Indoor Concentrations Research Articles

Comparing indoor and outdoor temperature and air pollution at an urban cooling center: a multiyear case study

Abstract Anthropogenic climate change and urbanization have resulted in increasing needs to provide public health protection from the hazards of elevated PM2.5, elevated ozone and extreme heat (or cold) to the public. This is particularly urgent issue for sensitive groups that are most subject to these hazards, such as the elderly, children, health compromised, and homeless populations. In this study, we compare the indoor versus outdoor temperature and air pollution levels between 17 May 2022 and 31 October 2023 in Salt Lake City, Utah at an older (Northwest Recreation Center) and newer building (Northwest Community Center). Differences between indoor and outdoor ozone were pronounced, with mean indoor ozone being generally ~40% of outdoor values. Indoor PM2.5 concentrations compared to outdoor show seasonal variability and were up to 200% higher during wildfires compared to indoor concentration during wintertime inversion events. We found that the older building was less protective against ozone and wilfire PM2.5 pollution than the newer building. Future research could focus on characterizing and quantifying the impact of building age, insulation, and mechanical ventilation on indoor pollutant migration and separate these factors from human activity.

Carcinogenic and non-carcinogenic risk estimation of indoor TVOCs, RSPM, FPM and SFPM on young women dwellers: a case study from the capital city of Uttar Pradesh, India

Total volatile organic compounds (TVOCs), respiratory suspended particulate matter (RSPM-PM10), fine particulate matter (FPM-PM2.5) and sub-fine particulate matter (SFPM-PM1) have been found to exert negative impact on the women health. This study was conducted to see the effect of indoor RSPM, FPM, SFPM and TVOCs on women health predominantly on young women dwellers (specifically categorized into pre-teenagers i.e., 8–12 years, teenagers i.e., 13–19 years and post-teenagers i.e., 20–21 years). Indoor monitoring was conducted from November 2022 to February 2023 in six different urban households of Lucknow, capital city of Uttar Pradesh state of India. Envirotech APM 550 for RSPM and FPM, APM 577 for SFPM and portable sensor-based instrument (BR-SMART) were used to measure TVOCs. The highest average indoor concentrations was found to be 250.1 ± 14.11 µg/m3 (PM10) at Rajajipuram, 140.62 ± 19.71 µg/m3 (PM2.5) at Indranagar, 27.60 ± 1.87 µg/m3 (PM1) and 934 ± 70.41 µg/m3 (TVOCs) at Kaiserbagh.Health risk assessment was also determined using average daily dose (ADD), excess lifetime cancer risk (ELCR) and hazard quotient (HQ) for carcinogenic and non-carcinogenic risk. ELCR values for PM1 and PM2.5 surpassed the permissible limit in every house and HQ values also exceeded the minimum allowable value for 20–21 year age group at all of the locations, indicating substantial health risk from exposure. International Committee of Radiological Protection Model (ICRP) and Multiple Path Particle Dosimetry (MPPD) model were used to see the regional deposition of PMs on the young women dwellers. To elucidate the spatial dynamics of these pollutants, the Inverse Distance Weighting (IDW) interpolation technique was employed. Additionally, site-specific analysis of PM mass ratios (PM2.5/PM10, PM1/PM2.5 and PM1/PM10) elucidated the particle size distribution and their sources, significantly enhancing the scientific understanding of aerosol dynamics in these urban settings.

Assessment of Indoor Classroom Environment Quality Associated with Student Sleepiness: Pathways Towards a Sustainable Environment Through a Pilot Study

