Negative ions offset cardiorespiratory benefits of PM2.5 reduction from residential use of negative ion air purifiers

Interventions for reducing exposure to air pollution from landscape fires in a changing environment: A systematic review

Emissions from more frequent and prolonged landscape fires (wildfires, risk reduction fires, agricultural burning) can expose populations to high levels of air pollution and exacerbate a range of health conditions. This systematic review aims to map, evaluate, and synthesise the scientific literature reporting interventions that can reduce exposure to landscape fire smoke (LFS). Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we searched PubMed, Scopus and Web of Science and reviewed relevant literature published until March 2024. Thirty-three studies from four countries met the eligibility criteria. Of the interventions evaluated, air filtration was the most frequently reported, and included use of portable air cleaners (PACs) with high efficiency particulate air (HEPA) filters, ventilation systems with standard and upgraded filters, and low-cost fan filter units (FFU). The effectiveness of PACs for fine particulate matter (PM2.5) reduction ranged between 54 %-92 %. In naturally ventilated residences, concentrations of PM2.5 were 0-44 % lower indoors, and depended on the duration of LFS, building operation, and permeability. Mechanical ventilation with minimum efficiency reporting value (MERV) 5/8 filters in buildings reduced LFS PM2.5 levels by 18-58 %; however, use of higher rated filters (e.g., MERV 12/13) achieved reductions of up to 87 %. Communication interventions, including smartphone apps and alerts/messages from various media sources (e.g., radio, television, internet) had mixed results; nevertheless, inclusion of spirometry and asthma control surveys during app use could improve health outcomes for vulnerable groups. The efficacy of facemasks (N95/P2) was up to 94 % for single pass PM2.5 removal, although they were relatively underutilised. Clean air shelters in public buildings can potentially provide a place for exposure reduction and social support, but have not been sufficiently tested during LFS events. Further research is needed on the effectiveness of interventions during prolonged smoke events, and in low- and middle-income countries.

Cleaning indoor air-what works for respiratory health: An updated literature review and recommendations

Indoor air pollution is a growing public health concern globally and is associated with increased respiratory symptoms and morbidity. Individuals spend most of their time indoors, and pollutant-related health effects are often driven by the indoor environment. Understanding effective interventions to improve indoor air quality and their impact on respiratory outcomes is key to decreasing the burden of air pollution for high-risk populations across the life-span. This review applies a hierarchy of interventions framework specific to respiratory health effects and focuses on recent studies of interventions to improve indoor air quality among high-risk populations with chronic respiratory disease published in the past 3 years. While policy and source control interventions are likely the most effective and equitable approaches to improve indoor air quality and benefit population health, these were less extensively investigated. Engineering interventions, such as air cleaner interventions, were the most widely studied. Several studies, including those focused on asthma and chronic obstructive pulmonary disease, demonstrated improvement in symptoms and medication receipt with interventions in both home- and school-based settings. Combined multilevel interventions with engineering and behavioral interventions led to improved respiratory outcomes in some, but not all, studies. Placing the recent work in the context of the broader literature, we identify gaps in research. Further research is needed to understand intervention effectiveness over time and an increased focus on policy and source control interventions that can mitigate risk in vulnerable populations.

A super sandstorm altered the abundance and composition of airborne bacteria in Beijing

Sandstorm, which injects generous newly emerging microbes into the atmosphere covering cities, adversely affects the air quality in built environments. However, few studies have examined the change of airborne bacteria during severe sandstorm events. In this work, we analyzed the airborne bacteria during one of the strongest sandstorms in East Asia on March 15th, 2021, which affected large areas of China and Mongolia. The characteristics of the sandstorm were compared with those of the subsequent clean and haze days. The composition of the bacterial community of air samples was investigated using quantitative polymerase chain reaction (qPCR) and high-throughput sequencing technology. During the sandstorm, the particulate matter (PM) concentration and bacterial richness were extremely high (PM2.5: 207 µg/m3; PM10: 1630 µg/m3; 5700 amplicon sequence variants/m3). In addition, the sandstorm brought 10 pathogenic bacterial genera to the atmosphere, posing a grave hazard to human health. As the sandstorm subsided, small bioaerosols (0.65-1.1 µm) with a similar bacterial community remained suspended in the atmosphere, bringing possible long-lasting health risks.

