Efficiency of an Air Cleaner Device in Reducing Aerosol Particulate Matter (PM) in Indoor Environments

Potential causal associations of PM2.5 and osteoporosis: a two-sample mendelian randomization study

Background: Observational studies suggest a potential association between atmospheric particulate matter 2.5 (PM2.5) and osteoporosis, but a causal association is unclear due to the presence of confounding factors. Methods: We utilized bone mineral density indices at four specific sites to represent osteoporosis: femoral neck (FN-BMD), lumbar spine (LS-BMD), forearm (FA-BMD), and heel (HE-BMD). The PM2.5 data was obtained from the UK Biobank database, while the datasets for FN-BMD, LS-BMD, and FA-BMD were obtained from the GEFOS database, and the dataset for HE-BMD was obtained from the EBI database. A two-sample Mendelian randomization analysis was conducted using mainly the inverse variance weighted method, horizontal pleiotropy and heterogeneity were also assessed. Results: The results indicated that PM2.5 was not correlated with a decrease in FN-BMD (β: -0.305, 95%CI: -0.762, 0.153), LS-BMD (β: 0.134, 95%CI: -0.396, 0.666), FA-BMD (β: -0.056, 95%CI: -1.172,1.060), and HE-BMD (β: -0.084, 95%CI: -0.261,0.093). Additionally, acceptable levels of horizontal pleiotropy and heterogeneity were observed. Conclusion: In contrast to most observational studies, our research did not discover a potential causal relationship between PM2.5 and the development of osteoporosis.

Preliminary Air Quality and Microclimatic Conditions Study in the Santuario della Beata Vergine dei Miracoli in Saronno (VA)

In the present work, the microclimatic conditions (temperature (T), relative humidity (RH), and illuminance (I)), together with the air quality (both aerosol particulate matter (PM) and gaseous pollutants), were monitored to evaluate the environmental conditions inside the Santuario della Beata Vergine dei Miracoli in Saronno (VA), a masterpiece of the Italian Renaissance. For this purpose, dataloggers were used to carry out the T, RH, and I measurements, whereas an optical particle counter (OPC) was employed to perform the particle count and determine the concentration of the aerosol PM. Finally, diffusive passive samplers were used to determine the concentration of nitrogen dioxide (NO2) and BTEX (benzene, toluene, ethylbenzene, and xylenes). To identify possible spatial variations, the studies were conducted at different sites and different heights in the Sanctuary. Particular focus was given to the Easter week during which liturgical services attracting large numbers of people were carried out. Additionally, a comparison with the outdoor values was performed to highlight the accumulation phenomena and other variations in the concentrations of the species. Despite the indoor concentrations of pollutants and variations in the thermohygrometric parameters being generally lower compared to the outdoors (e.g., 5.2-15.0 µg m-3 versus 17.7-45.3 µg m-3 for NO2), the microclimatic conditions were often not in line with the Italian legislation and technical standards.

Effectiveness of a Protocol to Reduce Children's Exposure to Particulate Matter and NO2 in Schools during Alert Days

Reducing children's exposure to air pollutants should be considered a primary goal, especially for the most vulnerable subjects. The goal of this study was to test the effectiveness of applying a protocol in the event of alert days, i.e., days with forecasted PM₁₀ levels above the EU limit value (50 µg/m³). The test was conducted, before the onset of SARS-CoV-2 restrictions, in a classroom of a primary school in Parma (Italy)-a highly polluted area in Northern Italy. The protocol included indications for the frequency of opening windows and doors, as well as the activation of an air purifier. Teachers and students were asked to apply the protocol only in the event of alert days, while no indications were provided for non-alert days. A monitoring system measuring PM₁, PM_2.5, PM₁₀, CO₂, and NO₂ was deployed in the classroom. Measurements of the same parameters were also performed outdoors near the school. The application of the protocol reduced the indoor/outdoor (I/O) ratio for all toxic pollutants. The reduction was also remarkable for PM₁₀-the most critical air quality parameter in the study area (1.5 and 1.1 for non-alert and alert days, respectively). Indoor concentrations of PM₁₀-especially during non-alert days-were often higher than outdoors, showing a major contribution from resuspension due to the movement of people and personal cloud. The protocol did not cause any increase in indoor CO₂ levels. Our findings showed that the application of a ventilation protocol together with the contribution of an air purifier may represent an effective way to reduce children's exposure to air pollution during severe air pollution episodes. Considering the onset of COVID-19 and the airborne transmission of pathogens, this protocol now has more meaningful implications for children's welfare, and can be integrated with protocols designed as measures against the spread of SARS-CoV-2.

