A pilot investigation of the relative toxicity of indoor and outdoor fine particles: in vitro effects of endotoxin and other particulate properties

Particle characterization in commercial buildings: A cross-sectional study in 40 offices in Singapore

There is a knowledge gap in understanding how existing office buildings are protecting occupants from exposure to particles from both indoor and outdoor sources. We report a cross-sectional study involving weekly measurements of size-resolved indoor and outdoor particle concentrations in forty commercial building offices in Singapore. The outdoor and indoor particles size distributions were single mode with daytime peak number concentrations at 36.5 nm and 48.7 nm. Outdoor concentrations were significantly greater than indoors for all particle diameters. Indoor particle concentrations were generally low due to: 1) relatively high indoor particle removal (IPR) rates; 2) low indoor source strengths; and 3) low indoor particle of outdoor proportion (IPOP). We found that the ventilation system type had a substantial effect on indoor particle levels, IPR and IPOP. Through linear mixed model analyses, we identified dependencies of IPR rates with the use of MERV13 filters in supply air and filter maintenance frequency, IPOP with the use of MERV13 filters in the fresh air and supply air ducts and low particle source strength with regular daily cleaning presumably due to dust reservoir removal. Lastly, the contribution of outdoor sources was mainly seen for ultrafine and fine particles but less pronounced for coarse particles. This study provided detailed understanding of particle exposure in building offices and their influencing factors, facilitating future research on health impact of particle exposures.

Nonlinear proinflammatory effect of short-term PM2.5 exposure: A potential role of lipopolysaccharide

The association between PM2.5 (particulate matter ≤ 2.5 µm) short-term exposure and its health effect is non-linear from the epidemiological studies. And this nonlinearity is suggested to be related with the PM2.5 heterogeneity, however, the underlying biological mechanism is still unclear. Here, a total of 38 PM2.5 filters were collected continuously for three weeks in winter Beijing, with the ambient PM2.5 varying between 10 and 270 µg/m3. Human monocytes-derived macrophages (THP-1) were treated with PM2.5 water-soluble elutes at 10 µg/mL to investigate the PM2.5 short-term exposure effect from a proinflammatory perspective. The proinflammatory cytokine tumor necrosis factor (TNF) induced by the PM2.5 elutes at equal concentrations were unequal, showing the heterogeneity of PM2.5 proinflammatory potentials. Of the various chemical and biological components, lipopolysaccharide (LPS) showed a strong positive association with the TNF heterogeneity. However, some outliers were observed among the TNF-LPS association. Specifically, for PM2.5 from relatively clean air episodes, the higher LPS amount corresponded to relatively low TNF levels. And this phenomenon was also observed in the promotion tests by treating macrophages with PM2.5 elutes dosed with additional trace LPS. Gene expression analysis indicated the involvement of oxidative-stress related genes in the LPS signaling pathway. Therefore, a potential oxidative-stress-mediated suppression on the PM2.5-borne LPS proinflammatory effect was proposed to be accounted for the outliers. Overall, the results showed the differential role of LPS in the heterogeneity of PM2.5 proinflammatory effects from a component-based perspective. Future experimental studies are needed to elucidate the signaling pathway of LPS attached on PM2.5 from different air quality episodes.

Air pollution induces pyroptosis of human monocytes through activation of inflammasomes and Caspase-3-dependent pathways

According to the World Health Organization (WHO), air pollution is one of the most serious threats for our planet. Despite a growing public awareness of the harmful effects of air pollution on human health, the specific influence of particulate matter (PM) on human immune cells remains poorly understood. In this study, we investigated the effect of PM on peripheral blood monocytes in vitro. Monocytes from healthy donors (HD) were exposed to two types of PM: NIST (SRM 1648a, standard urban particulate matter from the US National Institute for Standards and Technology) and LAP (SRM 1648a with the organic fraction removed). The exposure to PM-induced mitochondrial ROS production followed by the decrease of mitochondrial membrane potential and activation of apoptotic protease activating factor 1 (Apaf-1), Caspase-9, and Caspase-3, leading to the cleavage of Gasdermin E (GSDME), and initiation of pyroptosis. Further analysis showed a simultaneous PM-dependent activation of inflammasomes, including NLRP3 (nucleotide-binding oligomerization domain-like receptor pyrin domain containing 3) and Caspase-1, followed by cleavage of Gasdermin D (GSDMD) and secretion of IL-1β. These observations suggest that PM-treated monocytes die by pyroptosis activated by two parallel signaling pathways, related to the inorganic and organic PM components. The release of IL-1β and expression of danger-associated molecular patterns (DAMPs) by pyroptotic cells further activated the remnant viable monocytes to produce inflammatory cytokines (TNF-α, IL-6, IL-8) and protected them from death induced by the second challenge with PM.In summary, our report shows that PM exposure significantly impacts monocyte function and induces their death by pyroptosis. Our observations indicate that the composition of PM plays a crucial role in this process-the inorganic fraction of PM is responsible for the induction of the Caspase-3-dependent pyroptotic pathway. At the same time, the canonical inflammasome path is activated by the organic components of PM, including LPS (Lipopolysaccharide/endotoxin). PM-induced pyroptosis of human monocytes. Particulate matter (PM) treatment affects monocytes viability already after 15 min of their exposure to NIST or LAP in vitro. The remnant viable monocytes in response to danger-associated molecular patterns (DAMPs) release pro-inflammatory cytokines and activate Th1 and Th17 cells. The mechanism of PM-induced cell death includes the increase of reactive oxygen species (ROS) production followed by collapse of mitochondrial membrane potential (ΔΨm), activation of Apaf-1, Caspase-9 and Caspase-3, leading to activation of Caspase-3-dependent pyroptotic pathway, where Caspase-3 cleaves Gasdermin E (GSDME) to produce a N-terminal fragment responsible for the switch from apoptosis to pyroptosis. At the same time, PM activates the canonical inflammasome pathway, where activated Caspase-1 cleaves the cytosolic Gasdermin D (GSDMD) to produce N-terminal domain allowing IL-1β secretion. As a result, PM-treated monocytes die by pyroptosis activated by two parallel pathways-Caspase-3-dependent pathway related to the inorganic fraction of PM and the canonical inflammasome pathway dependent on the organic components of PM.

Personal exposure to PM2.5 in different microenvironments and activities for retired adults in two megacities, China

Microenvironmental concentrations and time-activity patterns influence personal exposure to fine particulate matter (PM_2.5). However, the variations and contributions of PM_2.5 exposures from various microenvironments (MEs) and activities remain unclear. In this study, gravimetrically corrected real-time personal PM_2.5 measurements were collected during routine activities in different MEs from 66 non-smoking retired adults. Exposure data were collected for five consecutive days over two seasons in Nanjing (NJ) and Beijing (BJ), China. Measured PM_2.5 concentrations varied substantially both between and within different MEs and activities. The highest average concentrations were observed in restaurants (NJ: mean 192 μg/m³, SD 242 μg/m³; BJ: mean 91 μg/m³, SD 79 μg/m³) and were associated with sources such as passive smoking and cooking emissions. Overall, PM_2.5 concentrations in different MEs and activities were moderately to highly correlated with outdoor PM_2.5 concentrations (Spearman's r = 0.51-0.97) except in restaurants and during passive smoking. The at-home ME contributed approximately 85 % of the total PM_2.5 exposure, corresponding to the participants spending about 87 % of their time there. The majority of household exposures occurred during sleeping, cooking, and other home-based activities. Transportation accounted for <5 % of total exposure. Our results indicate that improving indoor air quality, especially residential indoors, is important to reduce personal exposure to PM_2.5.

Effects of Streamer Discharge on PM2.5 Containing Endotoxins and Polyaromatic Hydrocarbons and Their Biological Responses In Vitro

Experimental and epidemiological studies have demonstrated that fine particulate matter with a diameter of <2.5 μm (PM2.5) affects both the respiratory and immune systems. However, effective approaches to reduce PM2.5-induced hazardous effects have not been discovered yet. Streamer discharge is a category of plasma discharge in which high-speed electrons collide with oxygen and nitrogen molecules. Although streamer discharge can reportedly eliminate bacteria, molds, chemical substances, and allergens, its ability to decontaminate PM2.5 has not been previously demonstrated. The present study explored whether streamer discharge treatment could reduce PM2.5-induced inflammatory responses by employing an in vitro system. PM2.5 was collected under four conditions (Bangkok (Sep.−Dec.), Bangkok (Dec.−Mar.), Singapore, and Taipei). Airway epithelial cells and antigen-presenting cells exposed to non-treated PM2.5 in several conditions resulted in inflammatory responses. Streamer-discharged PM2.5 (Bangkok (Sep.−Dec.)) decreased the expression of interleukin (IL)-6 and IL-8 compared to non-treated PM2.5. Moreover, composition analysis demonstrated that streamer discharge reduced some compounds, such as endotoxins and polycyclic aromatic hydrocarbons, included in PM2.5 that can elicit inflammatory responses. Streamer discharge treatment can reduce endotoxins, polycyclic aromatic hydrocarbons, and the subsequent inflammatory responses induced by PM2.5 in vitro.

