Assessing bias in personal exposure estimates when indoor air quality is ignored: A comparison between GPS-enabled mobile air sensor data and stationary outdoor sensor data.

Neglecting indoor air quality in exposure assessments may lead to biased exposure estimates and erroneous conclusions about the health impacts of exposure and environmental health disparities. This study assessed these biases by comparing two types of personal exposure estimates for 100 individuals: one derived from real-time particulate matter (PM2.5) measurements collected both indoors and outdoors using a low-cost portable air monitor (GeoAir2.0) and the other from PurpleAir sensor network data collected exclusively outdoors. The PurpleAir measurement data were used to create smooth air pollution surfaces using geostatistical methods. To obtain mobility-based exposure estimates, both sets of air pollution data were combined with the individuals' GPS tracking data. Paired-sample t-tests were then performed to examine the differences between these two estimates. This study also investigated whether GeoAir2.0- and PurpleAir-based estimates yielded consistent conclusions about gender and economic disparities in exposure by performing Welch's t-tests and ANOVAs and comparing their t-values and F-values. The study revealed significant discrepancies between GeoAir2.0- and PurpleAir-based estimates, with PurpleAir data consistently overestimating exposure (t = 5.94; p < 0.001). It also found that females displayed a higher average exposure than males (15.65 versus. 8.55 µg/m3) according to GeoAir2.0 data (t = 4.654; p = 0.055), potentially due to greater time spent indoors engaging in pollution-generating activities traditionally associated with females, such as cooking. This contrasted with the PurpleAir data, which indicated higher exposure for males (43.78 versus. 46.26 µg/m3) (t = 3.793; p = 0.821). Additionally, GeoAir2.0 data revealed significant economic disparities (F = 7.512; p < 0.002), with lower-income groups experiencing higher exposure-a disparity not captured by PurpleAir data (F = 0.756; p < 0.474). These findings highlight the importance of considering both indoor and outdoor air quality to reduce bias in exposure estimates and more accurately represent environmental disparities.

Air disinfection performance of upper-room ultraviolet germicidal irradiation (UR-UVGI) system in a multi-compartment dental clinic.

Multi-compartment dental clinics present significant airborne cross-infection risks. Upper-room ultraviolet germicidal irradiation (UR-UVGI) system have shown promise in preventing airborne pathogens, but its available application data are insufficient in multi-compartment dental clinics. Therefore, the UR-UVGI system's performance in a multi-compartment dental clinic was comprehensively evaluated in this study. The accuracy of the turbulence and drift flux models was verified by experimental data from ultrasonic scaling. The effects of the ventilation rate, irradiation zone volume, and irradiation flux on UR-UVGI performance were analyzed using computational fluid dynamics coupled with a UV inactivation model. Different patient numbers were considered. The results showed that UR-UVGI significantly reduced virus concentrations and outperformed increased ventilation rates alone. At a ventilation rate of six air changes per hour (ACH), UR-UVGI with an irradiation zone volume of 20% and irradiation flux of 5 µW/cm2 achieved a 70.44% average virus reduction in the whole room (WR), outperforming the impact of doubling the ventilation rate from 6 to 12 ACH without UR-UVGI. The highest disinfection efficiency of UR-UVGI decreased for WRs with more patients. The compartment treating patients exhibited significantly lower disinfection efficiency than others. Moreover, optimal UR-UVGI performance occurs at lower ventilation rates, achieving over 80% virus disinfection in WR. Additionally, exceeding an irradiation zone volume of 20% or an irradiation flux of 5 µW/cm2 notably reduces the improvement rates of UR-UVGI performance. These findings provide a scientific reference for strategically applying UR-UVGI in multi-compartment dental clinics.

A review of relevant parameters for assessing indoor air quality in educational facilities.

