Physicochemical and toxicological properties of wood smoke particulate matter as a function of wood species and combustion condition.

Wood burning is a major source of ambient particulate matter (PM) and has been epidemiologically linked to adverse pulmonary health effects, however the impact of fuel and burning conditions on PM properties has not been investigated systematically. Here, we employed our recently developed integrated methodology to characterize the physicochemical and biological properties of emitted PM as a function of three common hardwoods (oak, cherry, mesquite) and three representative combustion conditions (flaming, smoldering, incomplete). Differences in PM and off-gas emissions (aerosol number/mass concentrations; carbon monoxide; volatile organic compounds) as well as inorganic elemental composition and organic carbon functional content of PM0.1 were noted between wood types and combustion conditions, although the combustion scenario exerted a stronger influence on the emission profile. More importantly, flaming combustion PM0.1 from all hardwoods significantly stimulated the promoter activity of Sterile Alpha Motif (SAM) pointed domain containing ETS (E-twenty-six) Transcription Factor (SPDEF) in human embryonic kidney 293 (HEK-293 T) cells, a biomarker for mucin gene expression associated with mucus production in pulmonary diseases. However, no bioactivity was observed for smoldering and incomplete combustion, which was likely driven by differences in the organic composition of PM0.1. Detailed chemical speciation of organic components of wood smoke is warranted to identify the individual compounds that drive specific biological responses.

Evidence for the coupling of refill liquids content and new particle formation in electronic cigarette vapors.

The size and chemical content of particles in electronic cigarette vapors (e-vapors) dictate their fate in the human body. Understanding how particles in e-vapors are formed and their size is critical to identifying and mitigating the adverse consequences of vaping. Thermal decomposition and reactions of the refill liquid (e-liquid) components play a key role in new particles formation. Here we report the evolution of particle number concentration in e-vapors over time for variable mixtures of refill e-liquids and operating conditions. Particle with aerodynamic diameter < 300 nm accounted for up to 17% (or 780 µg/m3) of e-vapors particles. Two events of increasing particle number concentration were observed, 2-3 s after puff completion and a second 4-5 s later. The intensity of each event varied by the abundance of propylene glycol, glycerol, and flavorings in e-liquids. Propylene glycol and glycerol were associated with the first event. Flavorings containing aromatic and aliphatic unsaturated functional groups were strongly associated with the second event and to a lesser extent with the first one. The results indicate that particles in e-vapors may be formed through the heteromolecular condensation of propylene glycol, glycerol, and flavorings, including both parent chemicals and/or their thermal decomposition products.

Development of an Integrated Platform to Assess the Physicochemical and Toxicological Properties of Wood Combustion Particulate Matter.

Wood burning contributes to indoor and ambient particulate matter (PM) pollution and has been associated with increased morbidity and mortality. Here, we present an integrated methodology that allows to generate, sample, and characterize wood smoke derived from different moisture contents and representative combustion conditions using pine wood as a model. Flaming, smoldering, and incomplete combustion were assessed for low-moisture pine, whereas both low-moisture pine and high-moisture pine were investigated under flaming conditions. Real-time monitoring of carbon monoxide, volatile organic compounds, and aerosol number concentration/size in wood smoke was performed. The PM was size-fractionated, sampled, and characterized for elemental/organic carbon, organic functional groups, and inorganic elements. Bioactivity of PM was assessed by measuring the sterile alpha motif (SAM) pointed domain containing ETS (E-twenty-six) transcription factor (SPDEF) gene promoter activity in human embryonic kidney 293 (HEK-293T) cells, a biomarker for mucin gene expression. Findings showed that moisture content and combustion condition significantly affected the organic and inorganic elemental composition of PM0.1 as well as its bioactivity. Also, for a given moisture and combustion scenario, PM chemistry and bioactivity differed considerably with PM size. Importantly, PM0.1 from flaming combustion of low-moisture pine contained the highest abundance of the oxygenated saturated aliphatic functional group [H-C-O] and was also biologically most potent in stimulating SPDEF promoter activity, suggesting the role of organic compounds such as carbohydrates and sugar alcohols (that contain [H-C-O]) in driving mucus-related respiratory outcomes. Our platform enables further well-controlled parametric studies using a combination of in vitro and in vivo approaches to link wood burning parameters with acute and chronic inhalation health effects of wood smoke.

