Indoor Samples Research Articles

Exploring the curing condition and age effect on thermal conductivity of concrete

Energy piles are used around the world to partially heat/cool buildings or de-ice pavements. Thermal conductivity of concrete is one of the key parameters which highly affects the thermal performance of energy geostructures. Application of higher thermally conductive concrete in energy piles helps to harvest more shallow geothermal energy. Besides, higher thermally conductive concrete results in more uniform temperature distribution and will significantly increase the efficiency of the geothermal bridge deck de-icing. It is expected that the thermal conductivity of the concrete depends on its age and the applied curing conditions. The thermal conductivity of concrete can progress with the progression of hydration. While the hydration process is highly dependent on the curing condition that is applied. In this study, several concrete samples are prepared and cured under different conditions (inside the humidity room, indoor, and outdoor). Then the thermal conductivity of concrete samples at different ages are measured according to ASTM D5470-17. Results show an increase in thermal conductivity of concrete cured in humidity room for the first 30 to 40 days that thermal conductivity were measured In addition comparison of thermal conductivity of the outdoor and indoor samples show the importance of the ambient temperature and relative humidity on the thermal conductivity value.

Variations and characteristics of particulate matter, black carbon and volatile organic compounds in primary school classrooms

Abstract The effect of human activities on the characteristics and variations of indoor air pollutants is poorly understood, in particular for the classroom environment due to the limited reports at present. In this study, an observational campaign (17 days) was carried out in two selected classrooms (one equipped with air purifier) in a primary school of Hangzhou, China. Highly time-resolved particulate matter (PM) and black carbon (BC) were measured using Aerodynamic Particle Sizer (APS) and Aethalometer, and the diurnal variations of PM2.5, PM10, PM20 and BC were characterized in detail. It was found that the student activities occurred throughout the daytime and could result in rapid changes in air pollutants. For example, the daytime student activities (e.g., chasing and running) strongly enhanced the PM level and changed PM diurnal pattern, in particular for coarse particles (2.5–10 μm) with short-term spikes at intervals, which was not observed under vacant conditions. The indoor BC did not show clear diurnal patterns, regardless of working days and weekends. Through absorption exponent analysis, it was inferred that the source of indoor BC was stable at most of the time, and possibly related to traffic emission. Besides, three volatile organic compounds (VOCs) samples were collected from the two classrooms, and the laboratory analysis results showed that oxygenated VOCs was a major contributor to indoor VOCs. Through inter-comparison analysis of indoor and outdoor samples, it was further found that the VOC profile of classrooms has a similar pattern with outdoor environments. Finally, the most abundant VOC species of classroom environment were identified, and their potential sources were estimated.

Field sampling of indoor bioaerosols.

Because bioaerosols are related to adverse health effects in exposed humans and indoor environments represent a unique framework of exposure, concerns about indoor bioaerosols have risen over recent years. One of the major issues in indoor bioaerosol research is the lack of standardization in the methodology, from air sampling strategies and sample treatment to the analytical methods applied. The main characteristics to consider in the choice of indoor sampling methods for bioaerosols are the sampler performance, the representativeness of the sampling, and the concordance with the analytical methods to be used. The selection of bioaerosol collection methods is directly dependent on the analytical methods, which are chosen to answer specific questions raised while designing a study for exposure assessment. In this review, the authors present current practices in the analytical methods and the sampling strategies, with specificity for each type of microbe (fungi, bacteria, archaea and viruses). In addition, common problems and errors to be avoided are discussed. Based on this work, recommendations are made for future efforts towards the development of viable bioaerosol samplers, standards for bioaerosol exposure limits, and making association studies to optimize the use of the big data provided by high-throughput sequencing methods.