Indoor air quality (IAQ) in educational facilities is crucial due to the extended time students spend in those environments, affecting their health, academic performance, and attendance. This paper aimed to review relevant parameters (building characteristics and factors related with occupancy and activities) for assessing IAQ in educational facilities, and to identify the parameters to consider when performing an IAQ monitoring campaign in schools. It also intended to identify literature gaps and suggest future research directions. A narrative literature review was conducted, focusing on seven key parameters: building location, layout and construction materials, ventilation and air cleaning systems, finishing materials, occupant demographics, occupancy, and activities. The findings revealed that carbon dioxide (CO2) levels were predominantly influenced by classroom occupancy and ventilation rates, while particulate matter (PM) concentrations were significantly influenced by the building's location, design, and occupant activities. Furthermore, this review highlighted the presence of other pollutants, such as trace metals, polycyclic aromatic hydrocarbons (PAHs), carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), and radon, linking them to specific factors within the school environment. Different IAQ patterns, and consequently different parameters, were observed in various school areas, including classrooms, canteens, gymnasiums, computer rooms, and laboratories. While substantial literature exists on IAQ in schools, significant gaps still remain. This study highlighted the need for more studies in middle and high schools, as well as in other indoor microenvironments within educational settings beyond classrooms. Additionally, it underscored the need for comprehensive exposure assessments, long-term studies, and the impacts of new materials on IAQ including the effects of secondary reactions on surfaces. Seasonal variations and the implications of emerging technologies were also identified as requiring further investigation. Addressing those gaps through targeted research and considering the most updated standards and guidelines for IAQ, could lead to define more effective strategies for improving IAQ and safeguarding the students' health and performance.

Size-resolved particulate matter inside selected fire stations and preliminary evaluation of the effectiveness of washing machines in reducing its concentrations.

The study aimed to determine and compare the mass concentration and size distribution of particulate matter (PM) at two Polish fire stations, one equipped with a washing machine intended for the decontamination of uniforms (FSN) and the other not equipped with this type of device (FSC), to assess the effectiveness of washing machines in reducing PM concentrations inside fire stations and estimate PM doses inhaled by firefighters while performing activities in truck bays and changing rooms during one work shift. The average PM concentrations at the FSN were 18.2-28.9 µg/m3 and 27.5-37.3 µg/m3, while at FSC they were 27.4-37.9 µg/m3 and 24.6-32.8 µg/m3 in the truck bays and changing rooms, respectively. At each measurement point, most of the PM mass (65-75%) was accumulated as fine particles. The dominance of fine particles in the total mass of PM results in high values of PM deposition coefficients (0.59-0.61) in three sections of the respiratory tract at each monitoring site. This study initially indicates the effectiveness of washing machines in reducing the concentration of fine particles and demonstrates the necessity, as well as directions for further research in this area.

Association of anaemia with indoor air pollution among older Indian adult population: multilevel modelling analysis of nationally representative cross-sectional study.

INTRODUCTION: Anaemia is a disease of public health importance with multi-causal pathways. Previous literature suggests the role of indoor air pollution (IAP) on haemoglobin levels, but this has been studied less due to logistic constraints. A high proportion of the population in developing countries, including India, still depends on unclean fuel, which exacerbates IAP. The objective was to study the association between anaemia and IAP among the older Indian adult population (≥ 45 years) as per gender. METHODS: Our study analysed the nationally representative dataset of the Longitudinal Ageing Study in India (LASI 2017-18, Wave-1). We have documented the association of anaemia (outcome variable) with IAP (explanatory variable). To reduce the confounding effects of demographic and socioeconomic; health related and behavioural covariates; propensity score matching (PSM) was conducted. Nested multilevel regression modelling was conducted. States and union territories were categorised cross tabulated as low, middle and high as per anaemia and IAP exposure. P value < 0.05 was considered statistically significant. SATA version 17 was used for analysis. RESULTS: More than half (52.52%) of the participants were exposed to IAP (male (53.55%) > female (51.63%)). The odds of having anaemia was significantly 1.19 times higher (AOR 1.19 (1.09-1.31)) among participants using unclean/ solid fuel. The adjusted odds were significantly higher among participants exposed to pollution-generating sources (AOR 1.30; 1.18-1.43), and household indoor smoking (AOR 1.17 (1.07-1.29). The odds of having anaemia were significantly higher (AOR 1.26; 1.15-1.38) among participants exposed to IAP, which was higher in males (AOR 1.36; 1.15-1.61) than females (AOR 1.21; 1.08-1.35). Empowered Action Group (EAG) states like Uttar Pradesh, Chhattisgarh, Madhya Pradesh, Bihar had both high anaemia and IAP exposure. CONCLUSION: This study established the positive association of anaemia with indoor air pollution among older Indian adults through a nationally representative large dataset. The association was higher among men. Further research is recommended to understand detailed causation and to establish temporality. It is a high time to implement positive intervention nationally to decrease solid/ unclean fuel usage, vulnerable ventilation, indoor smoking, IAP and health hazards associated with these with more focused actions towards EAG states.