On the Role of Atmospheric Weathering on Paint Dust Aerosol Generated by Mechanical Abrasion of TiO2 Containing Paints.

In recent years, the introduction and use of new nanomaterials in construction has increased at a rapid rate. Exterior surface paints have been a product that have had these nanomaterials added to them. In this study, the effects of natural weathering and exposure to atmospheric agents was examined to determine the detrimental effects on outdoor paint that has been created with nanomaterials. Data collected over the course of the yearlong study indicate that the nanoparticles of the titanium dioxide were eliminated rapidly. Further testing indicated that various elements of weathering were affecting the physical integrity of the paint. The weathering agents that appeared to have the greatest effect on the samples were acid deposition and total precipitation. There was a strong association between carbon monoxide and the effects on the panels. These results can lead to new plans for assessments involving the synergistic effects of all weathering agents.

Characterization of exhaled breath condensate (EBC) non-exchangeable hydrogen functional types and lung function of wildland firefighters.

Inhalation of smoke is shown to be associated with adverse respiratory outcomes in firefighters. Due to invasiveness of procedures to obtain airways lining fluid, the immediate responses of the target organ (i.e. lung) are secondarily assessed through biomarkers in blood and urine. The objective of this study was to identify changes in metabolic profile of exhaled breath condensate (EBC) and lung function of firefighters exposed to wildfires smoke. A total of 29 subjects were studied over 16 events; 14 of these subjects provided cross-shift EBC samples. The predominant types of non-exchangeable hydrogen in EBC were saturated oxygenated hydrogen, aliphatic alkyl and allylic. Non-exchangeable allylic and oxygenated hydrogen concentrations decreased in post-exposure EBC samples. Longer exposures were correlated with increased abundance of oxidized carbon in ketones, acids and esters. Post-exposure lung function declines (forced expiratory volume in 1 s (FEV1): 0.08 l, forced vital capacity (FVC): 0.07 l, FEV1/FVC: 0.03 l, peak expiratory flow (PEF): 0.39 l s-1) indicated airways inflammation. They were related to exposure intensity (FEV1 and FVC) and exposure duration (PEF). This study showed that EBC characterization of non-exchangeable hydrogen types by NMR may provide insights on EBC molecular compositions in response to smoke inhalation and facilitate targeted analysis to identify specific biomarkers.

Characterization of paint dust aerosol generated from mechanical abrasion of TiO2-containing paints.

The purpose of the study was to determine the potential for release of titanium dioxide nanoparticles in paint dust. The coatings aerosol resuspension system was developed and used for testing the generation and physical, chemical, and morphological properties of paint dust particles from mechanical abrasion (i.e., sanding) of coated wood surfaces. The paint dust emissions from bare and coated wood surfaces with multiple coatings using variable sandpaper grits were evaluated. Substantially higher particle number concentrations were measured for paint dust containing particles in the nano range (particles with aerodynamic diameter less than 100 nm) than those measured for wood dust. The variability of particle number concentration and size distribution of paint dust derived under different conditions indicated that considerable quantities of nanoparticles might be released from mechanical abrasion of painted surfaces that may induce unhealthy exposure conditions. Moreover, spectroscopic and microscopic analysis identified the presence of paint and wood components in paint dust, including titanium dioxide agglomerates that were originally embedded in the paint. The agglomerates were mostly attached to particles with sizes <100 nm, enabling them to potentially penetrate into the lower respiratory tract. These results demonstrated that the paint dust exposure generation system can provide qualitative and quantitative information on particle emissions and the abundance of nanoparticles from paint sanding in realistic conditions and they may be used to assess occupational and environmental exposures and risks. Furthermore, the prevalence of titanium dioxide nanoparticles in paint dust highlights the potential for exposures of painters and other occupational groups to hazardous paint dust and the need for protective devices and strategies aiming to reduce exposures to nanoparticles.

Dose-response analysis of epigenetic, metabolic, and apical endpoints after short-term exposure to experimental hepatotoxicants.

