Air Filter Samples Research Articles

Campylobacter in chicken – Critical parameters for international, multicentre evaluation of air sampling and detection methods

The present pilot study aimed at evaluating air sampling as a novel method for monitoring Campylobacter in poultry farms. We compared the bacteriological isolation of Campylobacter from boot swabs and air filter samples using ISO 10272–1:2017. A secondary aim was to evaluate the use of molecular methods, i.e. real time PCR, on the same sample set. Samples from 44 flocks from five European countries were collected, and included air samples, in parallel with boot swabs.Campylobacter spp. was isolated from seven of 44 boot swabs from three of five partners using the enrichment method. Two of these positive boot swab samples had corresponding positive air samples. Using enrichment, one positive air sample was negative in the corresponding boot swabs, but Campylobacter spp. was isolated from direct plating of the boot swab sample. One partner isolated Campylobacter spp. from six of 10 boot swabs using direct plating. Overall, 33 air filter samples were screened directly with PCR, returning 14 positive results. In conclusion, there was a lack of correspondence between results from analysis of boot swabs and air filters using ISO 10272–1:2017. In contrast, the combination of air filters and direct real-time PCR might be a way forward. Despite the use of the detailed ISO protocols, there were still sections that could be interpreted differently among laboratories. Air sampling may turn into a multi-purpose and low-cost sampling method that may be integrated into self-monitoring programs.

Improving the sensitivity and reliability of radionuclide measurements at remote international monitoring stations

The Comprehensive Nuclear-Test-Ban Treaty is supported by a global network of monitoring stations that perform high-resolution gamma-spectrometry on air filter samples. The UK CTBT Radionuclide Laboratory has utilised cosmic veto systems to improve the sensitivity of measurements since 2010. During this study, a second detector system (with a cosmic veto) was deployed at the CTBT IMS station RN67, alongside the standard detector. This is an incredibly remote IMS station on the island of St Helena in the South Atlantic. A duplicate system was also tested at AWE to benchmark the remote systems performance.The cosmic veto system improved detection sensitivities by up to 10% across a range of radionuclides. As a system to re-measure samples 7 days after the primary measurement, detection sensitivities were improved by an order of magnitude, allowing a potentially crucial confirmation of signatures when timely transport to a laboratory is not feasible.Utilising the second detector in coincidence with the primary detector system (which would require reengineering of the shield), sensitivity improvements of up to two orders of magnitude can be achieved. These improvements are maintained even when the measurement takes place without any decay, potentially allowing a highly sensitive treaty measurement within 2 h of the end of collection.

Separation method for Pu, Am and Sr in large air filter sample sets

A sequential separation method for Pu, Am, and Sr was applied for unusually large sample sets of air filters. The sample sets were combined weekly air filters covering sampling time from three months to five years, while in original method, the analyzed air filters had sampling time of only 1-3 days, containing significantly less organic and inorganic matrix and natural radionuclides. The separation method is based on ashing and wet-ashing, followed by column separations with extraction chromatography and anion exchange. Reference materials IAEA-447, IAEA-384, and NIST-SRM-4353A were analyzed with the modified separation method. IAEA-384 was representing best the composition and radionuclide level in the air filter samples.•Compared to the original method, sample ashing took considerably longer time (one day vs. several days).•High concentration of natural radionuclides in the large air filter sample sets interfered first the determination of 241Am and 90Sr, until an anion exchange step was adopted for removal of 210Bi and 210Po from Am and Sr fractions.•After modification, the method is suitable for separating artificial radionuclides 238,239,240Pu, 241Am, and 90Sr from large sample sets of air filters.

