Assessment of air purifier on efficient removal of airborne bacteria, Staphylococcus epidermidis, using single-chamber method

Needle point bipolar ionization: environmental safety and inactivation of airborne bacteria and corona virus

Although there is an increasing interest after the COVID-19 pandemic, electronic ionization efficiency and impact on indoor air quality are not yet fully understood, and studies are insufficient. Therefore, in this study, the disinfection efficiency for viruses and bacteria and the change of indoor thermal comfort parameters (temperature, humidity, pressure) and air pollutants (CO2, NO2, VOC, O3, CH2O, PM2.5, Particle Number (PN) from 0.3 to 10 µm particle sizes) by a portable indoor air cleaner using the needle point bipolar ionization (NPBI) method were investigated. The highest antibacterial activity was achieved at hour 3 with a 99.8% reduction for Bacillus subtilis, 99.8% for Staphylococcus aureus, 98.8% for Escherichia coli, and 99.4% for Staphylococcus albus, and sustained at hour 4th. The ions had antiviral activity on surfaces with a 94% TCID50 reduction of the HCoV-229E virus after 2 h of NPBI-on. No significant changes were detected in thermal comfort parameters, NO2, and VOC during the NPBI-on. Moreover, it was found that O3 and CH2O were not generated when the NPBI system was operated in the room for 4 h. Consequently, an average particle number removal rate of 60% can be achieved with the NPBI system in much less time than with the natural decay time.

Development of optimal indoor air disinfection and ventilation protocols for airborne infectious diseases

Since the COVID-19 pandemic, there has been persistent emphasis on the importance of indoor air disinfection and ventilation in isolation units in the hospital environment. Nevertheless, no optimal and concrete disinfection protocol has been proposed to inactivate the viruses as quickly as possible. In this study, we experimentally evaluated various ventilation and disinfection protocols based on the combination of negative-pressure ventilation, ultraviolet (UV) light illumination, and Hypochlorous acid (HOCl) spray against three active virus species in a 3.5 cubic meters isolation unit. This small-size unit has gained attention during the pandemic due to the high demand for compact mobile laboratory systems capable of rapid disease diagnosis. In accordance with the WHO laboratory biosafety guidance, which states that all enclosed units where diagnostic work is conducted must ensure proper ventilation and disinfection activities, we aim to propose virus removal protocols for units compact enough to be installed within a van or deployed outdoor. The results confirmed the superiority (in terms of virus removal rate and time required) of the virus removal methods in the order of UV light, ventilation, and HOCl spray. Ultimately, we propose two optimal protocols: (i) UV light alone for three minutes, and (ii) UV light with ventilation for three minutes, followed by one-minute ventilation only. The time span of three minutes in the latter protocol is based on the clinical practice such that the medical staffs have a sufficient time to process the samples taken in transition to next patient to care.

Control technologies to prevent aerosol-based disease transmission in animal agriculture production settings: a review of established and emerging approaches

Transmission of infectious agents via aerosols is an ever-present concern in animal agriculture production settings, as the aerosol route to disease transmission can lead to difficult-to-control and costly diseases, such as porcine respiratory and reproductive syndrome virus and influenza A virus. It is increasingly necessary to implement control technologies to mitigate aerosol-based disease transmission. Here, we review currently utilized and prospective future aerosol control technologies to collect and potentially inactivate pathogens in aerosols, with an emphasis on technologies that can be incorporated into mechanically driven (forced air) ventilation systems to prevent aerosol-based disease spread from facility to facility. Broadly, we find that control technologies can be grouped into three categories: (1) currently implemented technologies; (2) scaled technologies used in industrial and medical settings; and (3) emerging technologies. Category (1) solely consists of fibrous filter media, which have been demonstrated to reduce the spread of PRRSV between swine production facilities. We review the mechanisms by which filters function and are rated (minimum efficiency reporting values). Category (2) consists of electrostatic precipitators (ESPs), used industrially to collect aerosol particles in higher flow rate systems, and ultraviolet C (UV-C) systems, used in medical settings to inactivate pathogens. Finally, category (3) consists of a variety of technologies, including ionization-based systems, microwaves, and those generating reactive oxygen species, often with the goal of pathogen inactivation in aerosols. As such technologies are typically first tested through varied means at the laboratory scale, we additionally review control technology testing techniques at various stages of development, from laboratory studies to field demonstration, and in doing so, suggest uniform testing and report standards are needed. Testing standards should consider the cost-benefit of implementing the technologies applicable to the livestock species of interest. Finally, we examine economic models for implementing aerosol control technologies, defining the collected infectious particles per unit energy demand.

