Effect of portable air purifier on indoor air quality: reduced exposure to particulate matter and health risk assessment

The Changing and Predicted Trends in Chronic Obstructive Pulmonary Disease Burden in China, the United States, and India from 1990 to 2030

Background

This study analyzed the burden of chronic obstructive pulmonary disease (COPD) in China, the United States, and India from 1990 to 2019 and projected the trends for the next decade.

Methods

This study utilized the GBD 2019 to compare the age-standardized incidence rate (ASIR), age-standardized mortality rate (ASMR), age-standardized disability-adjusted life years (DALYs) rate, and the proportion attributed to different risk factors in China, the United States, and India. Joinpoint models and autoregressive integrated moving average (ARIMA) models were employed to capture the changing trends in disease burden and forecast outcomes.

Results

From 1990 to 2019, China's age-standardized COPD incidence and mortality rates decreased by 29% and 70%, respectively. In the same period, India's rates decreased by 8% and 33%, while the United States saw an increase of 9% in COPD incidence and a 22% rise in mortality rates. Smoking and ambient particulate matter pollution are the two most significant risk factors for COPD, while household air pollution from solid fuels and low temperatures are the least impactful factors in the United States and India, respectively. The proportion of risk from household air pollution from solid fuels is higher in India than in China and the United States. Predictions for 2030 suggest that the age-standardized DALY rates, ASIR, and ASMR in the United States and India are expected to remain stable or decrease, while China's age-standardized incidence rate is projected to rise.

Conclusion

Over the past three decades, the incidence of COPD has been decreasing in China and India, while showing a slight increase in the United States. Smoking and ambient particulate matter pollution are the primary risk factors for men and women, respectively. The risk of household air pollution from solid fuels in India needs attention.

A systematic review and meta-analysis of field studies of portable air cleaners: Performance, user behavior, and by-product emissions

Indoor air quality is important for the health of building occupants, and public interest in controlling indoor airborne pathogens increased dramatically with the COVID-19 pandemic. Pollutant concentrations can be controlled locally using portable air cleaners (sometimes called air purifiers), which allow occupants to apply air cleaning technology to meet their needs in the location and times that they find appropriate. This paper provides a systematic review of scientific literature that describes field studies of the effectiveness of portable air cleaners. Over 500 papers were considered, and 148 were reviewed in detail, to extract 35 specific research results (e.g., particulate removal performance) or characteristics (e.g., type of building). These were aggregated to provide an overview of results and approaches to this type of research, and to provide meta-analyses of the results. The review includes: descriptions of the geographical location of the research; rate of publications over time; types of buildings and occupants in the field study; types of air cleaner technology being tested; pollutants being measured; resulting pollutant removal effectiveness; patterns of usage and potential barriers to usage by occupants; and the potential for by-product emissions in some air cleaner technologies. An example result is that 83 of the 148 papers measured reductions in fine particulates (PM2.5) and found a mean reduction of 49 % with standard deviation of 20 %. The aggregated results were approximately normally distributed, ranging from finding no significant reduction up to a maximum above 90 % reduction. Sixteen of the 148 papers considered gaseous pollutants, such as volatile organic compounds, nitrogen dioxide, and ozone; 36 papers considered biological pollutants, such as bacteria, viruses, pollen, fungi, etc. An important challenge, common to several studies, is that occupants run the air cleaners for shorter periods and on low airflow rate settings, because of concerns about noise, drafts, and electricity cost, which significantly reduces air cleaning effectiveness.

