Indoor Sources Research Articles

Urban–rural disparity in global estimation of PM2·5 household air pollution and its attributable health burden

Polluting fuels and inefficient stove technologies are still a leading cause of premature deaths worldwide, particularly in low-income and middle-income countries. Previous studies of global household air pollution (HAP) have neither considered the estimation of PM2·5 at national level nor the corresponding attributable mortality burden. Additionally, the effects of climate and ambient air pollution on the global estimation of HAP-PM2·5 exposure for different urban and rural settings remain largely unknown. In this study, we include climatic effects to estimate the HAP-PM2·5 exposure from different fuel types and stove technologies in rural and urban settings separately and the related attributable global mortality burden. Bayesian hierarchical models were developed to estimate an annual average HAP-PM2·5 personal exposure and HAP-PM2·5 indoor concentration (including both outdoor and indoor sources). Model variables were selected from sample data in 282 peer-reviewed studies drawn and updated from the WHO Global HAP dataset. The PM2·5 exposure coefficients from the developed model were applied to the external datasets to predict the HAP-PM2·5 exposure globally (personal exposure in 62 countries and indoor concentration in 69 countries). Attributable mortality rate was estimated using a comparative risk assessment approach. Using weighted averages, the national level 24 h average HAP-PM2·5 exposure due to polluting and clean fuels and related death rate per 100 000 population were estimated. In 2020, household use of polluting solid fuels for cooking and heating led to a national-level average personal exposure of 151 μg/m3 (95% CI 133-169), with rural households having an average of 171 μg/m3 (153-189) and urban households an average of 92 μg/m3 (77-106). Use of clean fuels gave rise to a national-level average personal exposure of 69 μg/m3 (62-76), with a rural average of 76 μg/m3 (69-83) and an urban average of 49 μg/m3 (46-53). Personal exposure-attributable premature mortality (per 100 000 population) from the use of polluting solid fuels at national level was on average 78 (95% CI 69-87), with a rural average of 82 (73-90) and an urban average of 66 (57-75). The average attributable premature mortality (per 100 000 population) from the use of clean fuels at the national level is 62 (54-70), with a rural average of 66 (58-74) and an urban average of 52 (47-57). The estimated HAP-PM2·5 indoor concentration shows that the use of polluting solid fuels resulted in a national-level average of 412 μg/m3 (95% CI 353-471), with a rural average of 514 μg/m3 (446-582) and an urban average of 149 μg/m3 (126-173). The use of clean fuels (gas and electricity) led to an average PM2·5 indoor concentration of 135 μg/m3 (117-153), with a rural average of 174 μg/m3 (154-195) and an urban average of 71 μg/m3 (63-80). Using time-weighted HAP-PM2·5 indoor concentrations, the attributable premature death rate (per 100 000 population) from the use of polluting solid fuels at the national level is on average 78 (95% CI 72-84), the rural average being 84 (78-91) and the urban average 60 (54-66). From the use of clean fuels, the average attributable premature death rate (per 100 000 population) at the national level is 59 (53-64), the rural average being 68 (62-74) and the urban average 45 (41-50). A shift from polluting to clean fuels can reduce the average PM2·5 personal exposure by 53% and thereby lower the death rate. For all fuel types, the estimated average HAP-PM2·5 personal exposure and indoor concentrations exceed the WHO's Interim Target-1 average annual threshold. Policy interventions are urgently needed to greatly increase the use of clean fuels and stove technologies by 2030 to achieve the goal of affordable clean energy access, as set by the UN in 2015, and address health inequities in urban-rural settings. Wellcome Trust, The Lancet Countdown, the Engineering and Physical Sciences Research Council, and the Natural Environment Research Council.

