly developed PM2.5 and the standard (PM1) aerodynamic lens were performed at an urban background site (Zurich) and at a rural site (Payerne) in Switzerland. Positive matrix factorization using the multilinear engine (ME-2) implementation was used to estimate the contribution of bacteria-like particles to non-refractory organic aerosol. The success of the method was evaluated by a size-resolved analysis of the organic mass and the analysis of single particle mass spectra, which were detected with a light scattering system integrated into the AMS. Use of the PM2.5 aerodynamic lens increased measured bacteria-like concentrations, supporting the analysis method. However, at all sites, the low concentrations of this component suggest that airborne bacteria constitute a minor fraction of non-refractory PM2.5 organic aerosol mass. Estimated average mass concentrations were below 0.1 μg/m3 and relative contributions were lower than 2% at both sites. During rainfall periods, concentrations of the bacteria-like component increased considerably reaching a short-time maximum of approximately 2 μg/m3 at the Payerne site in summer.

Relationships between airborne pollen grains, wind direction and land cover using GIS and circular statistics.

Airborne bio-aerosol content (mainly pollen and spores) depends on the surrounding vegetation and weather conditions, particularly wind direction. In order to understand this issue, maps of the main land cover in influence areas of 10km in radius surrounding pollen traps were created. Atmospheric content of the most abundant 14 pollen types was analysed in relation to the predominant wind directions measured in three localities of SW of Iberian Peninsula, from March 2011 to March 2014. Three Hirst type traps were used for aerobiological monitoring. The surface area for each land cover category was calculated and wind direction analysis was approached by using circular statistics. This method could be helpful for estimating the potential risk of exposure to various pollen types. Thus, the main land cover was different for each monitoring location, being irrigated crops, pastures and hardwood forests the main categories among 11 types described. Comparison of the pollen content with the predominant winds and land cover shows that the atmospheric pollen concentration is related to some source areas identified in the inventory. The study found that some pollen types (e.g. Plantago, Fraxinus-Phillyrea, Alnus) come from local sources but other pollen types (e.g. Quercus) are mostly coming from longer distances. As main conclusions, airborne particle concentrations can be effectively split by addressing wind with circular statistics. By combining circular statistics and GIS method with aerobiological data, we have created a useful tool for understanding pollen origin. Some pollen loads can be explained by immediate surrounding landscape and observed wind patterns for most of the time. However, other factors like medium or long-distance transport or even pollen trap location within a city, may occasionally affect the pollen load recorded using an air sampler.

Quantification of ultrafine airborne particulate matter generated by the wear of car brake materials

The wear of car brakes is one of the main sources of airborne particulate matter in urban environments. Ultrafine wear particles are of special environmental interest since they can easily penetrate the human body through inhalation and cause various diseases. In the present study, the contribution of ultrafine particles to airborne particulate matter emitted from car brake materials was investigated under different friction conditions. Particles were generated using a pin-on-disc machine located in a sealed chamber and analysed in terms of number, volume and mass concentrations. It was found that temperature has a strong influence on the size distribution of the emitted particles. At temperatures below 200°C, the ultrafine particles make no measurable contribution to the mass concentration of airborne particles with diameters smaller than 10µm (PM10). However, at temperatures above 200°C, the mass fraction of the ultrafine particles in PM10 reaches tens of percent. In general, this fraction increases with the temperature and decreases with the sliding duration. The mass contribution of ultrafine wear particles to PM10 is substantial, and it should not be neglected in environmental and tribological studies.

Analysis of Airborne Dust as a Result of Plaster Cast Sawing.

Plaster splints are used daily in surgical and orthopedic fields in order to immobilize injured children and adults. The aim of this study was to measure the aerodynamic diameter and concentration of dust particles in the air caused by sawing plaster splints (calcium sulfate dehy-drate). We performed fractional measurements of airborne dust particles. The measured particles, which can potentially be inhaled, may have a specific negative effect on human health. Measurements were conducted in laboratory research facilities that simulated hospital conditions within a casting room and the associated waiting room. Measurements within the casting room were made using two particle collector devices and one laser photometer. The measurement for the simulated waiting room was performed using the same principles and devices. The collected plaster dust particles differed in aerodynamic diameter and concentration according to the various locations observed. The highest concentration of particles of all sizes was recorded at the site of cast sawing. There was direct correlation between distance from the source and concentration of airborne particles; this concentration was lowest in the waiting room. The concentrations of plaster dust recorded were lower than the recommended minimal limit values for total and respiratory fractions in Croatia. Accordingly, it can be assumed that sawing of plaster splints has no harmful health effects on the exposed patients and health personnel.

Assessment of Indoor Bioaerosols in Public Spaces by Real-Time Measured Airborne Particles

ABSTRACTHumans spend a considerable amount of time indoors, and indoor biological airborne pollutants may harm human health. Active bioaerosol samplers and conventional microbiological culture methods, which are widely applied in studies of airborne microbial contamination, are not only unable to perform continuous monitoring over long periods, but are also time-consuming and expensive. In order to rapid assess indoor airborne microbial contamination, multiple linear regression models were constructed by statistically analyzing the measured bioaerosol samples and the real-time measured mass and number concentrations of airborne particles using a direct reading instrument from 43 air-conditioned public spaces. There were significant positive correlations of indoor airborne bacterial and fungal concentrations with indoor size-segregated particle mass and number concentrations. The predictive power of the model was sufficient for predicting indoor bacterial concentrations from the indoor and outdoor size-segregated particle number concentrations as independent variables. Particle number concentration outperforms particle mass concentration as an independent variable in predicting indoor bioaerosol concentrations. The prediction model for indoor bacterial bioaerosol levels constructed in this study could facilitate a rapid assessment of potential airborne bacterial contamination via the simple and feasible measurement of particle number concentration, thus helping to improve the management and maintenance of indoor air quality.

