Relationship between indoor and outdoor size-fractionated particulate matter in urban microenvironments: Levels, chemical composition and sources

Size-fractionated carbonaceous and iron-rich particulate matter in urban environments of France and Senegal

Road traffic is one of the main sources of particulate matter in the urban environment, emitting particulate organic and elemental carbon compounds and metal-rich particles through combustion and brakes and tires wear. In Western Africa, the carbon and metal composition of airborne particles is also influenced by additional sources linked to biomass combustion and recent industrialization. Here, we investigated the impact of combustion-related and non-combustion-related emissions on the distribution of carbonaceous fractions and iron-rich particles in two urban environments in France and Senegal. The supermicron fraction (D a > 1 µm) showed a significantly higher isothermal remanent magnetization (SIRM) than finer fractions, accounting for 79% in France and 81% in Senegal of the total SIRM. In the submicron fraction (D a < 1 µm), we noted significantly higher concentrations of total carbon (TC) and elemental carbon (EC) than for other fractions, both accounting for 71% in France and 68% and 75% in Senegal of the total and elemental particulate carbon concentration, respectively. Electron microscope observations revealed the presence of iron-rich particles forD a < 0.2 µm, however, associated with a weak SIRM. Such iron particles may be produced by combustion or abrasion while we suspect that emissions by the abrasion process produce larger particles.

Prenatal Exposure to Source-Specific Fine Particulate Matter and Autism Spectrum Disorder

In this study, associations between prenatal exposure to fine particulate matter (PM2.5) from 9 sources and development of autism spectrum disorder (ASD) were assessed in a population-based retrospective pregnancy cohort in southern California. The cohort included 318,750 mother-child singleton pairs. ASD cases (N = 4559) were identified by ICD codes. Source-specific PM2.5 concentrations were estimated from a chemical transport model with a 4 × 4 km2 resolution and assigned to maternal pregnancy residential addresses. Cox proportional hazard models were used to estimate the hazard ratios (HR) of ASD development for each individual source. We also adjusted for total PM2.5 mass and in a separate model for all other sources simultaneously. Increased ASD risk was observed with on-road gasoline (HR [CI]: 1.18 [1.13, 1.24]), off-road gasoline (1.15 [1.12, 1.19]), off-road diesel (1.08 [1.05, 1.10]), food cooking (1.05 [1.02, 1.08]), aircraft (1.04 [1.01, 1.06]), and natural gas combustion (1.09 [1.06, 1.11]), each scaled to standard deviation increases in concentration. On-road gasoline and off-road gasoline were robust for other pollutant groups. PM2.5 emitted from different sources may have different impacts on ASD. The results also identify PM source mixtures for toxicological investigations that may provide evidence for future public health policies.

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.

Size-segregated content of heavy metals and polycyclic aromatic hydrocarbons in airborne particles emitted by indoor sources

Indoor air quality is negatively affected by the emission of different combustion sources releasing airborne particles and related particle-bound toxic compounds (e.g., heavy metals and polycyclic aromatic hydrocarbons). To date, very few studies focused on the chemical characterization of the airborne particles emitted by indoor sources were carried out; moreover, no data on their size-resolved chemical compositions are available. In the present study, an experimental analysis aimed at determining the size-segregated content of heavy metals and polycyclic aromatic hydrocarbons in airborne particles (including sub-micrometric ones) emitted by widely-used indoor combustion sources (i.e., incenses, candles, mosquito-coils, and cooking activities) was carried out. To this purpose, airborne particles were collected through an electric low-pressure impactor and were post-analyzed by means of chromatography-mass spectrometry and atomic emission spectrometry techniques. Results of the analyses showed that the chemical composition of the emitted particles is not invariant to the particle size, indeed, an important contribution of sub-micrometric particle range to the total mass of chemical compounds emitted by the sources was noticed. These findings also demonstrated that significant underestimations of particle-bound compounds depositing in the lungs could occur if size-dependent compositions are not adopted.

To breathe or not to breathe: Inhalational exposure to heavy metals and related health risk

This study reviewed scientific literature on inhalation exposure to heavy metals (HMs) in various indoor and outdoor environments and related carcinogenic and non-carcinogenic risk. A systematic search in Web of Science, Scopus, PubMed, Embase, and Medline databases yielded 712 results and 43 articles met the requirements of the Population, Exposure, Comparator, and Outcomes (PECO) criteria. Results revealed that HM concentrations in most households exceeded the World Health Organization (WHO) guideline values, indicating moderate pollution and dominant anthropogenic emission sources of HMs. In the analyzed schools, universities, and offices low to moderate levels of air pollution with HMs were revealed, while in commercial environments high levels of air pollution were stated. The non-carcinogenic risk due to inhalation HM exposure exceeded the acceptable level of 1 in households, cafes, hospitals, restaurants, and metros. The carcinogenic risk for As and Cr in households, for Cd, Cr, Ni, As, and Co in educational environments, for Pb, Cd, Cr, and Co in offices and commercial environments, and for Ni in metros exceeded the acceptable level of 1 × 10-4. Carcinogenic risk was revealed to be higher indoors than outdoors. This review advocates for fast and effective actions to reduce HM exposure for safer breathing.

PSCF method for source identification of particulate matter in an agricultural background region in Brazil

The use of mathematical and statistical models to investigate potential sources of pollutants that have been transported by air masses to a study site is important for establishing control and monitoring measures for air pollutants such as PM10 and PM2.5. During the study period, from 2018 to 2021, the concentrations of PM10 and PM2.5 recorded in Ribeirão Preto (SP, Brazil) were higher during spring and winter, with a tendency to increase the amplitude and its maximum values relative to daily averages. The source-receptor model, Potential Source Contribution Function (PSCF), was used to identify probable sources of these pollutants, and the regions known as Triângulo Mineiro and Intermediate Geographic Region of Juiz de Fora (MG, Brazil) were the main regions associated with high PSCF probability values (> 0.5) as sources of PM. These regions indicate that the possible sources of PM emissions are associated with industrial complexes and agriculture, especially coffee production.