The infiltration of wildfire smoke and its potential dose on pregnant women: Lessons learned from Indonesia wildfires in 2019

The occurrence of wildfires in Indonesia is prevalent during drought seasons. Multiple toxic pollutants emitted from wildfires have deleterious effects on pregnant women. However, the evidence for these on pregnant women was underreported. The study conducted 24-h monitoring of fine particulate matter (PM2.5) concentrations indoors and outdoors in 9 low-income homes in Palangka Raya during the 2019 wildfire season and 6 low-income homes during the 2019 non-wildfire season. A hundred and seventy pregnant women had their PM exposure assessed between July and October 2019 using personal monitors. It was observed that outdoor air pollutant levels were greater than those found indoors without indoor sources. The findings indicate that indoor PM2.5 concentrations were modestly increased by 1.2 times higher than outdoor, suggesting that buildings only partially protected people from exposure during wildfires. The concentrations of PM2.5 were found to be comparatively higher indoors in residential buildings with wood material than in brick houses. The study findings indicate that 8 out of 12 brick houses exhibited a notable RI/O24 h of less than 1 during the wildfires, whereas all I/O24 h ratios during the non-wildfire season were >1, suggesting the influence of indoor sources. Based on the estimation of daily PM2.5 dose, pregnant women received around 21% of their total daily dose during sedentary activity involving cooking. The present research offers empirical support for the view that indoor air quality in low-income households is affected by a complex combination of factors, including wildfire smoke, air tightness, and occupant behaviour. Also, this situation is more likely a potential risk to pregnant women being exposed to wildfire smoke.

Ten questions concerning indoor ultrafine particles

Ultrafine particles (≤100 nm in diameter) are the smallest condensed-phase materials in air. By number, they are the most abundant particles both outdoors and indoors. Because of their small size, they contribute little to mass concentrations of fine particles, a regulated air pollutant with large associated health risks. Inhaling ultrafine particles raises health concerns, in part owing to their ability to migrate from the site of deposition in the respiratory tract. Buildings provide partial protection against ultrafine particles of outdoor origin. The degree of that protection is broadly variable, influenced by particle size and by building design and operational factors, such as ventilation rates and the efficiency of particle filters. Because of the large proportion of time spent by people indoors, much exposure to ultrafine particles occurs in buildings, even for particles of outdoor origin. Diverse indoor sources, including cooking and the use of candles, contribute materially to indoor ultrafine particle concentrations. Indoor sourced ultrafine particle concentrations are also influenced by building design and operational factors. Whether of indoor or outdoor origin, dynamic processes influence the concentrations, sizes, and chemical composition of ultrafine particles. Such processes include deposition to indoor surfaces, coagulation, and sorptive partitioning of semivolatile organic compounds. Advancing scientific and technical knowledge about building factors and dynamic processes that influence indoor ultrafine particle concentrations can contribute (a) to better understanding of associated health risks and (b) to the more effective design and implementation of mitigation strategies and technologies.

Airway and systemic biomarkers of health effects after short-term exposure to indoor ultrafine particles from cooking and candles – A randomized controlled double-blind crossover study among mild asthmatic subjects

BackgroundThere is insufficient knowledge about the systemic health effects of exposure to fine (PM2.5) and ultrafine particles emitted from typical indoor sources, including cooking and candlelight burning. We examined whether short-term exposure to emissions from cooking and burning candles cause inflammatory changes in young individuals with mild asthma. Thirty-six non-smoking asthmatics participated in a randomized controlled double-blind crossover study attending three exposure sessions (mean PM2.5 µg/m3; polycyclic aromatic hydrocarbons ng/m3): (a) air mixed with emissions from cooking (96.1; 1.1), (b) air mixed with emissions from candles (89.8; 10), and (c) clean filtered air (5.8; 1.0). Emissions were generated in an adjacent chamber and let into a full-scale exposure chamber where participants were exposed for five hours. Several biomarkers were assessed in relation to airway and systemic inflammatory changes; the primary outcomes of interest were surfactant Protein-A (SP-A) and albumin in droplets in exhaled air – novel biomarkers for changes in the surfactant composition of small airways. Secondary outcomes included cytokines in nasal lavage, cytokines, C-reactive protein (CRP), epithelial progenitor cells (EPCs), genotoxicity, gene expression related to DNA-repair, oxidative stress, and inflammation, as well as metabolites in blood. Samples were collected before exposure start, right after exposure and the next morning.ResultsSP-A in droplets in exhaled air showed stable concentrations following candle exposure, while concentrations decreased following cooking and clean air exposure. Albumin in droplets in exhaled air increased following exposure to cooking and candles compared to clean air exposure, although not significant. Oxidatively damaged DNA and concentrations of some lipids and lipoproteins in the blood increased significantly following exposure to cooking. We found no or weak associations between cooking and candle exposure and systemic inflammation biomarkers including cytokines, CRP, and EPCs.ConclusionsCooking and candle emissions induced effects on some of the examined health-related biomarkers, while no effect was observed in others; Oxidatively damaged DNA and concentrations of lipids and lipoproteins were increased in blood after exposure to cooking, while both cooking and candle emissions slightly affected the small airways including the primary outcomes SP-A and albumin. We found only weak associations between the exposures and systemic inflammatory biomarkers. Together, the results show the existence of mild inflammation following cooking and candle exposure.