The impact of household air cleaners on the oxidative potential of PM2.5 and the role of metals and sources associated with indoor and outdoor exposure

The health effects associated with human exposure to airborne fine particulate matter (PM2.5) have been linked to the ability of PM2.5 to facilitate the production of excess cellular reactive oxygen species (oxidative potential). Concern about the adverse human health impacts of PM2.5 has led to the increased use of indoor air cleaners to improve indoor air quality, which can be an important environment for PM2.5 exposure. However, the degree to which the oxidative potential of indoor and personal PM2.5 can be influenced by an indoor air cleaner remains unclear. In this study we enrolled 43 children with physician diagnosed asthma in suburban Shanghai, China and collected two paired-sets of 48-h indoor, outdoor, and personal PM2.5 exposure samples. One set of samples was collected under “real filtration” during which a functioning air cleaner was installed in the child's bedroom, and the other (“false filtration”) with an air cleaner without internal filters. The PM2.5 samples were characterized by inductively coupled plasma mass spectroscopy for elements, and by an alveolar macrophage assay for oxidative potential. The sources of metals contributing to our samples were determined by the EPA Positive Matrix Factorization model. The oxidative potential was lower under real filtration compared to sham for indoor (median real/sham ratio: 0.260) and personal exposure (0.813) samples. Additionally, the sources of elements in PM2.5 that were reduced indoors and personal exposure samples by the air cleaner (e.g. regional aerosol and roadway emissions) were found by univariate multiple regression models to be among those contributing to the oxidative potential of the samples. An IQR increase in the regional aerosol and roadway emissions sources was associated with a 107% (95% CI: 80.1–138%) and 38.1% (17.6–62.1%) increase in measured oxidative potential respectively. Our results indicate that indoor air cleaners can reduce the oxidative potential of indoor and personal exposure to PM2.5, which may lead to improved human health.

Indoor versus Outdoor Air Quality during Wildfires.

The human behavioral modification recommendations during wildfire events are based on particulate matter and may be confounded by the potential risks of gas-phase pollutants such as polycyclic aromatic hydrocarbons (PAHs). Moreover, the majority of adults spend over 90 percent of their time indoors where there is an increased concern of indoor air quality during wildfire events. We address these timely concerns by evaluating paired indoor and outdoor PAH concentrations in residential locations and their relationship with satellite model-based categorization of wildfire smoke intensity. Low-density polyethylene passive air samplers were deployed at six urban sites for 1 week in Eugene, Oregon with matched indoor and outdoor samples and 24 h time resolution. Samples were then quantitatively analyzed for 63 PAH concentrations using gas-chromatography-tandem mass spectrometry. A probabilistic principal components analysis was used to reduce all 63 PAHs into an aggregate measure. Linear regression of the first principal component against indoor versus outdoor shows that indoor gas-phase PAH concentrations are consistently equal to or greater than outdoor concentrations. Regression against a satellite-based model for wildfire smoke shows that outdoor, but not indoor gas-phase PAH concentrations are likely associated with wildfire events. These results point toward the need to include gas-phase pollutants such as PAHs in air pollution risk assessment.

Air-Quality Assessment of On-Site Brick-Kiln Worker Housing in Bhaktapur, Nepal: Chemical Speciation of Indoor and Outdoor PM2.5 Pollution.

Brick workers and their families in Nepal generally live in poorly ventilated on-site housing at the brick kiln, and may be at higher risk for non-occupational exposure to fine particulate matter air pollution and subsequent respiratory diseases due to indoor and outdoor sources. This study characterized non-occupational exposure to PM2.5 by comparing overall concentrations and specific chemical components of PM2.5 inside and outside of brick workers’ on-site housing. For all samples, the geometric mean PM2.5 concentration was 184.65 μg/m3 (95% confidence interval: 134.70, 253.12 μg/m3). PM2.5 concentrations differed by kiln number (p = 0.009). Kiln number was significantly associated with 16 of 29 (55%) air pollutant, temperature, or relative humidity variables. There was not a significant interaction between kiln number and location of sample for PM2.5 (p = 0.16), but there was for relative humidity (p = 0.02) and temperature (p = 0.01). Results were qualitatively similar when we repeated analyses using indoor samples only. There was no difference in the chemical makeup of indoor and outdoor PM2.5 in this study, suggesting that outdoor PM2.5 air pollution easily infiltrates into on-site brick worker housing. Outdoor and indoor PM2.5 concentrations found in this study far exceed recommended levels. These findings warrant future interventions targeted to this vulnerable population.

Air quality of an urban school in São Paulo city.

