Indoor air quality guidelines from across the world: An appraisal considering energy saving, health, productivity, and comfort

Health risk assessment of indoor formaldehyde exposure across Chinese residences: Effects of building material grades

Prolonged exposure to elevated indoor formaldehyde levels poses significant health risk. This study investigates the emission characteristics of building materials, indoor environmental parameters, and their impacts on Chinese residents. Eleven representative cities across five climate zones in China were analyzed to predict indoor formaldehyde concentrations, assess population exposure doses, and evaluate cancer risks for three grades of building materials (E1, E0, and ENF). Results indicate that the average indoor formaldehyde concentrations ranged from 0.008 to 0.028 mg/m3 for ENF, 0.014-0.057 mg/m3 for E0, and 0.027-0.109 mg/m3 for E1. Formaldehyde pollution was more severe in summer than winter and higher in bedrooms than in living rooms. Due to heating policies, indoor formaldehyde concentrations in severe cold (Zone I) and cold zones (Zone II) during winter were significantly higher than those in other climate zones, with a maximum difference of 2.34 times. The lifetime cancer risk for populations exposed to E1 grade building materials ranged from 3.0 × 10-4 to 8.6 × 10-4, exceeding acceptable risk thresholds. Infants exhibited daily exposure dose over 2.8 times higher than adults. Replacing E1 grade materials with ENF grade materials across various climate zones could reduce cancer risk by 62.2-78.2 %. Adopting higher-grade building materials is a feasible and effective strategy for mitigating health risks associated with indoor formaldehyde exposure.

Residential and occupational exposure to indoor radon and associated human health risk in Nigeria buildings assessed by multiple monitoring techniques

Indoor radon exposure is a significant public health concern, as it is the second leading cause of lung cancer globally. This systematic review evaluated radon concentrations and associated health risks in Nigerian buildings, including homes, schools, and workplaces, through various monitoring techniques such as CR-39 detectors and RAD7 monitors. A total of 47 eligible studies were included following PRISMA guidelines that covered the spatial variations of radon exposure across Nigeria, revealed a weighted mean indoor radon concentration of 104 Bq/m3, exceeding the WHO reference level of 100 Bq/m3 but below the USEPA action level of 148 Bq/m3. Certain locations such as Odo-Ona, Ibadan, recorded 531.85 Bq/m3, corresponding to an annual effective dose of 13.42 mSv/yr, an excess lifetime cancer risk of 51.66 × 10-3, and an estimated lung cancer burden of 242 cases/year per million people. Other regions, including Sokoto Metropolis and Oke-Ogun, also exceeded safety limits, while coastal areas like Lagos showed the lowest concentrations (7.52 Bq/m3). Geographic disparities were evident, with southwestern Nigeria showing the highest risk and accounting for 63 % of studies, while northern and southeastern regions remain underrepresented. Comparative analysis revealed that Nigerian hotspots surpass radon levels reported in several radon-prone countries, including Bulgaria and Northwest Spain, highlighting a significant health risk. This review presents Nigeria's first indoor radon exposure map in residential and occupational settings nationwide that clearly identified critical hotspots and emphasizing the urgent need for targeted interventions. Awareness of the presence of radon and its potential health effects is very low in Nigeria. Radon mitigation should integrate geological assessments with radon-resistant construction materials, proper ventilation, and sealed entry points, especially in uranium-rich and permeable soils. Public awareness, routine monitoring, and regulatory policies are essential, while future research should focus on underrepresented regions and uncover long-term exposure patterns.

A HoLDI mass spectrometry platform for airborne nanoplastic detection

There are no established protocols for nanoplastic detection within complex environmental matrices. Mass spectrometry (MS) analysis of environmental nanoplastics is impeded by methodological constraints. We present a versatile platform evolved from matrix-assisted laser desorption/ionization (MALDI) MS for airborne nano/microplastic research. The 3D-printed hollow-laser desorption/ionization (HoLDI) target enables efficient, high-throughput analysis of aerosols collected on simple substrates without pre/post-treatments. HoLDI-MS determines the chemical composition and relative quantity of real-world airborne nano/microplastics, while used with conventional portable samplers and particle analyzers. Polyethylene, polyethylene glycol, and polydimethylsiloxanes are detected in an indoor environment, with a higher amount in the micro-sized range. Polycyclic aromatic hydrocarbons present in an outdoor setting, with a higher quantity in the nano-sized range. Morphological and elemental data provide additional evidence for observed contaminants and support multidisciplinary research interests. HoLDI holds promise as a standardized analytical framework for any air or water samples, facilitating research harmonization worldwide.