Levels and health risk assessments of Phthalate acid esters in indoor dust of some microenvironments within Ikeja and Ota, Nigeria

The levels, profiles of Phthalate acid esters (PAEs) and their associated health risk in children and adults using indoor dust samples were assessed from nine (9) microenvironments in Nigeria. Six PAEs congeners were determined using Gas Chromatography-Mass Spectrometry and the human health risk assessments of PAEs exposure to children and adults were computed using the United States Environmental Protection Agency (USEPA) exposure model. The mean concentrations of the total PAEs (Σ6PAEs) in indoor dust across the study locations ranged from 1.61 ± 0.12 to 53.3 ± 5.27 μg/g with 72.0% of di-n-octyl phthalate (DnOP) as the most predominant contributor of PAEs in sample locations B, C, D, E, F and G. PAEs estimated daily intake results exceeded the USEPA value of 20 and 50 kg/bw/day for children and adults respectively in some locations. Non-carcinogenic risk exposure indicated no risk (HI < 1), while the carcinogenic risk was within the recommended threshold of 1.00 × 10-4 to 1.00 × 10-6 for benzyl butyl phthalate and bis-2-ethylhexyl phthalate. From our findings, lower levels of PAEs were observed in locations with good ventilation system. Also, the human health risk evaluation indicated indoor dust ingestion as the dominant exposure route of PAEs for both children and adults, while the children were at a higher risk of PAEs exposure. To protect children susceptible to these endocrine-disrupting pollutants, soft vinyl children's toys and teething rings should be avoided. Appropriate policies and procedures on the reduction of PAEs exposure to humans should be enacted by all stakeholders, including government regulatory agencies, industries, school administrators and the entire community.

The Representativeness of Outdoor Particulate Matter Concentrations for Estimating Personal Dose and Health Risk Assessment of School Children in Lisbon

This study investigated the suitability of outdoor particulate matter data obtained from a fixed monitoring station in estimating the personal deposited dose. Outdoor data were retrieved from a station located within the urban area of Lisbon and simulations were performed involving school children. Two scenarios were applied: one where only outdoor data were used assuming an outdoor exposure scenario, and a second one where an actual exposure scenario was adopted using the actual microenvironment during typical school days. Personal PM₁₀ and PM_2.5 dose (actual exposure scenario) was 23.4% and 20.2% higher than the ambient (outdoor exposure scenario) PM₁₀ and PM_2.5 doses, respectively. The incorporation of the hygroscopic growth in the calculations increased the ambient dose of PM₁₀ and PM_2.5 by 8.8% and 21.7%, respectively. Regression analysis between the ambient and personal dose showed no linearity with R² at 0.07 for PM₁₀ and 0.22 for PM_2.5. On the other hand, linear regression between the ambient and school indoor dose showed no linearity (R² = 0.01) for PM₁₀ but moderate (R² = 0.48) for PM_2.5. These results demonstrate that ambient data must be used with caution for the representativeness of a realistic personal dose of PM_2.5 while for PM₁₀ the ambient data cannot be used as a surrogate of a realistic personal dose of school children.

The role of systemic inflammation and oxidative stress in the association of particulate air pollution metal content and early cardiovascular damage: A panel study in healthy college students

Exposure to fine particulate matter (PM_2.5) has been associated with adverse cardiovascular outcomes. However, the effects of toxic metals in PM_2.5 on cardiovascular health remain unknown. To investigate the early cardiovascular effects of specific PM_2.5 metal constituents at the personal level, we conducted a panel study on 45 healthy college students in Caofeidian, China. Personal exposure concentrations and cardiovascular effect markers were monitored simultaneously within one year in four study periods. Four linear mixed-effects models were used to analyze the relationship between personal exposure to PM_2.5 and 15 metal fractions (Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sb, and Pb) with soluble CD36 (sCD36), C-reactive protein (CRP), and oxidized low-density lipoprotein (OX-LDL) levels, heart rate, and blood pressure. The concentrations of most individual metals (Mn, Cu, Zn, As, Se, Mo, Cd, Sb and Pb) were the highest in winter. Meanwhile, there were significant differences in inflammatory (sCD36 and CRP) and oxidative stress (OX-LDL) markers in the serum of participants over the four seasons. In particular, the estimated effects of personal metal exposure (such as V, As, Se, Cd, and Pb) on sCD36 and pulse pressure (PP) levels were consistently significant across the four LME models. A significant mediating role of sCD36 was also found in the relationship between personal exposure to Zn and Cr and changes in PP levels. Our findings provide clues and potential mechanisms regarding the cardiovascular effects of specific toxic constituents of PM_2.5 in healthy young adults.

Trace elements in outdoor and indoor PM2.5 in urban schools in Xi'an, Western China: characteristics, sources identification and health risk assessment

The PM_2.5-bounded elements were measured in outdoor and indoor from two urban middle schools in Xi'an. The PM_2.5 mass was from 42.4 to 283.7 µg/m³ with bounded element from 3.4 to 41.7 µg/m³. Both the particle mass and the bounded elements displayed higher levels compared with previous studies in school environments. The most abundant elements were Ca, K, Fe, S, Zn and Cl both indoor and outdoor in two schools, which accounted for about 90% of the total elements. Strong correlations between indoor and outdoor were obtained along with relative effect from students' and teachers' activities on the indoor distributions between workdays and weekends. There had different indoor/outdoor (I/O) distributions for the two schools. It revealed the main outdoor sources for elements in JT and predominance of indoor sources in HT. The principal component analysis investigated main sources of elements in this study were coal combustion, geogenic dust and industrial emission, even though there displayed differences in the two school classrooms. The health risk assessment showed that the cancer risk for Ni and Pb was below the safe value while As and Cr might pose acceptable potential threat to both students' and teachers' health. The total non-cancer risks of accumulative multi-metals in JT exhibited to be higher than 1, indicating that there existed the potential non-carcinogenic health risks of exposure metals.