Student sleepiness during classes is a frequently reported condition that can impair performance in the teaching–learning process and is even unsustainable for health. Although the environmental quality of the classroom may affect the students’ sleepiness, studies that exhaustively investigate the relationship between indoor environmental quality (IEQ) and sleepiness levels in classrooms are lacking. To this end, in the present paper, we carried out an experimental pilot study involving twenty-seven Italian adolescent students to determine the increase in their sleepiness rate during the school period utilizing the Epworth Sleepiness Scale (ESS). The analysis was performed in a classroom in which the indoor environmental quality was monitored, including measurements of the thermal comfort, sound pressure level, illuminance, carbon dioxide (CO2) concentrations, and airborne particle concentrations (both sub-micrometric particles and PM10). Three measurement days were considered. The results showed that student sleepiness significantly increased during the school period (Day 1 p = 0.00, Day 2 p = 0.03, and Day 3 p = 0.03). This increase was observed on measurement days characterized as having both perceived higher and lower thermal comfort and even in the presence of limited exposure to airborne particle concentrations, presenting an association with the high indoor concentration of CO2 detected in the classroom (Day 1 between 978 and 3261 ppm; Day 2 between 1044 and 2338 ppm; Day 3 between 1116 and 2623 ppm), due to reduced ventilation rates and the students’ sleepiness. Thus, the findings suggest that adequate ventilation rates can limit the increase in the rate of sleepiness, indicating, from our pilot study, that recommendations of sustainable environmental practices through comprehensive feasibility studies can promote positive changes in indoor environments such as classrooms.

TracMyAir smartphone application for modeling exposures to PM2.5 and ozone - Integration with air quality networks and location-activity sensors.

Epidemiologic studies of ambient fine particulate matter (PM2.5) and ozone (O3) often use outdoor concentrations from central-site monitors or air quality model estimates as exposure surrogates, which can result in exposure errors. We previously developed an exposure model called TracMyAir, which is an iPhone application that determines seven tiers of individual-level exposure metrics for ambient PM2.5 and O3 using outdoor concentrations, home building characteristics, weather, time-activities. The exposure metrics with increasing information needs and complexity include: outdoor concentration (Cout, Tier 1), building infiltration factor (Finf, Tier 2), indoor concentration (Cin, Tier 3), time spent in microenvironments (ME) (TME, Tier 4), personal exposure factor (Fpex, Tier 5), exposure (E, Tier 6), and inhaled dose (D, Tier 7). In this study, we extended TracMyAir with two sets of additional features: (1) time-resolved exposures using smartphone geolocations with a ME classification model (MicroTrac) and official PM2.5 and O3 monitoring network, and (2) exposures based on low-cost outdoor PurpleAir (PA) PM2.5 monitoring network, non-ambient indoor PM2.5 using indoor-outdoor PA monitors, and inhaled dose based on physical activity data from smartphone and smartwatch. To demonstrate the two sets of extended features, we applied TracMyAir to estimate hourly PM2.5 and O3 exposure metrics for two corresponding panel studies with participants living in central North Carolina, USA. For Tier 4, the MicroTrac estimates were compared with 24-h diary data, and correctly classified the ME for 97% of the daily time spent by the participants. Overall, the TracMyAir estimates showed considerable temporal and building-to-building variability of Finf, and Cin (Tiers 2-3), and person-to-person variability of Cout, TME, Fpex, E, and D (Tiers 1, 4-7). Our study demonstrates the capability of extending TracMyAir with air quality monitors, location-activity sensors, and models to determine fine-scale exposures, in support of epidemiologic studies and public health strategies to help reduce exposures to air pollutants.

THE EFFECT OF NANOPLASTICS AND MICROPLASTICS ON LUNG MORPHOLOGY AND PHYSIOLOGY: A SYSTEMATIC REVIEW

Airborne microplastic (NP) and nanoplastic (MP) pollution has emerged as a pressing environmental concern with significant implications for human health. While MPs are present both indoors and outdoors, indoor concentrations are generally higher due to the abrasion of household materials, furniture, and other domestic sources. MPs and NPs, when inhaled, accumulate in various lung regions, exerting toxic effects and potentially leading to respiratory diseases. This systematic review, conducted according to PRISMA guidelines, evaluates recent experimental studies on the pathogenic impact of nanomicroplastics (NMPs) on lung tissues using in vivo and in vitro models. The review included 10 studies analyzing MP accumulation in respiratory tissues and 90 studies examining pathogenetic mechanisms of MP exposure. Research data indicates a predominance of polymeric fibers such as polypropylene, polyethylene terephthalate, and polytetrafluoroethylene, with fibers accounting for nearly half of MP structures. NMPs in lung tissues exhibit size- and composition-dependent accumulation, with smaller and positively charged particles showing higher translocation potential to the systemic circulation and other organs. The review highlights the synergistic toxic effects of MPs with heavy metals and other pollutants, interaction with pulmonary surfactant, and the role of NMPs in exacerbating respiratory and systemic diseases. Current analysis underscores the growing interest in NMP-related respiratory health risks and identifies significant knowledge gaps, including the need for standardization in NMP toxicity testing and further exploration of NMPs interaction with biological systems. The findings emphasize the importance of mitigating NMPs exposure to safeguard respiratory health and pave the way for future research on the long-term impacts of airborne NMPs on human and environmental health.