Identification of sensitive and novel biomarkers or endpoints associated with toxicity and carcinogenesis is of a high priority. There is increasing interest in the incorporation of epigenetic and metabolic biomarkers to complement apical data; however, a number of questions, including the tissue specificity, dose-response patterns, early detection of those endpoints, and the added value need to be addressed. In this study, we investigated the dose-response relationship between apical, epigenetic, and metabolomics endpoints following short-term exposure to experimental hepatotoxicants, clofibrate (CF) and phenobarbital (PB). Male F344 rats were exposed to PB (0, 5, 25, and 100 mg/kg/day) or CF (0, 10, 50, and 250 mg/kg/day) for seven days. Exposure to PB or CF resulted in dose-dependent increases in relative liver weights, hepatocellular hypertrophy and proliferation, and increases in Cyp2b1 and Cyp4a1 transcripts. These changes were associated with altered histone modifications within the regulatory units of cytochrome genes, LINE-1 DNA hypomethylation, and altered microRNA profiles. Metabolomics data indicated alterations in the metabolism of bile acids. This study provides the first comprehensive analysis of the apical, epigenetic and metabolic alterations, and suggests that the latter two occur within or near the dose response curve of apical endpoint alterations following exposure to experimental hepatotoxicants.

Synergistic effects of engineered nanoparticles and organics released from laser printers using nano-enabled toners: potential health implications from exposures to the emitted organic aerosol.

Recent studies have shown that engineered nanoparticles (ENPs) are incorporated into toner powder used in printing equipment and released during their use. Thus, understanding the functional and structural composition and potential synergistic effects of this complex aerosol and released gaseous co-pollutants is critical in assessing their potential toxicological implications and risks. In this study, toner powder and PEPs were thoroughly examined for functional and molecular composition of the organic fraction and the concentration profile of 16 Environmental Protection Agency (EPA)-priority polycyclic aromatic hydrocarbons (PAH) using state of the art analytical methods. Results show significant differences in abundance of non-exchangeable organic hydrogen of toner powder and PEPs, with a stronger aromatic spectral signature in PEPs. Changes in structural composition of PEPs are indicative of radical additions and free-radical polymerization favored by catalytic reactions, resulting in formation of functionalized organic species. Particularly, accumulation of aromatic carbons with strong styrene-like molecular signatures on PEPs is associated with formation of semivolatile heavier aromatic species (i.e., PAHs). Further, the transformation of low molecular weight PAHs in the toner powder to high molecular weight PAHs in PEPs was documented and quantified. This may be a result of synergistic effects from catalytic metal/metal oxide ENPs incorporated into the toner and the presence/release of semi-volatile organic species (SVOCs). The presence of known carcinogenic PAHs on PEPs raises public health concerns and warrants further toxicological assessment.

Influence of ambient temperature on the heterogeneity of ambient fine particle chemical composition and disease prevalence.

In this study, we present the associations of fine particle nitrate, sulfate, and four organic carbon fractions with ambient temperature in urban and background monitoring sites in the United States for the 2011-2012 period. Nitrate concentrations increased for decreasing temperatures, while sulfate levels increased for temperatures higher than 14 °C. The profiles of organic carbon fractions for different temperatures were comparable to that observed for elemental carbon, a thermally stable and non-reactive component emitted from combustion-related sources. The trends for all parameters were comparable for the nine regions and independent to emission estimates of fine particles and their precursors. These patterns demonstrated that ambient temperature may manipulate fine particulate composition. These differences may be augmented by rising temperatures due to changing climate. Considering the causal associations between particulate pollution and pulmonary and cardiovascular diseases, changes in the composition of particulate pollution may imply adjustments on the human health impacts.

Characterization of water-soluble organic matter in urban aerosol by 1H-NMR spectroscopy.