Need for a Holistic Approach to Assessing Sustainable, Green, and Healthy Buildings

With the rising global population, economic development, and urbanization, building stock is bound to grow, warranting measures for optimizing their embodied and operational energy and resource consumption. Further, a building's indoor environment quality significantly affects occupants' health, productivity, and well-being since people spend almost 90% of their time indoors. Buildings safeguard occupant's well-being by shielding them from the outdoor air pollution and increasing climate extremes. However, buildings can also lead to acute and chronic exposure to pollutants trapped inside. The recent pandemic has demonstrated that indoor environments can prevent and promote airborne disease transmission depending on buildings' design and operation. The current segregated rating systems and regulations to gauge buildings' sustainability, health and safety, and energy efficiency have led to a fragmented approach hampering sustainable and healthy buildings' design, construction, and operations. This work discusses the environmental sustainability of buildings, their impacts on occupants' health and productivity, and if and how the existing global policies and frameworks regulate and promote the same. Developing a holistic and comprehensive framework is critical to ensure buildings' sustainability, occupants' health, and energy efficiency.

Glutathione S-transferase polymorphisms and their role in recurrent pregnancy loss: A genetic risk assessment

Objective

The frequency of recurrent pregnancy loss in society is 3-5%. Experts suggest that genetics account for over 80% of unexplained recurrent pregnancy loss. Glutathione S-transferase (GST) enzymes, regulated by GST genes, facilitate the detoxification of a variety of naturally occurring metabolites as well as environmentally derived chemicals. This research aimed to investigate GST gene polymorphisms as a potential risk factor in recurrent pregnancy loss etiology in the Turkish population.

Materials and Methods

This study involved 107 recurrent pregnancy loss patients who sought treatment at the Sivas Cumhuriyet University Faculty of Medicine, Department of Medical Genetics, along with a control group of 107 individuals who had a successful birth and no previous history of miscarriage. The multiplex polymerase chain reaction and restriction fragment length polymorphism techniques were employed to analyze GSTM1, GSTT1 and GSTP1 gene polymorphisms in these cases.

Results

GSTT1 null genotype (X2=4.74; p=0.029) and GSTT1/GSM1 null genotype (X2=3.333; p=0.047) were associated with statistically significant differences between the study groups. No statistical significance was detected when considering the GSTM1 null genotype (X2=3.326; p=0.068) or the GSTM1/GSTP1 and GSTT1/GSTP1 gene polymorphisms.

Conclusion

A statistically significant association was observed between the GSTT1 null genotype and the diseased group. Our research demonstrated a substantial increase in the risk of recurrent pregnancy loss in the Turkish population, specifically among individuals with the GSTM1-null genotype. No statistical correlation was found between the GSTM1 and GSTP1 gene polymorphisms and recurrent pregnancy loss. Furthermore, no statistical significance was observed when they were assessed together.

Electrospun Fibers from Biobased and Recycled Materials for Indoor Air Quality Enhancement

Air filters are crucial components of building ventilation systems. Compared to conventional air filter media like glass fibers and melt-blown fibers, electrospinning membranes are more efficient for capturing various pollutants due to the smaller pores present on the structure. In this paper, activated carbon filters were prepared with eco-friendly polylactic acid (PLA) and microcrystalline cellulose (MCC) using electrospinning to obtain a high-quality factor (QF) fibrous mat for aerosol particle matter (PM) filtration and volatile organic compounds (VOCs) adsorption. Several configurations of the final membranes were investigated and tested for fiber morphology and air filtration performance. Filtering efficiency and adsorption properties were evaluated in a real-scale room by measuring the particle penetration of the newly synthesized and commercial filters against neutralized aerosol particles (3% NaCl aqueous solution) and VOCs (methyl ethyl ketone). The calculated depolluting efficiencies were up to 98% in terms of PM and 55% for VOCs abatement, respectively. Our results indicate that the proposed hybrid membranes represent promising materials for highly efficient and sustainable air filters for home application systems.

Sources, levels, and determinants of indoor air pollutants in Europe: A systematic review

Clean air is a requirement for life, and the quality of indoor air is a health determinant since people spend most of their daily time indoors. The aim of this study was to systematically review the available evidence regarding the sources, determinants and concentrations of indoor air pollutants in a set of scenarios under study in K-HEALTHinAIR project. To this end, a systematic review was performed to review the available studies published between the years 2013-2023, for several settings (schools, homes, hospitals, lecture halls, retirement homes, public transports and canteens), conducted in Europe, where sources and determinants of the indoor pollutants concentrations was assessed. After a two-stage screening in abstract and full-text, 148 papers were included for data extraction. For particulate matter, carbon dioxide and volatile organic compounds, several emission sources were identified (occupancy, human activities, resuspension, cleaning products, disinfectants, craft activities, cooking, smoking), with ventilation, number of occupants, building characteristics, being considered as important determinants. This review made also possible to discuss some of the actions that are already in place or should be implemented in the future to prevent and control the presence of pollutants indoors.