Organohalogenated flame retardants and organophosphate esters from home and preschool dust in Sweden: Pollution characteristics, indoor sources and intake assessment

This study analysed settled dust samples in Sweden to assess children's combined exposure to 39 organohalogenated flame retardants (HFRs) and 11 organophosphate esters (OPEs) from homes and preschools. >94 % of the targeted compounds were present in dust, indicating widespread use of HFRs and OPEs in Swedish homes and preschools. Dust ingestion was the primary exposure pathway for most analytes, except BDE-209 and DBDPE, where dermal contact was predominant. Children's estimated intakes of ∑emerging HFRs and ∑legacy HFRs from homes were 1–4 times higher than from preschools, highlighting higher exposure risk for HFRs in homes compared to preschools. In a worst-case scenario, intakes of tris(2-butoxyethyl) phosphate (TBOEP) were 6 and 94 times lower than the reference dose for children in Sweden, indicating a potential concern if exposure from other routes like inhalation and diet is as high. The study also found significant positive correlations between dust concentrations of some PBDEs and emerging HFRs and the total number of foam mattresses and beds/m2, the number of foam-containing sofas/m2, and the number of TVs/m2 in the microenvironment, indicating these products as the main source of those compounds. Additionally, younger preschool building ages were found to be linked to higher ΣOPE concentrations in preschool dust, suggesting higher ΣOPE exposure. The comparison with earlier Swedish studies indicates decreasing dust concentrations for some banned and restricted legacy HFRs and OPEs but increasing trends for several emerging HFRs and several unrestricted OPEs. Therefore, the study concludes that emerging HFRs and OPEs are replacing legacy HFRs in products and building materials in homes and preschools, possibly leading to increased exposure of children.

Ion-Dipole Interaction Enabling Highly Efficient CsPbI3 Perovskite Indoor Photovoltaics.

Metal halide perovskites are ideal candidates for indoor photovoltaics (IPVs) because of their easy-to-adjust bandgaps, which can be designed to cover the spectrum of any artificial light source. However, the serious non-radiative carrier recombination under low light illumination restrains the application of perovskite-based IPVs (PIPVs). Herein, polar molecules of amino naphthalene sulfonates are employed to functionalize the TiO2 substrate, anchoring the CsPbI3 perovskite crystal grains with a strong ion-dipole interaction between the molecule-level polar interlayer and the ionic perovskite film. The resulting high-quality CsPbI3 films with the merit of defect-immunity and large shunt resistance under low light conditions enable the corresponding PIPVs with an indoor power conversion efficiency of up to 41.2% (Pin : 334.11µWcm-2 , Pout : 137.66µWcm-2 ) under illumination from a commonly used indoor light-emitting diode light source (2956 K, 1062 lux). Furthermore, the device also achieves efficiencies of 29.45% (Pout : 9.80µWcm-2 ) and 32.54% (Pout : 54.34µWcm-2 ) at 106 (Pin : 33.84µWcm-2 ) and 522 lux (Pin : 168.21µWcm-2 ), respectively.