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.

Association between exposure to smoke from cooking fuels and anaemia among women of reproductive age in Ghana.

In low- and middle-income countries, indoor air pollution (IAP) is a serious public health concern, especially for women and children who cook with solid fuels. IAP exposure has been linked to a number of medical conditions, including pneumonia, ischemic heart disease, stroke, chronic obstructive pulmonary disease (COPD), lung cancer, and anaemia. Around 500 million women of reproductive age (WRA) suffer from anaemia globally, with an estimated 190 million cases in sub-Saharan Africa (SSA). This study, which is based on prior research, investigates the relationship between IAP exposure and anaemia among WRA in Ghana. A diverse sample of 2,406 WRA living in Ghana were interviewed, of which 58.06% were anaemic and used high-pollutant fuels for cooking. Age, place of residence, region, education level, religion, ethnicity, wealth index, type of drinking water, type of toilet facility, and type of cooking fuels were all found to be significantly linked with anaemic state by bivariate analysis. Type of cooking fuels utilized, age, region of residence, and the type of residence were shown to be significant predictors of anaemia status using sequential binary logit regression models. The results emphasise the critical need for efforts to promote the usage of clean cooking fuel in an attempt to lower anaemia prevalence in Ghana. To reduce dependency on solid fuels for cooking, initiatives should promote the use of cleaner cooking fuels and enhance the socioeconomic status of households. These interventions could have significant public health effects by reducing the burden of anaemia and improving maternal and child health outcomes due to the prevalence of anaemia among WRA. Overall, this study sheds light on the relationship between IAP exposure and anaemia in Ghana and highlights the demand for focused public health initiatives to address this serious health problem.

Association of 1-bromopropane exposure with asthma prevalence: A Korean National Health and Nutritional Examination Survey (2020-2021)-based study1.

Exposure to 1-bromopropane (1-BP) is an emerging environmental and health concern due to its increasing environmental prevalence. Although the health effects of 1-BP exposure have been under-recognized, current evidence suggests the possibility of adverse pulmonary health effects due to 1-BP exposure. However, the association between 1-BP exposure and asthma prevalence remains unclear. Thus, we aimed to examine the association between 1-BP exposure and asthma prevalence in the general population. Using nationally representative data, we explored the potential impacts of indoor air quality (IAQ)-related behavioral factors on the level of 1-BP exposure. This study included 1,506 adults from the 2020-2021 Korea National Health and Nutrition Examination Survey. The prevalence of asthma was based on self-reported physician-diagnosed asthma. Urinary N-acetyl-S-(n-propyl)-L-cysteine (BPMA) levels were measured as a biomarker of 1-BP exposure, using high-performance liquid chromatography-mass spectrometry. Multiple logistic regression models were performed to investigate the associations between urinary BPMA metabolite and asthma prevalence after adjusting for potential confounders. Log-linear multiple regression models were used to examine the association between IAQ-related behavior and urinary BPMA concentration. Forty-seven individuals with asthma and 1,459 without asthma were included. Individuals in the highest quartile of urinary BPMA concentration had a 2.9 times higher risk of asthma than those in the lowest quartile (odds ratio [OR]: 2.85, 95% confidence interval [CI]: 1.02-7.98). The combination of natural and mechanical ventilation was associated with a reduced urinary BPMA concentration. Our findings suggest that 1-BP exposure is associated with the prevalence of asthma in adults and revealed higher urinary levels of BPMA in our study population compared to those in other countries. Given the emerging importance of IAQ, actively managing and modifying behavioral patterns to reduce 1-BP exposure in indoor environments could substantially attenuate the risk of asthma-related to 1-BP exposure.