Socioeconomic patterns in indoor environment in Denmark: cross-sectional studies from 2000 and 2021

OBJECTIVES

To examine changes and socioeconomic patterns in indicators of a poor indoor environment in 2000 and 2021.

STUDY DESIGN

Cross-sectional data from the Danish Health and Morbidity Survey in 2000 and 2021.

METHODS

The study included 27,068 participants. Indicators of indoor environment (annoyances from mould, temperature, draught, traffic and neighbour noise, and presence of water damage) were obtained from questionnaires (2021) and partly by interview (2000). Socioeconomic status included home ownership, educational level, and household income. The degree of social inequality in the indoor environment was estimated using the concentration index of inequality.

RESULTS

The prevalence of annoyances due to draught, temperature, and noise increased significantly from 2000 to 2021 (e.g., temperature 5.9%-25.1%, odds ratio (OR) 6.72, 95% confidence interval (CI) 6.12-7.38), whereas the prevalence of water damage decreased (17.7%-13.8%, OR 0.85, 95% CI 0.76-0.96). No difference was seen in annoyances due to mould (3.1% in 2000 and 2.5% in 2021, OR 0.90, 95% CI 0.69-1.17). Social inequality was present for thermal conditions, annoyances due to noise and presence of water damage when assessed by income but not by educational level. Conditions were more prevalent among individuals with low income in both 2000 and 2021.

CONCLUSIONS

The proportion of individuals reporting a poor indoor environment due to thermal conditions and noise increased in the period 2000-2021. Social inequality was observed in all indicators of a poor indoor environment for household income, whereas the inequality was less pronounced when assessed by educational level.

Associations between fine particulate matter, gene expression, and promoter methylation in human bronchial epithelial cells exposed within a classroom under air-liquid interface

Associations between indoor air pollution from fine particulate matter (PM with aerodynamic diameter dp < 2.5 μm) and human health are poorly understood. Here, we analyse the concentration-response curves for fine and ultrafine PM, the gene expression, and the methylation patterns in human bronchial epithelial cells (BEAS-2B) exposed at the air-liquid interface (ALI) within a classroom in downtown Rome. Our results document the upregulation of aryl hydrocarbon receptor (AhR) and genes associated with xenobiotic metabolism (CYP1A1 and CYP1B1) in response to single exposure of cells to fresh urban aerosols at low fine PM mass concentrations within the classroom. This is evidenced by concentrations of ultrafine particles (UFPs, dp < 0.1 μm), polycyclic aromatic hydrocarbons (PAH), and ratios of black carbon (BC) to organic aerosol (OA). Additionally, an interleukin 18 (IL-18) down-regulation was found during periods of high human occupancy. Despite the observed gene expression dysregulation, no changes were detected in the methylation levels of the promoter regions of these genes, indicating that the altered gene expression is not linked to changes in DNA methylation and suggesting the involvement of another epigenetic mechanism in the gene regulation. Gene expression changes at low exposure doses have been previously reported. Here, we add the possibility that lung epithelial cells, when singly exposed to real environmental concentrations of fine PM that translate into ultra-low doses of treatment, may undergo epigenetic alteration in the expression of genes related to xenobiotic metabolism. Our findings provide a perspective for future indoor air quality regulations. We underscore the potential role of indoor UFPs as carriers of toxic molecules with low-pressure weather conditions, when rainfall and strong winds may favour low levels of fine PM.

Influence of meteorological conditions on the variability of indoor and outdoor particulate matter concentrations in a selected Polish health resort

The article evaluates air pollution by particulate matter (PM) in indoor and outdoor air in one of the Polish health resorts, where children and adults with respiratory diseases are treated. The highest indoor PM concentrations were recorded during the winter season. Therefore, the maximum average daily concentration values in indoor air for the PM10, PM2.5, and PM1 fractions were 50, 42 and 23 µg/m3, respectively. In the case of outdoor air, the highest average daily concentrations of PM2.5 reached a value of 40 µg/m3. The analyses and backward trajectories of episodes of high PM concentrations showed the impact of supra-regional sources and the influx of pollutants from North Africa on the variability of PM concentrations. The correlation between selected meteorological parameters and PM concentrations shows the relationship between PM concentrations and wind speed. For example, the correlation coefficients between PM1(I) and PM1(O) concentrations and wind speed were - 0.8 and - 0.7 respectively. These factors determined episodes of high PM concentrations during winter periods in the outdoor air, which were then transferred to the indoor air. Elevated concentrations in indoor air during summer were also influenced by chimney/gravity ventilation and the appearance of reverse chimney effect.