PM2.5 elemental composition in indoor residential environments and co-exposure effects on respiratory health in an industrial area

This study aimed to identify and characterise indoor sources of particulate matter (PM) in domestic environments. 74 inhabited apartments located in the urban area of Gela (Sicily, Italy), close to a refinery, and in three villages of the hinterland were evaluated, in real-world conditions, for the elemental composition of PM_2.5. The samples were collected simultaneously inside and outside each apartment for 48 h. In addition, two of the apartments were simultaneously studied for four weeks. The elemental composition of PM_2.5 was determined by applying a chemical fractionation procedure followed by inductively-coupled plasma spectrometry analysis, with both optical emission and mass detection. The extractable, more bio-accessible fraction (_ext), and the mineralised residual fraction (_res) of each element were determined, thus increasing the selectivity of elements as source tracers. Indoor air in the considered apartments was affected by both outdoor pollution and specific indoor emission sources. The behaviour of each source was studied in detail, identifying a reliable tracer: Ti_res for soil, As_ext for industrial sources, V_ext for heavy oil combustion, Ce for cigarette smoking and Mo for the use of vacuum dust cleaners. As_ext and V_ext showed an excellent infiltration capacity, while the concentration of Ti_res was affected by a low infiltration capacity and by the contribution of particles re-suspension caused by the residents' movements. In the case of Ce and Mo, indoor concentrations were much higher than outdoor with a high variability among the apartments, due to the inhabitants' habits concerning cigarette smoke and use of electric appliances. To test the overall effect of the concomitant exposure to the identified sources on Wh12 M and on DDA, a WQS analysis was conducted. Cigarette smoking and heavily oil combustion driven the Wh12 M odds increase, while the DDA odds increase was mainly driven by heavily oil combustion and the use of vacuum dust cleaners.

Comparison of the Application of Three Methods for the Determination of Outdoor PM2.5 Design Concentrations for Fresh Air Filtration Systems in China

With the increasing popularity of fresh-air filtration systems, the methods of determining the outdoor PM_2.5 design concentration have become more important. However, the monitoring of atmospheric fine particles in China started relatively late, and there are relatively few cities with complete data, with obvious regional differences, which led to many problems in the selection of air filters for fresh-air filtration systems. In this paper, three methods of determining outdoor PM_2.5 design concentration were analyzed using the daily average concentration of PM_2.5 in 31 provincial capital cities from 2016 to 2020. Six typical cities in different regions were also taken as examples. The advantages and disadvantages of the three existing statistical methods were compared and analyzed, as well as the corresponding differences in the selection of outdoor PM_2.5 concentration value on the filter systems. The results showed that the method of mathematical induction was more accurate and reasonable for the calculation of outdoor PM_2.5 design concentrations. The local outdoor PM_2.5 design concentration could be quickly calculated using the recommended coefficient K and annual average PM_2.5 concentration of the region, especially for small and medium-sized cities without monitoring data. However, the recommended coefficient K should be provided based on the specific region, and should be divided into values for strict conditions and normal conditions during use. This would provide a simple and effective way to select the correct air filters for practical engineering.

Assessment of indoor air quality and risk of COVID-19 infection in Spanish secondary school and university classrooms

Despite the risk of transmission of SARS-CoV-2, Spanish educational centers were reopened after six months of lockdown. Ventilation was mostly adopted as a preventive measure to reduce the transmission risk of the virus. However, it could also affect indoor air quality (IAQ). Therefore, here we evaluate the ventilation conditions, COVID-19 risk, and IAQ in secondary school and university classrooms in Toledo (central Spain) from November 2020 to June 2021. Ventilation was examined by monitoring outdoor and indoor CO2 levels. CO2, occupancy and hygrothermal parameters, allowed estimating the relative transmission risk of SARS-CoV-2 (Alpha and Omicron BA.1), H r, under different scenarios, using the web app COVID Risk airborne . Additionally, the effect of ventilation on IAQ was evaluated by measuring indoor/outdoor (I/O) concentration ratios of O3, NO2, and suspended particulate matter (PM). University classrooms, particularly the mechanically ventilated one, presented better ventilation conditions than the secondary school classrooms, as well as better thermal comfort conditions. The estimated H r for COVID-19 ranged from intermediate (with surgical masks) to high (no masks, teacher infected). IAQ was generally good in all classrooms, particularly at the university ones, with I/O below unity, implying an outdoor origin of gaseous pollutants, while the source of PM was heterogeneous. Consequently, controlled mechanical ventilation systems are essential in educational spaces, as well as wearing well-fitting FFP2-N95 masks indoors is also highly recommended to minimize the transmission risk of COVID-19 and other airborne infectious diseases.

Barking up the Right Tree: Using Tree Bark to Track Airborne Particles in School Environment and Link Science to Society

Children's exposure to air pollution affects both their health and learning skills. Fine and ultrafine particulate matter (PM2.5, PM1), notably issued from traffic sources in urban centers, belong to the most potential harmful health hazards. However their monitoring and the society's awareness on their dangers need to be consolidated. In this study, raising teacher and pupil involvement for air quality improvement in their schools environment is reached through developing a passive monitoring technique (bio-sensors made of tree bark). The experiment was implemented in two urban elementary schools situated close to a main traffic road of the city of Toulouse (South of France). Magnetic properties, carbonaceous fraction measurements, and scanning electronic microscopy (SEM-EDX) investigations were realized both on passive bio-sensors and filters issued from active sampling. We find that traffic is the main PM1 source for both outdoors and indoors at schools. Higher levels of outdoor PM in the school's environments compared to urban background are reached especially in the cold period. The schools proximity to a main traffic source and lack of ventilation are the main causes for observed PM1 accumulation in classrooms. The co-working experiment with educational teams and pupils shows that the use of bio-sensors is a driver for children empowerment to air pollution and therefore represents a potential key tool for the teachers though limiting eco-anxiety. As PM accumulation is observed in many scholar environments across Europe, the proposed methodology is a step toward a better assessment of PM impact on pupil's health and learning skills.

