Toxicity screening of air extracts representing different source sectors in the Greater Toronto and Hamilton areas: In vitro oxidative stress, pro-inflammatory response, and toxicogenomic analysis

Assessing analyte recovery values and reporting standards for monitoring exposure to airborne semi-volatile organic compounds

Analyte recovery is a critical quality assurance and quality control (QA/QC) metric widely used to quantify bias when using sampling methods and measurement technologies. However, no study has systematically evaluated how well studies adhere to recommended recovery guidelines and reporting standards for measuring airborne semi-volatile organic compounds (SVOCs). This systematic review and meta-analysis evaluated 87 studies deploying passive and active air samplers to measure SVOC concentrations in air. We compared recoveries in the assessed studies to the US EPA and European Union's recommended threshold of 70-120% mean recovery and ≤20% relative standard deviation (RSD). Overall, 39% of recoveries were outside either the recommendation for mean recovery or RSD regardless of compound class and sorbent type. This deviation may be reasonable for qualitative studies but is concerning for quantitative assessment of airborne SVOCs. In assessed calibration studies, differences in recovery between passive and active air samplers did not explain uptake rate variability. We also found wide variation in how recoveries are reported and treated in the literature. Our findings highlight that poor recoveries are prevalent in studies assessing airborne exposure to SVOCs. Reporting and treatment of recoveries is also inconsistent across studies. We recommend future studies to report individual compound recoveries, their treatment, and to recovery correct. We also recommend studies to investigate sample preparation methods to identify steps that are most critical to poor recoveries. Our findings and recommendations presented in this work will help improve quantitative assessment of airborne chemical exposures and standardize recovery reporting across labs.

Multiphase Radical Chemical Processes Induced by Air Pollutants and the Associated Health Effects

Air pollution is increasingly recognized as a significant health risk, yet our understanding of its underlying chemical and physiological mechanisms remains incomplete. Fine particulate matter (PM2.5) and ozone (O3) interact with biomolecules in intracellular and microenvironments, such as the epithelial lining fluid (ELF), leading to the generation of reactive oxygen species (ROS). These ROS trigger cellular inflammatory responses and oxidative stress, contributing to a spectrum of diseases affecting the respiratory, cardiovascular, and central nervous systems. Extensive epidemiological and toxicological research highlights the pivotal role of ROS in air pollution-related diseases. It is crucial to comprehend the intricate chemical processes and accompanying physiological effects of ROS from air pollutants. This review aims to systematically summarize ROS generation mechanisms in the ELF and measurement techniques of oxidative potential (OP), taking the kinetic reactions of ROS cycling in the ELF as an example, and discusses the general health implications of ROS in respiratory, cardiovascular, and central nervous systems. Understanding these processes through interdisciplinary research is essential to develop effective and precise strategies as well as air quality standards to mitigate the public health impacts of air pollution globally.

Seasonal Changes in the Oxidative Potential of Urban Air Pollutants: The Influence of Emission Sources and Proton- and Ligand-Mediated Dissolution of Transition Metals

The inhalation of fine particulate matter (PM2.5) is a major contributor to adverse health effects from air pollution worldwide. An important toxicity pathway is thought to follow oxidative stress from the formation of exogenous reactive oxygen species (ROS) in the body, a proxy of which is oxidative potential (OP). As redox-active transition metals and organic species are important drivers of OP in urban environments, we investigate how seasonal changes in emission sources, aerosol chemical composition, acidity, and metal dissolution influence OP dynamics. Using a kinetic model of the lung redox chemistry, we predicted ROS (O2 •-, H2O2, •OH) formation with input parameters comprising the ambient concentrations of PM2.5, water-soluble Fe and Cu, secondary organic matter, nitrogen dioxide, and ozone across two years and two urban sites in Canada. Particulate species were the largest contributors to ROS production. Soluble Fe and Cu had their highest and lowest values in summer and winter, and changes in Fe solubility were closely linked to seasonal variations in chemical aging, the acidity of aerosol, and organic ligand levels. The results indicate three conditions that influence OP across various seasons: (a) low aerosol pH and high organic ligand levels leading to the highest OP in summer, (b) opposite trends leading to the lowest OP in winter, and (c) intermediate conditions corresponding to moderate OP in spring and fall. This study highlights how atmospheric chemical aging modifies the oxidative burden of urban air pollutants, resulting in a seasonal cycle with a potential effect on population health.