Assessment of children's personal and land use regression model-estimated exposure to NO2 in Springfield, Massachusetts

Ambient nitrogen dioxide (NO2) is derived from tailpipe vehicle emission and is linked with various of health outcomes. Personal exposure monitoring is crucial for accurate assessment of the associated disease risks. This study aimed to evaluate the utility of a wearable air pollutant sampler in determining the personal NO2 exposure of school children for comparison with a model-based personal exposure assessment. We employed cost-effective, wearable passive samplers to directly measure personal exposure of 25 children (aged 12–13 years) in Springfield, MA to NO2 over a five-day period in winter 2018. NO2 levels were additionally measured at 40 outdoor sites in the same region using stationary passive samplers. A land use regression (LUR) model was developed based on the ambient NO2 measures, with a good prediction performance (R2 = 0.72) using road lengths, distance to highway, and institutional land area as predictor variables. Time-weighted averages (TWA), which incorporated the time-activity patterns of participants and LUR-derived estimates in children's primary microenvironments (homes, the school and commute paths), were calculated as an indirect measure of personal NO2 exposure. Results indicated that the conventional residence-based exposure estimate approach, often used in epidemiological studies, differed from the direct personal exposure and could overestimate the personal exposure by up to 109 %. TWA improved personal NO2 exposure estimates by accounting for the time activity patterns of individuals, a difference of 5.4 % ± 34.2 % was found for exposures compared to wristband measurements. Nevertheless, the personal wristband measurements exhibited a large variability due to the potential contributions from indoor and in-vehicle NO2 sources. The findings suggest that exposure to NO2 can be highly personalized based on individual activities and contact with pollutants in specific microenvironments, reaffirming the importance of measuring personal exposure.

‘It feels smaller now’: The impact of the COVID-19 lockdown on apartment residents and their living environment – A longitudinal study

IntroductionThe COVID-19 pandemic and associated lockdown restrictions prolonged residents' exposure to their home environment. The impact of lockdowns could be heightened for apartment residents as they typically have smaller, less versatile homes, and share communal and circulation spaces. This study examined changes in apartment residents’ perceptions and experiences of their dwelling before and after the Australian COVID-19 national lockdown. MethodsParticipants consisted of 214 Australian adults who completed a survey on apartment living between 2017 and 2019 and a follow-up survey in 2020. Questions focused on residents’ perceptions of their dwelling design, apartment living experiences, and personal life events/changes due to the pandemic. Differences between pre- and post-lockdown periods were assessed via paired sample t-tests. The lived experience of a subset of residents (n = 91) following lockdown was also assessed using qualitative content analysis of free-text responses to an open-ended survey item. ResultsCompared to the pre-pandemic period, after the lockdown residents reported less satisfaction with the amount/layout of their apartment space and private open space (e.g., balconies or courtyards). Increased noise annoyance from indoor and outdoor noise sources was also reported, however disputes with neighbours decreased. The qualitative content analysis highlighted a complex interplay of personal, social and environmental impacts of the pandemic on residents. ConclusionsFindings suggest an increased ‘dose’ of the apartment facilitated by stay-at-home orders negatively influenced residents' apartment perceptions. Design strategies that maximise spacious, flexible dwelling layouts with health-promoting elements (e.g., enhanced natural light/ventilation and private open space) are recommended to promote healthy and restorative living environments for apartment residents.

Mechanical ventilation and indoor air quality in recently constructed U.S. homes in marine and cold-dry climates

Data were collected to characterize whole-house mechanical ventilation (WHMV) and indoor air quality (IAQ) in 55 homes in the Marine climate of Oregon and the Cold-Dry climate of Colorado in the U.S. Sixteen homes were monitored for two weeks, with and without WHMV operating. Ventilation airflows; airtightness; time-resolved CO2, PM2.5 and radon; and time-integrated NO2, NOX and formaldehyde were measured. Participants provided information about IAQ-impacting activities, perceptions and ventilation use. All homes had operational cooktop ventilation and bathroom exhaust. Thirty homes had equipment that could meet the ASHRAE 62.2–2010 standard with continuous or controlled runtime and 34 had some WHMV operating as found. Thirty-five of 46 participants with WHMV reported they did not know how to operate it, and only half of the systems were properly labeled. Two-week homes had lower formaldehyde, radon, CO2 and NO (NOX-NO2) when operated with WHMV, and had faster PM2.5 decays following indoor emission events. Overall IAQ satisfaction was similar in Oregon and Colorado, but more Colorado participants (19% vs 3%) felt their IAQ could be improved and more reported dryness as a problem (58% vs. 14%). The collected data indicate that there are benefits of operating WHMV, even when continuous use may not be needed because outdoor pollutant concentrations are low and indoor sources do not present substantial challenges.