Fungal aerobiota are not affected by time nor environment over a 13-y time series at the Mauna Loa Observatory

Fungi are ubiquitous and often abundant components of virtually all ecosystems on Earth, serving a diversity of functions. While there is clear evidence that fungal-mediated processes can influence environmental conditions, and in turn select for specific fungi, it is less clear how fungi respond to environmental fluxes over relatively long time frames. Here we set out to examine changes in airborne fungi collected over the course of 13 y, which is the longest sampling time to date. Air filter samples were collected from the Mauna Loa Observatory (MLO) on Hawaii Island, and analyzed using Illumina amplicon sequencing. As a study site, MLO is unique because of its geographic isolation and high elevation, making it an ideal place to capture global trends in climate and aerobiota. We found that the fungal aerobiota sampled at MLO had high species turnover, but compositional similarity did not decrease as a function of time between samples. We attribute these patterns to neutral processes such as idiosyncratic dispersal timing and trajectories. Furthermore, the composition of fungi at any given point was not significantly influenced by any local or global environmental variables we examined. This, and our additional finding of a core set of persistent fungi during our entire sampling period, indicates some degree of stability among fungi in the face of natural environmental fluctuations and human-associated global change. We conclude that the movement of fungi through the atmosphere is a relatively stochastic process.

Novel rapid oxidizing fusion method to determine Polonium-210 in air filters

A rapid method for the determination of polonium-210 in air filters has been developed for use following a radiological event and for routine environmental monitoring. Air filter samples, including cellulose and glass fiber, are fused with a sodium or potassium nitrate/sodium hydroxide flux material. The alkaline matrix minimizes polonium volatility during sample digestion steps, while efficiently dissolving the air filter and inorganic matter implanted on the filter. The addition of nitrate to the flux destroys organic material which can decrease Polonium recovery during precipitation, extraction and source preparation steps. Polonium is concentrated and separated from the sample matrix using an iron hydroxide precipitation and extraction chromatography with DGA Resin. Polonium-210 is subsequently measured by alpha spectrometry following rapid microprecipitation with bismuth phosphate. The new method employs extraction chromatographic purification to remove alpha emitting interferences and sample matrix constituents which can interfere with 210Po measurements using alpha spectrometry. The novel blend of sodium hydroxide and alkali metal nitrate digests the air filters quickly and effectively.

Bioburden in health care centers: Is the compliance with Portuguese legislation enough to prevent and control infection?

This study intends to assess the bioburden in ten Portuguese health care centers (PHCC) with a multi-approach protocol using active (air sampling by impaction and impinger) and passive (surface swabs and air-conditioning filters) sampling methods, and compare the results with compliance levels of IAQ Portuguese legislation for the assessment of bioburden. The fungal burden in the PHCC was also characterized through molecular detection of toxigenic species, antifungal resistance and mycotoxins profile. Concerning legal compliance criteria for bacteriota the first criteria [indoor] + 350 CFU. m−3 < [outdoor] was not complied in all PHCC analyzed. Regarding fungal load, 60% did not comply with the quantitative guideline (I/O < 1). Growth of four fungal genera (Chrysosporium, Cladosporium, Mucor and Penicillium) was observed in HVAC filter samples collected from 6 out of 10 assessed PHCC when using azole-supplemented SDA media. Overall, Aspergillus/Penicillium/Paecilomyces levels were above the detection limits, except in one PHCC. The presence of mycotoxins was found both in air and HVAC filter samples. From the air samples analyzed, nine were contaminated (ng/ml) with 1–5 different mycotoxins within the same sample, whereas in HVAC filters, four samples contained 1 or 2 mycotoxins in the same filter. Overall, it was possible to conclude that Portuguese legislation is not enough to ensure IAQ in health care settings. The multi-approach sampling protocol used in this study allowed to unveil a more real scenario regarding exposure to bioburden. Detection of mycotoxins reinforces the relevance of studying mycotoxins in the clinical environment.