Informing the public about chemical mixtures in the local environment: Currently applied indicators in the Netherlands and ways forward

The current use of chemicals puts pressure on human and ecological health. Based on the Aarhus Convention, citizens have the right to have access to information on substances in their local environment. Providing this information is a major challenge, especially considering complex mixtures, as the current substance-by-substance risk assessment may not adequately address the risk of co-exposure to multiple substances. Here, we provide an overview of the currently available indicators in the Netherlands to explore current scientific possibilities to indicate the impacts of complex chemical mixtures in the environment on human health and ecology at the local scale. This is limited to impact estimates on freshwater species for 701 substances, impact estimates of four metals on soil organisms, and impacts on human health for particulate matter (PM10) and nitrogen dioxide (NO2) in air. The main limiting factors in developing and expanding these indicators to cover more compartments and substances are the availability of emission and concentration data of substances and dose-response relationships at the population (human health) or community (ecology) level. As ways forward, we propose; 1) developing cumulative assessment groups (CAGs) for substances on the European Pollutant Transfer and Release Register and Water Framework Directive substance lists, to enable the development of mixture indicators based on mixture risk assessment and concentration addition principles; 2) to gain insight into local mixtures by also applying these CAGs to emission data, which is available for soil and air for more substances than concentrations data; 3) the application of analytical non-target screening methods as well as effect-based methods for whole-mixture assessment.

A method for measuring the bioaccessibility of polycyclic aromatic hydrocarbons in cell culture media

Airborne polycyclic aromatic hydrocarbons (PAHs) and their derivatives are of particular concern for population health due to their abundance and toxicity via inhalation. Lung toxicity testing includes exposing lung epithelial cell lines to PAHs in a culture medium containing inorganic species, lipids, proteins, and other biochemicals where the cell response is influenced among others by the toxic chemical accessibility in the medium. While inhalation bioaccessibility of PAHs and other toxicants was previously studied in surrogate lung fluids, studies measuring bioaccessibility in cell culture media are rare. In this work, a method was developed to characterize PAH bioaccessibility in a culture medium used for mouse lung epithelial (FE1) cells. Further, the optimised method was tested using commercially available standard reference material of urban particulate matter (PM) as well as polyurethane foam passive air samplers (PUF-PAS). The method provided a high precision and recovery of analytes, indicating no losses during sample processing and analysis. PAHs had non-linear concentration-responses, with the culture medium approaching saturation with PM concentration of 500 μg mL-1. The results showed that phenanthrene, a 3-ring PAH, was significantly more bioaccessible than ≥4-ring congeners in the culture medium (up to ∼2.5 folds; p < 0.05). Finally, using pre-deployed PUF-PAS from a residential and an industrial site, five PAHs were found in the culture medium, including naphthalene, phenanthrene, anthracene, fluoranthene, and pyrene. This work provides a proof of concept to enable future studies to assess the inhalation bioaccessibility of polycyclic aromatic compounds and other airborne pollutants collected using PUF-PAS.

State of the Art of Genomic Technology in Toxicology: A Review

The rapid growth of genomics techniques has revolutionized and impacted, greatly and positively, the knowledge of toxicology, ushering it into a "new era": the era of genomic technology (GT). This great advance permits us to analyze the whole genome, to know the gene response to toxicants and environmental stressors, and to determine the specific profiles of gene expression, among many other approaches. The aim of this work was to compile and narrate the recent research on GT during the last 2 years (2020-2022). A literature search was managed using the PubMed and Medscape interfaces on the Medline database. Relevant articles published in peer-reviewed journals were retrieved and their main results and conclusions are mentioned briefly. It is quite important to form a multidisciplinary taskforce on GT with the aim of designing and implementing a comprehensive, collaborative, and a strategic work plan, prioritizing and assessing the most relevant diseases, so as to decrease human morbimortality due to exposure to environmental chemicals and stressors.

Cytotoxic and Transcriptomic Effects in Avian Hepatocytes Exposed to a Complex Mixture from Air Samples, and Their Relation to the Organic Flame Retardant Signature

Assessing complex environmental mixtures and their effects is challenging. In this study, we evaluate the utility of an avian in vitro screening approach to determine the effects of passive air sampler extracts collected from different global megacities on cytotoxicity and gene expression. Concentrations of a suite of organic flame retardants (OFRs) were quantified in extracts from a total of 19 megacities/major cities in an earlier study, and levels were highly variable across sites. Chicken embryonic hepatocytes were exposed to serial dilutions of extracts from the 19 cities for 24 h. Cell viability results indicate a high level of variability in cytotoxicity, with extracts from Toronto, Canada, having the lowest LC50 value. Partial least squares (PLS) regression analysis was used to estimate LC50 values from OFR concentrations. PLS modeling of OFRs was moderately predictive of LC50 (p-value = 0.0003, r² = 0.66, slope = 0.76, when comparing predicted LC50 to actual values), although only after one outlier city was removed from the analysis. A chicken ToxChip PCR array, comprising 43 target genes, was used to determine effects on gene expression, and similar to results for cell viability, gene expression profiles were highly variable among the megacities. PLS modeling was used to determine if gene expression was related to the OFR profiles of the extracts. Weak relationships to the ToxChip expression profiles could be detected for only three of the 35 OFRs (indicated by regression slopes between 0.6 and 0.5 when comparing predicted to actual OFR concentrations). While this in vitro approach shows promise in terms of evaluating effects of complex mixtures, we also identified several limitations that, if addressed in future studies, might improve its performance.