Assessment of coarse, fine, and ultrafine particulate matter at different microenvironments of fire stations

The concentrations of respirable particulate matter (PM) and the impact on indoor air quality in occupational settings remains poorly characterized. This study assesses, for the first time, the cumulative and non-cumulative concentrations of 14 fractions of coarse (3.65–9.88 μm), fine (0.156–2.47 μm), and ultrafine (0.015–0.095 μm) PM inside the garage of heavy vehicles, firefighting personal protective equipment’ storage room, bar, and a common area of seven Portuguese fire stations. Sampling campaigns were performed during a regular work week at the fire stations. Levels of daily total cumulative PM ranged from 277.4 to 413.2 μg/m3 (maximum values of 811.4 μg/m3), with the bar (370.1 μg/m3) and the PPE’ storage room (361.3 μg/m3) presenting slightly increased levels (p > 0.05) than the common area (324.8 μg/m3) and the garage (339.4 μg/m3). The location of the sampling site, the proximity to local industries and commercial activities, the layout of the building, the heating system used, and indoor sources influenced the PM concentrations. Fine (193.8–301.0 μg/m3) and ultrafine (41.3–78.2 μg/m3) particles were predominant in the microenvironments of all fire stations and accounted for 71.5% and 17.8% of daily total cumulative levels, respectively; coarse particles (23.3–47.1 μg/m3) represented 10.7% of total PM. The permissible exposure limit (5.0 mg/m3) defined by the Occupational Safety and Health Organization for respirable dust was not overcome in the evaluated fire stations. Results suggest firefighters' regular exposure to fine and ultrafine PM inside fire stations which will contribute to cardiorespiratory health burden. Further studies are needed to characterize firefighters' exposure to fine and ultrafine PM inside fire stations, identify main emission sources, and evaluate the contribution of exposures at fire stations to firefighters’ occupational health risks.

Atypical Mycobacterial Infection: An Achilles heel for Clinician

Atypical mycobacteria or nontuberculous mycobacteria are organisms that cause various diseases such as skin and soft tissue infection, lymphadenitis, pulmonary infection, disseminated infection, and a wide range of more rarely encountered infections. The mycobacteria that most commonly cause this condition are most commonly found in the soil, indoor and outdoor water sources, and are recognized to colonize poorly sanitized medical equipment. Atypical mycobacteria most commonly infect young children, immunocompromised individuals, individuals with indwelling medical equipment, and those who have recently undergone surgical or non-surgical procedures. These bacteria can be further categorized into slow and rapidly growing organisms and grouped by the organ systems they commonly affect. Due to their morphology and growth patterns, atypical mycobacteria are difficult to identify on diagnostic testing. Treatment often requires extended courses of combination antibiotic therapy, frequently with surgical intervention. Bangladesh J Medicine 2023; Vol. 34, No. 2(1) Supplement: 184

69 S-Phenyl Mercapturic Acid as Urinary Biomarker of Indoor Exposure in Children

Abstract Indoor air quality is particularly important for children since they spend more than 90% of their time inside. If outdoor levels of hazardous hydrocarbons are principally traffic related, indoor levels also depend on a variety of sources such as heating and cooking systems, stored products and human behavior (e.g. smoking, cleaning). In this context, within the ENVIRONAGE cohort, was investigated the relationship between SPMA urinary concentration in 214 children (4 to 6-year-old), and indoor sources of air pollution like heating and cooking methods (gas based vs electric) and traffic related air pollution (focusing on NO2 and black carbon). The SPMA urinary concentration was determined developing a high-sensitive UPLC-MS/MS method (LOQ: 0.05 ng/mL). Parents of the children were asked, throughout questionnaire, information about sources of indoor air pollution, such as wood-burning stove, fireplace and gas-based methods of heating or as energy source for the cooking stove and their frequency of using. Interpolation techniques was used to model the regional background levels of NO2 and black carbon for each child's residential address. The use of gas based cooking methods in the residential home of the child was associated with a 74% increase in the mean SPMA concentration of the child (95% Cl: 1.07 to 2.83), correcting for sex, age, BMI, waist circumference, passive smoking, education level of the parents, and time of the day. Consequently, this finding indicates that urinary SPMA can be used as biomarker for looking at indoor determinants of hazard hydrocarbons exposure.