Indoor PM2.5 from occupied residences in Sweden caused higher inflammation in mice compared to outdoor PM2.5

We spend most of our time indoors; however, little is known about the effects of exposure to aerosol particles indoors. We aimed to determine differences in relative toxicity and physicochemical properties of PM_2.5 collected simultaneously indoors (PM_{2.5 INDOOR} ) and outdoors (PM_{2.5 OUTDOOR} ) in 15 occupied homes in southern Sweden. Collected particles were extracted from filters, pooled (indoor and outdoor separately), and characterized for chemical composition and endotoxins before being tested for toxicity in mice via intratracheal instillation. Various endpoints including lung inflammation, genotoxicity, and acute-phase response in lung and liver were assessed 1, 3, and 28 days post-exposure. Chemical composition of particles used in toxicological assessment was compared to particles analyzed without extraction. Time-resolved particle mass and number concentrations were monitored. PM_{2.5 INDOOR} showed higher relative concentrations (μg mg^-1 ) of metals, PAHs, and endotoxins compared to PM_{2.5 OUTDOOR} . These differences may be linked to PM_{2.5 INDOOR} causing significantly higher lung inflammation and lung acute-phase response 1 day post-exposure compared to PM_{2.5 OUTDOOR} and vehicle controls, respectively. None of the tested materials caused genotoxicity. PM_{2.5 INDOOR} displayed higher relative toxicity than PM_{2.5 OUTDOOR} under the studied conditions, that is, wintertime with reduced air exchange rates, high influence of indoor sources, and relatively low outdoor concentrations of PM. Reducing PM_{2.5 INDOOR} exposure requires reduction of both infiltration from outdoors and indoor-generated particles.

Partitioning indoor-generated and outdoor-generated PM2.5 from real-time residential measurements in urban and peri-urban Beijing

Limited number of projects have attempted to partition and quantify indoor- and outdoor-generated PM_2.5 (PM_2.5^ig and PM_2.5^og) where strong indoor sources (e.g., solid fuel, tobacco smoke, or kerosene) exist. This study aimed to apply and refine a previous recursive model used to derive infiltration efficiency (F_inf) to additionally partition pollution concentrations into indoor and outdoor origins within residences challenged by elevated ambient and indoor combustion-related sources. During the winter of 2016 and summer of 2017 we collected residential measurements in 72 homes in urban and peri-urban Beijing, 12 of which had additional paired residential outdoor measurements during the summer season. Local ambient measurements were collected throughout. We then compared the calculated PM_2.5^ig and using (i) outdoor and (ii) ambient measurements as model inputs. The results from outdoor and ambient measurements were not significantly different, which suggests that ambient measurements can be used as a model input for pollution origin partitioning when paired outdoor measurements are not available. From the results calculated using ambient measurements, the mean percentage contribution of indoor-generated PM_2.5 was 19 % (σ = 22 %), and 7 % (11 %) of the total indoor PM_2.5 for peri-urban and urban homes respectively during the winter; and 18 % (18 %) and 6 % (10 %) of the total indoor PM_2.5 during the summer. Partitioning pollution into PM_2.5^ig and PM_2.5^og is important to allow investigation of distinct associations between health outcomes and particulate mixes, often with different physiochemical composition and toxicity. It will also inform targeted interventions that impact indoor and outdoor sources of pollution (e.g., domestic fuel switching vs. power generation), which are typically radically different in design and implementation.

Sensitivity of modeled residential fine particulate matter exposure to select building and source characteristics: A case study using public data in Boston, MA

Many techniques for estimating exposure to airborne contaminants do not account for building characteristics that can magnify contaminant contributions from indoor and outdoor sources. Building characteristics that influence exposure can be challenging to obtain at scale, but some may be incorporated into exposure assessments using public datasets. We present a methodology for using public datasets to generate housing models for a test cohort, and examined sensitivity of predicted fine particulate matter (PM2.5) exposures to selected building and source characteristics. We used addresses of a cohort of children with asthma and public tax assessor's data to guide selection of floorplans of US residences from a public database. This in turn guided generation of coupled multi-zone models (CONTAM and EnergyPlus) that estimated indoor PM2.5 exposure profiles. To examine sensitivity to model parameters, we varied building floors and floorplan, heating, ventilating and air-conditioning (HVAC) type, room or floor-level model resolution, and indoor source strength and schedule (for hypothesized gas stove cooking and tobacco smoking). Occupant time-activity and ambient pollutant levels were held constant. Our address matching methodology identified two multi-family house templates and one single-family house template that had similar characteristics to 60 % of test addresses. Exposure to infiltrated ambient PM2.5 was similar across selected building characteristics, HVAC types, and model resolutions (holding all else equal). By comparison, exposures to indoor-sourced PM2.5 were higher in the two multi-family residences than the single family residence (e.g., for cooking PM2.5 exposure, by 26 % and 47 % respectively) and were sensitive to HVAC type and model resolution. We derived the influence of building characteristics and HVAC type on PM2.5 exposure indoors using public data sources and coupled multi-zone models. With the important inclusion of individualized resident behavior data, similar housing modeling can be used to incorporate exposure variability in health studies of the indoor residential environment.

Occurrence and fate of bacterial endotoxins in the environment (air, water, wastewater) and remediation technologies: An overview

Endotoxins as the outer membrane of most Gram-Negative Bacteria (GNB) and typical toxic biochemical produced by microorganisms are identified as one of the emerging pollutants. These microbial by-products are harmful compounds that can be present in various environments including air, water, soil, and other ecosystems which was discussed in detail in this review. Environmental and occupational exposure caused by endotoxin occurs in water and wastewater treatment plants, industrial plants, farming, waste recovery, and composting facilities. Even though the health risk related to endotoxin injection in intravenous and dialysis are well identified, the harmful effects of ingestion, inhalation, and other way of exposure are not well quantified and there is insufficient information on the potential health risks of endotoxins exposure in water environments, and another exposures. Because of limited studies, the outbreaks of diseases related to endotoxins in the various source of exposure not been well documented. Endotoxin removal from different environments are investigated in this review. The results of various studies have shown that conventional treatment methods have been unable to remove endotoxins from water and wastewater, therefore, monitoring the effectiveness of these processes in controlling this contaminant and also using the appropriate removal method is essential. However, management of water and wastewater treatment processes and the use of advanced processes such as Advanced Oxidation Processes (AOPs) can be effective in monitoring and reducing endotoxin levels during water and wastewater treatment. One of the limitations of endotoxin monitoring is the lack of sufficient information to develop monitoring levels. In addition, the lack of guidelinesand methods of controlling them at high levels may cause irreparable disaster.

A review and analysis of personal and ambient PM2.5 measurements: Implications for epidemiology studies

BACKGROUND

In epidemiology studies, ambient measurements of PM_2.5 are often used as surrogates for personal exposures. However, it is unclear the degree to which ambient PM_2.5 reflects personal exposures.

OBJECTIVE

In order to examine potential sources of bias in epidemiology studies, we conducted a review and meta-analysis of studies to determine the extent to which short-term measurements of ambient PM_2.5 levels are related to short-term measurements of personal PM_2.5 levels.

METHODS

We conducted a literature search of studies reporting both personal and ambient measurements of PM_2.5 published in the last 10 years (2009-2019) and incorporated studies published prior to 2009 from reviews.

RESULTS

Seventy-one studies were identified. Based on 17 studies reporting slopes, a meta-analysis revealed an overall slope of 0.56 μg/m³ (95% CI: [0.39, 0.73]) personal PM_2.5 per μg/m³ increase in ambient PM_2.5. Slopes for summer months were higher (slope = 0.73, 95% CI: [0.64, 0.81]) than for winter (slope = 0.46, 95% CI: [0.36, 0.57]). Based on 44 studies reporting correlations, we calculated an overall personal-ambient PM_2.5 correlation of 0.63 (95% CI: [0.55, 0.71]). Correlations were stronger in studies conducted in Canada (r = 0.86, 95% CI: [0.67, 0.94]) compared to the USA (r = 0.60, 95% CI: [0.49, 0.70]) and China (r = 0.60, 95% CI: [0.46, 0.71]). Correlations also were stronger in urban areas (r = 0.53, 95% CI: [0.43, 0.62]) vs. suburban areas (r = 0.36, 95% CI: [0.21, 0.49]).

SIGNIFICANCE

Our results suggest a large degree of variability in the personal-ambient PM_2.5 association and the potential for exposure misclassification and measurement error in PM_2.5 epidemiology studies.