Nuclear contamination sources in surface air of Finnish Lapland in 1965\u20132011 studied by means of 137Cs, 90Sr, and total beta activity

Radionuclides 137Cs and 90Sr and total beta activity were determined from air filters collected in Rovaniemi (Finnish Lapland) in 1965–2011. Nuclear contamination sources present in the air filter samples as well as temporal changes in radionuclide concentrations were examined. Ozone observations and meteorological modeling were used in combination with radionuclide analyses to study the reasons behind the observed seasonal concentration variation. In general, the magnitude and variation in activity concentrations of 137Cs and 90Sr and total beta activity in the surface air of Rovaniemi in 1965–2011 corresponded well with values from other countries. However, the obtained results prove in practice that hardly any refractory or intermediate radionuclides from the destroyed Chernobyl reactor fuel were introduced to Finnish Lapland. The main source of 137Cs and 90Sr and total beta activity in the surface air of Rovaniemi in 1965–2011 has been intense atmospheric nuclear weapon testing in 1950s–1960s and later tests performed in 1965–1980, as well as leakages from underground nuclear tests in Semipalatinsk, 1966, and Novaya Zemlya, 1987. For 137Cs and total beta activity, the influence of Chernobyl and Fukushima accidents was detected.

Radionuclide concentrations analysis of Duhok air atmosphere by gamma spectrometry

Introduction: Atmospheric air is directly related to human healthand irreplaceable to human life and thus an influential parameter ofenvironmental science. Radioactive materials in the air may resultin exposure of man every day of our lives by inhalation or ingestion of particulate matter suspended or deposited on vegetation orproducts derived from animals, which has been ubiquitous on earthsince its creation. The main goal of this study is to measure the radioactivity concentration of the natural and artificial radionuclidesof the Duhok air. Materials and Methods: Twenty samples of airfilters were collected from different locations of Duhok City andits surroundings by low volume air samplers pump in the summer/autumn and winter/spring seasons. Air filter samples were preparedand analyzed by a well-type thallium-activated sodium iodide NaI(-TI) detector. Results and Discussion: The average activity concentrations of 214Pb, 214Bi, 212Pb, 228Ac, 40K and 137Cs are4.98±1.20, 4.54±1.27, 9.76±1.17, 10.72±2.35, 211.91±62.19 and1.78±0.61 mBq/m3 respectively of the summer/autumn seasons.Whereas, in the winter/spring seasons are 3.89±1.23, 4.21±1.43,5.05±1.08, ND, 147.49±46.38 and 1.78±0.69 mBq/m3 respectively. Conclusions: The activity concentrations results confirmedseasonal variations for all study locations. Activities of all radionuclides, except an anthropogenic radionuclide 137Cs which remainsabout the same in both seasons, record higher values in summer/autumn season. Moreover, all activities are less than the acceptablelower level. It is clear that the prominent radioelements that affected by atmospheric condition is 40K even though it is less than thereported lower level of the EPA

Appraising city-scale pollution monitoring capabilities of multi-satellite datasets using portable pollutant monitors

The retrieval characteristics for a city-scale satellite experiment was explored over a Nigerian city. The study evaluated carbon monoxide and aerosol contents in the city atmosphere. We utilized the MSA Altair 5× gas detector and CW-HAT200 particulate counter to investigate the city-scale monitoring capabilities of satellite pollution observing instruments; atmospheric infrared sounder (AIRS), measurement of pollution in the troposphere (MOPITT), moderate resolution imaging spectroradiometer (MODIS), multi-angle imaging spectroradiometer (MISR) and ozone monitoring instrument (OMI). To achieve this, we employed the Kriging interpolation technique to collocate the satellite pollutant estimations over 19 ground sample sites for the period of 2015–2016. The portable pollutant devices were validated using the WHO air filter sampling model. To determine the city-scale performance of the satellite datasets, performance indicators: correlation coefficient, model efficiency, reliability index and root mean square error, were adopted as measures. The comparative analysis revealed that MOPITT carbon monoxide (CO) and MODIS aerosol optical depth (AOD) estimates are the appropriate satellite measurements for ground equivalents in Zaria, Nigeria. Our findings were within the acceptable limits of similar studies that utilized reference stations. In conclusion, this study offers direction to Nigeria's air quality policy organizers about available alternative air pollution measurements for mitigating air quality effects within its limited resource environment.