Portable air cleaners and residential exposure to SARS-CoV-2 aerosols: A real-world study

Individuals with COVID-19 who do not require hospitalization are instructed to self-isolate in their residences. Due to high secondary infection rates in household members, there is a need to understand airborne transmission of SARS-CoV-2 within residences. We report the first naturalistic intervention study suggesting a reduction of such transmission risk using portable air cleaners (PACs) with HEPA filters. Seventeen individuals with newly diagnosed COVID-19 infection completed this single-blind, crossover, randomized study. Total and size-fractionated aerosol samples were collected simultaneously in the self-isolation room with the PAC (primary) and another room (secondary) for two consecutive 24-h periods, one period with HEPA filtration and the other with the filter removed (sham). Seven out of sixteen (44%) air samples in primary rooms were positive for SARS-CoV-2 RNA during the sham period. With the PAC operated at its lowest setting (clean air delivery rate [CADR] = 263 cfm) to minimize noise, positive aerosol samples decreased to four out of sixteen residences (25%; p = 0.229). A slight decrease in positive aerosol samples was also observed in the secondary room. As the world confronts both new variants and limited vaccination rates, our study supports this practical intervention to reduce the presence of viral aerosols in a real-world setting.

Quantitative filter forensics for semivolatile organic compounds in social housing apartments

Residents from low-income social housing are vulnerable to adverse health effects from indoor air pollution. Particle-bound concentrations of eight phthalates and 12 polycyclic aromatic hydrocarbons (PAHs) in indoor air were measured using quantitative filter forensics with portable air cleaners deployed for three one-week periods from 2015 to 2017. The sample included 143 apartments across seven multi-unit social housing buildings in Toronto, Canada, that went through energy retrofits in 2016. Eight phthalates and six PAHs were found in more than 50% of the apartments in either of the three sampling periods. Di(2-ethylhexyl) phthalate (DEHP) and phenanthrene were the dominant phthalate and PAH, with median concentrations of 146, 143, and 130 ng/m³ and 1.51, 0.58, and 0.76 ng/m³ in the late spring of 2015, and after retrofits in late spring 2017 and winter of 2017, respectively. SVOC concentrations were generally lower after energy retrofits, with significant differences for phenanthrene, fluoranthene, and pyrene. Lower concentrations post-retrofit may be related to less overheating and less need for opening windows. Concentrations of phthalates and PAHs in this study were similar to or higher than those reported in the literature. Results suggest that the use of portable air filters is a promising method to assess concentrations of indoor particle-bound SVOCs.

Low-Cost Air Purifier Prototype Using a Ventilating Fan and Pump Against Haze Pollution

This study aimed to focus on the design and development of low-cost do-it-yourself (DIY) air purifiers, using a ventilating fan, air pump, water pump, and an ultrasonic generator that can be used during the haze pollution. Six types of household air purifiers were fabricated. The amount of particulate matter (PM) and carbon dioxide (CO2) levels were recorded at 0, 10, 20, 30, and 60 min (min), then, repeated 3 times. After 10 min of the 3rd experiment of each study, the last measurement of air pollution would be recorded. The results showed at 60 min, the high-efficiency particulate air (HEPA) filter and electrostatic fiber was the best technique regarding reduction of PM and CO2 levels. The highest PM reduction rate had occurred at 30 min using an air pump procedure (99.330 to 100%). The CO2 levels of all experiments had fluctuated at different times. After 10 min of a closed machine, PM levels of all air purifier systems were decreased, except HEPA filter and electrostatic fiber types. In conclusion, the best method for reducing particulate matter and cost without taking humidity into account is an air pump technique, whereas the HEPA filter and electrostatic fiber method is the best choice for lowering PM levels without increasing humidity and vapor production.

