Six-stage Andersen Sampler Research Articles

Ability of Essential Oil Vapours to Reduce Numbers of Culturable Aerosolised Coronavirus, Bacteria and Fungi.

Transmission of pathogens present in the indoor air can occur through aerosols. This study evaluated the efficacy of an evaporated mix of essential oils to reduce the numbers of culturable aerosolized coronavirus, bacterium and fungus. The essential oil-containing gel was allowed to vaporize inside a glass chamber for 10 or 20 min. Aerosols of a surrogate of SARS-CoV-2, murine hepatitis coronavirus MHV-1, Escherichia coli or Aspergillus flavus spores were produced using a collision nebuliser and passed through the essential oil vapours, then collected on a six-stage Andersen sampler. The six-stages of the impact sampler capture aerosols in sizes ranging from 7 to 0.65 µm. The number of culturable microbes present in the aerosols collected in the different stages were enumerated and compared to the number of culturable microbes in control microbial aerosols that were not exposed to the evaporated essential oils. After 10 and 20 min evaporation, the essential oils reduced the numbers of culturable aerosolized coronavirus by 48% (log10 reduction = 0.3; p = 0.002 vs. control) and 53% (log10 reduction = 0.3; p = 0.001 vs. control), respectively. The essential oils vaporised for 10 min, reduced the number of viable E. coli by 51% (log10 reduction = 0.3; p = 0.032 vs. control). The Aspergillus flavus spores were mostly observed in the larger aerosols (7.00 µm to 2.10 µm) and the essential oils vaporised for 10 min reduced the number of viable spores by 72% (log10 reduction = 0.6; p = 0.008 vs. control). The vapours produced by a gel containing naturally occurring essential oils were able to significantly reduce the viable numbers of aerosolized coronavirus, bacteria and fungal spores. The antimicrobial gel containing the essential oils may be able to reduce aerosol transmission of microbes when used in domestic and workplace settings.

DISPERSION OF AEROSOLIZED BACTERIA FROM ASIAN ELEPHANTS (ELEPHAS MAXIMUS).

Transmission of tuberculosis typically requires close and prolonged contact with an infected individual. However, several cases of transmission between elephants and from elephants to humans or other animals without direct contact or over long distances have been reported. Elephants have been shown to be capable of producing aerosolized bacterial droplets, suggesting a possible route of transmission that is magnified by the size and force of the elephant respiratory tract. To investigate the dispersion and viability of aerosolized bacteria generated from the elephant respiratory tract, a pre-existing model with a proxy organism was used. A six-stage Andersen sampler was used to detect the proxy organism, a commensal elephant respiratory bacterium, at different locations around an elephant barn at a zoo. The amount of proxy organism detected at various time points and distances from the elephants indicates they are capable of dispersing viable bacterial aerosols further than humans can. The concentration of these aerosols is dependent on proximity to the elephants and does not remain at a high level for prolonged periods of time. These findings support the model of aerosol-mediated transmission of bacteria from elephants and can be used to improve disease management practices and prevent the spread of pathogens from elephants in zoos and other facilities.

Pilot-scale biofiltration at a materials recovery facility: The impact on bioaerosol control

This study investigated the performance of four pilot-scale biofilters for the removal of bioaerosols from waste airstreams in a materials recovery facility (MRF) based in Leeds, UK. A six-stage Andersen sampler was used to measure the concentrations of four groups of bioaerosols (Aspergillus fumigatus, total fungi, total mesophilic bacteria and Gram negative bacteria) in the airstream before and after passing through the biofilters over a period of 11 months. The biofilters achieved average removal efficiency (RE) of 70% (35 to 97%) for A. fumigatus, 71% (35 to 94%) for total fungi, 68% (47 to 86%) for total mesophilic bacteria and 50% (-4 to 85%) for Gram negative bacteria, provided that the inlet concentration was high (103–105 cfu m−3), which is the case for most waste treatment facilities. The performance was highly variable at low inlet concentration with some cases showing an increase in outlet concentrations, suggesting that biofilters had the potential to be net emitters of bioaerosols. The gas phase residence time did not appear to have any statistically significant impact on bioaerosol removal efficiency. Particle size distribution varied between the inlet and outlet air, with the outlet having a greater proportion of smaller sized particles that represent a greater human health risk as they can penetrate deep into the respiratory system where gaseous exchange occurs. However, the outlet concentrations were low and would further be diluted by wind in full scale applications. In conclusion, this study shows that biofilters designed and operated for odour degradation can also achieve significant bioaerosol control in waste gas.