Source identification of pollution and health risks to metals in household indoor and outdoor dust: A cross-sectional study in a typical mining town, China

Dust is regarded as an important pathway of heavy metal(loid)s to the human body. Health risks posed by metal(loid)s from household dust are of particular concern. However, the contamination and sources of heavy metal(loid)s in household dust environments, as well as source identification of health risks related to heavy metal(loid)s from household dust for vulnerable populations such as children, have not been thoroughly studied in China, particularly for the areas involved with industrial activities such as ore mining. Thus, a cross-sectional study was conducted in a rural area famous for Pb/Zn ore mining, to assess the pollution sources and health risks of heavy metal(loid)s from household indoor and outdoor dust and to identify the contribution of household dust to the health risks for children. The results indicated that household environment was heavily contaminated by metal(loid)s, which were mainly attributed to mining activity. Meanwhile, the indoor/outdoor ratio and the redundancy analysis indicated that there were other pollution sources in indoor environments such as coal combustion, materials for interior building and decoration. Vapor inhalation was the main exposure pathway for Hg, while ingestion was the predominant pathway for other metal(loid)s. Although the cancer risks were relatively low, the HIt from household indoor and outdoor dust (2.19) was about twice the acceptable limit (1) and was primarily from Pb (64.52%) and As (23.42%). Outdoor dust was a larger contributor to the HI of Sb, As, Cr, Cd, Zn and Pb, which accounted for 51.37%, 58.63%, 52.14%, 59.66%, 52.87% and 64.47%, respectively, and the HIt was mainly from outdoor dust (60.76%). These results indicated that non-cancer health risks were largely from outdoor dust exposure, and strengthened the notion that concern should be given to the potential health risks from metal(loid)s in household dust both originating from mining activity and indoor environmental sources.

Toxicology of respiratory system: Profiling chemicals in PM10 for molecular targets and adverse outcomes

Numerous studies have shown that the increasing trend of respiratory diseases have been closely associated with the endogenous toxic chemicals (polycyclic aromatic hydrocarbons, heavy metal ions, etc.) in PM₁₀. In the present study, we aim to determine the strong correlations between the chemicals in PM₁₀ and the adverse consequences. We used the ChemView DB, the ToxRef DB and a comprehensive literature analysis to collect, identify, and evaluate the chemicals in PM₁₀ and their adverse effects on respiratory system, and then used the ToxCast DB to analyze their bioactivity and key targets through 1192 molecular targets and cell characteristic endpoints. Meanwhile, the bioinformatics analysis were carried out on the molecular targets to screen out prevention and treatment targets. A total of 310 chemicals related to the respiratory system were identified. An unsupervised two-directional heatmap was constructed based on hierarchical clustering of 227 chemicals by their effect scores. A subset of 253 chemicals with respiratory system toxicity had in vitro bioactivity on 318 molecular targets that could be described, clustered and annotated in the heatmap and bipartite network, which were analyzed based on the protein information in UniProt KB database and the software of GO, STRING, and KEGG. These results showed that the chemicals in PM₁₀ have strong correlation with different types of respiratory system injury. The main pathways of respiratory system injury caused by PM₁₀ are the Calcium signaling pathway, MAPK signaling pathway, and PI3K-AKT signaling pathway, and the core proteins in which are likely to be the molecular targets for the prevention and treatment of damage caused by PM₁₀.

The oxidative capacity of indoor source combustion derived particulate matter and resulting respiratory toxicity

Indoor air pollution sources with emissions of fine particles (PM_2.5), including environmental tobacco smoke (ETS) and incense smoke (IS) deteriorate indoor air quality and may cause respiratory diseases in humans. This study characterized the emission factors (EFs) of five types of tobacco and incense in Hong Kong using an environmental chamber. Human alveolar epithelial cells (A549) were exposed to PM_2.5 collected from different indoor sources to determine their cytotoxicity. The PM_2.5 EF of ETS (109.7±36.5 mg/g) was higher than IS (97.1±87.3 mg/g). The EFs of total polycyclic aromatic hydrocarbons (PAHs) and carbonyls for IS were higher than ETS, and these two combustion sources showed similar distributions of individual PAHs and carbonyls. Oxidative damage and inflammatory responses (i.e. DNA damage, 8-hydroxy-desoxyguanosine (8-OHdG), tumor necrosis factor-α (TNF-α) and interlukin-6 (IL-6)) of A549 cells was triggered by exposure to PM_2.5 generated from ETS and IS. Different indoor sources showed different responses to oxidative stress and inflammations due to the accumulation effects of mixed organic compounds. High molecular weight PAHs from incense combustion showed higher correlations with DNA damage markers, and most of the PAHs from indoor sources demonstrated significant correlations with inflammation. Exposure to anthropogenic produced combustion emissions such as ETS and IS results in significant risks (e.g. lung cancer) to the alveolar epithelium within the distal human respiratory tract, of which incense emissions posed a higher cytotoxicity.

Genotoxicity induced in vitro by water-soluble indoor PM2.5 fractions in relation to heavy metal concentrations

The aim of the present study was to examine the genotoxicity induced by water-soluble fractions of particulate matter (PM) and its potential relation with heavy metals. For this purpose, the genotoxicity induced on human peripheral lymphocytes by water-soluble PM_2.5 (particles with aerodynamic diameter ≤ 2.5 μm) collected from the indoor air of various workplaces in Greece (n = 20), was examined by the Sister Chromatid Exchange (SCE) induction assay and assessed in relation to the concentrations of the heavy metals Cu, Pb, Mn, Ni, Co, Zn, Cr, and Cd. The number of SCEs per metaphase (SCEs/metaphase), as an indicator of genotoxicity, the proliferation rate index (PRI), as an indicator of cytostaticity, and the mitotic index (MI), as an indicator of cytotoxicity, were measured and assessed in three water-soluble fractions of PM_2.5: the total water-soluble fraction WS_A (filtered through 0.45 μm), the dissolved fraction WS_B (filtered through 0.22 μm), and the non-chelexed dissolved fraction WS_C (filtered through Chelex-100 resin). Results showed statistically significant number of SCEs/metaphase in all water-soluble PM_2.5 fractions in relation to the control with large variabilities across the workplaces as a result of variations in indoor conditions, sources, and/or activities. The concentrations of genotoxicity were evaluated in terms of mass-normalized genotoxicity (SCEs/mg PM_2.5), that represents the genotoxic potency of particles, and air volume-normalized genotoxicity (SCEs/m³ air), that reflects the inhalation risk for people working or spending much time in these microenvironments. Correlation and linear regression analyses were further employed in order to investigate the potential relationships between genotoxicity and the water-soluble concentrations of PM_2.5-bounded heavy metals. According to the results, the highest mass-normalized genotoxicity values were found for PM_2.5 from the photocopying center, whereas the highest air volume-normalized genotoxicity was found in tavern-2. Significant positive correlations between the genotoxicity and water-soluble metals were derived, highlighting the role that heavy metals play in the genotoxicity of indoor PM_2.5. Among the targeted metals, Zn and Pb were found to be good predictors of the genotoxicity of water-soluble PM_2.5.

Ambient PM Toxicity Is Correlated with Expression Levels of Specific MicroRNAs

Uncertainties regarding optimized air pollution control remain as the underlying mechanisms of city-specific ambient particulate matter (PM)-induced health effects are unknown. Here, water-soluble extracts of PMs collected from four global cities via automobile air-conditioning filters were consecutively injected three times by an amount of 1, 2, and 2 mg into the blood circulation of Wistar rats after filtration by a 0.45 μm pore size membrane. Acute health effects, such as immune and inflammatory responses and hemorrhage in alveoli, were observed right after the PM extraction injection. Significant differences between cities in biomarker tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) levels were detected following the second and third PM injections. Rats' inflammatory responses varied substantially with the injections of city-specific PMs. Repeated PM extract exposure rendered the rats more vulnerable to subsequent challenges, and downregulation of certain microRNAs was observed in rats. Among the studied miRNAs, miR-125b, and miR-21 were most sensitive to the PM exposure, exhibiting a negative dose-response-type relationship with a source-specific PM (oxidative potential) toxicity (r² = 0.63 and 0.57; p-values < 0.05). The results indicated that city-specific PMs could induce different health effects by selectively regulating different miRNAs, and that certain microRNAs, e.g., miR-125b and miR-21, may be externally mediated to neutralize PM-related health damages.