A major campaign was carried out in indoor and outdoor environments in a school located in the university campus of the city of São Paulo. Elements, PAH, oxy-PAH, water-soluble ions and black carbon were determined and compared with preliminary campaigns. The results indicated that the concentrations of particles and organic compounds were higher indoors. Some high molecular weight compounds, attributed to vehicular emissions, were more abundant outdoors. The associated health risk was found to be low. 2-Methylanthraquinone and benzo(a)anthracene-7,12-dione were detected in the indoor samples, denoting the infiltration of vehicle exhaust. The observation of black carbon also corroborates the contribution of traffic emissions. For most of the elements, except for chromium, iron and manganese, the concentrations obtained in indoors were higher than outdoors, mainly due to soil resuspension. Chromium and manganese likely derived from emissions of the vehicle powered by mixtures of ethanol and gasoline. Water-soluble inorganic ions species denoted the influence of soil resuspension and human activities.

Graphene detection in air: a proposal based on thermogravimetric behaviour

Graphene’s production and application are growing in accelerated speed. In this scenario, it is imperative to guarantee the healthy and safe conditions to producers and consumers along the graphene value chain. Due to the unique characteristics of graphene, its characterization in complexes matrices is still a challenging endeavour. In this work, we show an ongoing methodology that aims to assess the exposition to nanomaterials inside a graphene pilot plant by adapting the current particulate matter sampling methodologies. A systematic study was performed by preparing different graphene dispersions which were deposited on clean quartz filters and on filters exposed to an outdoor environment. Real samples, containing indoor airborne material were also analyzed. Thermogravimetric analysis was performed in all samples and revealed that the thermal decomposition of the deposited graphene was detectable and occurred around 635 °C. The presence of a thermal decomposition event within the typical temperature range of graphene was also detectable in the real indoor sample. These results pointed out that thermogravimetric analysis can be used to detect small amounts of graphene suspended in air, being the key factor graphene’s high thermal stability being the key factor. The methodology provides a robust way to improve air quality surveillance and exposure evaluation.

INDOOR AIR QUALITY AND MICROBIAL ASSESSMENT OF A NIGERIAN UNIVERSITY CAMPUS IN LAGOS, NIGERIA

Good indoor air quality improves productivity at the workplace. On the other hand, poor indoor air quality could lead to losses in productivity as a result of comfort problems, ill health and sickness-absenteeism. The aim of the study was to assess indoor air quality in various rooms of university buildings covering the offices, lecture theatre, laboratory or workshops and public restroom across eight faculties in a conventional university. Investigations were conducted at twenty-nine indoor locations in the main campus of University of Lagos. Noise level, PM2.5, PM10, relative humidity and temperature, CO, SO2, NOx, and the microbial quality (fungal and bacterial) were all determined. The microbial quality was determined using the sedimentation method (open petri dishes) containing different culture media for sample collection. Noise level ranged from 61.60 to 84.10 dBA. The noise level is quite high in almost all sampling points especially in the workshops, yet there was no significant difference (P>0.05) across all the indoor sampling points and the WHO limit.SO2 were mostly absence, however, the highest value of 0.4 ppm was recorded which was higher than recommended limit of 0.1 ppm.PM2.5 ranged between 4.0–25.0 µg/m3 and PM10 were between 8.0–47.0 µg/m3. Though, there was high variation in PM2.5 and PM10 across all the indoor sampling points, there were no significant difference (P>0.05). They were below the maximum limit of 150 µg/m3.The total fungi load ranged from 10.4 to 963 CFU/m3. There was generally higher number of fungi in the restroom than all the other indoor environments and they were significant in Faculty of social sciences. Fungi isolates include Aspergillus spp. (86.2%), unidentified mold (13.77%) and Sporothrix schenckii (0.03%). Total bacteria load ranged from 96.3 to 689 CFU/m3. The lowest load of bacteria (9.63 x 101 CFU/m3) was recorded in the dean’s office at the faculty of environmental science. The rest rooms have higher bacterial load (6.89 x 102 CFU/m3), which was higher than the recommended maximum limit of 500 CFU/m3. Identification from the colonies showed that about 55% were gram negative and 45% were gram negative cells. Morphological studies showed that cocci were also more predominant over the bacillary shape bacteria (55% versus 45%).