Is there an infection risk when playing drums contaminated with Bacillus anthracis?

This study aims to investigate the aerosol release of a Bacillus anthracis spore surrogate from two different types of drums while playing, by; (i) quantifying the number of spores aerosolized during playing; (ii) investigating spore recovery from drums over long time periods, and (iii) measuring differences between (i) and (ii) for two different drums types. Two African drums were contaminated with Bacillus atrophaeus spores then sampled and played by hand over a number of days. During playing three air samplers were used to collect any aerosols generated, the choice of air samplers (Casella slit sampler, all glass impinger and six-stage Andersen sampler) allowed for characterization of the aerosols produced. Spore contamination of drums was found to be long-lasting with a small percentage of the spores being detached and aerosolized during drumming. The results of these studies have been used for a quantitative risk assessment of playing drums contaminated with B.anthracis spores. This demonstrates that the risk of inhalational exposure while playing drums contaminated with the levels linked to the US and UK cases is very low and that the resulting cases of inhalational anthrax can be explained by being unusual events involving highly susceptible persons.

Bacterial and fungal aerosols in the work environment of cleaners

Cleaning services are carried out in almost all sectors and branches of industry. Due to the above, cleaners are exposed to various harmful biological agents, depending on the tasks performed and the commercial sector involved. The aim of this study was to assess the exposure of cleaning workers to biological agents based on quantitative and qualitative characteristics of airborne microflora. A six-stage Andersen sampler was used to collect bioaerosols during the cleaning activities in different workplaces, including schools, offices, car services, healthy services and shops. Standard Petri dishes filled with blood trypticase soy agar and malt extract agar were used for bacterial and fungal sampling, respectively. The bioaerosol concentration values obtained during testing of selected workposts of cleaners were lower than the Polish recommended threshold limit values for microorganisms concentrations in public service. The most prevalent bacterial species in studied places were Gram-positive cocci (mainly of genera Micrococcus, Staphylococcus) and endospore-forming Gram-positive rods (mainly of genera Bacillus). Among the most common fungal species were those from genera Penicillium and Aspergillus. The size distribution analysis revealed that bioaerosols present in the air of workposts at shops, schools and car services may be responsible for nose and eye mucosa irritation and allergic reactions in the form of asthma or allergic inflammation in the cleaning workers. The study shows that occupational activities of cleaning workers are associated with exposure to airborne biological agents classified into risk groups, 1. and 2., according to their level of infection risk, posing respiratory hazard.

Assessment of microbial contamination within working environments of different types of composting plants

The objective of the study was to determine the degree of microbiological contamination, type of microflora, bioaerosol particle size distribution, and concentration of endotoxins in dust in different types of composting plants. In addition, this study provides a list of indicator microorganisms that pose a biological threat in composting facilities, based on their prevalence within the workplace, source of isolation, and health hazards. We undertook microbiological analysis of the air, work surfaces, and compost, and assessed the particle size distribution of bioaerosols using a six-stage Andersen sampler. Endotoxins were determined using gas chromatography–mass spectrometry (GC-MS). Microbial identification was undertaken both microscopically and using biochemical tests. The predominant bacterial and fungal species were identified using 16S rRNA and ITS1/2 analysis, respectively. The number of mesophilic microorganisms in composting plants amounted to 6.9 × 102–2.5 × 104 CFU/m3 in the air, 2.9 × 102–3.3 × 103 CFU/100 cm2 on surfaces, and 2.2 × 105–2.4 × 107 CFU/g in compost. Qualitative analysis revealed 75 microbial strains in composting plants, with filamentous fungi being the largest group of microorganisms, accounting for as many as 38 isolates. The total amount of endotoxins was 0.0062–0.0140 nmol/mg of dust. The dust fraction with aerodynamic particle diameter of 0.65–1.1 μm accounted for 28–39% of bacterial aerosols and 4–13% of fungal aerosols. We propose the following strains as indicators of harmful biological agent contamination: Bacillus cereus, Aspergillus fumigatus, Cladosporium cladosporioides, C. herbarum, Mucor hiemalis, and Rhizopus oryzae for both types of composting plants, and Bacillus pumilus, Mucor fragilis, Penicillium svalbardense, and P. crustosum for green waste composting plants. The biological hazards posed within these plants are due to the presence of potentially pathogenic microorganisms and the inhalation of respirable bioaerosol. Depending on the type of microorganism, these hazards may be aggravated or reduced after cleaning procedures.Implications: This study assessed the microbial contamination in two categories of composting plants: (1) facilities producing substrates for industrial cultivation of button mushrooms, and (2) facilities for processing biodegradable waste. Both workplaces showed potentially pathogenic microorganisms, respirable bioaerosol, and endotoxin. These results are useful to determine the procedures to control harmful biological agents, and to disinfect workplaces in composting plants.