The concentration and probabilistic health risk assessment attribute to PAHs in indoor air of Hormozgan aluminum plant, Iran.

We measured PAHs concentrations to understand the potential short and long-term health risks to workers. In the anode cooking area, the lowest and highest concentrations of PAHs were found for DahA (dibenzo[a,h]anthracene) at 0.373 ± 0.326 µg/m3 and Chry (chrysene) at 1.923 ± 1.258 µg/m3, respectively. In the anode-making area, these concentrations were higher, with DahA at 0.435 ± 0.221 µg/m3 and Chry peaking at 3.841 ± 1.702 µg/m3. Risk assessment based on these concentrations indicates a hierarchical order of individual PAHs risks in the anode cooking area, led by BaP (benzo[a]pyrene), followed by other specific PAHs compounds. The total hazard quotient (THQ) for PAH exposure in both anode-making and cooking areas significantly exceeds the threshold for considered cancer risk, emphasizing the considerable danger to workers. This study underscores the urgent need to mitigate exposure to PAHs in industrial settings to protect worker health from the carcinogenic risks of such hazardous compounds.

Implications of fuel poverty for indoor black carbon concentrations from space heating.

Despite the global transition towards cleaner energy sources observed over the last decade, disparities in access persist worldwide. The dependence on biomass for household heating exacerbates fuel poverty, as economically vulnerable households face challenges in obtaining certified firewood and often resort to using contaminated biomass as a substitute, either partially or completely. We examined black carbon (BC) particle concentrations -a marker for combustion- during wood stove operation through a five-day case study in a typical Chilean household. BC increased rapidly following the ignition of the stove, with the combustion of dry Eucalyptus globulus logs yielding a substantially lower peak (5.29 µg/m3) than when using unclean biomass: 35.75 µg/m3 with demolition wood and painted furniture, and 87.11 µg/m3 with the addition of a blend of particleboard with polystyrene foam. During the latter two events, BC particles remained indoors for about 20 h before the concentrations reverted to pre-spike levels. The slow decay in BC concentrations was further influenced by the infiltration of outdoor air. The mean indoor BC concentrations were comparable to or even exceeded those observed on busy roads in major cities worldwide. These results highlight the risks associated with limited access to clean fuels for indoor heating, alongside inadequate insulation. This study sheds light on the problem of fuel poverty and its adverse effects on health and well-being.

Assessing the risks associated with indoor and outdoor air quality in relation to the geographic placement of nursing home.