Assessment of indoor environmental quality and seasonal well-being of students in a combined historic technical school building in Slovakia

One of the major present challenges in the building sector is to construct sustainable and low-energy buildings with a healthy, safe, and comfortable environment. This study is designed to explore long-term impacts of indoor environmental quality (IEQ) parameters in a historic technical school building on the health and comfort of students. The main objective is to identify environmental problems in schools and to direct public policy towards the enhancement of in-service historic buildings. The collected data on five consecutive days in various seasons from five different classrooms indicate allergy in 45% and asthma in 10% of students. Environmental factors, such as temperature, draught, noise, or light, affected 51% of students' attention. Low temperature, unpleasant air, noise, and draught were found to be the most frequent concerns for students. The lowest temperature was measured during spring at 17.6 °C, the lowest humidity of 21.1% in winter, the largest CO2 amount in the air in autumn at 2041 ppm level, and the greatest total volatile organic compounds (TVOC) as 514 µg/m3. The experimental and statistical analysis results suggest the necessity of a comprehensive restoration of the building with a focus on enhancement of IEQ as well as replacement of old non-standard materials. An effective ventilation system is also necessary. The building requires major renovations to preserve its historic features while safeguarding the well-being and comfort of students and staff. Further research is needed on acoustics, lighting, and energy factors as well as the health effects of old building materials.

Efficiency of portable air purification on public buses: A pilot study

High concentrations of fine particulate matter (PM_2.5) have been frequently reported in public transit systems and can cause adverse health effect. The portable air purifier is an inexpensive solution that could potentially clean in-cabin PM_2.5. This study aims to find the PM_2.5 removal efficiency of portable air purifiers in a public transit bus. In various scenarios, after artificially preloading the in-cabin PM_2.5 concentration to 400 μg/m³, the concentrations were measured every 10 s, with and without the intervention of air purifiers. In a test bus with a volume of approximately 62.5 m³, three portable air purifiers were capable of reducing the average concentration of PM_2.5 by 42-74%, from 400 μg/m³, to levels below 15 μg/m³, the acceptable short-term exposure concentration recommended by WHO. When high concentrations of outdoor PM_2.5 entered the bus, purifiers maintained a relatively low level of in-cabin PM_2.5. Air purifiers were more effective in reducing in-cabin PM_2.5 than traditional air filtration and ventilation methods (air conditioning system filtration and door opening) in public transit buses. The deployed air purifiers reduced the concentration of particulate matter inside the bus, which may reduce the health risk of PM_2.5 exposure and the spreading of airborne infections in public transit, thus, implying the potential to enhance passengers' and drivers' health.

Micro-characteristics of a naturally ventilated classroom air quality under varying air purifier placements

A naturally-ventilated operational classroom was instrumented at 18 locations to assess spatial variations of classroom air pollution (CRAP), thermal comfort and ventilation indicators under 10 different scenarios (base scenario without air purifier (AP); three single AP scenarios; three scenarios with two APs at same locations; three scenarios with two APs at different locations). Unlike PM_2.5, monitored PM₁₀ and CO₂ concentrations followed the diurnal occupancy profile. Highest vertical variation (38%) in CO₂ was at the classroom entry zone at 40-300 cm height. CO₂ increased until 225 cm before stratifying further. PM₁₀ increased to highest levels at children sitting height (100 cm) before decreasing to adult breathing height (150 cm). Highest horizontal variations in CO₂ (PM₁₀) were 29% (22%) at 40 cm height between the entry and occupied zones. Teachers' exposure to CO₂ (PM₁₀) in breathing zone varied by up to 6% (3%); the corresponding variations across monitored locations were up to 14% (19%). Teachers' exposure to CO₂ was up to 13% higher than that of children and 18% lower for PM₁₀. Traffic emissions (PM_2.5 and NO_x), secondary pollutants (VOCs and O₃), thermal comfort parameters and noise level in the classroom varied insignificantly among scenarios. PM₁₀ reduction was not doubled by using two air purifiers, which were most effective when placed within the highest PM concentration zone. Cross-comparisons of scenarios showed: use of AP reduced classroom's spatial average PM₁₀ up to 14%; PM₁₀ was reduced by increasing the AP's filtration capacity; and AP had insignificant impact on spatial average CO₂. PM₁₀ showed a maximum reduction of 46% (teacher zone), 62% (occupied zone) and 50% (entry zone) at children's breathing height, depending on usage scenario. This study produced high-resolution data for validating the detailed numerical models for classrooms and informing decision-making on AP's placement to minimise children's exposure to CRAP and re-breathed CO₂.