Evaluation of mean transit time of aerosols from the area of origin to the Arctic with 210Pb/210Po daily monitoring data

In this study, the activity concentrations of 210Pb and 210Po on the 22 daily air filter samples, collected at CTBT Yellowknife station from September 2015 to April 2016, were analysed. To estimate the time scale of atmospheric long-range transport aerosol bearing 210Pb in the Arctic during winter, the mean transit time of aerosol bearing 210Pb from its origin was determined based on the activity ratios of 210Po/210Pb and the parent-progeny decay/ingrowth equation. The activity ratios of 210Po/210Pb varied between 0.06 and 0.21 with a median value of 0.11. The aerosol mean transit time based the activity ratio of 210Po/210Pb suggests longer mean transit time of 210Pb aerosols in winter (12 d) than in autumn (3.7 d) and spring (2.9 d).Four years 210Pb and 212Pb monitoring results and meteorological conditions at the Yellowknife station indicate that the 212Pb activity is mostly of local origin, and that 210Pb aerosol in wintertime are mainly from outside of the Arctic regions in common with other pollutants and sources contributing to the Arctic. The activity concentration ratios of 210Pb and 212Pb have a relatively constant value in summer with a significant peak observed in winter, centered in the month of February. Comparison of the 210Pb/212Pb activity ratios and the estimated mean 210Pb transit time, the mean aerosol transit times were real reflection of the atmosphere transport characteristics, which can be used as a radio-chronometer for the transport of air masses to the Arctic region.

Rapid sequential separation method for 210Po and actinides in air filter samples

This paper reports an analytical method for rapid sequential separation of 210Po and actinides (Pu, Am and U) in air filter samples. An extraction chromatographic column TEVA + TRU was used in the separation of 210Po and actinides from the filter matrix, followed by its determination using alpha spectrometry. TEVA resin is widely used in the separation of plutonium and neptunium from the environmental samples, in this work potential application of TEVA in the sequential separation of 210Po and plutonium from filter matrix has been evaluated. This new method is simple, robust and can be performed formed in a day.

Analysis of erionites from volcaniclastic sedimentary rocks and possible implications for toxicological research

Erionite occurs in volcaniclastic rocks and soils; in some villages in Turkey the presence of erionite in local rocks is associated with mesothelioma, a disease also associated with inhalation of airborne asbestos. Since volcaniclastic rocks containing erionite are widely present in the western U.S.A., there is a concern over potential health issues following inhalation of dust particles in these areas and thus there is a need to identify and quantify erionite particles found in air samples during hygienic investigations. Previous attempts to analyze the few micrometer-sized erionite particles found on air sample filters under transmission electron microscope (TEM) encountered difficulties due to electron beam damage. Recommendations are presented for accurate analysis by both energy-dispersive spectroscopy (EDS) and selected-area electron diffraction (SAED). Much of the work previously published to establish the crystal chemistry of erionite has involved the relatively large crystals found in vesicles in extrusive volcanic rocks. Analysis of these crystals gives a weight percent ratio of Si to Al in a narrow range around 2.7 (molar ratio 2.6), consistent with a unit-cell formula Al 10 Si 26 . In addition, the cation contents of these crystals generally meet the charge balance error formula for zeolites. However, erionites formed in volcaniclastic sedimentary rocks (tuffs) have very different Si:Al weight percent ratios, around 4.0, which is above the upper range for the analyses of the crystals found in vesicles. Analysis of many particles in samples from different locations reveal two other major differences between the erionites from the sedimentary situations and those found in vesicles. (1) The extra-framework alkali cation (Na, K, Ca) contents are lower than required for a stoichiometric balance with framework Al substitution for Si so that the cation charge balance error formula limits for zeolites are not met. (2) There is a large variability in measured cation contents from particle to particle from the same source as well as substantial differences in average compositions from different sources. However, sedimentary erionites cannot be termed a separate mineral species because the crystallographic data are consistent with erionite and new zeolite names cannot be proposed on the basis of Si:Al ratios alone. In addition to chemical differences between erionite from different sources, there are also morphological differences. By analogy with asbestos minerals, differences in composition and morphology may have implications for relative toxicity, and future research should include consideration of these aspects.