Indoor air quality significantly impacts the well-being and health of elderly residents in nursing homes. This study was conducted to explore the connection between indoor and outdoor PM (Particulate Matter) concentrations in nursing homes and their association with the facilities' location and construction characteristics. The findings revealed that indoor PM2.5 and PM10 concentrations ranged from 0.2 to 124 µg/m3 and 2-188.4 µg/m3, respectively, which were approximately 12.67 and 1.25 times higher than their outdoor counterparts. A strong correlation (P < 0.05) was identified between indoor PM levels and various factors, including proximity to parks, passenger terminals, and gas stations, as well as building attributes such as single-glazed windows, ceramic floor coverings, and the use of radiators. The risk assessment indicated that carcinogenic risk factors were well within acceptable limits for all nursing homes. However, it's important to note that certain PM components, particularly polycyclic aromatic hydrocarbons (PAH), may have long-term adverse effects on the health of nursing home residents. Even though indoor PM levels met the standards established by the U.S. Environmental Protection Agency (USEPA) for particulate matter risk assessments, the study emphasized that even low levels of indoor air pollutants can affect the health and well-being of older adults, particularly considering the increased vulnerability associated with aging. Consequently, the study underscores the importance of nursing home location selection and the regular monitoring of particulate matter concentrations. These measures are essential for enhancing air quality within nursing homes, ultimately contributing to the improved well-being and health of their residents.

Experimental evaluation of a full-scale in-duct UV germicidal irradiation system for bioaerosols inactivation.

Bioaerosols control techniques, especially ultraviolet germicidal irradiation (UVGI) are gaining attention due to increasing needs for controlling of health risk caused by airborne biocontaminants. The effectiveness of a full-scale in-duct UVGI air disinfection system was investigated. One bacterium, a wild type Escherichia coli, and three fungal spores, Penicillium aragonense, Rhodotorula glutinis, and Cladosporium sp., were selected as test organisms and their inactivation under different conditions representative of a real application in HVAC systems were investigated. The results demonstrated that inactivation of airborne E. coli by the UVGI system was extremely effective, with >99.5 % of the input E. coli inactivated at a residence time lower than 0.36 s in the disinfection section. Airborne fungal spores were less susceptible to UV irradiation than E. coli. Under same conditions, viable counts reduction of P. aragonense, R. glutinis, and Cladosporium sp. spores were 53 %, 63 % and 73 %, respectively. The effect of UV light intensity, air flowrate and relative humidity were analyzed separately. A simplified model based on redefinition of the parameters in the classical inactivation kinetic equation was used to simulate the inactivation of airborne contaminants in the in-duct system under different conditions. The results showed that the simplified model was adequate to estimate disinfection efficacy of different bioaerosols by the UVGI system which could be useful for system design. Overall, this study shows that such in-duct UVGI systems can provide significant control of bioaerosols.

Indoor air quality in subway microenvironments: Pollutant characteristics, adverse health impacts, and population inequity.

Rapidly increasing urbanization in recent decades has elevated the subway as the primary public transportation mode in metropolitan areas. Indoor air quality (IAQ) inside subways is an important factor that influences the health of commuters and subway workers. This review discusses the subway IAQ in different cities worldwide by comparing the sources and abundance of particulate matter (PM2.5 and PM10) in these environments. Factors that affect PM concentration and chemical composition were found to be associated with the subway internal structure, train frequency, passenger volume, and geographical location. Special attention was paid to air pollutants, such as transition metals, volatile/semi-volatile organic compounds (VOCs and SVOCs), and bioaerosols, due to their potential roles in indoor chemistry and causing adverse health impacts. In addition, given that the IAQ of subway systems is a public health issue worldwide, we calculated the Gini coefficient of urban subway exposure via meta-analysis. A value of 0.56 showed a significant inequity among different cities. Developed regions with higher per capita income tend to have higher exposure. By reviewing the current advances and challenges in subway IAQ with a focus on indoor chemistry and health impacts, future research is proposed toward a sustainable urban transportation systems.

CFD simulation study and experimental analysis of indoor air stratification in an unventilated classroom: A case study in Spain.