Synergistic Association of House Endotoxin Exposure and Ambient Air Pollution with Asthma Outcomes

Rationale: House endotoxin and ambient air pollution are risk factors for asthma; however, the effects of their coexposure on asthma are not well characterized.Objectives: To examine potential synergistic associations of coexposure to house dust endotoxin and ambient air pollutants with asthma outcomes.Methods: We analyzed data of 6,488 participants in the National Health and Nutrition Examination Survey 2005-2006. Dust from bedding and bedroom floor was analyzed for endotoxin content. The Community Multiscale Air Quality Modeling System (CMAQ) and Downscaler Model data were used to determine annual average particulate matter ≤2.5 μm in aerodynamic diameter (PM_2.5), ozone (O₃), and nitrogen dioxide (NO₂) exposures at participants' residential locations. The associations of the coexposures with asthma outcomes were assessed and tested for synergistic interaction.Measurements and Main Results: In adjusted analysis, PM_2.5 (CMAQ) (odds ratio [OR], 1.12; 95% confidence interval [CI], 1.07-1.18), O₃ (Downscaler Model) (OR, 1.07; 95% CI, 1.02-1.13), and log₁₀ NO₂ (CMAQ) (OR, 3.15; 95% CI, 1.33-7.45) were positively associated with emergency room visits for asthma in the past 12 months. Coexposure to elevated concentrations of house dust endotoxin and PM_2.5 (CMAQ) was synergistically associated with the outcome, increasing the odds by fivefold (OR, 5.01; 95% CI, 2.54-9.87). A synergistic association was also found for coexposure to higher concentrations of endotoxin and NO₂ in children (OR, 3.45; 95% CI, 1.65-7.18).Conclusions: Coexposure to elevated concentrations of residential endotoxin and ambient PM_2.5 in all participants and NO₂ in children is synergistically associated with increased emergency room visits for asthma. Therefore, decreasing exposure to both endotoxin and air pollution may help reduce asthma morbidity.

A framework for estimating the US mortality burden of fine particulate matter exposure attributable to indoor and outdoor microenvironments

Exposure to fine particulate matter (PM_2.5) is associated with increased mortality. Although epidemiology studies typically use outdoor PM_2.5 concentrations as surrogates for exposure, the majority of PM_2.5 exposure in the US occurs in microenvironments other than outdoors. We develop a framework for estimating the total US mortality burden attributable to exposure to PM_2.5 of both indoor and outdoor origin in the primary non-smoking microenvironments in which people spend most of their time. The framework utilizes an exposure-response function combined with adjusted mortality effect estimates that account for underlying exposures to PM_2.5 of outdoor origin that likely occurred in the original epidemiology populations from which effect estimates are derived. We demonstrate the framework using several different scenarios to estimate the potential magnitude and bounds of the US mortality burden attributable to total PM_2.5 exposure across all non-smoking environments under a variety of assumptions. Our best estimates of the US mortality burden associated with total PM_2.5 exposure in the year 2012 range from ~230,000 to ~300,000 deaths. Indoor exposure to PM_2.5 of outdoor origin is typically the largest total exposure, accounting for ~40-60% of total mortality, followed by residential exposure to indoor PM_2.5 sources, which also drives the majority of variability in each scenario.

Transition Metal Containing Particulate Matter Promotes Th1 and Th17 Inflammatory Response by Monocyte Activation in Organic and Inorganic Compounds Dependent Manner

In recent years, a significant increase in the frequency of disorders caused by air pollutants has been observed. Here we asked whether transition metal-containing particulate matter (TMCPM), a component of air pollution, has an effect on the activity of human CD4+ T cell subsets (Th1, Th2, Th17, and Treg). Peripheral blood mononuclear cells (PBMC) from healthy donors were cultured with or without NIST (SRM 1648a—standard urban particulate matter purchased from the National Institute for Standards and Technology) and LAP (SRM 1648a particulate matter treated within 120 min with cold oxygen plasma) preparations of TMCPM, differing in organic compounds content. Data show that TMCPM treatment increased the level of CD4+ cells positive for IFN-γ and IL-17A, specific for Th1 and Th17 cells, respectively. Moreover, a substantial decrease in frequency of Foxp3 positive CD4+ cells was observed in parallel. This effect was more pronounced for NIST particles, containing more organic components, including endotoxin (LPS - lipopolysaccharide) and required the presence of monocytes. Inactivation of LPS by treatment of TMCPM with polymyxin B reduced the inflammatory response of monocytes and Th subsets but did not abolish this activity, suggesting a role of their inorganic components. In conclusion, treatment of human PBMC with TMCPM skews the balance of Th1/Th2 and Treg/Th17 cells, promoting polarization of CD4+ T cells into Th1 and Th17 subsets. This phenomenon requires activation of monocytes and depends on the organic and inorganic fractions, including endotoxin content in TMCPM, as significantly higher inflammatory response was observed for the NIST comparing to LAP. This observation may shed a new light on the role of TMCPM in development and exacerbation of allergies, inflammatory, and autoimmune disorders.

Oxidative capacity and hemolytic activity of settled dust from moisture-damaged schools

Exposure to moisture-damaged indoor environments is associated with adverse respiratory health effects, but responsible factors remain unidentified. In order to explore possible mechanisms behind these effects, the oxidative capacity and hemolytic activity of settled dust samples (n = 25) collected from moisture-damaged and non-damaged schools in Spain, the Netherlands, and Finland were evaluated and matched against the microbial content of the sample. Oxidative capacity was determined with plasmid scission assay and hemolytic activity by assessing the damage to isolated human red blood cells. The microbial content of the samples was measured with quantitative PCR assays for selected microbial groups and by analyzing the cell wall markers ergosterol, muramic acid, endotoxins, and glucans. The moisture observations in the schools were associated with some of the microbial components in the dust, and microbial determinants grouped together increased the oxidative capacity. Oxidative capacity was also affected by particle concentration and country of origin. Two out of 14 studied dust samples from moisture-damaged schools demonstrated some hemolytic activity. The results indicate that the microbial component connected with moisture damage is associated with increased oxidative stress and that hemolysis should be studied further as one possible mechanism contributing to the adverse health effects of moisture-damaged buildings.

Automated in Vivo Nanosensing of Breath-Borne Protein Biomarkers

Toxicology and bedside medical condition monitoring is often desired to be both ultrasensitive and noninvasive. However, current biomarker analyses for these purposes are mostly offline and fail to detect low marker quantities. Here, we report a system called dLABer (detection of living animal's exhaled breath biomarker) that integrates living rats, breath sampling, microfluidics, and biosensors for the automated tracking of breath-borne biomarkers. Our data show that dLABer could selectively detect (online) and report differences (of up to 10³-fold) in the levels of inflammation agent interleukin-6 (IL-6) exhaled by rats injected with different ambient particulate matter (PM). The dLABer system was further shown to have an up to 10⁴ higher signal-to-noise ratio than that of the enzyme-linked immunosorbent assay (ELISA) when analyzing the same breath samples. In addition, both blood-borne IL-6 levels analyzed via ELISA in rats injected with different PM extracts and PM toxicity determined by a dithiothreitol (DTT) assay agreed well with those determined by the dLABer system. Video recordings further verified that rats exposed to PM with higher toxicity (according to a DTT assay and as revealed by dLABer) appeared to be less physically active. All the data presented here suggest that the dLABer system is capable of real-time, noninvasive monitoring of breath-borne biomarkers with ultrasensitivity. The dLABer system is expected to revolutionize pollutant health effect studies and bedside disease diagnosis as well as physiological condition monitoring at the single-protein level.

Airborne endotoxin concentrations in indoor and outdoor particulate matter and their predictors in an urban city

Endotoxins are an important biological component of particulate matter and have been associated with adverse effects on human health. There have been some recent studies on airborne endotoxin concentrations. We collected fine (PM_2.5 ) and coarse (PM_10-2.5 ) particulate matter twice on weekdays and weekends each for 48 hour, inside and outside 55 homes in an urban city in Japan. Endotoxin concentrations in both fractions were measured using the kinetic Limulus Amebocyte Lysate assay. The relationships between endotoxin concentrations and household characteristics were evaluated for each fraction. Both indoor and outdoor endotoxin concentrations were higher in PM_2.5 than in PM_10-2.5 . In both PM_2.5 and PM_10-2.5 , indoor endotoxin concentrations were higher than outdoor concentrations, and the indoor endotoxin concentrations significantly correlated with outdoor concentrations in each fraction (R² =0.458 and 0.198, respectively). Indoor endotoxin concentrations in PM_2.5 were significantly higher in homes with tatami or carpet flooring and in homes with pets, and lower in homes that used air purifiers. Indoor endotoxin concentrations in PM_10-2.5 were significantly higher in homes with two or more children and homes with tatami or carpet flooring. These results showed that the indoor endotoxin concentrations were associated with the household characteristics in addition to outdoor endotoxin concentrations.