Characteristics of airborne Staphylococcus aureus (including MRSA) in Chinese public buildings.

The aim of this study was to evaluate the concentration and size distribution of airborne culturable Staphylococcus aureus (S. aureus) (including MRSA) in Chinese public buildings. Air samples were collected, using six-stage Andersen sampler from five different public buildings in one large Chinese community. The mean indoor concentrations of the total and respirable airborne S. aureus were 72 and 50 CFU/m3 in the general hospital, 72 and 49 CFU/m3 in the kindergarten, 76 and 52 CFU/m3 in the hotel, 84 and 57 CFU/m3 in the movie theater, and 55 and 40 CFU/m3 in the university classroom. Respirable S. aureus amounted to approximately 57–73 % of the total S. aureus concentrations. Mean total and respirable concentrations of airborne MRSA were 32 and 20 CFU/m3 in the general hospital, 20 and 13 CFU/m3 in the kindergarten, 23 and 16 CFU/m3 in the hotel, 33 and 20 CFU/m3 in the movie theater, and 24 and 17 CFU/m3 in the university classroom. Respirable MRSA amounted to approximately 61–72 % of the total MRSA concentrations. The ratios of indoor and outdoor concentration for airborne S. aureus and MRSA were more than 1.0 in all the investigated public buildings. The size distribution results showed relatively high collection rates on stage 4 (2.1–3.3 μm) for both airborne culturable S. aureus and MRSA regardless of the type of public buildings.

Respiratory virus RNA is detectable in airborne and droplet particles

Aerosol transmission routes of respiratory viruses have been classified by the WHO on the basis of equilibrium particle size. Droplet transmission is associated with particles sized >5 µm in diameter and airborne transmission is associated with particles sized ≤5 µm in diameter. Current infection control measures for respiratory viruses are directed at preventing droplet transmission, although epidemiological evidence suggests concurrent airborne transmission also occurs. Understanding the size of particles carrying viruses can be used to inform infection control procedures and therefore reduce virus transmission. This study determined the size of particles carrying respiratory viral RNA produced on coughing and breathing by 12 adults and 41 children with symptomatic respiratory infections. A modified six-stage Andersen Sampler collected expelled particles. Each stage was washed to recover samples for viral RNA extraction. Influenza A and B, parainfluenza 1, 2 and 3, respiratory syncytial virus (RSV), human metapneumovirus and human rhinoviruses (hRV) were detected using RT-PCR. On breathing, 58% of participants produced large particles (>5 µm) containing viral RNA and 80% produced small particles (≤5 µm) carrying viral RNA. On coughing, 57% of participants produced large particles containing viral RNA and 82% produced small particles containing viral RNA. Forty five percent of participants produced samples positive for hRV viral RNA and 26% of participants produced samples positive for viral RNA from parainfluenza viruses. This study demonstrates that individuals with symptomatic respiratory viral infections produce both large and small particles carrying viral RNA on coughing and breathing.