Predicting indoor particle concentration in mechanically ventilated classrooms using neural networks: Model development and generalization ability analysis

This study presents a comprehensive analysis of the model development (structure, parameter settings, and prediction accuracy) and generalization ability of neural networks in the classroom setting. A normalized database for model prediction and verification including indoor parameters from 27 high school classrooms over the course of four semesters was set up (a total of 14,112 sets of data for each variable). Three different models were compared: a back propagation artificial neural network (BP-ANN), a nonlinear autoregressive exogenous neural network (NARX), and a long-term and short-term memory neural network (LSTM). For the prediction of PM1 and PM2.5, which are impacted by outdoor PM concentrations, the best performance was achieved by the NARX model: the mean absolute percentage error (MAPE), root mean squared error (RMSE), and coefficient of determination (R2) were 41–55%, 0.45–1.27 μg/m3, and 0.81–0.87, respectively. The R2 of this model was 22% higher than that of the BP-ANN model and much higher than that of the LSTM model. For the prediction of indoor PM10, which are mostly emitted by indoor sources, relatively good performance was achieved by the LSTM model. The trained NARX model was used successfully to predict indoor time-series PM2.5 concentration and source strength in classrooms in five Chinese cities and five American cities. The calculated indoor source strength was 95.5–119.1 μg/h/P, within the range of the measured indoor source strength. The indoor PM2.5 concentrations calculated by a theoretical equation without the consideration of indoor source were 20.8–60.0% smaller than those calculated by the trained model.

The menace and mitigation of air pollution in the built environment: A review

Air pollution has become one of the leading causes of death globally. This paper investigates the causes as well as sources of air pollution in the indoor and outdoor environment. It identifies anthropogenic activities related such as transportation and other activities involving the combustion of fossil fuel as the major causes of air pollution. The several and diverse health implications of air pollution were highlighted. The dangerous nature of carbon monoxide was x-rayed and the common indoor and outdoor sources were discussed. The risks of carbon monoxide poisoning from generator fumes and vehicle exhaust were clearly enumerated. Particulate matter (PM10, PM2.5 and ultra fine PM) were clearly shown to be the major casue of chronic and fatal respiratory and cardiovascular diseases. Indoor air quality, which is usually overlooked was brought to the fore and shown to be worse than outdoor air quaility in some cases, especially where ventilation is poor. The inextricable link between air pollution and climate change was also established. Mitigative measure such as policies/acts, replacement of fossil fuel with solar PVs, replacement of conventional vehicles with electric vehicles and establishment of urban forests were discussed. Frequent and evenly distributed air quality monitoring, especially using android-enabled portable devices was broached. Besides, policies and other global approaches, individuals must adopt personal protective measures to protect themselves from the menace of air pollution.

Volatile organic compounds in children's bedrooms, Shanghai, China: Sources and influential factors

Exposure to volatile organic compounds (VOCs) in the residential environment may cause harm to children's health. During 2013–2014, we collected air samples from 358 children's bedrooms in Shanghai, China, to quantify indoor volatile organic compounds (VOCs) levels, and investigate the influential factors and the sources of indoor VOCs. This study analyzed tested and analyzed all the collected air samples by gas chromatography-mass spectrometry. Twelve kinds of VOCs were found, and the most abundant VOCs in terms of median concentration was dodecane, followed by toluene and hexadecane. This study further analyzed three influential factors on the concentration of VOCs: building materials (floor and wall covering materials), household chemical products, and ambient exposures (traffic exposure, shopping center exposure, industrial area exposure, and river/lake exposure). Most of the VOCs concentrations were mainly dominated by indoor sources or the combination of indoor and outdoor sources. Indoor VOCs concentrations were positively associated with oil painting wall covering used in children's bedrooms, frequently usage of household chemical products, and ambient traffic exposure. The rank of the significant influential factors of indoor VOCs concentrations was obtained through the stratification analysis combined with the elimination and disturbance methods. Principal component analysis was used to identify potential sources of indoor VOCs, and four main factors in children's bedrooms were generated, including household chemical products, building materials, vehicle-related emissions, and organic solvents. This study can be used to control and manage the levels of VOCs in residential environments.

