Association between particulate compositional changes during filter extraction and the interpretation of filter-based PM2.5 toxicology

Ambient fine particulate matter (PM2.5) is a global public health concern as it has well-established adverse respiratory and cardiovascular outcomes. Additionally, health effects have been shown to vary based on PM2.5 composition highlighting the importance of the contribution of metallic and organic species. To better understand the biological plausibility of epidemiology associations to PM2.5, ambient filter-based toxicology studies are routinely performed. These studies require extraction of ambient PM2.5 from a filter and the methods for this extraction vary between research groups and differences in extraction methods utilized have been shown to result in differential toxicology outcomes. This study compared characterization data for both ambient filter-based and corresponding extraction solutions prepared for toxicology research to identify compositional changes that occur due to the extraction methods. PM2.5 was characterized for concentration, metals, and organic compounds present in both ambient and extracted samples. While total PM2.5 mass recovery was high following extraction, there were significant and near complete losses of health relevant compounds. Following these findings, a study to assess the impact these compositional changes have on the interpretation of associations to inflammatory responses was designed. The release of a pro-inflammatory cytokine, interleukin (IL)-6, was measured in an alveolar macrophage cell line and associations were made between IL-6 release and PM2.5 constituents in both ambient and extracted samples. When using ambient composition data, significant positive associations were made between IL-6 and a number of organic constituents, however these constituents were not detected in the extraction solution. Additionally, use of ambient composition values displayed significant negative associations to several health relevant metals, these associations were found to be positive when using the extracted values. This research established compositional changes from ambient PM2.5 due to extraction procedures and these changes led to a misinterpretation of associations between constituents and the release of a pro-inflammatory mediator The public health significance of PM2.5 exposure is evident as it is a ubiquitous exposure with established adverse health outcomes. Further developing toxicology studies that accurately assess ambient exposures of PM2.5 are essential to ultimately create constituent specific regulations to protect human health

Seasonal variation in the chemical composition and oxidative potential of pm\u3csub\u3e2.5\u3c/sub\u3e

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Exposure to fine particulate matter (PM2.5) has well-established systemic human health effects due in part to the chemical components associated with these exposures. Oxidative stress is a hypothesized mechanism for the health effects associated with PM2.5 exposures. The oxidative potential of PM2.5 has recently been suggested as a metric that is more indicative of human health effects than the routinely measured PM2.5 concentration. The purpose of this study was to analyze and compare the oxidative potential and elemental composition of PM2.5 collected at two locations during different seasons. PM2.5 was collected onto PTFE-coated filters (n = 16) along two highways in central Oregon, USA in the Winter (January) and Summer (July/August). PM2.5 was extracted from each filter via sonication in methanol. An aliquot of the extraction solution was used to measure oxidative potential using the dithiothreitol (DTT) assay. An additional aliquot underwent analysis via inductively coupled plasma—mass spectrometry (ICP-MS) to quantify elements (n = 20). Differences in PM2.5 elemental composition were observed between locations and seasons as well as between days in the same season. Overall, concentrations were highest in the winter samples but the contribution to total PM2.5 mass was higher for elements in the summer. Notably, the oxidative potential (nM DTT consumed/µg PM2.5 /min) differed between seasons with summer samples having nearly a two-fold increase when compared to the winter. Significant negative correlations that were observed between DTT consumption and several elements as well as with PM2.5 mass but these findings were dependent on if the data was normalized by PM2.5 mass. This research adds to the growing evidence and justification for investigating the oxidative potential and composition of PM2.5 while also highlighting the seasonal variability of these factors

Neurodevelopmental toxicity assessments of alkyl phenanthrene and Dechlorane Plus co-exposure in zebrafish.

Alkyl phenanthrene (A-Phen) and Dechlorane Plus (DP) are ubiquitous environmental pollutants that widely co-exist in the environment. It has been established that both A-Phen and DP elicit neurotoxicity, but the potential interactive toxicity of these contaminants is not well-known. To determine whether a mixture of A-Phen and DP would exhibit interactive effects on neurodevelopment, we co-exposed 3-methylphenanthrene (3-MP), a representative of A-Phen, with DP. Our results illustrated that exposure to 5 or 20 μg/L 3-MP alone or in combination with 60 μg/L DP caused neurobehavioral anomalies in zebrafish. In accordance with the behavioral deficits, 3-MP alone or co-exposed with DP significantly decreased axonal growth of secondary motoneurons, altered intracellular Ca2+ homeostasis and induced cell apoptosis in the muscle of zebrafish. Additionally, 3-MP alone or co-exposed with DP significantly increased reactive oxygen species (ROS) and the mRNA levels of apoptosis-related genes. These findings indicate that 3-MP alone or co-exposed with DP induces neurobehavioral deficits through the combined effects on neuronal connectivity and muscle function. Chemical analysis revealed significant increases in 3-MP and DP bioaccumulation in zebrafish co-exposed with 3-MP and DP. Elevated bioaccumulation resulting from mixture exposure may represent a significant contribution of the synergistic effects observed in combined chemical exposure