Experimental study on bioaerosols behavior and purification measures in a subway compartment

Bioaerosols in public transportation systems raise critical environmental concerns, seriously threatening passenger health and safety. In this study, we investigate the spread characteristics of bioaerosols in a standard type-B subway compartment using both air sampling and sediment sampling methods. Additionally, without compromising indoor passenger comfort, two self-designed air purification devices, based on intense field dielectric (IFD) and dielectric barrier discharge (DBD) technologies, respectively, are successfully applied for the improvement of the subway air quality. The results show that bioaerosols can propagate rapidly throughout the entire compartment in 5 min via airborne transmission. Under the effect of the symmetric air ducts and compartment structure, the difference in bioaerosol concentration in the air is less than 10% between both ends of the compartment. Concurrent substantial bioaerosol deposition on the ground, seats, and windows underscores the risk of contact transmission. Furthermore, the real-time purification rates of the two devices integrated into the air conditioning system reach 59.40% and 44.98%, respectively. With their demonstrated high efficiency in purifying bioaerosols and modular design featuring low energy consumption, easy cleaning, and reusability, these devices stand out as viable long-term solutions for large traffic vehicles. These research findings provide practical equipment recommendations and installation strategies for optimizing indoor air quality in subways and are applicable to other similar transportation systems.

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.

An updated systematic review and meta-analysis on portable air cleaners and blood pressure: Recommendations for users and manufacturers

Fine particulate matter (PM2.5) air pollution is a leading contributor to the global burden of cardiovascular disease (CVD). One important underlying mechanism is an increase in blood pressure (BP). A growing number of studies have reported a beneficial effect of portable air cleaners (PACs) on systolic and diastolic BP; SBP and DBP. We conducted an updated systematic review and meta-analysis of studies using true versus sham mode filtration reporting the effects on BP. Of 214 articles identified up to February 5, 2023, seventeen (from China, USA, Canada, South Korea and Denmark) enrolling approximately 880 participants (484 female) met the inclusion criteria for meta-analyses. Aside from studies conducted in China, research on PACs and BP has been conducted in relatively low pollution settings. Mean indoor PM2.5 concentrations during the active and sham mode purification were 15.9 and 41.2 µg/m3, respectively. The mean efficiency of PACs against indoor PM2.5 was 59.8 % (ranging from 23 % to 82 %). True mode filtration was associated with a pooled mean difference of - 2.35 mmHg (95 % confidence interval [CI]: - 4.5, - 0.2) and - 0.81 mmHg (95 % CI: - 1.86, 0.24) in SBP and DBP, respectively. After removing the studies with high risk of bias, the magnitude of the pooled benefits on SBP and DBP increased to - 3.62 mmHg (95 % CI: - 6.69, - 0.56) and - 1.35 mmHg (95 % CI: - 2.29, - 0.41), respectively. However, there are several barriers to the use of PACs, specifically in low- and middle-income countries (LMICs), such as the initial purchase cost and filter replacements. There may be several avenues to help overcome these economic burdens and improve cost effectiveness, such as implementing government or other subsidized programs to distribute PACs targeting vulnerable and higher-risk individuals. We propose that environmental health researchers and healthcare providers should be better trained to educate the public regarding the use of PACs to reduce the impacts of PM2.5 on cardiometabolic diseases globally.

Biological effects of negative air ions on human health and integrated multiomics to identify biomarkers: a literature review

Environmental pollution seriously affects human health. The concentration of negative air ions (NAIs), which were discovered at the end of the nineteenth century, is one of the factors used to evaluate air quality. Additionally, NAIs have been widely considered markers by scholars due to their unique biological function. The aim of this study was to summarize existing research and propose future research on the generation and temporal and spatial dynamic patterns of NAIs concentrations as well as the relationship between NAIs and human health. We identified 187 studies (published January 2013-January 2023) that met our inclusion criteria. Fourteen English studies evaluated the effects of NAIs on depression, the cardiovascular system, the respiratory system, reproduction and development, cognition, and sports muscle injury. Only two studies reported the associations of NAIs exposure with metabolic omics. NAIs concentrations vary temporally with solar radiation, air temperature, and relative humidity, while the temporal dynamic patterns of NAIs are affected by season, time, meteorological factors, air quality index, geographical location, forest vegetation, and other factors. Researchers have shown that exposure to NAIs may benefit our health by changing amino acid metabolism, which mainly manifests as increased anti-inflammation and reduced inflammation and antioxidation. Furthermore, exposure to NAIs promotes energy production, affects the expression of c-fos, and regulates 5-HT levels. There has been considerable interest in the potential effects of NAIs on human health and well-being, but the conclusions have been inconsistent and the mechanisms remain unclear. The use of omics to elucidate the biological mechanism of NAIs is relatively new and has some advantages.