Whole metagenome profiles of particulates collected from the International Space Station

BackgroundThe built environment of the International Space Station (ISS) is a highly specialized space in terms of both physical characteristics and habitation requirements. It is unique with respect to conditions of microgravity, exposure to space radiation, and increased carbon dioxide concentrations. Additionally, astronauts inhabit a large proportion of this environment. The microbial composition of ISS particulates has been reported; however, its functional genomics, which are pertinent due to potential impact of its constituents on human health and operational mission success, are not yet characterized.MethodsThis study examined the whole metagenome of ISS microbes at both species- and gene-level resolution. Air filter and dust samples from the ISS were analyzed and compared to samples collected in a terrestrial cleanroom environment. Furthermore, metagenome mining was carried out to characterize dominant, virulent, and novel microorganisms. The whole genome sequences of select cultivable strains isolated from these samples were extracted from the metagenome and compared.ResultsSpecies-level composition in the ISS was found to be largely dominated by Corynebacterium ihumii GD7, with overall microbial diversity being lower in the ISS relative to the cleanroom samples. When examining detection of microbial genes relevant to human health such as antimicrobial resistance and virulence genes, it was found that a larger number of relevant gene categories were observed in the ISS relative to the cleanroom. Strain-level cross-sample comparisons were made for Corynebacterium, Bacillus, and Aspergillus showing possible distinctions in the dominant strain between samples.ConclusionSpecies-level analyses demonstrated distinct differences between the ISS and cleanroom samples, indicating that the cleanroom population is not necessarily reflective of space habitation environments. The overall population of viable microorganisms and the functional diversity inherent to this unique closed environment are of critical interest with respect to future space habitation. Observations and studies such as these will be important to evaluating the conditions required for long-term health of human occupants in such environments.

Air and Surface Sampling Method for Assessing Exposures to Quaternary Ammonium Compounds Using Liquid Chromatography Tandem Mass Spectrometry.

This method was designed for sampling select quaternary ammonium (quat) compounds in air or on surfaces followed by analysis using ultraperformance liquid chromatography tandem mass spectrometry. Target quats were benzethonium chloride, didecyldimethylammonium bromide, benzyldimethyldodecylammonium chloride, benzyldimethyltetradecylammonium chloride, and benzyldimethylhexadecylammonium chloride. For air sampling, polytetrafluoroethylene (PTFE) filters are recommended for 15-min to 24-hour sampling. For surface sampling, Pro-wipe® 880 (PW) media was chosen. Samples were extracted in 60:40 acetonitrile:0.1% formic acid for 1 hour on an orbital shaker. Method detection limits range from 0.3 to 2 ng/ml depending on media and analyte. Matrix effects of media are minimized through the use of multiple reaction monitoring versus selected ion recording. Upper confidence limits on accuracy meet the National Institute for Occupational Safety and Health 25% criterion for PTFE and PW media for all analytes. Using PTFE and PW analyzed with multiple reaction monitoring, the method quantifies levels among the different quats compounds with high precision (<10% relative standard deviation) and low bias (<11%). The method is sensitive enough with very low method detection limits to capture quats on air sampling filters with only a 15-min sample duration with a maximum assessed storage time of 103 days before sample extraction. This method will support future exposure assessment and quantitative epidemiologic studies to explore exposure-response relationships and establish levels of quats exposures associated with adverse health effects.

Optical molecular fluorescence determination of ultra-trace beryllium in occupational and environmental samples using highly alkaline conditions