Determinants of Indoor NO2 and PM2.5 Concentration in Senior Housing with Gas Stoves.

Nitrogen dioxide (NO2) and particulate matter of 2.5 microns (PM2.5) are air pollutants that impact health, especially among vulnerable populations with respiratory disease. This study identifies factors influencing indoor NO2 and PM2.5 in low-income households of older adults with asthma who use gas stoves in Lowell, Massachusetts. Environmental sampling was conducted in 73 homes, measuring NO2, PM2.5, fractional stove-use, temperature, and humidity for 5-7 days. Participants were recruited between December 2020 and July 2022. Questionnaires were used to collect data on factors influencing indoor NO2 and PM2.5 concentrations. Daily outdoor NO2 and PM2.5 concentrations were obtained from a United States Environmental Protection Agency (EPA) monitoring station. Paired t-tests were conducted between indoor and outdoor NO2 and PM2.5 concentrations, and linear regression was used to evaluate factors influencing indoor NO2 and PM2.5 concentrations. The average indoor concentration for NO2 and PM2.5 were 21.8 (GSD = 2.1) ppb and 16.2 (GSD = 2.7) µg/m3, respectively. Indoor NO2 and PM2.5 concentrations exceeded outdoor concentrations significantly. In multiple regression models, season and pilot light stove use significantly predicted indoor NO2. Season and air freshener use for 6-7 days/week significantly predicted indoor PM2.5. Season-influenced higher indoor concentrations are likely due to reduced ventilation in colder months in the Northeast U.S.

Indoor Volatile Organic Compounds in Prefabricated Timber Buildings—Challenges and Opportunities for Sustainability

Prefabricated timber buildings offer a low-carbon approach that can help reduce the environmental impact of the building and construction sectors. However, construction materials such as manufactured timber products can emit a range volatile organic compounds (VOCs) that are potentially hazardous to human health. We evaluated 24 years (2000–2024) of peer-reviewed publications of VOCs within prefabricated timber buildings. Studies detected hazardous air pollutants such as formaldehyde, benzene, toluene, and acetaldehyde (indoor concentration ranges of 3.4–94.9 µg/m3, 1.2–19 µg/m3, 0.97–28 µg/m3, and 0.75–352 µg/m3, respectively), with benzene concentrations potentially exceeding World Health Organization indoor air quality guidelines for long/short term exposure. Most studies also detected terpenes (range of 1.8–232 µg/m3). The highest concentrations of formaldehyde and terpenes were in a prefabricated house, and the highest of benzene and toluene were in a prefabricated office building. Paradoxically, the features of prefabricated buildings that make them attractive for sustainability, such as incorporation of manufactured timber products, increased building air tightness, and rapid construction times, make them more prone to indoor air quality problems. Source reduction strategies, such as the use of low-VOC materials and emission barriers, were found to substantially reduce levels of certain indoor pollutants, including formaldehyde. Increasing building ventilation rate during occupancy is also an effective strategy for reducing indoor VOC concentrations, although with the repercussion of increased energy use. Overall, the review revealed a wide range of indoor VOC concentrations, with formaldehyde levels approaching and benzene concentrations potentially exceeding WHO indoor air quality guidelines. The paucity of evidence on indoor air quality in prefabricated timber buildings is notable given the growth in the sector, and points to the need for further evaluation to assess potential health impacts.

