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Environmental Research Jul 2012Air quality modeling could potentially improve exposure estimates for use in epidemiological studies. We investigated this application of air quality modeling by... (Comparative Study)
Comparative Study
Air quality modeling could potentially improve exposure estimates for use in epidemiological studies. We investigated this application of air quality modeling by estimating location-specific (point) and spatially-aggregated (county level) exposure concentrations of particulate matter with an aerodynamic diameter less than or equal to 2.5 μm (PM(2.5)) and ozone (O(3)) for the eastern U.S. in 2002 using the Community Multi-scale Air Quality (CMAQ) modeling system and a traditional approach using ambient monitors. The monitoring approach produced estimates for 370 and 454 counties for PM(2.5) and O(3), respectively. Modeled estimates included 1861 counties, covering 50% more population. The population uncovered by monitors differed from those near monitors (e.g., urbanicity, race, education, age, unemployment, income, modeled pollutant levels). CMAQ overestimated O(3) (annual normalized mean bias=4.30%), while modeled PM(2.5) had an annual normalized mean bias of -2.09%, although bias varied seasonally, from 32% in November to -27% in July. Epidemiology may benefit from air quality modeling, with improved spatial and temporal resolution and the ability to study populations far from monitors that may differ from those near monitors. However, model performance varied by measure of performance, season, and location. Thus, the appropriateness of using such modeled exposures in health studies depends on the pollutant and metric of concern, acceptable level of uncertainty, population of interest, study design, and other factors.
Topics: Air; Air Pollutants; Computer Simulation; Environmental Monitoring; Health Status; Humans; Inhalation Exposure; Particulate Matter; Population Dynamics; Seasons; United States
PubMed: 22579357
DOI: 10.1016/j.envres.2012.04.008 -
Journal of Healthcare Engineering 2019Surgical lights in the operating rooms are typically installed in a single axis in the center of the room or in two axes on both sides of the operating table. In the...
PURPOSE
Surgical lights in the operating rooms are typically installed in a single axis in the center of the room or in two axes on both sides of the operating table. In the single-axis installation, the air-conditioning outlet cannot be placed in the center of the ceiling, which may affect the air current. Therefore, we measured the air current and cleanliness in two equivalent operating rooms using a vertical laminar airflow system equipped with either single-axis or double-axis surgical lights.
METHODS
Air current was measured using a three-dimensional ultrasonic anemometer. Cleanliness was evaluated by measuring the amount of dust before and after air-conditioner activation. To visualize the air current, smoke was illuminated on a sheet of laser light while the air-conditioning was stopped, and changes after air-conditioning activation were observed.
RESULTS
In the single-axis room, an oblique fast air current flowing from the surrounding air outlet toward the center was observed, and the flow velocity fluctuated greatly. In the double-axis room, uniform downward laminar airflow was observed. The amount of dust at the center decreased significantly faster in the double-axis room; thus, the cleanliness at the center was higher in the double-axis room. Persistent stagnation of smoke was observed below the single-axis lighting, whereas smoke below the double-axis lighting was immediately dispersed and the air cleared even when surgical lights were in the position for surgery.
CONCLUSION
Uniform vertical laminar airflow was formed and high cleanliness was achieved in the center of the room when the surgical lights were arranged in two axes.
Topics: Air; Environment, Controlled; Environmental Monitoring; Lighting; Operating Rooms
PubMed: 31049187
DOI: 10.1155/2019/4861273 -
Scientific Reports Jun 2018Aerosol particles emitted from various human activities deteriorate air quality and are suggested to increase public health risk. Numerous studies have emphasized the...