Does modern space suit reduce intraoperative contamination in total joint replacement? An experimental study.

The purpose of this study was to evaluate a potential risk of intraoperative contamination associated with clothing systems and surgeon's motion in total joint replacement. The airborne particle concentrations at different locations around a single operating surgeon wearing standard surgical gown (SG) or modern "space suit" (SS) were compared. The particles in the size of ≥0.5μm (roughly corresponding to a mean diameter of squamous epithelial cells) were counted at the following three locations: (1) ≈10 cm inferior to the wrist; (2) ≈10 cm posterior to the feet; and (3) near the chest (operative field) under condition either with or without the surgeon's motion (stepping in place at ~1Hz). The difference in the surgical clothing systems did not significantly affect the mean particle counts detected near the wrist and chest (p=0.307 and 0.155, respectively). However, the particle count near the feet was 154 times higher in SS than SG (4630±2795 vs. 30±23N/F3, p=0.023). The simple stepping of the surgeon with SS increased contaminants near the chest 31 times as compared to the condition without motion (1053±709 vs. 34±31N/F3, p=0.0032). Although the particle count was less affected by the motion in SG than SS, contaminants near the chest increased ten times after the stepping in the use of SG (p=0.032). The present results suggest that the intraoperative motion of a surgeon may considerably increase airborne particle/bacterial concentration in the operative field. This can be a much higher likelihood in SS rather than SG because of air blow-off from the incorporated cooling fan.

Concentric Ring Method for generating pollen maps. Quercus as case study

Mapping pollen concentrations is of great interest to study the health impact and ecological implications or for forestry or agronomical purposes. A deep knowledge about factors affecting airborne pollen is essential for predicting and understanding its dynamics. The present work sought to predict annual Quercus pollen over the Castilla and León region (Central and Northern Spain). Also to understand the relationship between airborne pollen and landscape. Records of Quercus and Quercus pyrenaica pollen types were collected at 13 monitoring sites over a period of 8years. They were analyzed together with land use data applying the Concentric Ring Method (CRM), a technique that we developed to study the relationship between airborne particle concentrations and emission sources in the region.The maximum correlation between the Quercus pollen and forms of vegetation was determined by shrubland and “dehesa” areas. For the specific Qi pyrenaica model (Q. pyrenaica pollen and Q. pyrenaica forest distribution), the maximum influence of emission sources on airborne pollen was observed at 14km from the pollen trap location with some positive correlations up to a distance of 43km. Apart from meteorological behavior, the local features of the region can explain pollen dispersion patterns. The method that we develop here proved to be a powerful tool for multi-source pollen mapping based on land use.

The Effect of Operating Lamps on the Protected Area of a Unidirectional Down Flow (UDF) System.

Operating lamps are often seen as the most disruptive factors within the protective area in the operating theater (OT). The effect of the operation lamps (with different shapes) should be demonstrated in an OT by trial, since research on the effects of the lamps is still limited. The main aim of this study was to determine the effects of a skirt, different lamps, and the position of the lamp on the protected area. The concentration of airborne particles was measured under different circumstances, in order to determine the size and quality of the protected area. This entrainment/segregation test is based on the deliberate and controlled emission of particles outside the zone that is protected. The degree of protection (DP) at the center of the protected area was higher for the case with the skirt. This skirt stimulates more down flow and prevents the early entry of particles into the protected area. It can also be concluded that Lamp Y, due to its open shape, has the most positive effect on the DP at the center. It has also been shown that the position of the lamp has an effect on the protected area.

Ventilation improvement for reducing individual exposure to cooking-generated particles in Chinese residential kitchen

This paper investigates the situation of residential kitchen ventilation and individual exposure in China and attempts to reduce the exposure through organizing local make-up airflow. Measurements were conducted in a kitchen chamber to reproduce the real exposure to the cooking-generated particles under the mode of natural make-up airflow surveyed. Measurements results show that an individual cooking in a kitchen could be exposed to a concentration of airborne particles at ∼10 mg/m3 within a simplified cooking process of oil heating, in the case of an experimental kitchen chamber with an open window or closed window/door. Local make-up airflow through upward make-up air supply or downward make-up air supply was further investigated to determine the effectiveness for reduction of the exposure level. When the air-supply velocity at the outlet of the upward make-up air supply or downward make-up air supply mode was well defined, the individual exposure level could be reduced by 2–3 orders of magnitude, as compared to the baseline case when all the make-up air was from open window. Intake fraction of cooking-generated particles could be as low as ∼10−5 and ∼10−6 under the two modes. This finding has illustrated that well-organized local make-up airflow could largely reduce an individual’s exposure to the cooking-generated particles in Chinese residential kitchen.