Modeling indoor particulate exposures in inner-city school classrooms

Outdoor air pollution penetrates buildings and contributes to total indoor exposures. We investigated the relationship of indoor to outdoor particulate matter in inner-city school classrooms. The School Inner City Asthma Study investigates the effect of classroom-based environmental exposures on students with asthma in the northeast United States. Mixed effects linear models were used to determine the relationships between indoor PM2.5 (particulate matter) and black carbon (BC), and their corresponding outdoor concentrations, and to develop a model for predicting exposures to these pollutants. The indoor-outdoor sulfur ratio was used as an infiltration factor of outdoor fine particles. Weeklong concentrations of PM2.5 and BC in 199 samples from 136 classrooms (30 school buildings) were compared with those measured at a central monitoring site averaged over the same timeframe. Mixed effects regression models found significant random intercept and slope effects, which indicate that: (1) there are important PM2.5 sources in classrooms; (2) the penetration of outdoor PM2.5 particles varies by school and (3) the site-specific outside PM2.5 levels (inferred by the models) differ from those observed at the central monitor site. Similar results were found for BC except for lack of indoor sources. The fitted predictions from the sulfur-adjusted models were moderately predictive of observed indoor pollutant levels (out of sample correlations: PM2.5: r2=0.68, BC; r2=0.61). Our results suggest that PM2.5 has important classroom sources, which vary by school. Furthermore, using these mixed effects models, classroom exposures can be accurately predicted for dates when central site measures are available but indoor measures are not available.

Predictive and Prognostic Biomarkers of Respiratory Diseases due to Particulate Matter Exposure

Air pollution is getting severe and concerns about its toxicity effects on airway and lung disease are also increasing. Particulate matter (PM) is major component of air pollutant. It causes respiratory diseases, such as asthma, chronic obstructive pulmonary disease, lung cancer, and so on. PM particles enter the airway and lung by inhalation, causing damages to them. Especially, PM_2.5 can penetrate into the alveolus and pass to the systemic circulation. It can affect the cardiopulmonary system and cause cardiopulmonary disorders. In this review, we focused on PM-inducing toxicity mechanisms in the framework of oxidative stress, inflammation, and epigenetic changes. We also reviewed its correlation with respiratory diseases. In addition, we reviewed biomarkers related to PM-induced respiratory diseases. These biomarkers might be used for disease prediction and early diagnosis. With recent trend of using genomic analysis tools in the field of toxicogenomics, respiratory disease biomarkers associated with PM will be continuously investigated. Effective biomarkers derived from earlier studies and further studies might be utilized to reduce respiratory diseases.

Identification of PM10 characteristics involved in cellular responses in human bronchial epithelial cells (Beas-2B)

Notwithstanding evidence is present that physicochemical characteristics of ambient particles attribute to adverse health effects, there is still some lack of understanding in this complex relationship. At this moment it is not clear which properties (such as particle size, chemical composition) or sources of the particles are most relevant for health effects. This study investigates the in vitro toxicity of PM10 in relation to PM chemical composition, black carbon (BC), endotoxin content and oxidative potential (OP). In 2013-2014 PM10 was sampled (24h sampling, 108 sampling days) in ambient air at three sites in Flanders (Belgium) with different pollution characteristics: an urban traffic site (Borgerhout), an industrial area (Zelzate) and a rural background location (Houtem). To characterize the toxic potential of PM10, airway epithelial cells (Beas-2B cells) have been exposed to particles in vitro. Different endpoints were studied including cell damage and death (cell viability) using the Neutral red Uptake assay, the production of pro-inflammatory molecules by interleukin 8 (IL-8) induction and DNA-damaging activity using the FPG-modified Comet assay. The endotoxin levels in the collected samples were analysed and the capacity of PM10 particles to produce reactive oxygen species (OP) was evaluated by electron paramagnetic resonance (EPR) spectroscopy. Chemical characteristics of PM10 (BC, As, Cd, Cr, Cu, Mn, Ni, Pb, Zn) and meteorological conditions were recorded on the sampling days. PM10 particles exhibited dose-dependent cytotoxicity in Beas-2B cells and were found to significantly induce the release of IL-8 in samples from the three locations. Oxidatively damaged DNA was observed in exposed Beas-2B cells. Endotoxin levels above the detection limit were detected in half of the samples. OP was measurable in all samples. Associations between PM10 characteristics and biological effects of PM10 were assessed by single and multiple regression analyses. The reduction in cell viability was significantly correlated with BC, Cd and Pb. The induction of IL-8 in Beas-2B cells was significantly associated with Cu, Ni and Zn and endotoxin. Endotoxin levels explained 33% of the variance in IL-8 induction. A significant interaction between ambient temperature and endotoxin on the pro-inflammatory activity was seen. No association was found between OP and the cellular responses. This study supports the hypothesis that, on an equal mass basis, PM10 induced biological effects differ due to differences in PM10 characteristics. Metals (Cd, Cu, Ni and Zn), BC, and endotoxin were among the main determinants for the observed biological responses.

Characterization of ambient and extracted PM2.5 collected on filters for toxicology applications

Research on the health effects of fine particulate matter (PM2.5) frequently disregards the differences in particle composition between that measured on an ambient filter versus that measured in the corresponding extraction solution used for toxicological testing. This study presents a novel method for characterizing the differences, in metallic and organic species, between the ambient samples and the corresponding extracted solutions through characterization of extracted PM2.5 suspended on filters. Removal efficiency was found to be 98.0 ± 1.4% when measured using pre- and post-removal filter weights, however, this efficiency was significantly reduced to 80.2 ± 0.8% when measured based on particle mass in the extraction solution. Furthermore, only 47.2 ± 22.3% of metals and 24.8 ± 14.5% of organics measured on the ambient filter were found in the extraction solution. Individual metallic and organic components were extracted with varying efficiency, with many organics being lost entirely during extraction. Finally, extraction efficiencies of specific PM2.5 components were inversely correlated with total mass. This study details a method to assess compositional alterations resulting from extraction of PM2.5 from filters, emphasizing the need for standardized procedures that maintain compositional integrity of ambient samples for use in toxicology studies of PM2.5.

Xenobiotic pulmonary exposure and systemic cardiovascular response via neurological links

The cardiovascular response to xenobiotic particle exposure has been increasingly studied over the last two decades, producing an extraordinary scope and depth of research findings. With the flourishing of nanotechnology, the term "xenobiotic particles" has expanded to encompass not only air pollution particulate matter (PM) but also anthropogenic particles, such as engineered nanomaterials (ENMs). Historically, the majority of research in these fields has focused on pulmonary exposure and the adverse physiological effects associated with a host inflammatory response or direct particle-tissue interactions. Because these hypotheses can neither account entirely for the deleterious cardiovascular effects of xenobiotic particle exposure nor their time course, the case for substantial neurological involvement is apparent. Indeed, considerable evidence suggests that not only is neural involvement a significant contributor but also a reality that needs to be investigated more thoroughly when assessing xenobiotic particle toxicities. Therefore, the scope of this review is several-fold. First, we provide a brief overview of the major anatomical components of the central and peripheral nervous systems, giving consideration to the potential biologic targets affected by inhaled particles. Second, the autonomic arcs and mechanisms that may be involved are reviewed. Third, the cardiovascular outcomes following neurological responses are discussed. Lastly, unique problems, future risks, and hurdles associated with xenobiotic particle exposure are discussed. A better understanding of these neural issues may facilitate research that in conjunction with existing research, will ultimately prevent the untoward cardiovascular outcomes associated with PM exposures and/or identify safe ENMs for the advancement of human health.

Chemical and microbial components of urban air PM cause seasonal variation of toxicological activity

The chemical and microbial composition of urban air particulate matter (PM) displays seasonal variation that may affect its harmfulness on human health. We studied the in vitro inflammatory and cellular metabolic activity/cytotoxicity of urban air particulate samples collected in four size-ranges (PM10-2.5, PM2.5-1, PM1-0.2, PM0.2) during four seasons in relatively clean urban environment in Helsinki, Finland. The composition of the same samples were analyzed, including ions, elements, PAH compounds and endotoxins. In addition, microbial contribution on the detected responses was studied by inhibiting the endotoxin-induced responses with Polymyxin B both in the PM samples and by two different bacterial strains representing Gram-positive and -negative bacteria. Macrophage cell line (RAW 264.7) was exposed to the size segregated particulate samples as well as to microbe samples for 24h and markers of inflammation and cytotoxicity were analyzed. The toxicological responses were dependent on the dose as well as size range of the particles, PM10-2.5 being the most potent and smaller size ranges having significantly smaller responses. Samples collected during spring and autumn had in most cases the highest inflammatory activity. Soil components and other non-exhaust particulate emissions from road traffic correlated with inflammatory responses in coarse particles. Instead, PAH-compounds and K(+) had negative associations with the particle-induced inflammatory responses in fine particles, suggesting the role of incomplete biomass combustion. Endotoxin content was the highest in PM10-2.5 samples and correspondingly, the largest decrease in the responses by Polymyxin B was seen with the very same samples. We found also that inhibitory effect of Polymyxin B was not completely specific for Gram-negative bacteria. Thus, in addition to endotoxin, also other microbial components may have a significant effect on the toxicological responses by ambient particulate matter.