Health problems and respiratory diseases are associated with poor indoor air ventilation. We investigated the air quality inside a classroom-laboratory where no ventilation is provided. The case of study, consisting of an internal enclosure, is located at the Escuela Técnica Superior de Edificación (ETSEM) of Madrid (Spain). The high height favours air stratification which is analysed in terms of temperature and CO2 spatial distribution. Temperature, air humidity, atmospheric pressure and CO2 concentration measurements were taken in time at three different height locations. A CFD numerical model was established to analyse air quality. Flow circulation is derived by solving full 3D Navier - Stokes governing equations, coupled with the thermal problem. The diffusion problem of the CO2 produced by the inner occupants is then derived from the kinematics solution. Three scenarios were taken into account: occupants seated (1), standing (2), half seated, half standing (3). Results clearly show the air stratification as a result of density gradient, which is in turn determined by temperature difference between the occupants and the surrounding air. Temperature prediction maximum relative error is contained to 3.5 %. As expected, CO2 concentration increases over time, reaching maximum values depending on the configuration considered and height location.

Investigating Microbial Contamination of Indoor Air, Environmental Surfaces, and Medical Equipment in a Southwestern Ethiopia Hospital.

Introduction: Healthcare-associated infections, primarily caused by microorganisms, are widespread in healthcare facilities. These infections pose a significant challenge, especially in low and middle-income countries, and have a detrimental impact on patient outcomes. It is crucial to assess the level of microbial load and associated factors to prevent the spread of these infections. The objective of this study was to assess the microbial load and identify the factors associated with it in various wards at Jimma Medical Center. Method: A cross-sectional study conducted at Jimma Medical Center. Indoor air samples were collected using the settle plate method with a 1/1/1 scheme. Inanimate surfaces and medical equipment were sampled using Swabs from a 10 × 10 cm area. A total of 268 samples were collected from 10 rooms. Pertinent information regarding the associated factors was gathered using an observational checklist. A multiple linear regression model was used to identify any associations with the microbial load. Result: Out of the total samples, 181 (67.5%) tested positive for culture, and 270 microbes were isolated. The average load of bacteria and fungi in the indoor air ranged from 124.4 to 1607 and 96 to 814.6 Colony-forming unit (CFU)/m3, respectively. The mean total aerobic colony counts of bacteria and fungi from all surfaces in the wards ranged from 5.25 to 43.3 CFU/cm2. Crowdedness [ß = 2.748 (95% Confidence Interval (CI): 1.057-4.44)], the presence of waste material [ß = 1.747 (95% CI: 0.213-3.282)], and an unclean room [ß = 2.505 (95% CI: 0.990-4.019)] were significantly associated with the microbial load. Conclusion: The microbial load detected in indoor air, inanimate surfaces and medical equipment was posing potential health risks. Consequently, it is recommended to implement regular microbial surveillance of the hospital environment and enhance the infection prevention program to mitigate these concerns.

The selection of a nitrogen precursor for the construction of N-doped titanium dioxide with enhanced photocatalytic activity for the removal of gaseous toluene.

The preparation of nitrogen-doped TiO2 (i.e., N-TiO2) catalysts is a highly effective option to improve the photocatalytic activity of TiO2. Nonetheless, relatively little is known about the effects of dopant precursors selected for their preparation with regard to the photocatalytic efficacy. In this study, three types of dopants are selected and used as N sources (urea (U), melamine (M), and aqueous ammonia (A)) for N-TiO2 samples with the name codes of NTU, NTM, and NTA, respectively. The photocatalytic efficacy of these N-TiO2 samples is examined against toluene in a packed bed flow reactor. Under optimal conditions (e.g., relative humidity (RH) = 20% and gas hourly space velocity (GHSV) = 1698 h-1), the superiority of NTA is evident over others with a quantum efficiency (QE) of 7.03 × 10-4 molecules photon-1, a space time yield (STY) of 1.38 × 10-4 molecules photon-1 mg-1, and a specific clean air delivery rate (SCADR) of 1148.8 L g-1 h-1. The analysis based on in-situ diffuse reflectance infrared Fourier transform spectroscopy and gas chromatography-mass spectrometry confirms the formation of several intermediates such as benzyl alcohol, benzaldehyde, benzoic acid, and alkane species through ring opening reactions. In addition, the prepared NTA photocatalyst exhibits the highest toluene photocatalytic degradation efficiency among all TiO2-based catalysts surveyed to date. Overall, this study offers as a valuable guideline for the development of advanced TiO2 catalytic systems (such as N-TiO2) for the treatment of aromatic hydrocarbons in indoor air.