Validation of the efficacy of air purifiers using molecular techniques

The importance of air purifiers has increased in recent years, especially with the "coronavirus disease 2019" pandemic. The efficacy of air purifiers is usually determined under laboratory conditions before widespread application. The standard procedure for testing depends on virus cultivation and titration on cell culture. This, however, requires several days to deliver results. The aim of this study was to establish a rapid molecular assay which can differentiate between intact infectious and distorted non-infectious virus particles. Feline Coronavirus was selected as model for screening. First the samples were pretreated with enzymes (universal nuclease and RNase cocktail enzyme mixture) or viability dye (propidium monoazide) to eliminate any free nucleic acids. The ribonucleic acid (RNA) from intact virus was released via magnetic beads-based extraction, then the amount of the RNA was determined using real-time reverse transcription polymerase chain reaction (RT-PCR) or reverse transcription recombinase-aided amplification (RT-RAA). All results were compared to the infectivity assay based on the calculation of the 50% tissue culture infectious dose (TCID50). The nuclease has eliminated 100% of the free Feline Coronavirus RNA, while propidium monoazide underperformed (2.3-fold decrease in free RNA). Both RT-RAA and real-time RT-PCR produced similar results to the infectivity assay on cell culture with limit of detection of 102 TCID50/mL. Two UV-C air purifiers with prosperities of 100% inactivation of the viruses were used to validate the established procedure. Both real-time RT-PCR and RT-RAA were able to differentiate between intact virus particles and free RNA. To conclude, this study revealed a promising rapid method to validate the efficacy of air purifiers by combining enzymatic pretreatment and molecular assays.

Recent advances in photocatalytic removal of airborne pathogens in air

The abatement of airborne pathogens such as bacteria, viruses, and fungi has become an important goal of air-quality management. Efficient and effective treatment techniques such as photocatalysis are essential for disinfection of airborne microorganisms. This review focuses on recent advances in the formulation and development of photocatalytic disinfection, design of efficient photocatalysts, choice of photocatalytic reactor, removal and/or disinfection mechanisms, and the role of reactive ion species. Data from recent studies are analyzed to accurately assess the efficacy of such disinfection approaches. This review also highlights the application of innovative materials in individual and combined abatement systems against airborne bacterial, viral, and fungal pathogens. We discuss the efficiency and benefits presented by such systems, address the challenges, and provide a perspective for future research.

Physicochemical and microbiological characteristics of urban aerosols in Krakow (Poland) and their potential health impact

Eight aerosol samples were collected in Krakow using a low-volume sampler in February and March 2019 during variable meteorological conditions and times of the day, to study their single particles' properties (size, morphology and chemical composition analyzed using a scanning electron microscope fitted with an energy-dispersive spectrometer) and microbiological characteristics. The content of particles of different chemical compositions larger than 2.5 μm was low. Considering the number of the particles, submicron particles strongly dominated with a high content of ultrafine particles (nanoparticles). Tar ball-type particles were relatively common in the studied samples, while soot was the dominant component. Soot was present as small agglomerates composed of few particles, but also as bigger agglomerates. Metal-containing particles of various chemical characteristics were abundant, with transition metals commonly occurring in these particles. The physicochemical characteristics of aerosols indicate that despite a relatively low mass concentration, their adverse health impact could be very strong because of the high content of nanoparticles, the abundance of soot and other fuel combustion-related particles, and the high incidence of transition metal-rich particles. Microbiological analysis was based on cultures on both solid and liquid agar. The MALDI-TOF method was used for species identification-for bacteria and fungi. Twelve different species of bacteria were isolated from the collected samples of aerosols. The most frequently isolated species was Gram-positive sporulating Bacillus licheniformis. The isolated mold fungi were of the genus Aspergillus.

Effectiveness and Eco-Costs of Air Cleaners in Terms of Improving Fungal Air Pollution in Dwellings Located in Southern Poland—A Preliminary Study

Epidemiological evidence shows that air pollution is responsible for several million premature deaths per year. By virtue of being responsible for these deaths, economic evidence shows that air pollution also imposes a so-called economic cost to society of several trillion dollars per year. The diseases caused by biological air pollutants are of primary global concern for both social and economic reasons, and given that people may spend more than 90% of their time in enclosed spaces, the investigation into methods to remove indoor air pollutants is of paramount importance. One of the methods to improve indoor air quality (IAQ) is to use air cleaners (ACLs) with high-efficiency particulate air filters (HEPA) that remove biological indoor air pollutants from indoor environments. This work presents the results of a study of fungal aerosol samples collected during the summer season from inside two dwellings (DG1 and DG2) before and after starting the use of ACLs. The fungal aerosol samples collected from each of the six stages of the sampler were incubated on agar plates at 26 °C, and the colony forming units (CFU) were manually counted and statistically corrected. The concentration of living airborne fungi was expressed as the CFU in the volume of air (CFU·m−3). The average concentration of fungal aerosol decreased the most when the ACLs were active for 24 min. The reduction was from 474 CFU·m−3 to 306 CFU·m−3, and from 582 CFU·m−3 to 338 CFU·m−3 in DG1 and DG2, respectively. The use of ACLs was assessed by the life cycle assessment (LCA) methodology. This study highlights the benefits of controlling biological air pollutants in order to keep occupants of buildings happy and healthy.

Non-commercial Air Purifier—The Effectiveness and Safety

(1) Background: On the Internet, we can find the guidelines for homemade air purifiers. One of the solutions includes the use of a low-cost ozone generator to decrease the level of odors and biological contaminants. However, the authors do not notify about hazardous effects of ozone generation on human health; (2) Methods: We elaborated our test results on the bacterial and fungal aerosol reduction by the use of two technical solutions of homemade air purifiers. First, including a mesh filter and ozone generator, second including an ozone generator, mesh filter, and carbon filter. (3) Conclusions: After 20 min of ozone generation, the concentration of bacteria decreased by 78% and 48% without and with a carbon filter, while fungi concentration was reduced in the lower range 63% and 40%, respectively. Based on our test results, we proposed a precise periodical operation of homemade air purifier to maintain the permissible level of ozone for the occupants.