Short-Term Effects of Fine Particulate Matter and Temperature on Lung Function among Healthy College Students in Wuhan, China

Ambient fine particulate matter (PM) has been associated with impaired lung function, but the effect of temperature on lung function and the potential interaction effect between PM and temperature remain uncertain. To estimate the short-term effects of PM2.5 combined with temperature on lung function, we measured the daily peak expiratory flow (PEF) in a panel of 37 healthy college students in four different seasons. Meanwhile, we also monitored daily concentrations of indoor and outdoor PM2.5 (particulate matter with an aerodynamic diameter ≤2.5 μm), ambient temperature and relative humidity of the study area, where the study participants lived and attended school. Associations of air pollutants and temperature with lung function were assessed by generalized estimating equations (GEEs). A 10 μg/m3 increase of indoor PM2.5 was associated with a change of -2.09 L/min in evening PEF (95%CI: -3.73 L/min--0.51 L/min) after adjusting for season, height, gender, temperature and relative humidity. The changes of -2.17 L/min (95%CI: -3.81 L/min- -0.52 L/min) and -2.18 L/min (95%CI: -3.96 L/min--0.41 L/min) in evening PEF were also observed after adjusting for outdoor SO2 and NO2 measured by Environmental Monitoring Center 3 kilometers away, respectively. An increase in ambient temperature was found to be associated with a decrease in lung function and our results revealed a small but significant antagonistic interactive effect between PM2.5 and temperature. Our findings suggest that ambient PM2.5 has an acute adverse effect on lung function in young healthy adults, and that temperature also plays an important role.

Influence of combined dust reducing carpet and compact air filtration unit on the indoor air quality of a classroom

Primary schools mostly rely on natural ventilation but also have an interest in affordable technology to improve indoor air quality (IAQ). Laboratory tests show promising results for dust reducing carpets and compact air filtration systems but there is no information available on the performance of these interventions in actual operating classrooms. An exploratory study was performed to evaluate a combination of the two systems in a primary school. Measurements of PM-10 and PM-2.5 were performed by filter sampling and aerosol spectrometry. Other IAQ parameters included black smoke (BS), volatile organic compounds (VOC), nitrogen dioxide (NO2) and formaldehyde. Both interventions were introduced in one classroom during one week, using another classroom as a reference. In a second week the interventions were moved to the other classroom, using the first as a reference (cross-over design). In three remaining weeks the classrooms were compared without interventions. Indoor IAQ parameters were compared to the corresponding outdoor parameters using the indoor/outdoor (I/O) ratio. When the classrooms were occupied (teaching hours) interventions resulted in 27-43% reductions of PM-10, PM-2.5 and BS values. During the weekends the systems reduced these levels by 51-87%. Evaluations using the change in I/O ratios gave comparable results. Levels of VOC, NO2 and formaldehyde were rather low and a contribution of the interventions to the improvement of these gas phase IAQ parameters was inconclusive.

Titanium dioxide nanoparticles enhance macrophage activation by LPS through a TLR4-dependent intracellular pathway

TiO₂nanoparticles enhance LPS-dependent NO production and cytokine secretion through a mechanism that involves TLR4-mediated p38-signalling and requires phagocytosis.

Personal inhalation exposure to polycyclic aromatic hydrocarbons in urban and rural residents in a typical northern city in China

Personal inhalation exposure samples were collected and analyzed for polycyclic aromatic hydrocarbons (PAHs) for 126 selected volunteers during heating and non-heating seasons in a typical northern Chinese city, Taiyuan. Measured personal PAH exposure levels for the urban residents in the heating and non-heating seasons were 690 (540-1051) and 404 (266-544) ng/m(3) , respectively, while, for the rural residents, they were 770 (504-1071) and 312 (201-412) ng/m(3) , respectively. Thus, rural residents are exposed to lower PAH contamination in comparison with the urban residents in the non-heating seasons. In the heating season, personal PAH inhalation exposure levels were comparable between the urban and rural residents, in part owing to the large rate of residential solid fuel consumption in the rural area for household cooking and heating. The estimated incremental lifetime cancer risks (ILCR) due to PAH exposure in Taiyuan were 3.36 × 10(-5) and 2.39 × 10(-5) for the rural and urban residents, respectively, significantly higher than the literature-reported national average level, suggesting an urgent need of PAH pollution control to protect human health.

Characteristics of airborne bacteria in Mumbai urban environment

Components of biological origin constitute small but a significant proportion of the ambient airborne particulate matter (PM). However, their diversity and role in proinflammatory responses of PM are not well understood. The present study characterizes airborne bacterial species diversity in Mumbai City and elucidates the role of bacterial endotoxin in PM induced proinflammatory response in ex vivo. Airborne bacteria and endotoxin samples were collected during April-May 2010 in Mumbai using six stage microbial impactor and biosampler. The culturable bacterial species concentration was measured and factors influencing the composition were identified by principal component analysis (PCA). The biosampler samples were used to stimulate immune cells in whole blood assay. A total of 28 species belonging to 17 genera were identified. Gram positive and spore forming groups of bacteria dominated the airborne culturable bacterial concentration. The study indicated the dominance of spore forming and human or animal flora derived pathogenic/opportunistic bacteria in the ambient air environment. Pathogenic and opportunistic species of bacteria were also present in the samples. TNF-α induction by PM was reduced (35%) by polymyxin B pretreatment and this result was corroborated with the results of blocking endotoxin receptor cluster differentiation (CD14). The study highlights the importance of airborne biological particles and suggests need of further studies on biological characterization of ambient PM.

Estimating the concentration of indoor particles of outdoor origin: a review

Recent toxicological results highlight the importance of separating exposure to indoor- and outdoor-generated particles, due to their different physicochemical and toxicological properties. In this framework, a number of studies have attempted to estimate the relative contribution of particles of indoor and outdoor origins to indoor concentrations, using either statistical analysis of indoor and outdoor concentration time-series or mass balance equations. The aim of this work is to review and compare the methodologies developed in order to determine the ambient particle infiltration factor (F(INF)) (i.e., the fraction of ambient particles that enter indoors and remains suspended). The different approaches are grouped into four categories according to their methodological principles: (1) steady-state assumption using the steady-state form of the mass balance equation; (2) dynamic solution of the mass balance equation using complex statistical techniques; (3) experimental studies using conditions that simplify model calculations (e.g., decreasing the number of unknowns); and (4) infiltration surrogates using a particulate matter (PM) constituent with no indoor sources to act as surrogate of indoor PM of outdoor origin. Examination of the various methodologies and results reveals that estimating infiltration parameters is still challenging. The main difficulty lies in the separate calculation of penetration efficiency (P) and deposition rate (k). The values for these two parameters that are reported in the literature vary significantly. Deposition rate presents the widest range of values, both between studies and size fractions. Penetration efficiency seems to be more accurately calculated through the application of dynamic models. Overall, estimates of the infiltration factor generated using dynamic models and infiltration surrogates show good agreement. This is a strong argument in favor of the latter methodology, which is simple and easy to apply when chemical speciation data are available.

Indoor dust and air concentrations of endotoxin in urban and rural environments

SIGNIFICANCE AND IMPACT OF THE STUDY

Rural dairy farming is associated with high exposure to indoor endotoxins as compared to rural nonfarming houses and urban houses. The time spent on the mattress (7 h for an adult) and of the proximity of the contaminated source should be taken into account with the other causes of exposure. Studies in European children from a farming background have shown that these children have a reduced risk of asthma and atopic sensitization compared to their urban counterparts. It has been suggested that this might be due to exposure to high levels of endotoxin in the farming environment. The aim of this study was to compare indoor endotoxin concentrations in air and dust samples from randomly selected urban and rural dwellings. In the rural area, endotoxins were analysed in farmhouses and nonfarmhouses as well as housing characteristics, lifestyle factors and agricultural practices likely to influence air and dust endotoxin levels. Endotoxin levels were significantly higher in floor (6600 ± 6100 vs 3600 ± 5600 and 3800 ± 17,000 ng g⁻¹; P < 0·001) and mattress dust (2900 ± 4100 vs 1100 ± 2400 and 800 ± 2600 ng g⁻¹; P < 0·001) from farmhouses compared to other rural and urban homes. However, no difference was observed between endotoxin concentrations in the air of urban and rural houses, and airborne endotoxin levels did not correlate to dust levels. Lack of ventilation and direct entry into the house were correlated with an increase in dust endotoxin levels. These results confirm that dairy farming is associated with high exposure to endotoxins in indoor dust samples. No difference was observed between indoor airborne concentrations between urban and rural houses. These results suggest that measuring endotoxin in dust is the most relevant method to assess endotoxin exposure.