ABSTRACTExposures to beryllium (Be), even at extremely low levels, can cause severe health effects in a percentage of those exposed; consequently, occupational exposure limits (OELs) promulgated for this element are the lowest established for any element. This work describes the advantages of using highly alkaline dye solutions for determination of Be in occupational hygiene and environmental samples by means of an optical molecular fluorescence technique after sample extraction in 1–3% (w˖w−1) aqueous ammonium bifluoride (NH4HF2). Improved attributes include the ability to further enhance the detection limits of Be in extraction solutions of high acidity with minimal dilution, which is particularly beneficial when NH4HF2 solutions of higher concentration are used for extraction of Be from soil samples. Significant improvements in Be method detection limits (MDLs) are obtained at levels manyfold below those reported previously for this methodology. Notably, MDLs for Be of <0.01 ng L−1 /0.1 ng per sample have been attained, which are superior to MDLs routinely reported for this element by means of the most widely used ultra-trace elemental measurement technique, inductively coupled plasma mass spectrometry (ICP-MS). Very low MDLs for Be are essential in consideration of reductions in OELs for this element in workplace air by health organisations and regulatory agencies in the USA and internationally. Applications of enhanced Be measurements to air filter samples, surface wipe samples, soils and newly designed occupational air sampler inserts are illustrated.

Assessment of Health Risk from Historical Use of Cosmetic Talcum Powder.

This study's objective is to assess the risk of asbestos-related disease being contracted by past users of cosmetic talcum powder. To our knowledge, no risk assessment studies using exposure data from historical exposures or chamber simulations have been published. We conducted activity-based sampling with cosmetic talcum powder samples from five opened and previously used containers that are believed to have been first manufactured and sold in the 1960s and 1970s. These samples had been subject to conflicting claims of asbestos content; samples with the highest claimed asbestos content were tested. The tests were conducted in simulated-bathroom controlled chambers with volunteers who were talc users. Air sampling filters were prepared by direct preparation techniques and analyzed by phase contrast microscopy (PCM), transmission electron microscopy (TEM) with energy-dispersive x-ray (EDX) spectra, and selective area diffraction (SAED). TEM analysis for asbestos resulted in no confirmed asbestos fibers and only a single fiber classified as "ambiguous." Hypothetical treatment of this fiber as if it were asbestos yields a risk of 9.6 × 10-7 (under one in one million) for a lifetime user of this cosmetic talcum powder. The exposure levels associated with these results range from zero to levels far below those identified in the epidemiology literature as posing a risk for asbestos-related disease, and substantially below published historical environmental background levels. The approaches used for this study have potential application to exposure evaluations of other talc or asbestos-containing materials and consumer products.

Fukushima Daiichi reactor source term attribution using cesium isotope ratios from contaminated environmental samples.

Source term attribution of environmental contamination following the Fukushima Daiichi Nuclear Power Plant (FDNPP) disaster is complicated by a large number of possible similar emission source terms (e.g. FDNPP reactor cores 1-3 and spent fuel ponds 1-4). Cesium isotopic analyses can be utilized to discriminate between environmental contamination from different FDNPP source terms and, if samples are sufficiently temporally resolved, potentially provide insights into the extent of reactor core damage at a given time. Rice, soil, mushroom, and soybean samples taken 100-250 km from the FDNPP site were dissolved using microwave digestion. Radiocesium was extracted and purified using two sequential ammonium molybdophosphate-polyacrylonitrile columns, following which (135)Cs/(137) Cs isotope ratios were measured using thermal ionization mass spectrometry (TIMS). Results were compared with data reported previously from locations to the northwest of FDNPP and 30 km to the south of FDNPP. (135)Cs/(137)Cs isotope ratios from samples 100-250 km to the southwest of the FDNPP site show a consistent value of 0.376 ± 0.008. (135)Cs/(137)Cs versus (134)Cs/(137)Cs correlation plots suggest that radiocesium to the southwest is derived from a mixture of FDNPP reactor cores 1, 2, and 3. Conclusions from the cesium isotopic data are in agreement with those derived independently based upon the event chronology combined with meteorological conditions at the time of the disaster. Cesium isotopic analyses provide a powerful tool for source term discrimination of environmental radiocesium contamination at the FDNPP site. For higher precision source term attribution and forensic determination of the FDNPP core conditions based upon cesium, analyses of a larger number of samples from locations to the north and south of the FDNPP site (particularly time-resolved air filter samples) are needed.

Air sampling filtration media: Collection efficiency for respirable size-selective sampling.