Development and experimental validation of a thermal inactivation model for airborne bacteria and its application in Trombe wall systems

Thermal inactivation technology is an effective and safe method to control indoor bioaerosols. A predictive mathematical model describing the effect of residence time and exposure temperature on the thermal inactivation process of Klebsiella pneumoniae (K. pneumoniae), Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) in aerosol was developed. A continuous flow experimental system was set up to determine the survival ratio of bioaerosols under the wall temperature of 45–120 °C and residence time of 1.5–12 s. The experimental results showed that the thermal stability in the order from high to low was S. aureus > K. pneumoniae > E. coli. The inactivation model was developed based on the first-order kinetic model and Arrhenius equation and the model parameters were identified through particle swarm optimization (PSO) algorithm with the input of time-dependent exposure temperature calculated by computational fluid dynamics (CFD). The survival ratio calculated by the present model corresponded well with that observed in the experiment, with root mean square error (RMSE) being 0.0445, 0.0433 and 0.0376 for K. pneumoniae, E. coli and S. aureus, respectively. Based on the heat and mass transfer model for Trombe wall, it was found that solar-driven thermal inactivation could reduce the indoor bacterial concentration by up to 57 % for E. coli with thermal efficiency being 0.424 under solar irradiance of 496 W/m2 and ambient temperature of 12.8 °C. In this way, solar driven thermal inactivation is a promising and sustainable method to deal with indoor bioaerosols.

Modelling of Carbon Monoxide and Suspended Particulate Matter Concentrations in a Rural Area Using Artificial Neural Networks

Air pollution is a growing concern in rural areas where agricultural production can be reduced by it. This article analyses data obtained as part of a research project. The aim of this study is to understand the influence of atmospheric pressure, air temperature, air relative humidity, longitude and latitude of the location, and indoor and outdoor environment on local rural workplace diversity of air pollutants such as carbon monoxide (CO) and suspended particulate matter (SPM), as well as the contribution of these variables to changes in such air pollutants. The focus is on four topics: motivation, innovation and creativity, leadership, and social responsibility. Furthermore, this study developed an artificial neural network (ANN) model to predict CO and SPM concentrations in the air based on data collected from the mentioned inputs. The related sensors were assembled on an Arduino Mega 2560 board to form a field-portable device to detect air pollutants and meteorological parameters. The sensors included an MQ7 sensor for CO concentration measurement, a Sharp GP2Y1010AU0F dust sensor for SPM concentration measurement, a DHT11 sensor for air temperature and air relative humidity measurement, and a BMP180 sensor for air pressure measurements. The longitude and latitude of the location were measured using a smartphone. Measurements were conducted from 20 December 2021 to 16 July 2022. Results showed that the overall average outdoor CO and SPM concentrations were 10.97 ppm and 231.14 μg/m3 air, respectively. The overall average indoor concentrations were 12.21 ppm and 233.91 μg/m3 air for CO and SPM, respectively. Results showed that the ANN model demonstrated acceptable performance in predicting CO and SPM in both the training and testing phases, exhibiting a coefficient of determination (R2) of 0.575, a root mean square error (RMSE) of 1.490 ppm, and a mean absolute error (MAE) of 0.994 ppm for CO concentrations when applying the testing dataset. For SPM concentrations, the R2, RMSE, and MAE using the test dataset were 0.497, 30.301 μg/m3 air, and 23.889 μg/m3 air, respectively. The most influential input variable was air pressure, with contribution rates of 22.88% and 22.82% in predicting CO and SPM concentrations, respectively. The acceptable performance of the developed ANN model provides potential advances in air quality management and agricultural planning, enabling a more accurate and informed decision-making process regarding air pollution. The results of short-term estimation of CO and SPM concentrations suggest that the accuracy of the ANN model needs to be improved through more comprehensive data collection or advanced machine learning algorithms to improve the prediction results of these two air pollutants. Moreover, as even lower cost devices can predict CO and SPM concentrations, this study could lead to the development some kind of virtual sensor, as other air pollutants can be estimated from measurements of particulate matters.

Assessment of Formaldehyde’s Impact on Indoor Environments and Human Health via the Integration of Satellite Tropospheric Total Columns and Outdoor Ground Sensors

Formaldehyde (HCHO) is harmful to human health and an adequate assessment of its concentrations, both in outdoor and indoor environments, is necessary in the context of sustainable policies designed to mitigate health risks. In this research, ground indoor and outdoor HCHO measurements are integrated with the analysis of tropospheric total columns obtained by satellite surveys to assess the concentrations of HCHO in a number of environments, exploiting the proximity of a World Meteorological Organization—Global Atmosphere Watch (WMO/GAW) observation site in Calabria, Southern Italy to a National Institute for Insurance against Accidents at Work (INAIL) department in the municipality of Lamezia Terme. The meteorological parameters used by the WMO station are also used to provide additional data and test new correlations. Using statistical significance tests, this study demonstrates the presence of a correlation between indoor and outdoor HCHO concentrations, thus showing that an exchange between indoor and outdoor formaldehyde does occur. Rooms located in the local INAIL building where indoor measurements took place also demonstrate degrees of susceptibility to HCHO exposure, which are correlated with the orientation of prevailing wind corridors in the area. The new findings constitute an unprecedented characterization of HCHO hazards in Calabria and provide regulators with new tools with which to mitigate formaldehyde-related risks.