Inflammatory and degranulation effect of yellow sand on RBL-2H3 cells in relation to chemical and biological constituents

Recent studie pointed out that allergic diseases have increased during the Asian dust storm event (ADSE) in Japan. Daily observations and the atmospheric concentrations of yellow sand (YS) aerosol have been increasing. In this study, YS samples collected from three sites of Japan during ADSE in 2009-2010 were used. The particles were analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray fluorescence-energy dispersive spectrometer (XRF-EDS). We investigate ability of YS extract on enhancing the chemical mediator release and cytokine production from rat basophilic leukemia (RBL-2H3) cells. The dust particles at Fukuoka and Tsukuba were abundant in aluminum (Al), iron (Fe), potassium (K) and titan (Ti) than those at Naha. Concentration of the trace endotoxin and Cryptomeria japonica pollen allergen (Cry j 1) were measured in YS extract. After exposure of RBL-2H3 cells to YS extract, the β-hexosaminidase (β-hex) release, tumor necrosis factor-alpha (TNF-α) production were enhanced in RBL-2H3 cells. This process depends on endotoxin, Cry j 1 and other allergen present in the YS extract. YS water extract also show a strong cytotoxic effect on the cells. This data suggest that low levels of endotoxin and Cry j 1 in YS may cause allergy during the ADSE.

A significant role for nitrate and peroxide groups on indoor secondary organic aerosol

This paper reports indoor secondary organic aerosol, SOA, composition based on the results from an improved model for indoor air chemistry. The model uses a detailed chemical mechanism that is near-explicit to describe the gas-phase degradation of relevant indoor VOC species. In addition, gas-to-particle partitioning is included for oxygenated products formed from the degradation of limonene, the most ubiquitous terpenoid species in the indoor environment. The detail inherent in the chemical mechanism permits the indoor SOA composition to be reported in greater detail than currently possible using experimental techniques. For typical indoor conditions in the suburban UK, SOA concentrations are ~1 μg m(-3) and dominated by nitrated material (~85%), with smaller contributions from peroxide (12%), carbonyl (3%), and acidic (1%) material. During cleaning activities, SOA concentrations can reach 20 μg m(-3) with the composition dominated by peroxide material (73%), with a smaller contribution from nitrated material (21%). The relative importance of these different moieties depends crucially (in order) on the outdoor concentration of O(3), the deposition rates employed and the scaling factor value applied to the partitioning coefficient. There are currently few studies that report observation of aerosol composition indoors, and most of these have been carried out under conditions that are not directly relevant. This study highlights the need to investigate SOA composition in real indoor environments. Further, there is a need to measure deposition rates for key indoor air species on relevant indoor surfaces and to reduce the uncertainties that still exist in gas-to-particle phase parametrization for both indoor and outdoor air chemistry models.

Toxicity and elemental composition of particulate matter from outdoor and indoor air of elementary schools in Munich, Germany

Outdoor particulate matter (PM(10)) is associated with detrimental health effects. However, individual PM(10) exposure occurs mostly indoors. We therefore compared the toxic effects of classroom, outdoor, and residential PM(10). Indoor and outdoor PM(10) was collected from six schools in Munich during teaching hours and in six homes. Particles were analyzed by scanning electron microscopy and X-ray spectroscopy (EDX). Toxicity was evaluated in human primary keratinocytes, lung epithelial cells and after metabolic activation by several human cytochromes P450. We found that PM(10) concentrations during teaching hours were 5.6-times higher than outdoors (117 ± 48 μg/m(3) vs. 21 ± 15 μg/m(3), P < 0.001). Compared to outdoors, indoor PM contained more silicate (36% of particle number), organic (29%, probably originating from human skin), and Ca-carbonate particles (12%, probably originating from paper). Outdoor PM contained more Ca-sulfate particles (38%). Indoor PM at 6 μg/cm(2) (10 μg/ml) caused toxicity in keratinocytes and in cells expressing CYP2B6 and CYP3A4. Toxicity by CYP2B6 was abolished with the reactive oxygen species scavenger N-acetylcysteine. We concluded that outdoor PM(10) and indoor PM(10) from homes were devoid of toxicity. Indoor PM(10) was elevated, chemically different and toxicologically more active than outdoor PM(10). Whether the effects translate into a significant health risk needs to be determined. Until then, we suggest better ventilation as a sensible option.

PRACTICAL IMPLICATIONS

Indoor air PM(10) on an equal weight base is toxicologically more active than outdoor PM(10). In addition, indoor PM(10) concentrations are about six times higher than outdoor air. Thus, ventilation of classrooms with outdoor air will improve air quality and is likely to provide a health benefit. It is also easier than cleaning PM(10) from indoor air, which has proven to be tedious.

Markers of inflammation in alveolar cells exposed to fine particulate matter from prescribed fires and urban air

OBJECTIVE

To assess the effect of fine particulate matter (PM(2.5)) from different particle sources on tumor necrosis factor- (TNF-) α, we measured TNF production from rat alveolar macrophages (AM) and human dendritic cells (DC) exposed to PM(2.5) from different sources.

METHODS

Fire-related PM(2.5) samples, rural ambient, and urban indoor and outdoor samples were collected in the Southeast United States. Tumor necrosis factor release was measured from rat AM and human DC following incubation with PM(2.5).

RESULTS

Tumor necrosis factor release in AMs was greatest for fire-related PM(2.5) compared with other samples (TNF: P value = 0.005; mortality: P value = 0.005). Tumor necrosis factor releases from the DCs and AMs exposed to fire-associated PM(2.5) were strongly correlated (r = 0.87, P value < 0.0001).

CONCLUSIONS

Particulate matter exposure produces TNF release consistent with pulmonary inflammation in rat AMs and human DCs, with the response in rat AMs differing by particle source.

PM10-biogenic fraction drives the seasonal variation of proinflammatory response in A549 cells

PM10 was collected in a Milan urban site, representative of the city air quality, during winter and summer 2006. Mean daily PM10 concentration was 48 μg m(-3) during summer and 148 μg m(-3) during winter. Particles collected on Teflon filters were chemically characterized and the endotoxin content determined by the LAL test. PM10-induced cell toxicity, assessed with MTT and LDH methods, and proinflammatory potential, monitored by IL-6 and IL-8 cytokines release, were investigated on the human alveolar epithelial cell line A549 exposed to increasing doses of PM. Besides untreated cells, exposure to inert carbon particles (2-12 μm) was also used as additional control. Both cell toxicity and proinflammatory potency resulted to be higher for summer PM10 with respect of winter PM10, with IL-6 showing the highest dose-dependent release. The relevance of biogenic components adsorbed onto PM10 in eliciting the proinflammatory mediators release was investigated by inhibition experiments. Polymixin B (Poly) was used to inhibit particle-bind LPS while Toll-like receptor-2 antibody (a-TLR2) to specifically block the activation of this receptor. While cell viability was not modulated in cells coexposed to PM10 and Poly or a-TLR2 or both, inflammatory response did it, with IL-6 release being the most inhibited. In conclusion, Milan PM10-induced seasonal-dependent biological effects, with summer particles showing higher cytotoxic and proinflammatory potential. Cytotoxicity seemed to be unaffected by the PM biogenic components, while inflammation was significantly reduced after the inhibition of some biogenic activated pathways. Besides, the PM-associated biogenic activity does not entirely justify the PM-induced inflammatory effects. © 2010 Wiley Periodicals, Inc. Environ Toxicol 2012.

Asian dust and titanium dioxide particles-induced inflammation and oxidative DNA damage in C57BL/6 mice

Inhaled particulate matter (PM) might influence many adverse health effects in human body, including increased exacerbations of pulmonary and cardiovascular diseases. In this study, we examined the associations between PM and pulmonary adverse effects. Two types of particles, Asian dust (AD) and titanium dioxide (TiO(2)), were administered intratracheally to C57BL/6 mice. The mice were exposed to saline and saline suspensions of 20 mg/kg of AD, TiO(2) particles twice a week for 12 weeks. Following exposure with these particles, the lungs were analyzed histopathologically by hematoxylin and eosin (H&E) and Masson's trichrome (MT) staining. Oxidative injuries were determined by immunohistochemistry (IHC) for 8-oxoguanine in the lungs and Comet assays in peripheral blood mononuclear cells (PBMCs) of C57BL/6 mice. Mice exposed to AD and TiO(2) showed significant inflammatory changes and oxidative damages in the lungs as compared with the control group. DNA damage in PBMCs was also increased significantly in AD and TiO(2)-exposed mice. However, lung fibrosis was minimal and there was no significant difference between PM exposed and control mice. Exposure to AD and TiO(2) particles-induced similar inflammatory damages in the lungs and elicited oxidative DNA damage in the PBMCs.