Lessons from the COVID-19 pandemic for ventilation and indoor air quality

The rapid global spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at the beginning of 2020 presented the world with its greatest health challenge in decades. It soon became clear that governments were unprepared to respond appropriately to this crisis. National and international public health authorities were confused about the transmission routes of the virus and the control measures required to protect against it. In particular, the need to reduce the risk of infection through sufficient and effective ventilation of indoor spaces was given little attention. In this review, we discuss insights and key lessons learned from the COVID-19 pandemic regarding the role of ventilation as an effective means against airborne transmission of pathogens and, more broadly, for supporting good indoor air quality.

Cleaner heating policies contribute significantly to health benefits and cost-savings: A case study in Beijing, China

Cleaner heating policies aim to reduce air pollution and may bring about health benefits to individuals. Based on a fixed-effect model focusing on Beijing, this study found that after the onset of air pollution, daily clinic visits, hospitalization days, and hospitalization expenses increased several days after the occurrence of air pollution. These hospitalization changes were observed in males and females and three different age groups. A difference-in-differences (DID) model was constructed to identify the influences of cleaner heating policies on health consequences. The study revealed that the policy positively affects health outcomes, with an average decrease of 3.28 thousand clinic visits for all diseases. The total hospitalization days and expenses tend to decrease by 0.22 thousand days and 0.34 million CNY (Chinese Yuan), respectively. Furthermore, implementing the policy significantly reduced the number of daily clinic visits for respiratory diseases, asthma, stroke, diabetes, and chronic obstructive pulmonary diseases (COPDs).

Numerical Analysis of Indoor Air Characteristics and Window Screen Influence on Particulate Matter Dispersion in a Childcare Center Using Computational Fluid Dynamics

Indoor exposure to outdoor pollutants adversely affects health, varying with building dimensions and particularly ventilation that have critical role on their indoor dispersion. This study assesses the impact of outdoor air on indoor air quality in a child care center. Computational fluid dynamics was utilized to analyze the dispersion of particulate matter, with a specific focus on window screens featuring 6 distinct pore sizes ranging from 0.8 mm to 2 mm and 2 different thicknesses of 0.5 mm and 0.1 mm. Results indicate that the presence of a window screen offers significant advantages in controlling particle infiltration compared to scenarios without a screen, as larger particles tend to pass directly through the window within the breathing zone. The scenario without window screens minimizes pressure drop but lacks enhanced particle capture capabilities. However, for effective particle reduction, the window screen with a pore size of 0.8 mm (R0.8T2) and a thickness of 0.5 mm proves to be the most beneficial, achieving the particle filtering efficiency of approximately 54.16%, while the larger window screen with a pore size of 2 mm and a thickness of 1 mm exhibits the lowest efficiency at about 23.85%. Nonetheless, screens with very small sizes are associated with a high-pressure drop, impacting energy efficiency, and overall window performance. Larger pores with smaller thicknesses (0.5 mm) reduced particle count by approximately 45.97%. Therefore, the significance of window screen thickness beyond pore size for particle reduction efficiency is highlighted, emphasizing screens' role in indoor air quality and health protection.

Estimating indoor air temperature by obtaining outdoor building window surface temperature using infrared technology: An exploratory approach

The determination of the indoor air temperature is necessary for evaluating human comfort, health, and living conditions. Existing measuring methods require entering a room, which can disturb the daily lives of residents and consume large amounts of manpower, material, and financial resources. To overcome these obstacles, an exploratory approach was proposed in this study to estimate the indoor air temperature by obtaining the outdoor building window surface temperature without intrusion using infrared technology. A numerical model was established to describe the heat transfer process between the indoor and outdoor air via window glass. Experiments were conducted in a test room to capture infrared images of the exterior window and measure indoor air temperatures and window surface temperatures under different modes. The estimated indoor air temperatures were compared with the experimental data. The effects of window property parameters and ambient parameters on indoor air temperature estimation were analyzed. Results show that the deviations of the indoor air temperature between estimated and measured values in heating, natural ventilation, and cooling modes varied from -0.7 °C to 0.6 °C, -1.1 °C-0.7 °C, and -0.1 °C-1.3 °C, respectively. Based on the sensitivity analysis, the outer surface temperature of the window outer layer was crucial for estimating the accuracy of the indoor air temperature in practical applications. The proposed exploratory approach provides a potential means for remotely obtaining indoor air temperatures using infrared technology.

Carbon monoxide as an indicator of indoor air quality

Carbon monoxide is a priority pollutant that is suitable as an indicator for assessing indoor air quality. Monitoring should preferably be embedded in an intelligent network of different sensors.