The functional and 13C isotopic compositions of water-soluble organic carbon (WSOC) in atmospheric aerosol were determined by nuclear magnetic resonance (1H-NMR) and isotope ratio mass spectrometry (IRMS) in an urban location in the Southern Mississippi Valley. The origin of WSOC was resolved using the functional distribution of organic hydrogen, δ13C ratio, and positive matrix factorization (PMF). Three factors were retained based on NMR spectral bins loadings. Two factors (factors 1 and 3) demonstrated strong associations with the aliphatic region in the NMR spectra and levoglucosan resonances. Differences between the two factors included the abundance of the aromatic functional group for factor 1, indicating fresh emissions and, for factor 3, the presence of resonances attributed to secondary ammonium nitrate and low δ13C ratio values that are indicative of secondary organic aerosol. Factors 1 and 3 added 0.89 and 1.08 µgC m-3, respectively, with the highest contribution in the summer and fall. Factor 2 retained resonances consistent with saccharides and was attributed to pollen particles. Its contribution to WSOC varied from 0.22 µgC m-3 in winter to 1.04 µgC m-3 in spring.

Thermal decomposition of nano-enabled thermoplastics: Possible environmental health and safety implications.

Nano-enabled products (NEPs) are currently part of our life prompting for detailed investigation of potential nano-release across their life-cycle. Particularly interesting is their end-of-life thermal decomposition scenario. Here, we examine the thermal decomposition of widely used NEPs, namely thermoplastic nanocomposites, and assess the properties of the byproducts (released aerosol and residual ash) and possible environmental health and safety implications. We focus on establishing a fundamental understanding on the effect of thermal decomposition parameters, such as polymer matrix, nanofiller properties, decomposition temperature, on the properties of byproducts using a recently-developed lab-based experimental integrated platform. Our results indicate that thermoplastic polymer matrix strongly influences size and morphology of released aerosol, while there was minimal but detectable nano-release, especially when inorganic nanofillers were used. The chemical composition of the released aerosol was found not to be strongly influenced by the presence of nanofiller at least for the low, industry-relevant loadings assessed here. Furthermore, the morphology and composition of residual ash was found to be strongly influenced by the presence of nanofiller. The findings presented here on thermal decomposition/incineration of NEPs raise important questions and concerns regarding the potential fate and transport of released engineered nanomaterials in environmental media and potential environmental health and safety implications.

In Vitro Toxicity and Epigenotoxicity of Different Types of Ambient Particulate Matter.

Exposure to ambient particulate matter (PM) has been associated with adverse health effects, including pulmonary and cardiovascular disease. Studies indicate that ambient PM originated from different sources may cause distinct biological effects. In this study, we sought to investigate the potential of various types of PM to cause epigenetic alterations in the in vitro system. RAW264.7 murine macrophages were exposed for 24 and 72 h to 5- and 50-µg/ml doses of the water soluble extract of 6 types of PM: soil dust, road dust, agricultural dust, traffic exhausts, biomass burning, and pollen, collected in January-April of 2014 in the area of Little Rock, Arkansas. Cytotoxicity, oxidative potential, epigenetic endpoints, and chromosomal aberrations were addressed. Exposure to 6 types of PM resulted in induction of cytotoxicity and oxidative stress in a type-, time-, and dose-dependent manner. Epigenetic alterations were characterized by type-, time-, and dose-dependent decreases of DNA methylation/demethylation machinery, increased DNA methyltransferases enzymatic activity and protein levels, and transcriptional activation and subsequent silencing of transposable elements LINE-1, SINE B1/B2. The most pronounced changes were observed after exposure to soil dust that were also characterized by hypomethylation and reactivation of satellite DNA and structural chromosomal aberrations in the exposed cells. The results of our study indicate that the water-soluble fractions of the various types of PM have differential potential to target the cellular epigenome.

Air pollution and cardiovascular and respiratory emergency visits in Central Arkansas: A time-series analysis.