Indoor and Outdoor Exposure to Volatile Organic Compounds and Health Risk Assessment in Residents Living near an Optoelectronics Industrial Park

This study aimed to determine indoor and outdoor levels of volatile organic compounds (VOCs) and to assess potential risks among residents living in the vicinity of an optoelectronics industrial park in 2006–2007. We used steel canisters to collect 72 indoor samples and 80 outdoor samples over 24 h. Gas chromatography with a mass-selective detector was used for qualitative and quantitative analyses. The amounts of time residents spent doing activities in different microenvironments were determined by the self-administered questionnaire. The chronic hazard index (HIc) and cancer risk were applied to assess the non-carcinogenic and carcinogenic risks of VOCs among residents. Four VOCs of ethanol (indoor: 77.8 ± 92.8 μg/m3; outdoor: 26.8 ± 49.6 μg/m3), toluene (67.0 ± 36.7 μg/m3; 56.9 ± 19.0 μg/m3), m/p-xylene (50.8 ± 66.1 μg/m3; 21.2 ± 20.3 μg/m3), and acetone (37.7 ± 27.5 μg/m3; 25.8 ± 9.8 μg/m3) were identified as dominant components in both the indoor and outdoor environments. Total VOCs and six VOCs of benzene, toluene, ethylbenzene, m/p-xylene, o-xylene, and ethanol in indoor sites were significantly higher than those in outdoor sites (all p-values < 0.05). All estimated HIc values were less than unity and the cancer risk of benzene exposure was 1.8 × 10−4 (range: 9.3 × 10−5 to 3.4 × 10−4) based on resident time-weighted patterns. Strategies to reduce benzene exposure should be implemented to protect public health.

Does the presence of certain bacterial family in the microbiome indicate specific indoor environment characteristics? A factorial design approach for identifying bio-fingerprints

The study applies the current knowledge on microbiome in built environments towards identifying microbes, specifically bacteria as bio-fingerprints which can reflect indoor space and occupant characteristics. Data were collected from the literature on the bacterial family and the indoor environment. The factorial design approach was applied to quantify and compare the influence of selected indoor environmental parameters, sampling region (air or surface), sampling locations (residence or non-residence), gender and age and their interactions on the types and concentration of detected bacterial families. Factorial design analysis identified and confirmed Corynebacteriaceae and Lactobacillaceae as the gender signature for males and females, respectively. The significant bacterial families across all scenarios are: Corynebacteriaceae, Propionibacteriaceae, Bacillaceae, Staphylococcaceae, Lactobacillaceae, Methylobacteriaceae, Moraxellaceae, Micrococcaceae, Enterobacteriaceae, Rhodobacteraceae, Streptococcaceae and Pseudomonadaceae. Higher concentrations of Propionibacteriaceae indicate that the specific location is an adult-occupied space. Staphylococcaceae presence is the bio-fingerprint of contaminated air of hospitals bio-fingerprint and Moraxellaceae on hospital surfaces are distinct characteristics. Streptococcaceae is a bio-fingerprint of contaminated air of schools and other children-occupied spaces. Enterobacteriaceae is a bio-fingerprint of contaminated air of non-residence locations. Bacillaceae does not indicate any indoor characteristics.

Spatial Gradients of Fungal Abundance and Ecology throughout a Damp Building

Dampness and fungal (mold) growth in buildings is a persistent environmental health problem. This study sought to determine the extent to which fungi grown on damp materials are distributed throughout a single family home. Samples were collected from fungi growing directly on building materials in the basement (direct mold), and, as a proxy for indoor and outdoor air, settled dust was collected from the top of door frames (basement, first, and second floor, exterior). Direct mold in the basement influenced both the fungal richness and ecology of air throughout the building. Fungal communities clustered by sample type (ANOSIM R=0.62, p-value=0.001) and floor (indoor samples: ANOSIM R=0.58, p-value=0.001) with the direct mold ecologies dominated by taxa (i.e. Sterigmatomyces, Stachybotrys, Aspergillus) associated with mold growth on building materials, and not present in outdoor samples. The relative abundances of these highly enriched direct mold taxa were also found to be inversely correlated to the dista...

Wearable Environmental Monitor To Quantify Personal Ambient Volatile Organic Compound Exposures.