Can individual protective measures safeguard cardiopulmonary health from air pollution? A systematic review and meta-analysis

Evidence supporting the effect of individual protective measures (IPMs) on air pollution is relatively scarce. In this study, we performed a systematic review and meta-analysis to investigate the effects of air purifiers, air-purifying respirators, and cookstove changes on cardiopulmonary health outcomes. We searched PubMed, Scopus, and Web of Science until December 31, 2022, 90 articles and 39,760 participants were included. Two authors independently searched and selected the studies, extracted information, and assessed each study's quality and risk of bias. We performed meta-analyses when three or more studies were available for each IPMs, with comparable intervention and health outcome. Systematic review showed that IPMs were beneficial in children and elderly with asthma along with healthy individuals. Meta-analysis results showed a reduction in cardiopulmonary inflammation using air purifiers than in control groups (with sham/no filter) with a decrease in interleukin 6 by -0.247 μg/mL (95% confidence intervals [CI] = -0.413, -0.082). A sub-group analysis for air purifier as an IPMs in developing counties reduced fractional exhaled nitric oxide by -0.208 ppb (95% confidence intervals [CI] = -0.394, -0.022). However, evidence describing the effects of air purifying respirator and cook stove changes on cardiopulmonary outcomes remained insufficient. Therefore, air purifiers can serve as efficient IPMs against air pollution. The beneficial effect of air purifiers is likely to have a greater effect in developing countries than in developed countries.

Large-scale evaluation of microorganism inactivation by bipolar ionization and photocatalytic devices

The COVID-19 pandemic has raised awareness in the spread of disease via airborne transmission. As a result, there has been increasing interest in technologies that claim to reduce concentrations of airborne pathogens in indoor environments. The efficacy of many of these emerging technologies is not fully understood, and the testing that has been done is often conducted at a small scale and not representative of applied settings. There is currently no standard test method for evaluating air treatment technologies, making it difficult to compare results across studies or technology types. Here, a consistent testing approach in an operational-scale test chamber with a mock recirculating heating, ventilation, and air conditioning (HVAC) system was used to evaluate the efficacy of bipolar ionization and photocatalytic devices against the non-enveloped bacteriophage MS2 in the air and on surfaces. Statistically significant differences between replicate sets of technology tests and control tests (without technologies active) are apparent after 1 h, ranging to a maximum of 0.88 log10 reduction for the bipolar ionization tests and 1.8 log10 reduction for the photocatalytic device tests. It should be noted that ozone concentrations were elevated above background concentrations in the test chamber during the photocatalytic device testing. No significant differences were observed between control and technology tests in terms of the amount of MS2 deposited or inactivated on surfaces during testing. A standardized, large-scale testing approach, with replicate testing and time-matched control conditions, is necessary for contextualizing laboratory efficacy results, translating them to real-world conditions, and for facilitating technology comparisons.

Associations of forest negative air ions exposure with cardiac autonomic nervous function and the related metabolic linkages: A repeated-measure panel study

Forest environment has many health benefits, and negative air ions (NAI) is one of the major forest environmental factors. Many studies have explored the effect of forest environment on cardiac autonomic nervous function, while forest NAI in the among function and the underlying mechanism still remain unclear. To explore the associations and molecular linkages between short-term exposure to forest NAI and heart rate variability (HRV), a repeated-measure panel study was conducted among 31 healthy adults. Participants were randomly selected to stay in a forest park for 3 days and 2 nights. Individual exposures including NAI were monitored simultaneously and HRV indices were measured repeatedly at the follow-up period. Urine samples were collected for non-targeted metabolomics analysis. Mixed-effect models were adopted to evaluate associations among NAI, HRV indices and metabolites. The median of NAI concentration was 68.11 (138.20) cm^-3 during the study period. Short-term exposure to forest NAI was associated with the ameliorative HRV indices, especially the excitatory parasympathetic nerve. For instance, per interquartile range increase of 5-min moving average of NAI was associated with 9.99 % (95%CI: 8.95 %, 11.03 %) increase of power in high frequency. Eight metabolites were associated with NAI exposure. The down-regulated tyrosine metabolism was firstly observed, followed by other amino acid metabolic alterations. The NAI-related metabolic changes reflect the reduction of inflammation and oxidative stress. HRV indices were associated with 25 metabolites, mainly including arginine, proline and histidine metabolism. Short-term exposure to forest NAI is beneficial to HRV, especially to the parasympathetic nerve activity, by successively disturbing different metabolic pathways which mainly reflect the increased anti-inflammation and the reduced inflammation. The results will provide epidemiological evidences for developing forest therapy and improving cardiac autonomic nervous function.