Aerosol particles emitted from various human activities deteriorate air quality and are suggested to increase public health risk. Numerous studies have emphasized the relationship between the mass and/or number concentration of aerosols (or commonly known as particulate matter (PM)) in the atmosphere and the incidence of respiratory and cardiovascular diseases, while very few have examined the deposition efficiency of inhaled particles in the respiratory tract. We present the first examination of particles deposition based on, detailed simulation of aerosol physico-chemical properties by a recently developed particle-resolved aerosol model and the mixing state dependent hygrosocpic growth and deposition computed at particle-level by deposition model. Furthermore, we elucidate the impact of mixing state on deposition efficiency by using a recently introduced aerosol mixing state index. We find that without considering mixing-state-dependent hygroscopic growth of particles leads to overestimation of deposition efficiency; whereas considering an average mixing state leads to underestimation of 5% to 20% of soot particle deposition efficiency in human alveoli. We conclude that aerosol mixing state, which evolves during the interaction between atmospheric chemistry and meteorology, is important for the comprehensive evaluation of air quality and its implication to public health requires further investigation.
Topics: Aerosols; Air; Air Pollutants; Air Pollution; Environmental Monitoring; Humans; Particle Size; Particulate Matter; Respiratory System; Soot; Wettability
PubMed: 29891990
DOI: 10.1038/s41598-018-27156-z -
Bioresource Technology Jul 2008Sampling devices differing greatly in shape, size and operating condition have been used to collect air samples to determine rates of emission of volatile substances,... (Comparative Study)
Comparative Study Review
Sampling devices differing greatly in shape, size and operating condition have been used to collect air samples to determine rates of emission of volatile substances, including odour. However, physical chemistry principles, in particular the partitioning of volatile substances between two phases as explained by Henrys Law and the relationship between wind velocity and emission rate, suggests that different devices cannot be expected to provide equivalent emission rate estimates. Thus several problems are associated with the use of static and dynamic emission chambers, but the more turbulent devices such as wind tunnels do not appear to be subject to these problems. In general, the ability to relate emission rate estimates obtained from wind tunnel measurements to those derived from device-independent techniques supports the use of wind tunnels to determine emission rates that can be used as input data for dispersion models.
Topics: Air; Air Movements; Air Pollutants; Air Pollution; Biotechnology; Chemistry, Physical; Environmental Monitoring; Equipment Design; Materials Testing; Odorants; Smell; Volatilization; Water
PubMed: 17512194
DOI: 10.1016/j.biortech.2007.03.043 -
Proceedings of the National Academy of... Feb 2022Hydrogen peroxide (HO) plays a key role in environmental chemistry, biology, and medicine. HO concentrations typically are 6 to 10 orders of magnitude lower than that of...
Hydrogen peroxide (HO) plays a key role in environmental chemistry, biology, and medicine. HO concentrations typically are 6 to 10 orders of magnitude lower than that of water, making its quantitative detection challenging. We demonstrate that optimized NMR spectroscopy allows direct, interference-free, quantitative measurements of HO down to submicromolar levels in a wide range of fluids, ranging from exhaled breath and air condensate to rain, blood, urine, and saliva. NMR measurements confirm the previously reported spontaneous generation of HO in microdroplets that form when condensing water vapor on a hydrophobic surface, which can interfere with atmospheric HO measurements. Its antimicrobial activity and strong seasonal variation speculatively could be linked to the seasonality of respiratory viral diseases.
Topics: Air; Blood; Blood Chemical Analysis; Body Fluids; Exhalation; Feces; Humans; Hydrogen Peroxide; Magnetic Resonance Spectroscopy; Rain; Saliva; Urine
PubMed: 35165177
DOI: 10.1073/pnas.2121542119 -
Environmental Research Oct 2015Access to detailed comparisons in air quality variations encountered when commuting through a city offers the urban traveller more informed choice on how to minimise...