Air pollution can cause acute and chronic health problems. It has many components, and one component of interest is volatile organic compounds (VOCs). While the outdoor environment may have regulations regarding exposure limits, the indoor environment is often unregulated and VOCs often appear in greater concentrations in the indoor environment. Therefore, it is equally critical to monitor both the indoor and outdoor environments for ambient chemical levels that an individual person is exposed to. While a number of different chemical detectors exist, most lack the ability to provide portable monitoring. We have developed a portable and wearable sampler that collects environmental VOCs in a person's immediate "exposure envelope" onto custom micro-preconcentrator chips for later benchtop analysis. The system also records ambient temperature and humidity and the GPS location during sampling, and the chip cartridges can be used in sequence over time to complete a profile of individual chemical exposure over the course of hours/days/weeks/months. The system can be programmed to accumulate sample for various times with varying periodicity. We first tested our sampler in the laboratory by completing calibration curves and testing saturation times for various common chemicals. The sampler was also tested in the field by collecting both indoor and outdoor personal exposure samples. Additionally under IRB approval, a teenaged volunteer wore the sampler for 5 days during which it sampled periodically throughout a 12 h period each day and the volunteer replaced the micro-preconcentrator chip each day.

Typological Characterisation of Mineral and Combustion Airborne Particles Indoors in Primary Schools

This study was carried out using a scanning electron microscope (SEM) analysis of airborne fine particles and indoor samples, obtained in the interiors of seven primary schools located along the Mediterranean coast in an area with an important industrial nucleus. The objectives of this study are to create a catalogue that gathers the principle particles found in the three environments examined and to assess the influence of outside sources of particulate matter on particles found indoors. The particles identified in the fine particle samples have been grouped into two main groups: mineral compounds and particles originating from combustion processes. The mineral particles emanating from natural emissions and anthropogenics were classified according to their morphology into: isometric alotriomorphs or subidiomorphs, with tabular, acicular, and pure crystalline forms. The compounds originating from combustion processes present two types of morphology: spheric-like particles and dendritic soot ones. On the other hand, in lesser proportion, spherical particles were also identified as being associated with industrial processes at high temperatures. To conclude a summary table is presented, that gathers the characteristics (morphology, type and size) along with the origins of the principle particles identified in the interior airborne fine particle samples obtained from primary schools located in three different environments.

Assessing the seasonality of occupancy number-associated CO2 level in a Taiwan hospital.

This study enabled the assessment of indoor CO2 levels and evaluated the relationship between occupancy numbers with CO2 levels in a Taiwan hospital. The measurements were conducted over four seasons for five working days (Monday to Friday), with sampling conducted simultaneously from 09:00 am to 5:00 pm and across six locations (for spatial variability): hall (H), registration and cashier (RC), waiting area (WA), occupational therapy room (OT), physical therapy room (PT), and outdoors (O). Based on the analysis, three of the five indoor sampling sites showed significant differences in seasonal CO2 concentrations (p < 0.0001). Based on our result, the physical therapy room had the highest level of CO2 concentration that exceeded the IAQ standard in Taiwan Environmental Protection Agency (EPA) in all seasons, in that the number of occupants contributing to nearly 40% of the variation in CO2 measured. Our results also showed that the indoor/outdoor (I/O) ratios of CO2 concentration for all locations and seasons exceeded 1 in ~ 100% of those locations. The median I/O ratio at sites WA and OT was 2.37 and 2.08 during four seasons, respectively. The highest median I/O ratio was found at site PT, with a calculated range of 2.69 in spring to 3.90 in fall. The highest correlation of occupancy number and CO2 concentration also occurred in PT which correlation coefficients were estimated at 0.47, 0.65, 0.63, and 0.40 in spring, summer, fall, and winter. The findings of the present study can be used to understand occupancy number and its effect on CO2 levels in a hospital environment, as well as the effect of time of day (Monday to Friday) on the number of patients admitted.