The health impact of PM2.5 and O3 in Beijing modified by infiltration factors from 2014 to 2022.

PM2.5 and O3 are significant threats to the health of residents and modern residents spend more than 80% of their time indoors, so quantifying indoor exposure of residents has a positive influence on formulating policies and improving health indicators. Analysis of monitoring data shows a consistent decrease in the annual average concentration of outdoor PM2.5 in Beijing from 90.1 to 30.4μg/m3, and the equivalent human exposure concentration also declined from 55.2 to 18.6μg/m3 modified by infiltration factors from 2014 to 2022, while during the peak season, the average value of O3-8h concentration in Beijing has consistently remained between 159.3 and 225.3μg/m3; the equivalent human exposure concentration remained between 64.7 and 92.3μg/m3 modified by infiltration factors from 2014 to 2023. The equivalent exposure concentration is calculated by weighting the concentration of indoor and outdoor pollutants, the proportion of indoor and outdoor activity time of the population, and the permeability coefficient of outdoor pollutants into the room, so as to quantify the actual concentration of pollutants exposed to the human body in a certain time. Previous studies have primarily focused on the impact of annual changes in pollutant concentrations on health estimates, often neglecting indoor concentrations and behavior patterns. This limitation should be addressed. Therefore, this study utilized equivalent human exposure concentration and AirQ + , the authoritative software released by the World Health Organization (WHO), to evaluate quantitatively the impact of PM2.5 and O3 on the health of Beijing residents by combining pollutant concentration, annual population, and mortality of various diseases and other indicators to enhance the credibility of the study. The number of deaths related to PM2.5 has decreased from 28,182 people in 2014 to 10,250 people in 2022 (age ≥ 30). The number of premature deaths in 2022 was only 36.4 percent of that in 2014 and was decreasing by 1992 per year. The number of deaths related to O3 varies between 550 and 3358 people. Lowering PM2.5 and O3 concentrations can effectively reduce natural premature death as well as cardiovascular and respiratory diseases caused by air pollution. The government should persist in enhancing the regulation of PM2.5 and accord significance to the oversight of O3. Concurrently, there is a need to reinforce the cooperative regulation addressing both PM2.5 and O3.

A population-level framework to estimate unequal exposure to indoor heat and air pollution

As people in the UK spend 95% of their time indoors, buildings are an important modifier of exposure to both non-optimal temperatures and air pollution. High ambient temperature and high PM2.5 (particulate matter) concentrations often occur together in urban areas. Residential building types prone to overheating (e.g. purpose-built flats) are often also more common in urban areas. Together, this may lead to spatial and demographic inequalities in indoor exposure to heat and PM2.5 from outdoor sources. By combining building simulations (EnergyPlus), a spatially distributed description of the residential building stock—from publicly available Energy Performance Certificate (EPC) data, ambient temperature, PM2.5 data and area-level (40–250 households) socio-demographic data—we estimated these inequalities in exposure for the population of England and Wales. Maximum indoor temperature was higher in areas with larger ethnic minority and infant populations, and lower in areas with a higher proportion of people aged ≥ 65 years. Indoor concentrations of outdoor-source PM2.5 were higher in areas with larger ethnic minority and low-income populations. With rising inequality in England and Wales, housing and environmental conditions play an important role in contributing to health inequalities from social disadvantage. Policy relevance Differences in environmental exposures may partly explain inequalities in health outcomes. These differences are mediated by dwelling type and quality. Identifying the driving factors for differences in environmental exposures may allow for the development of interventions to address health inequalities more effectively. This study finds differences in indoor exposure across socio-demographic groups due to both location and housing. This could be of interest to national, regional and local authorities responsible for targeting building retrofit interventions across the housing stock.