Negative air ions through the action of antioxidation, anti-inflammation, anti-apoptosis and angiogenesis ameliorate lipopolysaccharide induced acute lung injury and promote diabetic wound healing in rat

Negative air ions (NAIs) being bioactive and negative charged molecules may confer antioxidant and anti-inflammatory activity. We assessed the effect of NAIs on two inflammatory diseases in animal models including lipopolysaccharide (LPS) induced acute lung injury (ALI) and wound healing in diabetic rats. We used intra-tracheal infusion of LPS to induce ALI and made a full-thickness cutaneous wound in streptozotocin-induced diabetic female Wistar rats. We evaluated NAIs effects on reactive oxygen species amount, leukocyte infiltration, wound healing rate, western blot, and immunohistochemistry in the lungs of ALI and skin sections of wounds. Our data found NAIs exposed saline displayed higher antioxidant activity vs. non-exposed saline. NAIs exposure did not significantly affect arterial blood pressure and respiratory frequency in control and LPS treated groups. LPS increased leukocyte infiltration, caspase 3/Poly-ADP-ribose-polymerase-mediated apoptosis formation and decreased Beclin-1/LC3-II-mediated autophagy in lungs. NAIs exposure conferred pulmonary protection by depressed leukocyte infiltration and caspase 3/Poly-ADP-ribose-polymerase mediated apoptosis and enhanced LC3-II-mediated autophagy in LPS induced ALI. NAIs treatment resulted in a significantly accelerated wound closure rate, decreased erythrocyte accumulation and leukocyte infiltration mediated oxidative stress and inflammation, and upregulated expression of skin collagen, vascular endothelial growth factor receptor-2 (VEGFR-2) and factor transforming growth factor-beta 1 (TGF-β1) vs non-treated group. Based on these results, it is suggested that NAIs conferred a protection through the upregulating LC3-II-dependent autophagy mechanism and downregulating leukocyte infiltration mediated inflammation and caspase 3/Poly-ADP-ribose-polymerase signaling in the LPS-treated ALI and promoted diabetic wound healing through the enhancing skin collagen synthesis, VEGFR-2 and TGF-β1 pathways.

Association of long-term exposure to PM2.5 in workplace with fasting plasma glucose among asymptomatic adults: A multicenter study in North China

BACKGROUND

The impacts of long-term high exposure to PM2.5 in workplace on glucose metabolism in asymptomatic working adults (AWAs) have rarely been explored.

OBJECTIVES

To assess the relationship between long-term exposure to workplace PM2.5 and glucose metabolism in asymptomatic general working adults in heavily polluted regions.

METHODS

We used the baseline data of the asymptomatic working participants from the Beijing-Tianjin-Hebei Medical Examination Cohort, which recruited adults undergoing medical examinations. A machine learning-based spatial-temporal model was used to estimate daily average PM2.5 concentrations in the participants' workplaces. We assessed the association of long-term PM2.5 concentrations (three years prior to the interview) and fasting plasma glucose (FPG) using generalized linear mixed-effects models (GLMM) with inclusion of potential confounders. Stratified analyses by sex, age, BMI and smoking status, and two pollutant models were further performed.

RESULTS

A total of 37,619 individuals were interviewed and 28,865 were included in the analyses. The mean FPG was 5.20 (0.96) mmol/L, and the estimated three-year average concentration of PM2.5 exposure was 69.51 (6.92) μg/m3. We detected a significant association of long-term exposure to workplace PM2.5 and FPG, a 10 µg/m3 increase in the long-term workplace PM2.5 exposure was associated with 0.075 (95%CI: 0.050-0.100) mmol/L elevated FPG and 25% (OR = 1.25, 95%CI: 1.05-1.50) elevated odds of abnormal fasting glucose metabolism with control of the potential confounding. The detected association between workplace PM2.5 and FPG metabolism remained significant in males, individuals aged > 44 years, overweight and/or obese people, both smokers and non-smokers, and when NO2, SO2, O3, and CO were included in the model.

CONCLUSIONS

Long-term exposure to workplace PM2.5 was associated with elevated FPG and/or odds of abnormal glucose metabolism among AWAs. Male, middle-aged, overweight and/or obese AWAs were more susceptible to workplace PM2.5 regardless of smoking status.