Monitoring of bioaerosol inhalation risks in different environments using a six-stage Andersen sampler and the PCR-DGGE method

Increasing evidences show that inhalation of indoor bioaerosols has caused numerous adverse health effects and diseases. However, the bioaerosol size distribution, composition, and concentration level, representing different inhalation risks, could vary with different living environments. The six-stage Andersen sampler is designed to simulate the sampling of different human lung regions. Here, the sampler was used in investigating the bioaerosol exposure in six different environments (student dorm, hospital, laboratory, hotel room, dining hall, and outdoor environment) in Beijing. During the sampling, the Andersen sampler was operated for 30 min for each sample, and three independent experiments were performed for each of the environments. The air samples collected onto each of the six stages of the sampler were incubated on agar plates directly at 26 °C, and the colony forming units (CFU) were manually counted and statistically corrected. In addition, the developed CFUs were washed off the agar plates and subjected to polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) for diversity analysis. Results revealed that for most environments investigated, the culturable bacterial aerosol concentrations were higher than those of culturable fungal aerosols. The culturable bacterial and fungal aerosol fractions, concentration, size distribution, and diversity were shown to vary significantly with the sampling environments. PCR-DGGE analysis indicated that different environments had different culturable bacterial aerosol compositions as revealed by distinct gel band patterns. For most environments tested, larger (>3 μm) culturable bacterial aerosols with a skewed size distribution were shown to prevail, accounting for more than 60 %, while for culturable fungal aerosols with a normal size distribution, those 2.1-4.7 μm dominated, accounting for 20-40 %. Alternaria, Cladosporium, Chaetomium, and Aspergillus were found abundant in most environments studied here. Viable microbial load per unit of particulate matter was also shown to vary significantly with the sampling environments. The results from this study suggested that different environments even with similar levels of total microbial culturable aerosol concentrations could present different inhalation risks due to different bioaerosol particle size distribution and composition. This work fills literature gaps regarding bioaerosol size and composition-based exposure risks in different human dwellings in contrast to a vast body of total bioaerosol levels.

Fungal spore concentrations in two haematopoietic stem cell transplantation (HSCT) units containing distinct air control systems.

Invasive fungal diseases have emerged as important causes of morbidity and mortality in haematological patients. In this study air samples were collected in two haematopoietic stem cell transplantation (HSCT) units, in which distinct air-control systems were in place. In hospital 1 no high-efficiency particulate air (HEPA) filter was available whereas in hospital 2 HSCT rooms were equipped with HEPA filters, with positive air pressure in relation to the corridor. A total of 117 samples from rooms, toilets and corridors were obtained during December 2009 to January 2011, using a six-stage Andersen sampler. In both hospitals, the concentration of potentially pathogenic fungi in the air was reduced in patients' rooms compared to corridors (P < 0·0001). Despite the presence of a HEPA filter in hospital 2, rooms in both hospitals showed similar concentrations of potentially pathogenic fungi (P = 0·714). These findings may be explained by the implementation of additional protective measures in hospital 1, emphasizing the importance of such measures in protected environments.

Effects of microwave irradiation on concentration, diversity and gene mutation of culturable airborne microorganisms of inhalable sizes in different environments

Previously, we have investigated the inactivation of total environmental bioaerosols using microwave irradiation at 2450 MHz. Here, the effects of microwave irradiation on the concentration, diversity and possible gene mutations of airborne culturable microorganisms of different size ranges were investigated. Air samples were collected in different environments (office, hotel and outdoor) using a six-stage Andersen sampler operated at its standard flow rate of 28.3 L/min without and with the microwave irradiation at three different power levels(119, 385 and 700 W) corresponding to energy doses of 7.1, 22 and 31.5 kJ, respectively. For each experimental condition, three to five independent replicates were conducted. Air samples collected onto different stages of the Andersen sampler were incubated at 26 °C, and colony forming units (CFUs) were manually counted and statistically corrected. The bacterial CFUs were further washed off from agar plates using deionized water, and subjected to polymerase chain reaction (PCR)-denaturing gradient gel electrophoresis (DGGE) for diversity and possible gene mutation analysis. Results revealed that for the outdoor environment, larger size (>3.3 μm) bacterial species dominated, while for the indoor environments those of smaller size (<2.1 μm) did. Use of the high power level (700 W) in general resulted in lower culturable bacterial counts regardless of the sampler stage and the sampling environment. The inactivation efficiencies of the microwave treatment were shown to strongly depend on the environments and the microwave energy dose under the experimental conditions tested. PCR-DGGE analysis indicated that use of the high power microwave irradiation (31.5 kJ) generally resulted in less culturable bacterial aerosol richness, while for medium (22 kJ) and low (7.1 kJ) energy doses their culturable species richness appeared to be similar to those of the control experiments. In contrast, smaller (1.1–2.2 μm) culturable fungal species were found to dominate regardless of sampling environments. In addition, culturable bacterial aerosol gene mutations with a high frequency after the microwave treatment were detected in the colonies developed. The results from this study provide further information in developing microwave-based bioaerosol inactivation technology.