Personal exposure to PM2.5-bound organic species from domestic solid fuel combustion in rural Guanzhong Basin, China: Characteristics and health implication

Domestic solid fuels combustion produces a mass of fine particulate matter (PM2.5). PM2.5-bound organics, including polycyclic aromatic hydrocarbons (PAHs), oxygenated-PAHs (OPAHs), phthalate esters (PAEs) and hopanes, were quantified in indoor, outdoor and personal exposure samples collected in rural Guanzhong Basin, China. The average concentration of total quantified PAHs in personal exposure samples was 310 ± 443 ng m−3, 1.5 times of those of indoor (211 ± 120 ng m−3) and outdoor (189 ± 115 ng m−3). Similar observations were found for the OPAHs and PAEs, i.e., much higher concentrations were seen in personal exposure samples. Hopanes average personal exposure concentration (13 ± 9.7 ng m−3) was comparable to indoors (15 ± 9.7 ng m−3) and outdoors (13 ± 9.6 ng m−3). Among four common heating ways applied in Chinese dwelling, the highest exposure levels to PAHs, OPAHs and PAEs were found for indoor coal chunks stoves. Concentration under electric power was 1.2–4.5 folds lower than those with solid fuels in this study, proved to be the cleanest energy for the household heating. The exposures to PM2.5 on cell viabilities were also investigated. The largest reduction of 70% on cell viabilities was seen for indoor coal chunks stove housewives, indicating that the emissions from coal combustion had the greatest cytotoxic effects. The results evidenced that the heating ways in rural area could greatly impact on the housewife health in northwestern China. Advanced heating technology and protection should be conducted to reduce the personal exposures to PM2.5 from domestic solid fuel combustions.

Impact of Aquaculture Practices on Intestinal Bacterial Profiles of Pacific Whiteleg Shrimp Litopenaeus vannamei.

Considering the crucial role of the gut microbiome in animal health and nutrition, solutions to shrimp aquaculture challenges, such as improving disease resistance and optimizing growth on lower cost feeds, may lie in manipulation of their microbial symbionts. However, achieving this goal will require a deeper understanding of shrimp microbial communities and how their composition is influenced by diet formulation, environmental conditions, and host factors. In this context, the current study investigated the intestinal bacterial communities of the Pacific whiteleg shrimp (Litopenaeus vannamei—the most widely aquaculture-farmed shrimp worldwide) reared in indoor aquaculture facilities and outdoor pond systems. While samples showed very consistent intestinal bacterial community profiles within each production system, major differences were uncovered between the two practices. Indeed, bacteria affiliated with Rhodobacteraceae (Proteobacteria) and Actinobacteria were significantly more abundant in indoor samples (84.4% vs. 5.1%; 3.0% vs. 0.06%, respectively), while Vibrionaceae (Proteobacteria), Firmicutes, Fusobacteria and Cyanobacteria were predominant in pond samples (0.03% vs. 44.8%; 0.7% vs. 36.0%; 0.0% vs. 7.9%; 0.001% vs. 1.6%, respectively). Accordingly, the abundance of 11 of the 12 most prominent Operational Taxonomic Units (OTUs) were found to be statistically different between the two production environments. Together, these results indicate that aquaculture practices greatly influence the intestinal bacterial profile of the whiteleg shrimp, and further suggest that bacterial communities of this economically important crustacean could be effectively manipulated using diet composition or environmental conditions.

Indoor vs. outdoor airborne element array: A novel approach using moss bags to explore possible pollution sources

This study investigated by the moss-bag approach the pattern of air dispersed elements in 12 coupled indoor/outdoor exposure sites, all located in urban and rural residential areas. The aims were to discriminate indoor vs. outdoor element composition in coupled exposure sites and find possible relation between moss elemental profile and specific characteristics of each exposure site.Elements were considered enriched when in 60% of the sites, post-exposure concentration exceeded pre-exposure concentration plus two folds the standard deviation. Of the 53 analyzed elements, 15 (As, B, Ca, Co, Cr, Cu, Mn, Mo, Ni, Sb, Se, Sn, Sr, V, Zn) were enriched in moss exposed outdoor, whereas a subset of 7 elements (As, B, Cr, Mo, Ni, Se, V) were enriched also in indoor moss samples. The cluster analysis of the sites based on all elements, clearly separated samples in two groups corresponding to mosses exposed indoor and outdoor, with the latter generally exceeding the first. Among outdoor sites, urban were most impacted than rural; whereas other factors (e.g., heating and cooking systems, building material, residence time and family life style) could affect element profile of indoor environments. Based on the indoor/outdoor ratio, As derived from outdoor and indoor sources, B, Mo and Se were enriched mostly in outdoor sites; Ni, Cr and V were specifically enriched in most indoor samples, supporting the presence of indoor emitting sources for these elements. A PCA of all indoor sites based on enriched elements and site characteristics showed that traffic affected indoor pollution in urban areas. The moss bag approach provided useful information for a global assessment of human exposure.