Access to detailed comparisons in air quality variations encountered when commuting through a city offers the urban traveller more informed choice on how to minimise personal exposure to inhalable pollutants. In this study we report on an experiment designed to compare atmospheric contaminants inhaled during bus, subway train, tram and walking journeys through the city of Barcelona. Average number concentrations of particles 10-300 nm in size, N, are lowest in the commute using subway trains (N<2.5×10(4) part. cm(-3)), higher during tram travel and suburban walking (2.5×10(4) cm(-3)
5.0×10(4) cm(-3)), with extreme transient peaks at busy traffic crossings commonly exceeding 1.0×10(5) cm(-3) and accompanied by peaks in Black Carbon and CO. Subway particles are coarser (mode 90 nm) than in buses, trams or outdoors (<70 nm), and concentrations of fine particulate matter (PM2.5) and Black Carbon are lower in the tram when compared to both bus and subway. CO2 levels in public transport reflect passenger numbers, more than tripling from outdoor levels to >1200 ppm in crowded buses and trains. There are also striking differences in inhalable particle chemistry depending on the route chosen, ranging from aluminosiliceous at roadsides and near pavement works, ferruginous with enhanced Mn, Co, Zn, Sr and Ba in the subway environment, and higher levels of Sb and Cu inside the bus. We graphically display such chemical variations using a ternary diagram to emphasise how "air quality" in the city involves a consideration of both physical and chemical parameters, and is not simply a question of measuring particle number or mass. Topics: Air; Air Pollutants; Environmental Monitoring; Humans; Inhalation Exposure; Metals, Heavy; Particulate Matter; Spain; Transportation; Urbanization; Vehicle Emissions; Walking
PubMed: 26277386
DOI: 10.1016/j.envres.2015.07.022 -
Brazilian Dental Journal 2017This study evaluated the effect of air-abrasion on t®m phase transformation, roughness, topography and the elemental composition of three Y-TZP (Yttria-stabilized...
This study evaluated the effect of air-abrasion on t®m phase transformation, roughness, topography and the elemental composition of three Y-TZP (Yttria-stabilized tetragonal zirconia polycrystal) dental ceramics: two conventional (Lava Frame and IPS ZirCad) and one with high-translucency (Lava Plus). Plates obtained from sintered blocks of each ceramic were divided into four groups: AS (as-sintered); 30 (air-abrasion with 30 mm Si-coated Al2O3 particles); 50 (air-abrasion with 50 mm Al2O3 particles) and 150 (air-abrasion with 150 mm Al2O3 particles). After the treatments, the plates were submitted to X-ray diffractometry; 3-D profilometry and SEM/EDS. The AS surfaces were composed of Zr and t phases. All treatments produced t®m phase transformation in the ceramics. The diameter of air-abrasion particles influenced the roughness (150>50>30>AS) and the topography. SEM analysis showed that the three treatments produced groove-shaped microretentions on the ceramic surfaces, which increased with the diameter of air-abrasion particles. EDS showed a decrease in Zr content along with the emergence of O and Al elements after air-abrasion. Presence of Si was also detected on the plates air-abraded with 30 mm Si-coated Al2O3 particles. It was concluded that irrespective of the type and diameter of the particles, air-abrasion produced t®m phase transformation, increased the roughness and changed the elemental composition of the three Y-TZP dental ceramics. Lava Plus also behaved similarly to the conventional Y-TZP ceramics, indicating that this high translucency ceramic could be more suitable to build monolithic ceramic restorations in the aesthetic restorative dentistry field.
Topics: Air; Ceramics; Dental Materials; Materials Testing; Microscopy, Electron, Scanning; Spectrometry, X-Ray Emission; X-Ray Diffraction
PubMed: 28301026
DOI: 10.1590/0103-6440201701035 -
International Journal of Hyperthermia :... 2009Contact flexible microstrip applicators (CFMA), operating at 434 MHz, are applied at the Academic Medical Center (AMC) for superficial hyperthermia (e.g. chest wall... (Comparative Study)
Comparative Study
INTRODUCTION
Contact flexible microstrip applicators (CFMA), operating at 434 MHz, are applied at the Academic Medical Center (AMC) for superficial hyperthermia (e.g. chest wall recurrences and melanoma). This paper investigates the performance of CFMA, evaluating the stability of the specific absorption rate (SAR) distribution, effective heating depth (EHD) and effective field size (EFS) under different conditions.
METHODS
Simulations were performed using finite differences and were compared to existing measurement data, performed using a rectangular phantom with a superficial fat-equivalent layer of 1 cm and filled with saline solution. The electrode plates of the applicators measure approximately 7 x 20, 29 x 21 and 20 x 29 cm(2). Bolus thickness varied between 1 and 2 cm. The impact of the presence of possible air layers between the rubber frame and the electrodes on the SAR distribution was investigated.