Systematic summary and analysis of Chinese HVAC guidelines coping with COVID-19

Heating, Ventilation, and Air-Conditioning (HVAC) system that is almost indispensable service system of modern buildings is recognized as the most important engineering control measure against pandemics. However, the effectiveness of HVAC systems has been questioned on their ability to control airborne transmission. After the outbreak of COVID-19, China has controlled the spread within a relatively short period. Considering the large population, high population density, busy transportation and the overall underdeveloped economy, China's control measures may have some implications to other countries, especially those with limited resources. This paper intends to provide a systematic summary of Chinese ventilation guidelines issued to cope with COVID-19 transmission. The following three aspects are the main focus of these guidelines: (1) general operation and management schemes of various types of HVAC systems, (2) operation and management schemes of HVAC system in typical types of buildings, and (3) design schemes of HVAC system of makeshift hospitals. In addition, some important differences in HVAC guidelines between China and other countries/institutions are identified and compared, and the possible reasons are discussed. Further discussions are made on the following topics, including the required fresh air supply, the extended operation time, the use of auxiliary equipment, the limited capacity of existing systems, and the use of personalized systems.

Nickel Coated Polyester Sponge for Delaying the Specific Aggregation of Fine Particles Induced by Negative Air Ions

Negative air ions (NAIs) produced by corona discharge is often used for indoor air purification; however, the specific aggregation of suspended particles caused by NAIs, especially fine particles (FPs), needs to be considered. Here, a nickel coated conductive sponge (NCCS) was used as the main adsorption interface for delaying the obstinate aggregation caused by NAIs on another surface. The specific aggregation of FPs is caused by the directional transfer of electric charge, and the oxidation characteristic of NAIs results in the surface reaction of FPs simultaneously. The conductivity and roughness of the adsorption interface determine the migration direction and enrichment number of FPs, respectively. Nickel coated conductive sponge with high conductivity and high specific surface area can effectively adsorb the FPs affected by NAIs and can effectively delay the specific aggregation on the surface of indoor objects.

Electric charge of atmospheric nanoparticles and its potential implications with human health

This research presents a pilot project developed within the framework of the COST Action 15,211 in which atmospheric nanoparticles were measured in July 2018, in a maritime environment in the city of Santander in Northern Spain. ELPI® + (Electrical Low-Pressure Impactor) was used to measure nanoparticle properties (electric charge, number, size distribution and surface area) from 6 nm to 10,000 nm with 14 size channels. This study focused on the range between 6 and 380 nm. It considered atmospheric nanoparticle electric charge with surface area, deposited and number by size distribution at human respiratory tract regions in a standard person in Santander according to the human respiratory tract model of ICRP 94. An empirical distribution of nanoparticles deposited in the human respiratory tract model and its electric charge is presented for the city of Santander as the main output. Percentages of total and regional deposition in human respiratory tract model were calculated for the Atlantic climate. Nanoparticles have shown an alveolar surface area deposition plateau with a size distribution range between 6 nm to 150 nm. Negative charge of nanoparticles was clearly associated with primary atmospheric nanoparticles being mainly deposited in the alveolar region where a Brownian mechanism of deposition is predominant. We can demonstrate that electric charge may be a key element in explaining Brownian deposition of the smallest particles in the human respiratory tract and that it can be linked to theoretical positive and negative impacts on human health according to several biometeorological studies. To support our analysis, aerosol samples were characterized with transmission electron microscopy and Confocal Raman spectrometer to determinate morphology, size, chemical composition, and structure. The toxicological effects of the samples with the alveolar surface area had a greater deposition, remain to be studied.

Negative Ion Purifier Effects on Indoor Particulate Dosage to Small Airways

Indoor air quality is an important health factor as we spend more than 80% of our time indoors. The primary type of indoor pollutant is particulate matter, high levels of which increase respiratory disease risk. Therefore, air purifiers are a common choice for addressing indoor air pollution. Compared with traditional filtration purifiers, negative ion air purifiers (NIAPs) have gained popularity due to their energy efficiency and lack of noise. Although some studies have shown that negative ions may offset the cardiorespiratory benefits of air purifiers, the underlying mechanism is still unclear. In this study, we conducted a full-scale experiment using an in vitro airway model connected to a breathing simulator to mimic inhalation. The model was constructed using computed tomography scans of human airways and 3D-printing technology. We then quantified the effects of NIAPs on the administered dose of 0.5-2.5 μm particles in the small airway. Compared with the filtration purifier, the NIAP had a better dilution effect after a 1-h exposure and the cumulative administered dose to the small airway was reduced by 20%. In addition, increasing the negative ion concentration helped reduce the small airway exposure risk. NIAPs were found to be an energy-efficient air purification intervention that can effectively reduce the small airway particle exposure when a sufficient negative ion concentration is maintained.