Prospective association of air purifier use during pregnancy with the neurodevelopment of toddlers in the Japan Environment and Children's Study

We examined the association between maternal air purifier use during pregnancy and neurodevelopmental delay in toddlers by analysing data from 82,457 mother-toddler pairs. Air purifier use was measured using a simple yes/no question. Developmental delays at 1.5, 2.0, 2.5, and 3.0 years were assessed using the Ages and Stages Questionnaire, Third Edition. Generalized additive mixed model analysis with 21 covariates revealed that air purifier use was associated with lower prevalence of developmental delay in all five areas—communication, gross motor, fine motor, problem solving, and personal-social—at all four time points (adjusted risk ratios ranged from 0.827 to 0.927, and only one 95% confidence interval crossed the reference). These findings suggest a negative association between air purifier use during pregnancy and neurodevelopmental delay in toddlers.

Trial registration: UMIN000030786 (15/01/2018).

Improving indoor air quality through an air purifier able to reduce aerosol particulate matter (PM) and volatile organic compounds (VOCs): Experimental results

The adverse effects of fine particulate matter (PM) and many volatile organic compounds (VOCs) on human health are well known. Fine particles are, in fact, those most capable of penetrating in depth into the respiratory system. People spend most of their time indoors where concentrations of some pollutants are sometimes higher than outdoors. Therefore, there is the need to ensure a healthy indoor environment and for this purpose the use of an air purifier can be a valuable aid especially now since it was demonstrated that indoor air quality has a high impact on spreading of viral infections such as that due to SARS-COVID19. In this study, we tested a commercial system that can be used as an air purifier. In particular it was verified its efficiency in reducing concentrations of PM10 (particles with aerodynamic diameter less than 10 μm), PM2.5 (particles with aerodynamic diameter less than 2.5 μm), PM1 (particles with aerodynamic diameter less than 1 μm), and particles number in the range 0.3 μm-10 μm. Furthermore, its capacity in reducing VOCs concentration was also checked. PM measurements were carried out by means of a portable optical particle counter (OPC) instrument simulating the working conditions typical of a household environment. In particular we showed that the tested air purifier significantly reduced both PM10 and PM2.5 by 16.8 and 7.25 times respectively that corresponds to a reduction of about 90% and 80%. A clear reduction of VOCs concentrations was also observed since a decrease of over 50% of these gaseous substances was achieved.

Effect of filter collection efficiency on the clean air delivery rate in an air cleaner

The performance of an air cleaner is evaluated by the clean air delivery rate (CADR), which is defined as the measure of the delivery of contaminant-free air. Herein, we conducted comparative analyses of various particulate air filters with various collection efficiencies. We installed each filter in identical commercial air cleaners to determine the effects of the collection efficiency on the CADR. Three different filters (E11, E12, and H13 classes) were prepared to determine the effects of the filter collection efficiency and pressure drop on the air cleaner performance (ie, the CADR). Based on experimental data, filters E11 and E12 had similar CADRs and flow rates. However, filter H13, which had the highest collection efficiency and the lowest flow rate, had the lowest CADR. This indicates that even if a filter with higher collection efficiency is installed in an air cleaner, the larger pressure drop causes a reduction in the air flow rate. The CADR value is widely distributed for a flow rate range for commercially available models; however, the collection efficiencies for most air cleaners on the market lie in a narrow range. Therefore, the flow rate has the most direct impact on the performance of a commercial air cleaner.