BACKGROUND: Heart disease and stroke mortality and morbidity rates in Arkansas are among the highest in the U.S. While the effect of air pollution on cardiovascular health was identified in traffic-dominated metropolitan areas, there is a lack of studies for populations with variable exposure profiles, demographic and disease characteristics. OBJECTIVE: Determine the short-term effects of air pollution on cardiovascular and respiratory morbidity in the stroke and heart failure belt. METHODS: We investigated the associations of fine particles and ozone with respiratory and cardiovascular emergency room visits during the 2002-2012 period for adults in Central Arkansas using Poisson generalized models adjusted for temporal, seasonal and meteorological effects. We evaluated sensitivity of the associations to mutual pollutant adjustment and effect modification patterns by sex, age, race and season. RESULTS: We found effects on cardiovascular and respiratory emergencies for PM2.5 (1.52% [95% (confidence interval) CI: -1.10%, 4.20%]; 1.45% [95%CI: -2.64%, 5.72%] per 10 µg/m3) and O3 (0.93% [95%CI: -0.87%, 2.76%]; 0.76 [95%CI: -1.92%, 3.52%] per 10 ppbv) during the cold period (October-March). The effects were stronger among whites, except for the respiratory effects of O3 that were higher among Blacks/African-Americans. Effect modification patterns by age and sex differed by association. Both pollutants were associated with increases in emergency room visits for hypertension, heart failure and asthma. Effects on cardiovascular and respiratory emergencies were observed during the cold period when particulate matter was dominated by secondary nitrate and wood burning. CONCLUSION: Outdoor particulate pollution during winter had an effect on cardiovascular morbidity in central Arkansas, the region with high stroke and heart disease incidence rates.

Response of transposable elements to environmental stressors.

Transposable elements (TEs) comprise a group of repetitive sequences that bring positive, negative, as well as neutral effects to the host organism. Earlier considered as "junk DNA," TEs are now well-accepted driving forces of evolution and critical regulators of the expression of genetic information. Their activity is regulated by epigenetic mechanisms, including methylation of DNA and histone modifications. The loss of epigenetic control over TEs, exhibited as loss of DNA methylation and decondensation of the chromatin structure, may result in TEs reactivation, initiation of their insertional mutagenesis (retrotransposition) and has been reported in numerous human diseases, including cancer. Accumulating evidence suggests that these alterations are not the simple consequences of the disease, but often may drive the pathogenesis, as they can be detected early during disease development. Knowledge derived from the in vitro, in vivo, and epidemiological studies, clearly demonstrates that exposure to ubiquitous environmental stressors, many of which are carcinogens or suspected carcinogens, are capable of causing alterations in methylation and expression of TEs and initiate retrotransposition events. Evidence summarized in this review suggests that TEs are the sensitive endpoints for detection of effects caused by such environmental stressors, as ionizing radiation (terrestrial, space, and UV-radiation), air pollution (including particulate matter [PM]-derived and gaseous), persistent organic pollutants, and metals. Furthermore, the significance of these effects is characterized by their early appearance, persistence and presence in both, target organs and peripheral blood. Altogether, these findings suggest that TEs may potentially be introduced into safety and risk assessment and serve as biomarkers of exposure to environmental stressors. Furthermore, TEs also show significant potential to become invaluable surrogate biomarkers in clinic and possible targets for therapeutic modalities for disease treatment and prevention.

An integrated methodology for the assessment of environmental health implications during thermal decomposition of nano-enabled products.

The proliferation of nano-enabled products (NEPs) renders human exposure to engineered nanomaterials (ENMs) inevitable. Over the last decade, the risk assessment paradigm for nanomaterials focused primarily on potential adverse effect of pristine, as-prepared ENMs. However, the physicochemical properties of ENMs may be drastically altered across their life-cycle (LC), especially when they are embedded in various NEP matrices. Of a particular interest is the end-of-life scenario by thermal decomposition. The main objective of the current study is to develop a standardized, versatile and reproducible methodology that allows for the systematic physicochemical and toxicological characterization of the NEP thermal decomposition. The developed methodology was tested for an industry-relevant NEP in order to verify its versatility for such LC investigations. Results are indicative of potential environmental health risks associated with waste from specific NEP families and prompt for the development of safer-by-design approaches and exposure control strategies.

Linking Exposures of Particles Released From Nano-Enabled Products to Toxicology: An Integrated Methodology for Particle Sampling, Extraction, Dispersion, and Dosing.