Personal Interventions to Reduce Exposure to Outdoor Air Pollution

Unhealthy levels of air pollution are breathed by billions of people worldwide, and air pollution is the leading environmental cause of death and disability globally. Efforts to reduce air pollution at its many sources have had limited success, and in many areas of the world, poor air quality continues to worsen. Personal interventions to reduce exposure to air pollution include avoiding sources, staying indoors, filtering indoor air, using face masks, and limiting physical activity when and where air pollution levels are elevated. The effectiveness of these interventions varies widely with circumstances and conditions of use. Compared with upstream reduction or control of emissions, personal interventions place burdens and risk of adverse unintended consequences on individuals. We review evidence regarding the balance of benefits and potential harms of personal interventions for reducing exposure to outdoor air pollution, which merit careful consideration before making public health recommendations with regard to who should use personal interventions and where, when, and how they should be used. Expected final online publication date for the Annual Review of Public Health, Volume 43 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Indoor air quality improvement and purification by atmospheric pressure Non-Thermal Plasma (NTP)

Non-thermal plasma (NTP) is a promising technology for the improvement of indoor air quality (IAQ) by removing volatile organic compounds (VOCs) through advanced oxidation process (AOP). In this paper, authors developed a laboratory scale dielectric barrier discharge (DBD) reactor which generates atmospheric NTP to study the removal of low-concentration formaldehyde (HCHO), a typical indoor air VOC in the built environment associated with cancer and leukemia, under different processing conditions. Strong ionization NTP was generated between the DBD electrodes by a pulse power zero-voltage switching flyback transformer (ZVS-FBT), which caused ionization of air molecules leading to active species formation to convert HCHO into carbon dioxide (CO₂) and water vapor (H₂O). The impact of key electrical and physical processing parameters i.e. discharge power (P), initial concentration (C_in), flow rate (F), and relative humidity (RH) which affect the formaldehyde removal efficiency (ɳ) were studied to determine optimum conditions. Results show that, the correlation coefficient (R²) of removal efficiency dependence on the processing parameters follow the order R² (F) = 0.99 > R² (RH) = 0.96, > R² (C_in) = 0.94 > R² (P) = 0.93. The removal efficiency reached 99% under the optimum conditions of P = 0.6 W, C_in = 0.1 ppm, F = 0.2 m³/h, and RH = 65% with no secondary pollution. The study provided a theoretical and experimental basis for the application of DBD plasma for air purification in the built environment.

Effects of Different Site Conditions on the Concentration of Negative Air Ions in Mountain Forest Based on an Orthogonal Experimental Study

The negative air ions (NAI) in a forest play an important and positive role in promoting the health of people using the forest for recreation. The purpose of this study was to explore the environmental characteristics that can effectively represent high concentrations of NAI in mountain forests to help the recreational users to seek out sites with high NAI concentrations for personal health reasons. In order to achieve this goal, we selected the mountain forest of Taibai Mountain National Forest Park, Shaanxi Province, China, as the research object and adopted an orthogonal experimental design with three factors and three levels to study the effects of terrain, altitude, and forest canopy density on the forest NAI concentrations. The results show that obvious peak–valley fluctuation occurs during 6:31 a.m. to 18:30 p.m., with the highest concentration of NAI at 8:00 a.m. (Average: 163 ions/cm3) and the lowest at 16:00 p.m. (Average: 626 ions/cm3). The altitude (p < 0.01) and canopy density (p < 0.05) were found to significantly affect NAI concentrations. The combination of site conditions in the mountain forest observed to have the highest NAI concentrations was valley topography, low altitude, and high canopy density. In addition, the highest NAI concentration was between 14:00 p.m. and 16:00 p.m., under this combination, which was thus identified as the most suitable time for health-promotion activities in mountain forests. The results provide insights into the NAI concentration characteristics and variations, along with identifying important environmental factors for the selection of health-promotion activities in mountain forests.

Effectiveness of indoor air purification intervention in improving cardiovascular health: A systematic review and meta-analysis of randomized controlled trials

Indoor air purifiers are increasingly marketed for their health benefits, but their cardiovascular effects remain unclear. We systematically reviewed and meta-analysed randomized controlled trials (RCTs) on the cardiovascular effects of indoor air purification interventions in humans of all ages. We searched Embase, Medline, PubMed, and Web of Science from inception to 22 August 2020. Fourteen cross-over RCTs (18 publications) were included. Systolic blood pressure (SBP) was significantly reduced after intervention (-2.28 (95% CI: -3.92, -0.64) mmHg). There were tendencies of reductions in diastolic blood pressure (-0.35 [-1.52, 0.83] mmHg), pulse pressure (PP) (-0.86 [-2.07, 0.34] mmHg), C-reactive protein (-0.23 [-0.63, 0.18] mg/L), and improvement in reactive hyperaemia index (RHI) (0.10 [-0.04, 0.24]) after indoor air purification, although the effects were not statistically significant. However, when restricting the analyses to RCTs using physical-type purifiers only, significant improvements in PP (-1.56 [-2.98, -0.15] mmHg) and RHI (0.13 [0.01, 0.25]) were observed. This study found potential evidence on the short-term cardiovascular benefits of using indoor air purifiers, especially for SBP, PP and RHI. However, under the Grading of Recommendations Assessment, Development and Evaluation framework, the overall certainty of evidence was very low, which discourage unsubstantiated claims on the cardiovascular benefits of air purifiers. We have also identified several key methodological limitations, including small sample size, short duration of intervention, and the lack of wash-out period. Further RCTs with larger sample size and longer follow-up duration are needed to clarify the cardiovascular benefits of air purification interventions.