Potential ecological and health risks of heavy metals for indoor and corresponding outdoor dust in Hefei, Central China

The harm caused by indoor dust has received increasing attention in recent years. However, current studies have ignored comparisons with the corresponding outdoor dust. This study aimed to investigate the distribution of heavy metals in indoor and corresponding outdoor dust and the ecological and health risks they pose in Hefei, Central China. We analyzed O/I (outdoor/indoor concentration ratios) values, background comparison, and correlation analysis (heavy metal concentrations vs. particle size) and found that Cu, Zn, and Cd mainly existed in indoor sources, while V, Co, and As mainly existed in outdoor sources, and both family sizes and floor number influenced the variation of O/I. Through a new potential ecological risk assessment method, we determined that Cd risk levels in indoor and outdoor dust were extreme and high to extreme, respectively. Additionally, the carcinogenic risks of Ni, As, and Cr were not negligible. The risk of indoor dust was higher than that of outdoor dust for the heavy metals studied, implying a poor indoor environment. Notably, indoor dust from families with smaller sizes, lower floors, and smokers had higher ecological and carcinogenic risks.

Source apportionment of children daily exposure to particulate matter

The present study aims to investigate the sources of particulate pollution in indoor and outdoor environments, with focus on determining their contribution to the exposure of children to airborne particulate matter (PM). To this end, parallel indoor and outdoor measurements were carried out for a selection of 40 homes and 5 schools between September 2017 and October 2018. PM2.5 and PM2.5-10 samples were collected during five days in each microenvironment (ME) and analysed by X-Ray Fluorescence (XRF), for the determination of elements, and by a thermal-optical technique, for the measurement of organic and elemental carbon. The source apportionment analysis of the PM composition data, by means of the receptor model SoFi (Source Finder) 8 Pro, resulted in the identification of nine sources: exhaust and non-exhaust emissions from traffic, secondary particles, heavy oil combustion, industry, sea salt, soil, city dust, and an indoor source characterized by high levels of organic carbon. Integrated daily exposure to PM2.5 was on average 21 μg/m³. The organic matter, resulting from cleaning, cooking, smoking and biological material, was the major source contributing by 31% to the PM2.5 exposure. The source city dust, which was highly influenced by the resuspension of dust in classrooms, was the second main source (26%), followed by traffic (24%). The major sources affecting the integrated exposure to PM10, which was on average 33 μg/m³, were the city dust (39%), indoor organics (24%) and traffic (16%). This study provides important information for the design of measures to reduce the exposure of children to PM.

Fluorine mass balance analysis and per- and polyfluoroalkyl substances in the atmosphere

Given that only a small number of per- and polyfluoroalkyl substances (PFAS) are routinely monitored, levels of PFAS in the atmosphere may be underestimated. A protocol including analyses of target PFAS (n = 50), water-soluble fluoride, and total fluorine has been proposed and applied to atmospheric samples. The whole method recovery (including extraction recovery and sampling efficiency) of 90-110% were obtained for the majority of compounds (48/50) with low deviations between replicates (< 20%). Fluorotelomer alcohols were the most prevalent PFAS in the indoor air, while the outdoor air was dominated by the ultrashort-chain ionic PFAS (e.g., trifluoroacetic acid and perfluoropropanoic acid). Concentrations of organofluorine (OF) compounds calculated from the fluorine mass balance ranged from 1.74 ng F/m³ to 14.3 ng F/m³ and from 52.0 ng F/m³ to 1100 ng F/m³ in the particulate and gaseous phases, respectively, whereas only a minor proportion (around 1%) could be explained by target PFAS. In indoor air, OF compounds were observed in relatively high levels and with a shift to the fine particles (PM_<1) . Our results reveal a large proportion of unidentified OF signatures in the atmosphere and suggest the need to use multiple approaches to improve our understanding of airborne fluorinated substances.

Indoor Air Pollution and the Health of Vulnerable Groups: A Systematic Review Focused on Particulate Matter (PM), Volatile Organic Compounds (VOCs) and Their Effects on Children and People with Pre-Existing Lung Disease

Air pollution affects health, but much of the focus to this point has been on outdoor air. Higher indoor pollution is anticipated due to increasingly energy-efficient and less leaky buildings together with more indoor activities. Studies of indoor air pollution focusing on children and people with respiratory disease from the database Web of Science (1991–2021) were systemically reviewed according to the PRISMA guidelines, with 69 studies included in the final selection. Emissions from building materials affected indoor air quality, and ventilation also had an influence. The main indoor air pollutants are Volatile Organic Compounds (VOCs) and Particulate Matter (PM). PM sources included smoking, cooking, heating, candles, and insecticides, whereas sources of coarse particles were pets, housework and human movements. VOC sources included household products, cleaning agents, glue, personal care products, building materials and vehicle emissions. Formaldehyde levels were particularly high in new houses. Personal exposure related to both indoor and outdoor pollutant levels, highlighting home characteristics and air exchange rates as important factors. Temperature, humidity, educational level, air purifiers and time near sources were also related to personal exposure. There was an association between PM and Fractional exhaled Nitric Oxide (FeNO), lung function, oxygen saturation, childhood asthma and symptoms of chronic obstructive pulmonary disease (COPD) patients. High VOCs were associated with upper airways and asthma symptoms and cancer. Effective interventional studies for PM in the future might focus on human behavior together with air purifiers and increased ventilation, whereas VOC interventions might center more on building materials and household products, alongside purification and ventilation.

Children's exposure to size-fractioned particulate matter: Chemical composition and internal dose

The health effects of the particulate matter (PM) depend not only on its aerodynamic diameter (AD) and chemical composition, but also on the time activity pattern of the individuals and on their age. The main objective of this work was to assess the exposure of children to aerosol particles by using personal instruments, to study the particle size and composition of the inhaled PM, and to estimate their transport and deposition into the human respiratory tract (HRT). The average daily PM2.5 exposure was 19 μg/m³ and the size fractions with the greatest contribution to PM2.5 concentrations were 1 < AD <2.5 μm and AD <0.25 μm. Results indicated a contribution of 9% from the mineral aerosol, 7.2% from anthropogenic sulphate, 6.7% from black carbon and 5% from anthropogenic trace elements to the daily exposure to PM2.5. The levels of mineral and marine elements increased with increasing particle size, while anthropogenic elements were present in higher concentrations in the finest particles. Particle size has been shown to influence the variability of daily dose deposited between the extrathoracic and alveolar-interstitial zones. On average, 3% of the PM deposited in the bronchial region, whereas 5% to 8% were found in the bronchiolar region. The level of physical activity had a significant contribution to the total daily dose.