Bioaerosol Generation at Large-Scale Green Waste Composting Plants

Bioaerosol release from composting plants is a cause of concern because of the potential health impacts on site workers and local residents. A one-year monitoring was undertaken in a typical composting plant treating green wastes by windrowing in the open. Aspergillus fumigatus spores and mesophilic bacteria were used as monitoring parameters and were collected in a six-stage Andersen sampler impactor from the air at different locations and during different operational activities. Background concentrations of both microorganisms were generally below 1000 colony-forming units m−3 when no vigorous activity was taking place. Shredding of fresh green wastes, pile turning, and screening of mature compost were identified as the activities generating the highest amounts of both bioaerosols 40 m downwind of the composting pad. These air concentrations were ∼2 log units higher than background levels. Screening of mature compost generated lower amounts of A. fumigatus than the other two activities (an average of 1 log unit higher than background levels). Workers were identified as the main potential receptors of high bioaerosol concentrations in areas close to the composting pad, whereas no major risk for local residents was expected because the concentrations recorded at distances of 200 and 300 m downwind of the operational area were not significantly different from background levels.

Airborne Bacteria Control Under Chamber and Test-Home Conditions

The research reported in this paper investigates the ability of a portable UV-based control device (size=21in.×12in.×12in.) to reduce airborne indoor bacteria levels to at or below outdoor ambient levels. Under controlled conditions, laboratory scale chamber (size=48in.×36in.×48in.) experiments and field scale residence experiments were conducted using the UV control device. Pure cultures of Staphylococcus aureus were grown in culture media and atomized into bioaerosols in the laboratory chamber. The airborne levels of the bacteria were sampled using a six-stage Andersen sampler containing selective culture media plates, and the levels were counted as number of colony forming units per cubic meter of air. The UV control device reduced the atomizer-generated laboratory chamber Staphylococcus aureus levels from a range of 5,000–15,000 cfu/m3 to below 120 cfu/m3 within a 2 h period. Continuous operation of the UV control device in the bedroom and bathroom of a single-resident apartment reduced the Staphyloco...

Comparison of commonly used samplers with a novel bioaerosol sampler with automatic plate exchange

A newly designed automatic bioaerosol sampler (ABS) was commissioned for studies of microbial bioaerosols. The original feature of the ABS is the facility for unattended, microprocessor-controlled sampling with automatic replacement of the agar Petri dishes after each sample. The ABS was compared with a six-stage Andersen sampler, an all-glass impinger and a Casella slit sampler. The air in two cattle and two poultry livestock buildings was sampled for the concentration of total bacteria and total fungi including yeast cells. Slightly smaller concentrations of total bacteria and total fungi were measured with the automatic bioaerosol sampler than with the reference samplers. The automatic bioaerosol sampler correlated best with the Andersen sampler and its cutoff diameter was estimated to be about 1.5 μm. Overall, this new sampler was found to be a useful development in the technology of sampling airborne microbes.