Survey on NLOS Identification and Error Mitigation for UWB Indoor Positioning

Ultra-wideband (UWB) positioning systems often operate in a non-line-of-sight (NLOS) environment. NLOS propagation has become the main source of ultra-wideband indoor positioning errors. As such, how to identify and correct NLOS errors has become a key problem that must be solved in high-accuracy indoor positioning technology. This paper firstly describes the influence of the NLOS propagation path on localization accuracy and the generation method of ultra-wideband signals, and secondly classifies and analyzes the currently available algorithms for ultra-wideband non-line-of-sight (NLOS) identification and error suppression. For the identification of NLOS, the residual analysis judgement method, statistical feature class identification method, machine learning method and geometric feature judgement method are discussed. For the suppression of NLOS propagation errors, weighting-based methods, filtering-based methods, line-of-sight reconstruction algorithms, neural network algorithms, optimization methods with constraints, and path tracing methods are discussed. Finally, we conclude the paper and point out the problems that need to be solved in NLOS indoor positioning.

Monitoring and apportioning sources of indoor air quality using low-cost particulate matter sensors

Air quality is one of the most important factors in public health. While outdoor air quality is widely studied, the indoor environment has been less scrutinised, even though time spent indoors is typically much greater than outdoors. The emergence of low-cost sensors can help assess indoor air quality. This study provides a new methodology, utilizing low-cost sensors and source apportionment techniques, to understand the relative importance of indoor and outdoor air pollution sources upon indoor air quality. The methodology is tested with three sensors placed in different rooms inside an exemplar house (bedroom, kitchen and office) and one outdoors. When the family was present, the bedroom had the highest average concentrations for PM2.5 and PM10 (3.9 ± 6.8 ug/m3 and 9.6 ± 12.7 μg/m3 respectively), due to the activities undertaken there and the presence of softer furniture and carpeting. The kitchen, while presenting the lowest PM concentrations for both size ranges (2.8 ± 5.9 ug/m3 and 4.2 ± 6.9 μg/m3 respectively), presented the highest PM spikes, especially during cooking times. Increased ventilation in the office resulted in the highest PM1 concentration (1.6 ± 1.9 μg/m3), highlighting the strong effect of infiltration of outdoor air for the smallest particles. Source apportionment, via positive matrix factorisation (PMF), showed that up to 95 % of the PM1 was found to be of outdoor sources in all the rooms. This effect was reduced as particle size increased, with outdoor sources contributing >65 % of the PM2.5, and up to 50 % of the PM10, depending on the room studied. The new approach to elucidate the contributions of different sources to total indoor air pollution exposure, described in this paper, is easily scalable and translatable to different indoor locations.

Ambient formaldehyde concentrations in summer in 30 Chinese cities and impacts on air cleaning of built environment

Formaldehyde is an important carcinogen commonly found indoors. Its indoor sources have been intensively investigated. But study on outdoor formaldehyde concentration, which is potentially an important source to indoors, remains scarce. This study attempts to characterize temporal and spatial distribution of the atmospheric formaldehyde concentration in Chinese cities. Diurnal variation of ambient formaldehyde was examined in 6 cities and peak hours were identified between 12:00 pm and 3:00 pm. Consequently, outdoor formaldehyde concentrations were measured in the peak hours in 30 cities during the summer months of Jul.-Aug., 2022. The formaldehyde concentrations in the peak hours fell into a range of 0.005–0.087 mg/m3 (median value is 0.027 mg/m3), 87.7% of which have exceeded the chronic reference exposure criteria of 0.009 mg/m3 set by Office of Environmental Health Hazard Assessment. Health risk analysis suggests that exposure to ambient formaldehyde could cause a median carcinogenic risk of 1.9 × 10−5 (3.17×10−6–6.13×10−5), higher than threshold limit of 10−6. Pearson correlation analysis of the 30 cities shows that ambient summertime atmospheric formaldehyde concentrations of the city are positively correlated with its Gross Domestic Product (r = 0.48). We also found that the outdoor formaldehyde concentrations in urban areas (median: 0.017 mg/m3) is slightly higher than those in suburban areas (median: 0.013 mg/m3). Results here prove that outdoor formaldehyde is ubiquitous in Chinese cities and reduces effectiveness of ventilation in dilution indoor concentrations. Neglecting it would underestimate air cleaner capacity needed by a factor of about two. It should be accounted for in health analysis and air quality engineering control design of built environment in the future.