RESULTS
The EHD was approximately 1.4 cm and the EFS ranged between approximately 60 and approximately 300 cm(2), depending on the applicator type. Both measurements and simulations showed a split-up of the SAR focus with a 2 cm water bolus. The extent and location of air layers has a strong influence on the shape and size of the iso-SAR contours with a value higher than 50%, but the impact on EFS and EHD is limited.
CONCLUSION
Simulations, confirmed by measurements, showed that the presence of air between the rubber and the electrodes changes the iso-SAR contours, but the impact on the EFS and EHD is limited.
Topics: Air; Computer Simulation; Electrodes; Humans; Hyperthermia, Induced; Models, Theoretical; Phantoms, Imaging
PubMed: 19657850
DOI: 10.1080/02656730903008493 -
Medical Physics Jul 2017The aim of this study was to examine the effect of submillimeter air gaps that may exist between an ionization chamber and solid phantoms when measurements are performed...
PURPOSE
The aim of this study was to examine the effect of submillimeter air gaps that may exist between an ionization chamber and solid phantoms when measurements are performed in a magnetic field.
METHODS
Geant4 Monte Carlo simulations were performed using a model of a PTW 30013 Farmer chamber in a water phantom. Symmetrical and asymmetrical air gaps of various thicknesses were modeled surrounding the chamber, and the dose to the air cavity of the chamber was scored in each case. Magnetic fields were modeled parallel to the long axis of the chamber with strengths of 0, 0.35 T, 1.0 T, and 1.5 T. To examine the phenomenon in more detail, the gyroradii of the electrons responsible for the energy deposited in the chamber were scored as they entered the chamber and the total energy deposited was split into three components: energy originating from inside the chamber, in the immediate vacinity of the chamber, or outside the chamber.
RESULTS
Differences in the chamber dose of 1.6% were observed for asymmetric air gaps just 0.2 mm thick. No effect greater than 0.5% was observed for the symmetrical air gaps investigated in this work (1.4 mm thick or less) for this chamber/magnetic field configuration. The mean gyroradius of contributing electrons as they first enter the chamber was 4 mm. The presence of the air gap reduced the energy contributions from electrons released in the immediate vicinity of the chamber, and this loss was not completely compensated for when a magnetic field was present.
CONCLUSIONS
The gyroradius of most electrons was too large to be responsible for the air gap effect via the electron return effect; instead, the effect is attributed to the loss of energy contributions from electrons originating inside the air gap volume, which is not completely compensated for by more distant electrons owing to their reduced range in the magnetic field. When the chamber is parallel with the magnetic field, symmetric air gaps have a smaller effect (< 0.5%) compared to asymmetric air-gaps (up to 1.6%) on the chamber response.
Topics: Air; Electrons; Magnetic Fields; Monte Carlo Method; Phantoms, Imaging; Radiometry
PubMed: 28432792
DOI: 10.1002/mp.12290 -
Environment International Oct 2013Different household insecticide applications via two electric vaporizers emitting transfluthrin were realized in a full-scale experimental room under controlled air... (Comparative Study)
Comparative Study
Different household insecticide applications via two electric vaporizers emitting transfluthrin were realized in a full-scale experimental room under controlled air exchange rate conditions. On-line high-time resolved measurements of the gas-phase concentrations of the active substance during and immediately after the spreading periods were performed with a High Sensitivity Proton-Transfer-Reaction Mass Spectrometer (HS-PTR-MS). Experimental and modelled data from the ConsExpo 4.0 software were also compared to evaluate the sources of differences. Different application scenarios were also compared. Averaged inhaled concentrations over 1h, 1week, and 5months were estimated to be 8.3, 1.8, and 1.8μg.m(-3), respectively. Corresponding margins of exposures range from 1000 to 10,000, claiming for the absence of effect. Dermal and dust ingestion pathways, although roughly estimated, seems being non-negligible. This claims for a more in-depth integrated risk assessment.
Topics: Air; Air Pollution, Indoor; Cyclopropanes; Fluorobenzenes; Gases; Inhalation Exposure; Insecticides; Models, Chemical; Nebulizers and Vaporizers
PubMed: 23973617
DOI: 10.1016/j.envint.2013.07.011