The strength in numbers: comprehensive characterization of house dust using complementary mass spectrometric techniques

Untargeted analysis of a composite house dust sample has been performed as part of a collaborative effort to evaluate the progress in the field of suspect and nontarget screening and build an extensive database of organic indoor environment contaminants. Twenty-one participants reported results that were curated by the organizers of the collaborative trial. In total, nearly 2350 compounds were identified (18%) or tentatively identified (25% at confidence level 2 and 58% at confidence level 3), making the collaborative trial a success. However, a relatively small share (37%) of all compounds were reported by more than one participant, which shows that there is plenty of room for improvement in the field of suspect and nontarget screening. An even a smaller share (5%) of the total number of compounds were detected using both liquid chromatography–mass spectrometry (LC-MS) and gas chromatography–mass spectrometry (GC-MS). Thus, the two MS techniques are highly complementary. Most of the compounds were detected using LC with electrospray ionization (ESI) MS and comprehensive 2D GC (GC×GC) with atmospheric pressure chemical ionization (APCI) and electron ionization (EI), respectively. Collectively, the three techniques accounted for more than 75% of the reported compounds. Glycols, pharmaceuticals, pesticides, and various biogenic compounds dominated among the compounds reported by LC-MS participants, while hydrocarbons, hydrocarbon derivatives, and chlorinated paraffins and chlorinated biphenyls were primarily reported by GC-MS participants. Plastics additives, flavor and fragrances, and personal care products were reported by both LC-MS and GC-MS participants. It was concluded that the use of multiple analytical techniques was required for a comprehensive characterization of house dust contaminants. Further, several recommendations are given for improved suspect and nontarget screening of house dust and other indoor environment samples, including the use of open-source data processing tools. One of the tools allowed provisional identification of almost 500 compounds that had not been reported by participants.

Temporal variations of PM2.5-bound organophosphate flame retardants in different microenvironments in Beijing, China, and implications for human exposure

In the present study, the temporal distribution of PM2.5-bound organophosphate flame retardants (OPFRs) was comprehensively investigated in various indoor environments as well as outdoor air in Beijing, China over a one-year period. The mean concentrations of Σ9OPFRs were 22.7 ng m−3 and 1.40 ng m−3 in paired indoor and outdoor PM2.5, respectively. The concentrations of tri-n-butyl phosphate (TNBP), tris (2-chloroethyl) phosphate (TCEP) and tris (2-chloroisopropyl) phosphate (TCIPP) in indoor PM2.5 were significantly correlated with those in outdoor PM2.5. For different indoor microenvironments, mean concentrations of Σ9OPFRs were in the order of office (29.0 ± 11.7 ng m−3) > home (24.0 ± 9.4 ng m−3) > dormitory (19.4 ± 4.9 ng m−3) > activity room (14.4 ± 3.1 ng m−3). TCIPP was the most abundant compound in the indoor PM2.5, followed by TCEP. Significantly higher concentrations of OPFRs were observed in indoor environments with more furnishing, electronics or other materials (p < 0.05). Moreover, lower levels of OPFRs in indoor air were observed at well-ventilated (with higher air exchange rate) indoor sampling sites. Concentrations of Σ9OPFRs in the activity room, dormitory, homes and outdoor sites generally increased in summer and heating seasons (November 2016 to February 2017). Significant correlations (p < 0.05) were observed between temperatures and mass concentrations of OPFRs with higher vapor pressures, i.e. TNBP, TCEP and TCIPP in all indoor and outdoor samples. Seasonal differences in human exposure were observed and the highest daily exposure dose occurred in summer. Toddlers may suffer the highest exposure risk of PM2.5-bound OPFRs via inhalation among all age groups. This is one of the very few studies that have revealed the seasonal variation and human exposure of PM2.5-bound OPFRs in different microenvironments, which shed light on emission sources and fate of OPFRs and potential human exposure pathway.