Measuring Markers of Oxidative Stress from Fine Particulate Matter

Allie Sidwell is a rising junior in Biology, and mentored by Courtney Roper, Ph.D., Assistant Professor of Environmental Toxicology and Assistant Research Professor in the Research Institute of Pharmaceutical Sciences

Airborne and Dermal Collection Methods of Gunshot Residue for Toxicity Studies

Gunshot residue (GSR) has potential negative health effects on humans as a result of inhalation and dermal exposure to the chemical and physical characteristics of GSR such as Pb, Sb, Ba, nitrocellulose, nitroglycerine, and particulate size fraction. Filter (size selective) and double-sided tape (non-size selective) samples collected airborne GSR during single and triple firing of a 0.22 caliber revolver. Dermal exposures were considered using hand swabs and de-leading wipes, designed to remove the heavy metals. The samples underwent analysis to investigate physical (morphology, size distribution, zeta potential), chemical (black carbon and element concentrations), and potential to induce oxidative stress (oxidative potential via the dithiothreitol (DTT) assay). All sample types detected Pb concentrations higher than national ambient air standards. The de-leading wipes reduced the metal content on the hands of the shooter for Pb (15.57 ± 12.99 ppb and 3.13 ± 4.95 ppb). Filter samples provided health relevant data for airborne PM2.5 for all of the analysis methods except for GSR morphology. This work identified collection and analysis methods for GSR in an outdoor setting, providing protocols and considerations for future toxicological studies related to inhalation and dermal exposures to particulate GSR. Future studies should investigate the influence of meteorological factors on GSR exposure in an outdoor setting

Seasonal Variation in the Chemical Composition and Oxidative Potential of PM2.5

Exposure to fine particulate matter (PM2.5) has well-established systemic human health effects due in part to the chemical components associated with these exposures. Oxidative stress is a hypothesized mechanism for the health effects associated with PM2.5 exposures. The oxidative potential of PM2.5 has recently been suggested as a metric that is more indicative of human health effects than the routinely measured PM2.5 concentration. The purpose of this study was to analyze and compare the oxidative potential and elemental composition of PM2.5 collected at two locations during different seasons. PM2.5 was collected onto PTFE-coated filters (n = 16) along two highways in central Oregon, USA in the Winter (January) and Summer (July/August). PM2.5 was extracted from each filter via sonication in methanol. An aliquot of the extraction solution was used to measure oxidative potential using the dithiothreitol (DTT) assay. An additional aliquot underwent analysis via inductively coupled plasma—mass spectrometry (ICP-MS) to quantify elements (n = 20). Differences in PM2.5 elemental composition were observed between locations and seasons as well as between days in the same season. Overall, concentrations were highest in the winter samples but the contribution to total PM2.5 mass was higher for elements in the summer. Notably, the oxidative potential (nM DTT consumed/µg PM2.5/min) differed between seasons with summer samples having nearly a two-fold increase when compared to the winter. Significant negative correlations that were observed between DTT consumption and several elements as well as with PM2.5 mass but these findings were dependent on if the data was normalized by PM2.5 mass. This research adds to the growing evidence and justification for investigating the oxidative potential and composition of PM2.5 while also highlighting the seasonal variability of these factors

Neurodevelopmental toxicity assessments of alkyl phenanthrene and Dechlorane Plus co-exposure in zebrafish

Alkyl phenanthrene (A-Phen) and Dechlorane Plus (DP) are ubiquitous environmental pollutants that widely coexist in the environment. It has been established that both A-Phen and DP elicit neurotoxicity, but the potential interactive toxicity of these contaminants is not well-known. To determine whether a mixture of A-Phen and DP would exhibit interactive effects on neurodevelopment, we co-exposed 3-methylphenanthrene (3-MP), a representative of A-Phen, with DP. Our results illustrated that exposure to 5 or 20 mu g/L 3-MP alone or in combination with 60 mu g/L DP caused neurobehavioral anomalies in zebrafish. In accordance with the behavioral deficits, 3-MP alone or co-exposed with DP significantly decreased axonal growth of secondary motoneurons, altered intracellular Ca2+ homeostasis and induced cell apoptosis in the muscle of zebrafish. Additionally, 3-MP alone or co-exposed with DP significantly increased reactive oxygen species (ROS) and the mRNA levels of apoptosis-related genes. These findings indicate that 3-MP alone or co-exposed with DP induces neurobehavioral deficits through the combined effects on neuronal connectivity and muscle function. Chemical analysis revealed significant increases in 3-MP and DP bioaccumulation in zebrafish co-exposed with 3-MP and DP. Elevated bioaccumulation resulting from mixture exposure may represent a significant contribution of the synergistic effects observed in combined chemical exposure