Health Risks Posed by Dermal and Inhalation Exposure to High Concentrations of Chlorinated Paraffins Found in Soft Poly(vinyl chloride) Curtains

Chlorinated paraffins (CPs) are used in many products, including soft poly(vinyl chloride) curtains, which are used in many indoor environments. Health hazards posed by CPs in curtains are poorly understood. Here, chamber tests and an indoor fugacity model were used to predict CP emissions from soft poly(vinyl chloride) curtains, and dermal uptake through direct contact was assessed using surface wipes. Short-chain and medium-chain CPs accounted for 30% by weight of the curtains. Evaporation drives CP migration, like for other semivolatile organic plasticizers, at room temperature. The CP emission rate to air was 7.09 ng/(cm2 h), and the estimated short-chain and medium-chain CP concentrations were 583 and 95.3 ng/m3 in indoor air 21.2 and 172 μg/g in dust, respectively. Curtains could be important indoor sources of CPs to dust and air. The calculated total daily CP intakes from air and dust were 165 ng/(kg day) for an adult and 514 ng/(kg day) for a toddler, and an assessment of dermal intake through direct contact indicated that touching just once could increase intake by 274 μg. The results indicated that curtains, which are common in houses, could pose considerable health risks through inhalation of and dermal contact with CPs.

The impact of automated control of indoor air pollutants on cardiopulmonary health, environmental comfort, sleep quality in a simulated apartment: A crossover experiment protocol

Air pollution makes an impact on cardio-pulmonary health. Since people spend over 90% of their time indoors, exposures to the indoor environment make the most significant impact on health. Among indoor sources, cooking emits the most particles that disperse through the residential indoor environment and expose occupants. We use fully controlled simulated residential modules to conduct exposure experiments. In the pilot study, participants stayed in modules for 1 week, and in the main study, 14 participants will stay in the module for 4 weeks. One module is operated as a classical US house air supply recommendation. The second module has an advanced control system that, alongside the standard air supply, activates air quality interventions: stove hood, portable air cleaners, bathroom exhaust and air flush (increasing air supply ∼3 times) as a function of the PM2.5 levels in the space. Environmental sensors based on Internet of Things technology simultaneously monitored Particulate Matter (PM2.5), CO2, Total Volatile Organic Compounds Relative Humidity and air temperature in all spaces and operated air quality interventions. Participant’s scheduled activities include morning and evening tasks, Monday through Friday. Participants may leave the module during the day. They will be asked to cook breakfast and dinner using lab-provided recipes. We measured each participant’s blood pressure, heart rate, and heart rate variability. Blood and urine samples were collected 3 times per participant in the pilot and will be collected 2 times a week in the main study. Up to 20 ml of blood and a minimum of 30 ml of urine will be sampled per collection. Analysis of blood and urine was performed for 8-hydroxy-2-deoxyguanosine (8-OHdG, urine), von Willebrand Factor (vWF, blood plasma), high sensitivity C-Reactive Protein (hsCRP, blood serum), Interleukin-6 (blood plasma), CD11b (blood), Fibrinogen (blood plasma), and Myeloperoxidase (blood serum). We conducted a Pilot for 2 weeks with 3 participants to test the study protocol and data collection. We adjusted the protocol for the main study based on the pilot results. Results showed that the proposed study protocol could be completed, and the methodology adopted in this study will provide valuable insights into the relationship between exposure to cooking particles and occupants' health.Trial registration: Mayo Clinic IRB 20-007908.