A novel dataset of indoor environmental conditions in work-from-home settings

During the last week of March 2020, millions of workers around the world transitioned to working from home due to the COVID-19 pandemic. While much research has explored the behavioural and psychological aspects of work-from-home (WFH), few studies have provided data-driven evaluations of indoor environmental quality (IEQ). This paper presents findings from a summer 2022 field study of IEQ conditions in WFH settings, involving 95 participants in the North American Pacific Northwest. Sensors installed on participants' work desks continuously measured total volatile organic compounds (tVOC), particulate matter (PM2.5), carbon dioxide (CO2) air temperature, humidity, and sound pressure levels (SPLs). Participants also completed surveys on home and workspace characteristics, as well as their subjective assessments of IEQ, well-being, and productivity. The study found that mean indoor concentrations of tVOC, PM2.5, and CO2 were 262 ppb, 5 µg/m3, and 712 ppm, respectively. Indoor air temperature ranged between 14.7–32.3 °C, with a mean of 22.8 °C, while relative humidity and SPL averaged at 52.5 % and 53.7 dBA. Statistically-significant associations were observed between IEQ variables and factors such as residence type, cooking habits, workspace type, and window availability. A future paper will assess the surveyed behavioural and psychological characteristics in greater detail.

Energy retrofits: Factors affecting a just transition to better indoor air quality

In comparison with other European countries, Ireland has a disproportionately high number of poorly performing energy-inefficient buildings. Consequently, Ireland has one of the most ambitious energy retrofit programmes in Europe. The aim of this study was to evaluate the impact of deep energy renovation measures i.e. (replacement of heating system and upgrade to building envelope) on indoor air quality, thermal comfort and ventilation in a sample of primarily social housing in Ireland. A mixed methods approach including measurement of indoor air quality and a thermal comfort questionnaire survey was employed. Indoor concentration measurements of PM2.5, carbon dioxide, formaldehyde, and radon along with measurements of air temperature and relative humidity were made (N=14). Occupants (n=56) completed a thermal comfort questionnaire survey pre- and post-retrofit. Data collection ran from autumn 2020 until autumn 2023.Thermal comfort improved post-retrofit along with occupant satisfaction with the indoor thermal environment and heating-systems. Post-retrofit, higher bedroom CO2, and higher PM2.5 concentrations were recorded in both living areas and bedrooms. Occupant behaviours e.g. blocking wall vents were significant predictors of poorer ventilation while smoking indoors was related to higher concentrations of PM2.5. In general, homes that had mechanical ventilation systems installed were better ventilated. Underventilation, as indicated by visible condensation or mould was observed in half of the social homes surveyed and reported by questionnaire respondents (26 %). Tailored communications to occupants regarding the important role of ventilation and indoor air quality is required as part of retrofit to optimise impacts on IEQ.

Indoor/Outdoor particulate matter (respirable dust) and respirable crystalline silica source tracking in households located proximal to gold mine tailings in Johannesburg, South Africa

Introduction: This study aimed to investigate the concentration of Respirable Crystalline Silica (RCS) and respirable dust, Particulate matters (PM4) concentration in samples measured indoors and outdoors of the nine(9) selected households located proximal to gold mine tailings in Riverlea, Johannesburg. Materials and methods: Sampling locations were separated according to grids, based on distance from the tailings; A (<500 m from the dump), B (>500m<1 km) and C (1 km-3 km). Three households were selected from each grid zone to measure indoor and outdoor PM4 samples continuously over 24 h using GilAir constant sampling pumps. Samples were collected during dry and wet seasons, and respirable crystalline silica in PM4 samples were analysed by an X-ray diffraction method. Results: The mean indoor and outdoor PM4 mass concentrations ranged from 2.02±0.02 µg/m3 to 2.26±0.02 µg/m3, respectively. The dry season mean for PM4 mass concentrations were higher than the wet season PM4 mass concentrations in all zones. The pairwise comparison of PM4 mass concentration for dry and wet seasons revealed no statistically significant difference (p<0.05). The dry season means the indoor/outdoor ratio was greater than one across all zones, suggesting indoor activities as the primary source of PM. In both seasons, the mean indoor and outdoor RCS ranged from 0.02±0.01% to 0.06±0.03%. The mean indoor and outdoor 24 h RCS concentrations in both seasons were below the California Office of Environmental Health Hazard Assessment (OEHHA) defined 24 h ambient exposure threshold of 3 µg/m3. Conclusion: The study found that PM4 concentration was directly proportional to distance from the gold mine tailings. Using RCS as a signature chemical, we found a similar chemical composition in all samples collected in winter and dry season at varied distances. It is concluded that the gold mine tailings are the significant source of PM4 emissions. Therefore, further dust control measures needs to be implemented at the gold mine tailings.