A novel air quality monitoring and improvement system based on wireless sensor and actuator networks using LoRa communication

In this paper, we study the air quality monitoring and improvement system based on wireless sensor and actuator network using LoRa communication. The proposed system is divided into two parts, indoor cluster and outdoor cluster, managed by a Dragino LoRa gateway. Each indoor sensor node can receive information about the temperature, humidity, air quality, dust concentration in the air and transmit them to the gateway. The outdoor sensor nodes have the same functionality, add the ability to use solar power, and are waterproof. The full-duplex relay LoRa modules which are embedded FreeRTOS are arranged to forward information from the nodes they manage to the gateway via uplink LoRa. The gateway collects and processes all of the system information and makes decisions to control the actuator to improve the air quality through the downlink LoRa. We build data management and analysis online software based on The Things Network and TagoIO platform. The system can operate with a coverage of 8.5 km, where optimal distances are established between sensor nodes and relay nodes and between relay nodes and gateways at 4.5 km and 4 km, respectively. Experimental results observed that the packet loss rate in real-time is less than 0.1% prove the effectiveness of the proposed system.

Personal Interventions for Reducing Exposure and Risk for Outdoor Air Pollution: An Official American Thoracic Society Workshop Report

Poor air quality affects the health and wellbeing of large populations around the globe. Although source controls are the most effective approaches for improving air quality and reducing health risks, individuals can also take actions to reduce their personal exposure by staying indoors, reducing physical activity, altering modes of transportation, filtering indoor air, and using respirators and other types of face masks. A synthesis of available evidence on the efficacy, effectiveness, and potential adverse effects or unintended consequences of personal interventions for air pollution is needed by clinicians to assist patients and the public in making informed decisions about use of these interventions. To address this need, the American Thoracic Society convened a workshop in May of 2018 to bring together a multidisciplinary group of international experts to review the current state of knowledge about personal interventions for air pollution and important considerations when helping patients and the general public to make decisions about how best to protect themselves. From these discussions, recommendations were made regarding when, where, how, and for whom to consider personal interventions. In addition to the efficacy and safety of the various interventions, the committee considered evidence regarding the identification of patients at greatest risk, the reliability of air quality indices, the communication challenges, and the ethical and equity considerations that arise when discussing personal interventions to reduce exposure and risk from outdoor air pollution.

Effects of air purification of indoor PM2.5 on the cardiorespiratory biomarkers in young healthy adults

Ambient fine particulate matter (PM_2.5 ), as one of the predominant air pollutants, has achieved effective control in recent years in China. Whether the use of indoor air purifiers is still necessary needs further exploration. A randomized crossover trial was conducted in 54 healthy students in Beijing, China. Participants were randomized assigned to the use of real or sham high-efficiency particulate air filter (HEPA) for a week and changed the status after a washout period. Health measurements of cardiorespiratory biomarkers were performed at the end of each period. Linear mixed-effects models were used to evaluate the association between PM_2.5 exposure and cardiorespiratory biomarkers. Compared with sham air purification, average diastolic blood pressure (DBP), fractional exhaled nitric oxide (FeNO), and 8-isoprostane (8-isoPGF2α) levels decreased significantly in the real purification. The effects of indoor air purification on lung function indicators including forced expiratory volume in one second (FEV₁ ), peak expiratory flow (PEF), and forced expiratory flow between the 25th and 75th percentile of forced vital capacity (FEF_25%-75% ) were also significant. Our findings showed a protective effect of indoor HEPA air purifiers on cardiorespiratory health of young healthy adults reflected by the decreased blood pressure, respiratory inflammation, and systematic oxidative stress and improved lung function.