The relationship between occupant behaviour and indoor air quality in Malaysian hospital outpatient departments: A multistage cross-sectional study.

Introduction: Poor indoor air quality (IAQ) in healthcare settings may adversely impact occupants' well-being and promote transmission of infectious respiratory disease. However, evidence on its potentially modifiable determinants, including occupant behaviour, remains scarce. This study aims to determine the relationship between occupant behaviour and IAQ in Malaysian hospital outpatient departments (OPDs). Methods: A multistage cross-sectional study of six randomly selected Malaysian public hospital OPDs was conducted. In stage one, IAQ parameters, including temperature, relative humidity (RH), air velocity (AV), carbon dioxide (CO2), total bacterial count (TBC), and total fungal count (TFC) were measured. In stage two, an observation form based on the Korsavi and Montazami tool for measuring adaptive behaviour was used to examine occupant density, activities, and operation of building envelopes and appliances. Simple correlation, partial correlation, and linear regression analyses were performed to examine the relationship between occupant behaviour and IAQ parameters. Results: The IAQ of selected hospital OPDs complied with established standards, except for temperature and AV. Occupant density was positively correlated with temperature and CO2. Meanwhile, occupants' activities including slow walking and brisk walking were positively correlated with temperature, AV, CO2, TBC and TFC. Conversely, occupants' opening of windows and doors were positively correlated with temperature and AV but negatively correlated with CO2, TBC and TFC. Finally, turning on fans was positively correlated with AV but negatively correlated with TBC, whereas turning on air conditioner was positively correlated with CO2. Among occupants' behaviour, opening of windows and doors contributed the most to variation in IAQ parameters. Conclusions: The study findings suggest that IAQ in hospital OPDs are influenced by occupant density, activities, and operation of doors, windows, and appliances. Prospective hospital IAQ guidelines should incorporate policies and measures targeting these factors to ensure occupants' best practices in maintaining healthy hospital indoor air environments.

The catalytic efficacy of modified manganese-cobalt oxides for room-temperature oxidation of formaldehyde in air.

Formaldehyde (FA) is a hazardous indoor air pollutant with carcinogenic propensity. Oxidation of FA in the dark at low temperature (DLT) is a promising strategy for its elimination from indoor air. In this light, binary manganese-cobalt oxide (0.1 to 5 mol L-1-MnCo2O4) is synthesized and modified in an alkaline medium (0.1-5 mol L-1 potassium hydroxide) for FA oxidation under room temperature (RT) conditions. Accordingly, 1-MnCo2O4 achieves 100 % FA conversion at RT (50 ppm and 7022 h-1 gas hourly space velocity (GHSV)). The catalytic activity of 1-MnCo2O4 is assessed further as a function of diverse variables (e.g., catalyst mass, relative humidity, FA concentration, molecular oxygen (O2) content, flow rate, and time on-stream). In situ diffuse reflectance infrared Fourier-transform spectroscopy confirms that FA molecules are adsorbed onto the active surface sites of 1-MnCo2O4 and oxidized into water (H2O) and carbon dioxide (CO2) through dioxymethylene (DOM) and formate (HCOO-) as the reaction intermediates. According to the density functional theory simulations, the higher catalytic activity of 1-MnCo2O4 can be attributed to the combined effects of its meritful surface properties (e.g., the firmer attachment of FA molecules, lower energy cost of FA adsorption, and lower desorption energy for CO2 and H2O). This work is the first report on the synthesis of alkali (KOH)-modified MnCo2O4 and its application toward the FA oxidative removal at RT in the dark. The results of this study are expected to provide valuable insights into the development of efficient and cost-effective non-noble metal catalysts against indoor FA at DLT.