Evaluation on Air Purifier's Performance in Reducing the Concentration of Fine Particulate Matter for Occupants according to its Operation Methods

Fine particulate matter entering the body through breathing cause serious damage to humans. In South Korea, filter-type air purifiers are used to eliminate indoor fine particulate matter, and there has been a broad range of studies on the spread of fine particulate matter and air purifiers. However, earlier studies have not evaluated an operating method of air purifiers considering the inflow of fine particulate matter into the body or reduction performance of the concentration of fine particulate matter. There is a limit to controlling the concentration of fine particulate matter of the overall space where an air purifier is fixed in one spot as the source of indoor fine particulate matter is varied. Accordingly, this study analyzed changes in the concentration of indoor fine particulate matter through an experiment according to the discharging method and location of a fixed air purifier considering the inflow route of fine particulate matter into the body and their harmfulness. The study evaluated the purifiers' performance in reducing the concentration of fine particulate matter in the occupants' breathing zone according to the operation method in which a movable air purifier responds to the movement of occupants. The results showed the concentration of fine particulate matter around the breathing zone of the occupants had decreased by about 51 μg/m³ compared to the surrounding concentration in terms of the operating method in which an air purifier tracks occupants in real-time, and a decrease of about 68 μg/m³ in terms of the operating method in which an air purifier controls the zone. On the other hand, a real-time occupant tracking method may face a threshold due to the moving path of an air purifier and changes in the number of occupants. A zone controlling method is deemed suitable as an operating method of a movable air purifier to reduce the concentration of fine particulate matter in the breathing zone of occupants.

Assessment of the Equivalence of Low-Cost Sensors with the Reference Method in Measuring PM10 Concentration Using Selected Correction Functions

The aim of the work is to demonstrate the possibility of building models to correct the results of measurements of particulate matter PM10 concentrations obtained using low-cost devices. Such devices apply the optical method to values comparable with those obtained using the reference gravimetric method. An additional goal is to show that the results corrected in this way can be used to carry out the procedure for testing equivalence of these methods. The study used generalized regression models (GRMs) to construct corrective functions. The constructed models were assessed using the coefficients of determination and the methodology of calculating the measurement uncertainty of the device. Measurement data from the two tested devices and the reference method were used to estimate model parameters. The measurement data were collected on a daily basis from 1 February to 30 June 2018 in Nowy Sącz. Regression allowed building multiple models with various functional forms and very promising statistical properties as well as good ability to describe the variability of reference measurements. These models also had very low values of measurement uncertainty. Of all the models constructed, a linear model using the original PM10 concentrations from the tested devices, air humidity, and wind speed was chosen as the most accurate and simplest model. Apart from the coefficient of determination, expanded relative uncertainty served as the measure of quality of the obtained model. Its small value, much lower than 25%, indicates that after correcting the results it is possible to carry out the equivalence testing procedure for the low-cost devices and confirm the equivalence of the tested method with the reference method.

Prospective Association of Air-Purifier Usage during Pregnancy with Infant Neurodevelopment: A Nationwide Longitudinal Study-Japan Environment and Children's Study (JECS)

Fetal exposure to particulate matter (PM) is associated with infant developmental delay likely via neuroinflammation and prefrontal cortex lesions; however, whether air-purifier usage, which can reduce indoor PM levels, is related to infant developmental delay remains unknown. We therefore examined the prospective relationship between air-purifier usage during pregnancy and infant developmental delay by analyzing 82,441 mother-infant pairs using a simple yes/no questionnaire. Developmental delays at 6 and 12 months were assessed in five areas using the Ages and Stages Questionnaire, Third Edition. A generalized linear mixed model analysis was used to derive adjusted odds ratios (AORs) and 95% confidence intervals (95% CIs) while controlling for 20 covariates. The analysis revealed that air-purifier usage was associated with developmental delays in fine motor (AOR: 0.91, 95% CI: 0.83-0.99) and problem solving (AOR: 0.83, 95% CI: 0.77-0.90) at 6 months and in communication (AOR: 0.86, 95% CI: 0.79-0.93), fine motor (AOR: 0.87, 95% CI: 0.82-0.92), problem solving (AOR: 0.83, 95% CI: 0.77-0.88), and personal-social (AOR: 0.79, 95% CI: 0.72-0.86) at 12 months. In conclusion, a negative association exists between air-purifier usage during pregnancy and infant neurodevelopmental delay that strengthens with time. Our results outline the potential role of air purifiers in inhibiting infant neurodevelopmental delay.