Air pollution by BTEX and the related health risks due to the tobacco smoke, a systematic review

BTEX is a group of hazardous chemical compounds that include benzene, toluene, ethylbenzene, and xylene. The indoor concentration of BTEX is mostly influenced by tobacco smoking, the region within the house, and seasonal variations. This systematic review analyzed studies on BTEX concentrations in indoor air, using data from Google Scholar, Science Direct, and Springer from 2010 to 2020, and performed statistical analysis with R after thorough data extraction and evaluation. Duplicate studies were removed, and disagreements during the article selection process were resolved by a third reviewer. Out of the 1351 articles obtained from the keyword search, only 13 were eventually selected for this study. The most abundant compound found in houses among BTEX was toluene, with a concentration of 13.80±16.50 µg/m3. The results indicated that the concentration of ƩBTEX in houses where smoking occurred was lower than in houses where no smoking occurred (18.52 vs. 27.66 µg/m3); However, the concentration of benzene in smoking houses was higher than in non-smoking houses (7.17±9.42 vs. 2.65±3.77 µg/m3, unpaired Wilcoxon test: p>0.05). The concentration of BTEX in houses was substantially lower than that in cafes (21.10±31.10 vs. 15,100±9740 µg/m3, unpaired Wilcoxon test: p<0.05). The urban region had the most significant accumulation of all BTEXs, with the industrial and rural sectors following suit. The findings indicated that the average concentration of BTEX in warm months (such as spring and summer) were higher than in cold months (such as fall and winter) within houses (28.50±44.30 vs. 8.60±7.77 µg/m3, unpaired Wilcoxon test: p>0.05). The findings indicated that the Cancer Risk (CR) associated with houses (3.11×10-6) and cafes (3.54×10-3) exceeded the permissible threshold. Moreover, the waterpipe cafes that utilized fruit-flavored tobacco had the greatest CR (4.98×10-3). Furthermore, the presence of smoking, regional factors, and seasonal variations did not result in an increase in the hazard quotient (HQ) in houses beyond the acceptable thresholds. Finally, smoking, seasonal variations, and region had critical impact on indoor BTEX concentrations, and they could increase the risk of carcinogenic potential in the indoor environments.

Emergency evacuation risk assessment for toxic gas attacks in airport terminals: Model, algorithm, and application

Transportation infrastructure has often been the target of terrorist attacks, and mitigation of the risk of toxic gas attacks is a challenging task in the design of indoor emergency evacuation systems. Considering multiple emergency response modes, we propose an agent-based risk assessment model and its algorithm to integrate gas diffusion and pedestrian movement data for emergency response, quickly assessing average individual exposure risk. We assessed the exposure status of individuals with respect to their emergency response actions following a toxic gas attack in an airport terminal. The results indicate that in the event of a general gas attack on an airport terminal, ventilation must be immediately ceased along with early evacuation. In areas with a shelter-in-place environment, the ventilation mode and shelter-in-place time should be determined based on the concentration of indoor and outdoor gases. In areas with nerve gas exposure and high population density, a new exit must be established at evacuation bottlenecks, and pedestrians must be guided to evacuate while promptly closing ventilation. These results offer suggestions and strategies for emergency response and decision-making in airport terminals during such incidents.