Characterization and proinflammatory response of airborne biological particles from wastewater treatment plants

Wastewater contains a variety of microorganisms, and unit operations in the plants could release these biological components into the air environment. These airborne biological particles could have adverse health effects on plant workers and the downwind population. This study provides a first report on the concentration and characterization of the airborne biological particles in six wastewater treatment plants in Mumbai, India. The study indicates that 49% and 27% of the samples exceed, respectively, the exposure limit for airborne endotoxin and bacteria in occupational settings. Endotoxin was identified as the single most important component of the particulate matter responsible for induction of proinflammatory indicator (tumor necrosis factor-α) in in vitro assay. Identification of several clinically important bacterial species in the samples suggests that the workers at the treatment plant are exposed to opportunistic and infectious bacteria. Principal component analysis was used to identify the groups among the bacterial species which serves as the signature for transport study. Analysis also shows that the component related to spore-forming bacteria is present in all samples.

The use of cytokine array to examine cytokine profiles of two human cell lines exposed to indoor dust

Human cytokine array was used to investigate the cytokine profile of U937 and KERTr after exposure to indoor dust or dust extracts. The release of MCP-1 was increased while release of IL-8 and IL-1β on U937 were decreased after exposure to indoor dust. The releases of RANTES, IL-8 and VEGF from KERTr after exposure to dust extract were increased. The results of IL-8 ELISA assay were consistent with the cytokine array. Real-time RT-PCR was performed to analyze relative changes in gene expression. The MCP-1 mRNA levels were increased after U937 exposure to 18 indoor dust samples, whereas, IL-8 and IL-1β mRNA level showed both up-regulation and down-regulation. The dose-related increase and decrease response was observed on MCP-1 and IL-8, respectively. Most indoor dust extracts increased RANTES, IL-8 and VEGF mRNA levels on KERTr. The dose-dependent response was observed on RANTES and IL-8. A significant correlation (r=0.48, p<0.05) was obtained between the total PAHs concentration in dust extracts and the induction of RANTES mRNA.

Estimating error in using residential outdoor PM2.5 concentrations as proxies for personal exposures: a meta-analysis

BACKGROUND

Studies examining the health effects of particulate matter <or= 2.5 microm in aerodynamic diameter (PM2.5) commonly use ambient PM2.5 concentrations measured at distal monitoring sites as proxies for personal exposure and assume spatial homogeneity of ambient PM2.5. An alternative proxy-the residential outdoor PM2.5 concentration measured adjacent to participant homes-has few advantages under this assumption.

OBJECTIVES

We systematically reviewed the correlation between residential outdoor PM2.5 and personal PM2.5 (-rj) as a means of comparing the magnitude and sources of measurement error associated with their use as exposure surrogates.

METHODS

We searched seven electronic reference databases for studies of the within-participant residential outdoor-personal PM2.5 correlation.

RESULTS

The search identified 567 candidate studies, nine of which were abstracted in duplicate, that were published between 1996 and 2008. They represented 329 nonsmoking participants 6-93 years of age in eight U.S. cities, among whom -rj was estimated (median, 0.53; range, 0.25-0.79) based on a median of seven residential outdoor-personal PM2.5 pairs per participant. We found modest evidence of publication bias (symmetric funnel plot; pBegg = 0.4; pEgger = 0.2); however, we identified evidence of heterogeneity (Cochran's Q-test p = 0.05). Of the 20 characteristics examined, earlier study midpoints, eastern longitudes, older mean age, higher outdoor temperatures, and lower personal-residential outdoor PM2.5 differences were associated with increased within-participant residential outdoor-personal PM2.5 correlations.

CONCLUSIONS

These findings were similar to those from a contemporaneous meta-analysis that examined ambient-personal PM2.5 correlations (rj = median, 0.54; range, 0.09-0.83). Collectively, the meta-analyses suggest that residential outdoor-personal and ambient-personal PM2.5 correlations merit greater consideration when evaluating the potential for bias in studies of PM2.5-mediated health effects.

Modeling human health risks of airborne endotoxin in homes during the winter and summer seasons

Endotoxin, a component of gram-negative bacterial cell walls, is a pro-inflammatory agent that induces local and systemic inflammatory responses in normal subjects which can contribute to the risk of developing asthma and chronic obstructive lung diseases. A probabilistic approach linking models of exposure, internal dosimetry, and health effects was carried out to quantitatively assess the potential inhalation risk of airborne endotoxin in homes during the winter and summer seasons. Combining empirical data and modeling results, we show that the half-maximum effect of the endotoxin dose (ED50) was estimated to be 707.9 (95% confidence interval (CI): 308.8-1287.0) endotoxin units (EU) for body temperature change, 481.8 (95% CI: 333.2-630.3) EU for elevation of neutrophils, and 1174.5 (95% CI: 816.0-1532.9) EU for elevation of the cytokine, interleukin-6. Our study also suggests that airborne endotoxin in homes may pose potential risks, and a higher risk for elevation of neutrophils and cytokine interleukin-6 appeared in winter season than in summer. Our study offers a risk-management framework for discussion of future studies of human respiratory exposure to airborne endotoxin.

Particle dose estimation from frying in residential settings

Fumes produced during frying have been implicated as a potential cause for the increased incidence of adenocarcinoma. Particulate matter exposure has also been linked with other pulmonary and coronary disease. This study investigated the contribution of frying in residential settings to ultrafine and fine particulate matter (UFP, PM2.5, respectively) exposure in homes. Production rates of 44 +/- 26 particles (pt)/cm3 s (mean +/- standard deviation) and 0.13 +/- 0.12 microg/m3 s were found for UFP and PM2.5, respectively, from frying a variety of foods at medium heat in a loft-style apartment. Rates of 290 +/- 150 pt/cm3 s and 3.5 +/- 4.9 microg/m3 s were found for UFP and PM2.5, respectively, from frying with vegetable oil alone in five homes; the higher rates were ascribed to differences between the homes rather than the absence of food. The elimination of UFP and PM2.5 was found to be primarily through exhaust fans in these homes, and it was found to follow a first-order process with an elimination rate constant of 6.1 x 10(-4) +/- 2.5 x 10(-4) s(-1). The dose to an individual from frying was estimated based on the measured production and elimination rates and found to be significant when compared with the typical daily dose incurred within a home because of outside sources.

PRACTICAL IMPLICATIONS

The contribution of indoor sources to particulate matter exposure in homes remains poorly understood. Yet common household activities such as frying may produce substantial concentrations of potentially toxic particles. Because of the potential adverse health impacts associated with exposure to air pollution, potentially vulnerable individuals may be advised to remain indoors at certain times so as to reduce their overall exposure. Such interventions can be negated without proper guidance regarding the exposure involved in various indoor activities such as cooking. This paper outlines a methodology to estimate the dose to particulate matter incurred during frying and shows that this can represent a significant source of daily exposure.

Is PM More Toxic Than the Sum of Its Parts? Risk-Assessment Toxicity Factorsvs.PM-Mortality “Effect Functions”

Epidemiology studies of populations living in areas with good air quality report correlations between levels of ambient particulate matter (PM) and mortality rates. These associations occur at low PM concentrations that are below current air quality standards. Can such concentrations cause mortality, given the toxicity of PM chemical constituents? We examined chemical-specific, dose-response data typically used in U.S. EPA human health risk assessments. These assessments rely on established, no-effect thresholds for noncancer health endpoints. We found that chemicals identified as constituents of ambient PM are present at concentrations considerably below the regulatory thresholds used in risk assessment (i.e., below the RfCs and RfDs that identify levels for which no adverse health effects are anticipated). From the perspective of risk assessment, exposure to the concentrations of chemicals in ambient PM (e.g., sulfate, nitrate, and elemental carbon) cannot be expected to cause death. Hence, the health effects attributed to ambient PM in "regulatory impact analyses" appear to be at odds with what would be predicted from a standard U.S. EPA health-risk assessment for PM chemicals. Four possible resolutions of this paradox are that (1) the mixtures of chemicals present in ambient PM are vastly more toxic than the sum of individual components, (2) small portions of the general population are vastly more sensitive to certain ambient PM chemicals than reflected in U.S. EPA toxicity factors, (3) the toxicity of ambient PM is unrelated to its chemical constituents, or (4) PM mass concentration is not the causal factor in the reported associations. The associations may arise because ambient PM concentrations (1) are a surrogate for unmeasured copollutants (e.g., HAPs), (2) covary with confounding factors that cannot be fully controlled (e.g., weather, demographics), or (3) covary with unmeasured (e.g., societal, behavioral, or stress) factors.