Assessment of children's exposure to carbonaceous matter and to PM major and trace elements

Particulate matter (PM) pollution is one of the major environmental concerns due to its harmful effects on human health. As children are particularly vulnerable to particle exposure, this study integrates the concentration of PM chemical compounds measured in the micro-environments (MEs) where children spend most of their time to assess the daily exposure and inhaled dose. PM samples were analysed for organic and elemental carbon and for major and trace elements. Results showed that the MEs that contribute most to the children's daily exposure (80%) and inhaled dose (65%) were homes and schools. Results indicated that the high contribution of particulate organic matter (POM) indoors indicate high contributions of indoor sources to the organic fraction of the particles. The highest concentrations of PM chemical compounds and the highest Indoor/Outdoor ratios were measured in schools, where the contribution of mineral elements stands out due to the resuspension of dust caused by the students and to the chalk used in blackboards. The contribution of the outdoor particles to inhaled dose (24%) was higher than to the exposure (12%), due to the highest inhalation rates associated with the activities performed outdoor. This study indicates the importance of indoor air quality for the children's exposure and health.

Exposure and dose assessment of school children to air pollutants in a tropical coastal-urban area

This study estimates exposure and inhaled dose to air pollutants of children residing in a tropical coastal-urban area in Southeast Brazil. For that, twenty-one children filled their time-activities diaries and wore the passive samplers to monitor NO₂. The personal exposure was also estimated using data provided by the combination of WRF-Urban/GEOS-Chem/CMAQ models, and the nearby monitoring station. Indoor/outdoor ratios were used to consider the amount of time spent indoors by children in homes and schools. The model's performance was assessed by comparing the modelled data with concentrations measured by urban monitoring stations. A sensitivity analyses was also performed to evaluate the impact of the model's height on the air pollutant concentrations. The results showed that the mean children's personal exposure to NO₂ predicted by the model (22.3 μg/m³) was nearly twice to those measured by the passive samplers (12.3 μg/m³). In contrast, the nearest urban monitoring station did not represent the personal exposure to NO₂ (9.3 μg/m³), suggesting a bias in the quantification of previous epidemiological studies. The building effect parameterisation (BEP) together with the lowering of the model height enhanced the air pollutant concentrations and the exposure of children to air pollutants. With the use of the CMAQ model, exposure to O₃, PM₁₀, PM_2.5, and PM₁ was also estimated and revealed that the daily children's personal exposure was 13.4, 38.9, 32.9, and 9.6 μg/m³, respectively. Meanwhile, the potential inhalation daily dose was 570-667 μg for PM_2.5, 684-789 μg for PM₁₀, and 163-194 μg for PM₁, showing to be favourable to cause adverse health effects. The exposure of children to air pollutants estimated by the numerical model in this work was comparable to other studies found in the literature, showing one of the advantages of using the modelling approach since some air pollutants are poorly spatially represented and/or are not routinely monitored by environmental agencies in many regions.

Seasonal variation and size distribution of inorganic and carbonaceous components, source identification of size-fractioned urban air particles in Kuala Lumpur, Malaysia

This study aims to determine the inorganic and carbonaceous components depending on the seasonal variation and size distribution of urban air particles in Kuala Lumpur. Different fractions of particulate matter (PM) were measured using a Nanosampler from 17 February 2017 until 27 November 2017. The water-soluble inorganic ions (WSIIs) and carbonaceous components in all samples were analysed using ion chromatography and carbon analyser thermal/optical reflectance, respectively. Total PM concentration reached its peak during the southwest (SW) season (70.99 ± 6.04 μg/m³), and the greatest accumulation were observed at PM_0.5-1.0 (22%-30%, 9.55 ± 1.03 μg/m³) and PM_2.5-10 (22%-25%, 10.34 ± 0.81 μg/m³). SO₄^2-, NO₃^- and NH₄⁺ were major contributors of WSIIs, and their formation was favoured mainly during SW season (80.5% of total ions). PM_0.5-1.0 and PM_2.5-10 exhibited the highest percentage of WSII size distribution, accounted for 28.4% and 13.5% of the total mass, respectively. The average contribution of carbonaceous species (OC + EC) to total carbonaceous concentrations were higher in PM_0.5-1.0 (35.2%) and PM_2.5-10 (26.6%). Ultrafine particles (PM_<0.1) consistently indicated that the sources were from vehicle emission while the SW season was constantly dominated by biomass burning sources. Using the positive matrix factorization (PMF) model, secondary inorganic aerosol and biomass burning (30.3%) was known as a significant source of overall PM. As a conclusion, ratio and source apportionment indicate the mixture of biomass burning, secondary inorganic aerosols and motor vehicle contributed to the size-segregated PM and seasonal variation of inorganic and carbonaceous components of urban air particles.

Selection of metric for indoor-outdoor source apportionment of metals in PM2.5 : mg/kg versus ng/m3

Trends in the elemental composition of fine particulate matter (PM_2.5 ) collected from indoor, outdoor, and personal microenvironments were investigated using two metrics: ng/m³ and mg/kg. Pearson correlations that were positive using one metric commonly disappeared or flipped to become negative when the other metric was applied to the same dataset. For example, the correlation between Mo and S in the outdoor microenvironment was positive using ng/m³ (p < 0.05) but negative using mg/kg (p < 0.05). In general, elemental concentrations (mg/kg) within PM_2.5 decreased significantly (p < 0.05) as PM_2.5 concentrations (µg/m³ ) increased-a dilution effect that was observed in all microenvironments and seasons. An exception was S: in the outdoor microenvironment, the correlation between wt% S and PM_2.5  flipped from negative in the winter (p < 0.01) to positive (p < 0.01) in the summer, whereas in the indoor microenvironment, this correlation was negative year-round (p < 0.05). Correlation analyses using mg/kg indicated that elemental associations may arise from Fe-Mn oxyhydroxide sorption processes that occur as particles age, with or without the presence of a common anthropogenic source. Application of mass-normalized concentration metrics (mg/kg or wt%), enabled by careful gravimetric analysis, revealed new evidence of the importance of indoor sources of elements in PM_2.5 .