Nano-enabled products (NEPs) represent a growing economic global market that integrates nanotechnology into our everyday lives. Increased consumer use and disposal of NEPs at their end of life has led to increased environmental, health and safety (EHS) concerns, due to the potential environmental release of constituent engineered nanomaterials (ENMs) used in the production of NEPs. Although, there is an urgent need to assess particulate matter (PM) release scenarios and potential EHS implications, no current standardized methodologies exist across the exposure-toxicological characterization continuum. Here, an integrated methodology is presented, that can be used to sample, extract, disperse and estimate relevant dose of life cycle-released PM (LCPM), for in vitro and in vivo toxicological studies. The proposed methodology was utilized to evaluate two "real world" LCPM systems simulating consumer use and disposal of NEPs. This multi-step integrated methodology consists of: (1) real-time monitoring and sampling of size fractionated LCPM; (2) efficient extraction of LCPM collected on substrates using aqueous or ethanol extraction protocols to ensure minimal physicochemical alterations; (3) optimized LCPM dispersion preparation and characterization; (4) use of dosimetric techniques for in vitro and in vivo toxicological studies. This comprehensive framework provides a standardized protocol to assess the release and toxicological implications of ENMs released across the life cycle of NEPs and will help in addressing important knowledge gaps in the field of nanotoxicology.

Trends of non-accidental, cardiovascular, stroke and lung cancer mortality in Arkansas are associated with ambient PM2.5 reductions.

The cardiovascular and stroke mortality rates in Arkansas are among the highest in the USA. The annual trends of stroke and cardiovascular mortality are barely correlated to smoking cessation; while the prevalence of risk factors such as obesity; cholesterol and hypertension increased over the 1979-2007 period. The study determined the effect of chronic exposure to PM2.5 on non-accidental; cardiovascular; stroke and lung cancer mortality in Arkansas over the 2000-2010 period using the World Health Organization's log-linear health impact model. County chronic exposures to PM2.5 were computed by averaging spatially-resolved gridded concentrations using PM2.5 observations. A spatial uniformity was observed for PM2.5 mass levels indicating that chronic exposures were comparable throughout the state. The reduction of PM2.5 mass levels by 3.0 µg/m3 between 2000 and 2010 explained a significant fraction of the declining mortality. The effect was more pronounced in southern and eastern rural Arkansas as compared to the rest of the state. This study provides evidence that the implementation of air pollution regulations has measurable effects on mortality even in regions with high prevalence of major risk factors such as obesity and smoking. These outcomes are noteworthy as efforts to modify the major risk factors require longer realization times.

Nuclear magnetic resonance spectroscopy for determining the functional content of organic aerosols: a review.

The knowledge deficit of organic aerosol (OA) composition has been identified as the most important factor limiting our understanding of the atmospheric fate and implications of aerosol. The efforts to chemically characterize OA include the increasing utilization of nuclear magnetic resonance spectroscopy (NMR). Since 1998, the functional composition of different types, sizes and fractions of OA has been studied with one-dimensional, two-dimensional and solid state proton and carbon-13 NMR. This led to the use of functional group ratios to reconcile the most important sources of OA, including secondary organic aerosol and initial source apportionment using positive matrix factorization. Future research efforts may be directed towards the optimization of experimental parameters, detailed NMR experiments and analysis by pattern recognition methods to identify the chemical components, determination of the NMR fingerprints of OA sources and solid state NMR to study the content of OA as a whole.

Epigenetic alterations induced by ambient particulate matter in mouse macrophages.

Respiratory mortality and morbidity has been associated with exposure to particulate matter (PM). Experimental evidence suggests involvement of cytotoxicity, oxidative stress, and inflammation in the development of PM-associated pathological states; however, the exact mechanisms remain unclear. In the current study, we analyzed short-term epigenetic response to PM10 (particles with aerodynamic diameter less than 10 µm) exposure in mouse ascitic RAW264.7 macrophages (BALB/C Abelson murine leukemia virus-induced tumor). Ambient PM10 was collected using a high volume sampler in Little Rock, AR. Analysis revealed that PM10 was composed mainly of Al and Fe, and the water soluble organic fraction was dominated by aliphatic and carbohydrate fragments and minor quantities of aromatic components. Exposure to PM10 compromised the cellular epigenome at concentrations 10-200 µg/ml. Specifically, epigenetic alterations were evident as changes in the methylation and expression of repetitive element-associated DNA and associated DNA methylation machinery. These results suggest that epigenetic alterations, in concert with cytotoxicity, oxidative stress, and inflammation, might contribute to the pathogenesis of PM-associated respiratory diseases.