The collection efficiencies of commonly used membrane air sampling filters in the ultrafine particle size range were investigated. Mixed cellulose ester (MCE; 0.45, 0.8, 1.2, and 5 μm pore sizes), polycarbonate (0.4, 0.8, 2, and 5 μm pore sizes), polytetrafluoroethylene (PTFE; 0.45, 1, 2, and 5 μm pore sizes), polyvinyl chloride (PVC; 0.8 and 5 μm pore sizes), and silver membrane (0.45, 0.8, 1.2, and 5 μm pore sizes) filters were exposed to polydisperse sodium chloride (NaCl) particles in the size range of 10-400 nm. Test aerosols were nebulized and introduced into a calm air chamber through a diffusion dryer and aerosol neutralizer. The testing filters (37 mm diameter) were mounted in a conductive polypropylene filter-holder (cassette) within a metal testing tube. The experiments were conducted at flow rates between 1.7 and 11.2 l min-1. The particle size distributions of NaCl challenge aerosol were measured upstream and downstream of the test filters by a scanning mobility particle sizer (SMPS). Three different filters of each type with at least three repetitions for each pore size were tested. In general, the collection efficiency varied with airflow, pore size, and sampling duration. In addition, both collection efficiency and pressure drop increased with decreased pore size and increased sampling flow rate, but they differed among filter types and manufacturer. The present study confirmed that the MCE, PTFE, and PVC filters have a relatively high collection efficiency for challenge particles much smaller than their nominal pore size and are considerably more efficient than polycarbonate and silver membrane filters, especially at larger nominal pore sizes.

Efficient photocatalytic degradation of NO by ceramic foam air filters coated with mesoporous TiO2 thin films

Ceramic foam air filters with three-dimensional (3D) porous structures and high surface areas were coated with mesoporous TiO2 thin films by the reverse micellar method. The mesoporous TiO2 thin films efficiently photocatalytically degraded nitrogen oxide (NO). More than 92.5% of NO was degraded in a single pass for air filter samples containing different pore densities. The 3D porous structure of the ceramic air filters enhanced flow turbulence and mixing. This provided the catalytic system with excellent gas-dynamic properties, and sufficient contact between the reactant gas and catalyst surface. The higher pore density of the ceramic foam filters resulted in a higher photocatalytic rate. More adsorption sites for water vapor and the reactant and product gases improved the photocatalytic activity. The porous ceramic air filters coated with mesoporous TiO2 had large surface areas, and thus high photocatalytic activity. This overcame the common disadvantages associated with using powdered TiO2 photocatalysts on substrates. The 3D porous ceramic foam filters coated with mesoporous TiO2 thin films exhibited a higher photocatalytic degradation rate of NO in air than the same thin film deposited on flat ceramic tiles. No deactivation was observed. A consistently high NO degradation rate was obtained between reaction cycles for the TiO2-coated 3D porous ceramic filters.

Highly Bactericidal Polyurethane Effective Against Both Normal and Drug-Resistant Bacteria: Potential Use as an Air Filter Coating.

The battle against the prevalence of hospital-acquired infections has underscored the importance of identifying and maintaining the cleanliness of possible infection transmission sources in the patient's environment. One of the most crucial lines of defense for mitigating the spread of pathogens in a healthcare facility is the removal of microorganisms from the environment by air filtration systems. After removing the pathogenic microorganisms, the filters used in these systems can serve as reservoirs for the pathogens and pose a risk for secondary infection. This threat, combined with the ever-growing prevalence of drug-resistant bacterial strains, substantiates the need for an effective bactericidal air filter. To this end, a broad-spectrum bactericidal polyurethane incorporating immobilized quaternary ammonium groups was developed for use as an air filter coating. In this study, the bactericidal activity of the polymer coating on high-efficiency particulate air (HEPA) filter samples was quantified against eight bacterial strains commonly responsible for nosocomial infection-including drug-resistant strains, and confirmed when applied as a filter coating in conditions mimicking those of its intended application. The coated HEPA filter samples exhibited high bactericidal activity against all eight strains, and the polyurethane was concluded to be an effective coating in rendering HEPA filters bactericidal.