Sequential Multiscale Simulation of a Filtering Facepiece for Prediction of Filtration Efficiency and Resistance in Varied Particulate Scenarios

This study explores a novel approach of multiscale modeling and simulation to characterize the filtration behavior of a facepiece in varied particulate conditions. Sequential multiscale modeling was performed for filter media, filtering facepiece, and testing setup. The developed virtual models were validated for their morphological characteristics and filtration performance by comparing with the data from the physical experiments. Then, a virtual test was conducted in consideration of a time scale, simulating diverse particulate environments with different levels of particle size distribution, particle concentration, and face velocity. An environment with small particles and high mass concentration resulted in a rapid buildup of resistance, reducing the service life. Large particles were accumulated mostly at the entrance of the filter layer, resulting in a lower penetration and slower buildup of resistance. This study is significant in that the adopted virtual approach enables the prediction of filtration behavior and service life, applying diverse environmental conditions without involving the costs of extra setups for the physical experiments. This study demonstrates a novel and economic research method that can be effectively applied to the research and development of filters.

Evaluation of life expectancy loss associated with submicron and fine particulate matter (PM1 and PM2.5) air pollution in Nanjing, China

Particulate matters with an aerodynamic diameter ≤1 μm (PM₁) significantly increased mortality risk, and the effect of PM₁ was even greater than that of PM_2.5 (aerodynamic diameter ≤2.5 μm). But the quantitative impact of PM₁ on life expectancy was unknown. We aim to examine the extent to which that people's life expectancy was shortened by PM₁ and PM_2.5. We obtained daily data on deaths, PM₁ and PM_2.5 records, and weather variables during 2016-2017 in Nanjing, China. Years of life lost (YLLs) were calculated by matching each decedent's age and sex to the Chinese life table. The fitted nonlinear dose-response associations of YLLs with PM₁ and PM_2.5 were estimated by utilizing a generalized additive model with a Gaussian link that controlled for confounding factors including meteorological variables, day of week, and long-term trend and seasonality. The effect estimates were presented as the YLLs when PM₁ and PM_2.5 concentrations fell in different ranges. Life expectancy losses attributable to PM₁ and PM_2.5 were calculated. Stratified analyses were also performed by age, sex, and death causes. Significant PM-YLL associations were observed, with greater increases in YLLs associated with PM₁ (68.9 thousand). PM₁ was estimated to reduce life expectancy, which was greater than PM_2.5 (PM₁: 1.67 years; PM_2.5: 1.55 years). For PM₁, greater years of loss in PM-related life expectancy were found in the female group, ≥65 years group, and cardiovascular disease group. Exposure to PM₁ had a greater impact on life expectancy loss than did PM_2.5. Constant efforts are urgently needed to control PM₁ air pollution to improve people's longevity.

Physicochemical Properties of Indoor and Outdoor Particulate Matter 2.5 in Selected Residential Areas near a Ferromanganese Smelter

Particulate matter (PM) of different sizes and elemental composition is a leading contributor to indoor and outdoor air pollution in residential areas. We sought to investigate similarities between indoor and outdoor PM_2.5 in three residential areas near a ferromanganese smelter in Meyerton to apportion the emission source(s). Indoor and outdoor PM_2.5 samples were collected concurrently, using GilAir300 plus samplers, at a flow rate of 2.75 L/min. PM_2.5 was collected on polycarbonate membrane filters housed in 37 mm cassettes coupled with PM_2.5 cyclones. Scanning electron microscopy coupled with energy-dispersive spectroscopy was used to study the morphology, and inductively coupled plasma-mass spectroscopy was used to analyse the elemental composition of the PM_2.5. Mean indoor and outdoor PM_2.5 mass concentrations were 10.99 and 24.95 µg/m³, respectively. Mean outdoor mass concentration was 2.27-fold higher than the indoor concentration. Indoor samples consisted of irregular and agglomerated particles, ranging from 0.09 to 1.06 µm, whereas outdoor samples consisted of irregular and spherical particles, ranging from 0.10 to 0.70 µm. Indoor and outdoor PM_2.5 were dominated by manganese, silicon, and iron, however, outdoor PM_2.5 had the highest concentration of all elements. The ferromanganese smelter was identified as the potential main contributing source of PM_2.5 of different physicochemical properties.

Performance Evaluation of Particulate Matter and Indoor Microclimate Monitors in University Classrooms under COVID-19 Restrictions

Optical monitors have proven their versatility into the studies of air quality in the workplace and indoor environments. The current study aimed to perform a screening of the indoor environment regarding the presence of various fractions of particulate matter (PM) and the specific thermal microclimate in a classroom occupied with students in March 2019 (before COVID-19 pandemic) and in March 2021 (during pandemic) at Valahia University Campus, Targoviste, Romania. The objectives were to assess the potential exposure of students and academic personnel to PM and to observe the performances of various sensors and monitors (particle counter, PM monitors, and indoor microclimate sensors). PM1 ranged between 29 and 41 μg m⁻³ and PM10 ranged between 30 and 42 μg m⁻³. It was observed that the particles belonged mostly to fine and submicrometric fractions in acceptable thermal environments according to the PPD and PMV indices. The particle counter recorded preponderantly 0.3, 0.5, and 1.0 micron categories. The average acute dose rate was estimated as 6.58 × 10⁻⁴ mg/kg-day (CV = 14.3%) for the 20–40 years range. Wearing masks may influence the indoor microclimate and PM levels but additional experiments should be performed at a finer scale.

Chemical constituents and sources of indoor PM2.5 and cardiopulmonary function in patients with chronic obstructive pulmonary disease: Estimation of individual and joint effects

BACKGROUND

The cardiopulmonary effects of chemical constituents and sources of indoor fine particulate matter (PM_2.5) remain unclear.

OBJECTIVES

To examine the individual and joint effects of constituents of indoor PM_2.5 on cardiopulmonary function of patients with chronic obstructive pulmonary disease (COPD) and the role of identified sources.