Comparative Study of Computational Models for Reducing Air Pollution through the Generation of Negative Ions

Today, air quality is one of the global concerns that governments are facing. One of the main air pollutants is the particulate matter (PM) which affects human health. This article presents the modeling of a purification system by means of negative air ions (NAIs) for air pollutant removal, using computational intelligence methods. The system uses a high-voltage booster output to ionize air molecules from stainless steel electrodes; its particle-capturing efficiency reaches up to 97%. With two devices (5 cm × 2 cm × 2.5 cm), 2 trillion negative ions are produced per second, and the particulate matter (PM 2.5) can be reduced from 999 to 0 mg/m3 in a period of approximately 5 to 7 minutes (in a 40 cm × 40 cm × 40 cm acrylic chamber). This negative ion generator is a viable and sustainable alternative to reduce polluting emissions, with beneficial effects on human health.

Using circular economy principles to recycle materials in guiding the design of a wet scrubber-reactor for indoor air disinfection from coronavirus and other pathogens

An arduous need exists to discover rapid solutions to avoid the accelerated spread of coronavirus especially through the indoor environments like offices, hospitals, and airports. One such measure could be to disinfect the air, especially in indoor environments. The goal of this work is to propose a novel design of a wet scrubber-reactor to deactivate airborne microbes using circular economy principles. Based on Fenton's reaction mechanism, the system proposed here will deactivate airborne microbes (bioaerosols) such as SARS-CoV-2. The proposed design relies on using a highly porous clay-glass open-cell structure as an easily reproducible and cheap material. The principle behind this technique is an in-situ decomposition of hydrogen peroxide into highly reactive oxygen species and free radicals. The high porosity of a tailored ceramic structure provides a high contact area between atomized oxygen, free radicals and supplied polluted air. The design is shown to comply with the needs of achieving sustainable development goals.

Personal Exposure to PM2.5 Oxidative Potential in Association with Pulmonary Pathophysiologic Outcomes in Children with Asthma

Fine particulate matter (PM_2.5) with a higher oxidative potential has been thought to be more detrimental to pulmonary health. We aim to investigate the associations between personal exposure to PM_2.5 oxidative potential and pulmonary outcomes in asthmatic children. We measured each of the 43 asthmatic children 4 times for airway mechanics, lung function, airway inflammation, and asthma symptom scores. Coupling measured indoor and outdoor concentrations of PM_2.5 mass, constituents, and oxidative potential with individual time-activity data, we calculated 24 h average personal exposures 0-3 days prior to a health outcome measurement. We found that increases in daily personal exposure to PM_2.5 oxidative potential were significantly associated with increased small, large, and total airway resistance, increased airway impedance, decreased lung function, and worsened scores of individual asthma symptoms and the total symptom score. Among the PM_2.5 constituents, organic matters largely of indoor origin contributed the greatest to PM_2.5 oxidative potential. Given that the variability in PM_2.5 oxidative potential was a stronger driver than PM_2.5 mass for the variability in the respiratory health outcomes, it is suggested to reduce PM_2.5 oxidative potential, particularly by reducing the organic matter constituent of indoor PM_2.5, as a targeted source control strategy in asthma management.

The ventilation of buildings and other mitigating measures for COVID-19: a focus on wintertime

The year 2020 has seen the emergence of a global pandemic as a result of the disease COVID-19. This report reviews knowledge of the transmission of COVID-19 indoors, examines the evidence for mitigating measures, and considers the implications for wintertime with a focus on ventilation.

Individual- and Household-Level Interventions to Reduce Air Pollution Exposures and Health Risks: a Review of the Recent Literature

PURPOSE OF REVIEW

We reviewed recent peer-reviewed literature on three categories of individual- and household-level interventions against air pollution: air purifiers, facemasks, and behavior change.

RECENT FINDINGS

High-efficiency particulate air/arresting (HEPA) filter air purifier use over days to weeks can substantially reduce fine particulate matter (PM2.5) concentrations indoors and improve subclinical cardiopulmonary health. Modeling studies suggest that the population-level benefits of HEPA filter air purification would often exceed costs. Well-fitting N95 and equivalent respirators can reduce PM2.5 exposure, with several randomized crossover studies also reporting improvements in subclinical cardiovascular health. The health benefits of other types of face coverings have not been tested and their effectiveness in reducing exposure is highly variable, depends largely on fit, and is unrelated to cost. Behavior modifications may reduce exposure, but there has been little research on health impacts. There is now substantial evidence that HEPA filter air purifiers reduce indoor PM2.5 concentrations and improve subclinical health indicators. As a result, their use is being recommended by a growing number of government and public health organizations. Several studies have also reported subclinical cardiovascular health benefits from well-fitting respirators, while evidence of health benefits from other types of facemasks and behavior changes remains very limited. In situations when emissions cannot be controlled at the source, such as during forest fires, individual- or household-level interventions may be the primary option. In most cases, however, such interventions should be supplemental to emission reduction efforts that benefit entire communities.