Concentration of respirable dust and bioaerosols and identification of certain microbial types in a hog-growing facility

In order to assess the effects of ventilation rate, temperature, relative humidity and source of air on bioaerosol levels and dust with particle size &lt; 10 μm, a total of 120 pigs housed in 12 pens in two separate rooms were used. Pigs averaged 30 kg initially and the trials were discontinued when 20% of the pigs were marketed. A six-stage Andersen sampler and a light scattering particle counter were used to determine bioaerosols and respirable dust (0.1–10 μm), respectively. Total bioaerosols were assessed using Trypticase Soy Agar. Potato Dextrose Agar was used for fungal aeorsols and Baird-Parker Agar used for isolation of Staphylococcus aureus. Moulds amounted to less than 1% of total microorganisms. Gram positive bacteria made up 72% of the bacterial isolates. Respirable dust was not correlated with respirable bioaerosols. Ventilation rate (2, 5 or 8 changes h−1) did not affect bioaerosol level or respirable dust. Total bioaerosols were significantly reduced (P &lt; 0.05) in higher temperatures only. Relative humidity did not influence total bioaerosols but in one series respirable bioaerosols were significantly (R = 0.53) (P &lt; 0.05) correlated with RH. Total bioaerosols were not different in outside air or attic air. Key words: Dust, bioaerosols, pigs, ventilation

Viable fungi in corn dust.

Numbers of viable fungal propagules in corn dusts in southern Georgia were estimated during various farm and grain elevator operations in 1979, 1980, and 1982. A six-stage Andersen sampler for viable microbial particles was used to sample the dusts with various agar media. The most abundant fungi in corn dusts were species of yeasts: Aspergillus, Penicillium, Cladosporium, Alternaria. Helminthosporium, and Fusarium. However, the relative abundance of these fungi differed between years. There was a greater incidence of the Aspergillus flavus group in the hot, dry year of 1980 compared with the cooler, wetter years of 1979 and 1982. Fungi in the corn dusts sampled numbered between 10(4) and 10(9) viable propagules per m3 of air. By contrast, outdoor air often contained fewer than 10(4) viable fungal propagules per m3. Most A. flavus propagules were deposited at stages three and four of the Andersen sampler, with correspond to the trachea, primary bronchi, and secondary bronchi in the human respiratory system. In an assessment of the air spores by exposing sterile petri dishes, more large-spored fungi, like Alternaria tenuis, and fewer small-spored fungi, such as A. flavus, were detected when compared with colony counts from petri dishes exposed to air in the Anderson sampler.

Non-ideal collection characteristics of inertial impactors—II. Cascade impactors

Calibration of the four-stage Lundgren impactor and the six-stage Andersen sampler with oil particles, and particle bounce in the Andersen sampler with solid particles are described. Collection characteristics of oil-coated steel plates, uncoated steel plates, glass fiber filters and Whatman filters in the Andersen sampler were determined using monodisperse polystyrene latex and methylene blue aerosols. For the Lundgren impactor, whose design and operation satisfy the assumptions of impactor theory, the calibration curves are in good agreement with the theoretical curves. However, the calibration curves of the Andersen sampler are less steep and are shifted towards higher aerodynamic dia. With oil-coated steel plates, the collection efficiency curves rise monotonically from zero to 100% efficiency. However, with uncoated steel plates, the efficiency curves rise up to 20 or 50% and then drop. The peak efficiency of stages is very sensitive to jet velocity and to some extent to particle size. The use of glass fiber filters as collection surface minimizes bounce, but modifies the collection characteristics. Some Whatman filter papers are unsatisfactory as collection surfaces.

Lead and cadmium distribution in the particulate effluent from a coal-fired boiler.

This study was designed to evaluate the total emissions and the distribution of concentration with particle size for cadmium and lead in the particulate effluent from a coal-fired boiler. Particular attention was given to the concentration and amounts of these materials in the respirable size range (<5 microns). Particulates were collected by means of a sampling train which consisted of a Los Alamos Scientific Laboratory miniature cyclone, followed by a six-stage Andersen sampler, followed by an inline membrane filter. After collection, the various size ranges of particulates were analyzed quantitatively for cadmium and lead by using atomic absorption spectroscopy. These analyses showed that ithe largest amounts of cadmium and lead were in the respirable size ranges. An increase in concentration with decreasing particle size was also shown for lead and cadmium.