METHODS

This panel study recruited 43 stable COPD patients from November 2015 to May 2016 in Beijing, China. Daily indoor and outdoor PM_2.5 were collected for five consecutive days simultaneously. Twenty-four elements were measured and principal component analysis was used for source appointment. Pulmonary function and blood pressure (BP) were also measured at daily visit. The linear mixed-effect models were used to estimate the effect of each constituent and source. Bayesian kernel machine regression (BKMR) models were used to estimate the overall effect of all measured constituents.

RESULTS

The combustion, indoor soil/dust and road dust sources were identified as the main sources of indoor PM_2.5 and combustion sources contributed over 40% during the heating season. Most constituents were significantly associated with elevated BP of COPD patients and the joint effects of mixed exposures were also significant especially during the heating season. Most associations of chemical constituents with pulmonary function were negative but not statistically significant during the heating season, as was the joint effect. Few associations were observed during the non-heating season. Further, we observed combustion sources throughout the study period and road dust sources during the heating season were significantly associated with increased BP but not decreased pulmonary function.

CONCLUSION

The combustion and road dust sources and their related constituents of indoor PM_2.5 could cause adverse effects on cardiovascular function of COPD patients especially during the heating season, but the effect on pulmonary function still needs to be further studied.

PM2.5 Magnetic Properties in Relation to Urban Combustion Sources in Southern West Africa

The physico-chemical characteristics of particulate matter (PM) in African cities remain poorly known due to scarcity of observation networks. Magnetic parameters of PM are robust proxies for the emissions of Fe-bearing particles. This study reports the first magnetic investigation of PM2.5 (PM with aerodynamic size below 2.5 μm) in Africa performed on weekly PM2.5 filters collected in Abidjan (Ivory Coast) and Cotonou (Benin) between 2015 and 2017. The magnetic mineralogy is dominated by magnetite-like low coercivity minerals. Mass normalized SIRM are 1.65 × 10−2 A m2 kg−1 and 2.28 × 10−2 A m2 kg−1 for Abidjan and Cotonou respectively. Hard coercivity material (S-ratio = 0.96 and MDF = 33 mT) is observed during the dry dusty season. Wood burning emits less iron oxides by PM2.5 mass when compared to traffic sources. PM2.5 magnetic granulometry has a narrow range regardless of the site or season. The excellent correlation between the site-averaged element carbon concentrations and SIRM suggests that PM2.5 magnetic parameters are linked to primary particulate emission from combustion sources.

Biogenic secondary organic aerosol formation in an urban area of eastern central India: Seasonal variation, size distribution and source characterization

Samples of ambient aerosols were collected at an urban site of eastern central India from monsoon to summer 2016-17 for the characterization of biogenic secondary organic aerosols (BSOA). The BSOA tracers derived from isoprene, α/β-pinene and β-caryophyllene in size-distributed aerosols were studied. Concentrations of total SOAI (Isoprene secondary organic aerosols) were found more abundant than α/β-pinene in summer, while contradictory trends were found in the winter season, where SOAM (monoterpene derived SOA) and SOAS (sesquiterpenes derived SOA) were dominated. Size-distribution study revealed that most of the BSOA were formed in the aerosol phase and dominated in fine mode, except cis-pinonic acid. They were formed in the gaseous phase and partitioned onto the aerosol phase. The alkaline nature of mineral dust particles that triggered the adsorption of gaseous species onto pre-existing particles could be the reason for bimodal size distribution with major coarse mode peak and miner fine mode peak. Temporal variations suggest that the BSOA must be derived from terrestrial vegetation and biomass burning. The isoprene SOC (secondary organic carbon) contributed 0.91%, 1.38%, 0.88% and 1.04% to OC during winter, summer, post-monsoon and monsoon season, respectively. The isoprene SOC in fine mode was found to be higher than the coarse mode.

Seasonal Variations in the Chemical Composition of Indoor and Outdoor PM10 in University Classrooms

In the VIEPI project (Integrated evaluation of the exposure to indoor particulate matter) framework, we carried out a 1-year study of the concentration and chemical composition of particulate matter (PM) in a 5 story building in the Sapienza University of Rome (Italy). Each sampling had a duration of 1 month and was carried out indoors and outdoors in six classrooms. The chemical analyses were grouped to obtain information about the main PM sources. Micro-elements in their soluble and insoluble fractions were used to trace additional sources. Indoor PM composition was dominated by soil components and, to a lesser extent, by the organics, which substantially increased when people crowded the sites. The penetration of PM components was regulated by their chemical nature and by the dimensions of the particles in which they were contained. For the first time in crowded indoor environments, three different chemical assays aimed to determine PM redox properties complemented chemical composition measurements. These preliminary tests showed that substantially different redox properties characterised atmospheric particles in indoor and outdoor sites. The innovative characteristics of this study (time duration, number of considered environments) were essential to obtain relevant information about PM composition and sources in indoor academic environments and the occupants’ role.

Short-term effects of size-fractionated particulate matters and their constituents on renal function in children: A panel study

Evidence available on the effects of size-fractionated particulate matters and their constituents on children's renal function is lack. We conducted a longitudinal panel study among 144 children aged 4-12 years with up to 3 repeated visits from 2018 to 2019. We estimated the effects of size-fractionated particle number counts (PNCs) and their 13 constituents on estimated glomerular filtration rate (eGFR) over different lag times with linear mixed-effects models and Bayesian kernel machine regression. We found the inverse dose-responsive associations of 3 sizes PNCs with eGFR were the strongest at lag 2 day. Compared to PNC_0.5, PNC₁ and PNC_2.5 showed stronger and similar effects on eGFR reduction. On average, an interquartile range increase in PNC_0.5, PNC₁ and PNC_2.5 were significantly associated with 1.70%, 2.82% and 2.76% decrease in eGFR, respectively. Girls were more susceptible to the toxicity of PNC₁ and PNC_2.5 exposure on eGFR. Several constituents including organic carbon (OC), Mg⁺, PO₃^- and HC₂O₄^- in 3 sizes PNCs were robustly and consistently linked to eGFR reduction at lag 2 day. Moreover, the cumulative effects of different constituents on lower eGFR were significant, when they were all at or above a size-independent threshold (the 60th, 65th, and 70th percentiles in PNC_0.5, PNC₁ and PNC_2.5 constituents, respectively), compared to their median value. And only OC displayed a significantly detrimental effect on eGFR when all the other constituents were fixed at 25th, 50th, and 75th percentiles. In summary, short-term exposure to PNCs were size-dependent related to reduced eGFR in dose-responsive manner among healthy children, and OC might play a more important role in PNC-induced nephrotoxicity than others.