Impact of Air Conditioning Type on Outdoor Ozone Intrusion into Homes in a Semi-Arid Climate

Outdoor ozone (O3) is elevated on hot, sunny days when residential air conditioning is used most. We evaluated the impact of direct evaporative coolers (ECs) and vapor-compression air conditioners (ACs) on indoor O3 concentrations in homes (N = 31) in Utah County, Utah, United States of America. Indoor and outdoor O3 concentrations were measured for 24 h at each home using nitrite-impregnated glass-fiber filters. AC homes (n = 16) provided a protective envelope from outdoor O3 pollution. Only one AC home had O3 levels above the limit of detection (LOD). Conversely, EC homes (n = 15) provided minimal protection from outdoor O3. Only one EC home had O3 levels below the LOD. The average indoor O3 concentration in EC homes was 23 ppb (95% CI 20, 25). The indoor-to-outdoor (I/O) ratio for O3 in EC homes was 0.65 (95% CI 0.58, 0.72), while the upper bound for the I/O ratio for AC homes was 0.13 (p < 0.001). Indoor exposure to O3 for residents in EC homes is approximately five times greater than for residents of AC homes. Although ECs offer energy and cost-saving advantages, public health awareness campaigns in O3-prone areas are needed, as well as research into O3 pollution controls for direct ECs such as activated carbon filtration.

Indoor Air Quality at an Urban Primary School in Madrid (Spain): Influence of Surrounding Environment and Occupancy.

Monitoring indoor air quality (IAQ) in schools is critical because children spend most of their daytime inside. One of the main air pollutant sources in urban areas is road traffic, which greatly influences air quality. Thus, this study addresses, in depth, the linkages of meteorology, ambient air pollution, and indoor activities with IAQ in a traffic-influenced school situated south of Madrid. The measurement period was from 22 November to 21 December 2017. Simultaneous measurements of indoor and outdoor PM1, PM2.5, and PM10 mass concentrations, ultrafine particle number concentration (PNC) and equivalent black carbon (eBC) were analyzed under different meteorological conditions. PNC and eBC outdoor concentrations and their temporal trend were similar among the sampling points, with all sites being influenced in the same way by traffic emissions. Strong correlations were found between indoor and outdoor concentrations, indicating that indoor pollution levels were significantly affected by outdoor sources. Especially, PNC and eBC had the same indoor/outdoor (I/O) trend, but indoor concentrations were lower. The time delay in indoor vs. outdoor concentrations varied between 0.5 and 2 h, depending on wind speed. Significant differences were found between different meteorological conditions (ANOVA p-values < 2.14 × 10-6). Atmospheric stability periods led to an increase in indoor and outdoor pollutant levels. However, the highest I/O ratios were found during atmospheric instability, especially for eBC (an average of 1.2). This might be related to rapid changes in the outdoor air concentrations induced by meteorology. Significant variations were observed in indoor PM10 concentrations during classroom occupancy (up to 230 µg m-3) vs. non-occupancy (up to 19 µg m-3) days, finding levels higher than outdoor ones. This was attributed to the scholarly activities in the classroom. Conversely, PNC and eBC concentrations only increased when the windows of the classroom were open. These findings have helped to establish practical recommendations and measures for improving the IAQ in this school and those of similar characteristics.

Examining the role of density-driven transport on chlorinated vapor intrusion

This study investigates the influence of density-driven transport on chlorinated vapor intrusion through modeling and experiments. Density-driven transport involves downward vapor advection, potentially reducing vapor intrusion into buildings. A 1-D steady-state numerical model was developed using COMSOL Multiphysics, considering upward diffusion and downward density-driven advection in the subsoil and in the granular fill layer beneath building's foundations. Source vapor concentration and granular fill layer permeability emerged as the key factors affecting density-driven transport. Regardless of building characteristics, for permeabilities in the granular fill layer exceeding 10−7 m2, density-driven transport is expected to become relevant at vapor concentrations of 1 mg m−3, while for lower soil permeabilities (10−8-10−10 m2), density-driven transport impact is expected for vapor concentrations exceeding 1 g m−3. The results of laboratory column trichloroethylene (TCE) diffusion tests through sand and gravel supported these findings, showing a vertical stratification of TCE vapor concentrations consistent with the model. The trends expected by modeling also align with the findings of different field studies, where the source to building attenuation factors (AF) were found to decrease with increasing source vapor concentration. These outcomes highlight that the common approach adopted for vapor intrusion screening from soil gas data based on default AF values independent of source vapor concentration, may potentially lead to an overestimation of indoor concentrations in the presence of high vapor concentrations and highly permeable soils. Given the use of permeable granular fill layers in building construction, this study underscores the importance of accounting for density-driven transport to improve the accuracy of vapor intrusion risk assessment.