Bioaerosol Contribution to Atmospheric Particulate Matter in Indoor University Environments

Within the framework of the project “Integrated Evaluation of Indoor Particulate Exposure”, we carried out a 4-week field study to determine indoor bioaerosol, and its contribution to particulate matter (PM)10 and organic matter. The study was carried out in university classrooms, where most of the common indoor sources of atmospheric particles are missing. Bioaerosol was determined by a method based on propidium iodide staining, observation by fluorescence microscopy, and image analysis. Indoor bioaerosol concentrations were compared with outdoor values, which were determined simultaneously. The samplings periods were scheduled to divide weekday hours, when the students were inside, from night-time hours and weekends. Very high bioaerosol concentrations were detected inside the classrooms with respect to outdoor values. The mean difference was 49 μg/m3 when the students were inside, 5.4 μg/m3 during the night, and it became negative during the weekends. Indoor-to-outdoor ratios were 6.0, 4.2, and 0.7, respectively. Bioaerosol contributed 26% to organics and 10% to PM10. In indoor samples collected during the day, the microscope images showed numerous skin fragments, which were mostly responsible for the increase in the bioaerosol mass. People’s presence proved to be responsible for a significant increase in bioaerosol concentration in crowded indoor environments.

Fine particulate matter constituents and heart rate variability: A panel study in Shanghai, China

BACKGROUND

Short-term exposure to fine particulate matter (PM_2.5) has been associated with reduced heart rate variability (HRV), an established indicator of cardiac autonomic function, but it remains uncertain which specific constituents of PM_2.5 had key impacts.

OBJECTIVE

To examine the short-term associations between various PM_2.5 constituents and HRV measures.

METHODS

We conducted a retrospective panel study among 78 participants who received repeated 24-h electrocardiogram testing in Shanghai, China from 2015 to 2019. We obtained daily concentrations of 14 main chemical constituents of PM_2.5 from a fixed-site monitor. During 3 or 4 rounds of follow-ups, we measured 6 HRV parameters, including 3 frequency-domain parameters (power in very low frequency, low frequency and high frequency) and 3 time-domain parameters (standard deviation of normal-to-normal intervals, root mean square successive difference and percent of adjacent normal R-R intervals with a difference ≥50 msec). We used linear mixed-effects models to analyze the data after controlling for time trends, environmental and individual risk factors.

RESULTS

The average daily PM_2.5 exposure was 45.8 μg/m³ during the study period. The present-day exposure to PM_2.5 had the strongest negative influences on various HRV indicators. These associations attenuated greatly on lag 1 d or lag 2 d. Elemental carbon, organic carbon, nitrate, sulfate, arsenic, cadmium, chromium and nickel were consistently associated with reduced HRV parameters in both single-constituent models and constituent-PM_2.5 models.

CONCLUSION

Our study highlighted the key roles of traffic-related components of PM_2.5 in inhibiting cardiac autonomic function.

Micro-RNAs: Crossroads between the Exposure to Environmental Particulate Pollution and the Obstructive Pulmonary Disease

Environmental pollution has reached a global echo and represents a serious problem for human health. Air pollution encompasses a set of hazardous substances, such as particulate matter and heavy metals (e.g., cadmium, lead, and arsenic), and has a strong impact on the environment by affecting groundwater, soil, and air. An adaptive response to environmental cues is essential for human survival, which is associated with the induction of adaptive phenotypes. The epigenetic mechanisms regulating the expression patterns of several genes are promising candidates to provide mechanistic and prognostic insights into this. Micro-RNAs (miRNAs) fulfil these features given their ability to respond to environmental factors and their critical role in determining phenotypes. These molecules are present in extracellular fluids, and their expression patterns are organ-, tissue-, or cell-specific. Moreover, the experimental settings for their quantitative and qualitative analysis are robust, standardized, and inexpensive. In this review, we provide an update on the role of miRNAs as suitable tools for understanding the mechanisms behind the physiopathological response to toxicants and the prognostic value of their expression pattern associable with specific exposures. We look at the mechanistic evidence associable to the role of miRNAs in the processes leading to environmental-induced pulmonary disease (i.e., chronic obstructive pulmonary disease).

Source Apportionment of Fine Organic and Inorganic Atmospheric Aerosol in an Urban Background Area in Greece

Fine particulate matter (PM) originates from various emission sources and physicochemical processes. Quantification of the sources of PM is an important step during the planning of efficient mitigation strategies and the investigation of the potential risks to human health. Usually, source apportionment studies focus either on the organic or on the inorganic fraction of PM. In this study that took place in Patras, Greece, we address both PM fractions by combining measurements from a range of on- and off-line techniques, including elemental composition, organic and elemental carbon (OC and EC) measurements, and high-resolution Aerosol Mass Spectrometry (AMS) from different techniques. Six fine PM2.5 sources were identified based on the off-line measurements: secondary sulfate (34%), biomass burning (15%), exhaust traffic emissions (13%), nonexhaust traffic emissions (12%), mineral dust (10%), and sea salt (5%). The analysis of the AMS spectra quantified five factors: two oxygenated organic aerosols (OOA) factors (an OOA and a marine-related OOA, 52% of the total organic aerosols (OA)), cooking OA (COA, 11%) and two biomass burning OA (BBOA-I and BBOA-II, 37% in total) factors. The results of the two methods were synthesized, showcasing the complementarity of the two methodologies for fine PM source identification. The synthesis suggests that the contribution of biomass burning is quite robust, but that the exhaust traffic emissions are not due to local sources and may also include secondary OA from other sources.