This study presents the first global data set of measured chlorinated paraffins (CPs), including short-chain (SCCPs), medium-chain (MCCPs), and long-chain chlorinated paraffins (LCCPs) in ambient air, derived from a single coordinated sampling network, i.e., the Global Atmospheric Passive Sampling (GAPS) network, using a passive sampling approach. Concentrations exhibited pronounced regional disparities, with the combined levels in two megacities-Lagos, Nigeria (512,000 pg/m(3)) and Beijing, China (258,000 pg/m(3)) exceeding by more than 1.5-fold the combined total levels observed across the rest of the world (similar to 459,000 pg/m(3)). Evidence of long-range atmospheric transport was observed at remote sites in western Canada (Little Fox Lake and Whistler), influenced by trans-Pacific air trajectories during the sampling period. These findings underscore the substantial global heterogeneity in the spatial distribution of CPs and the heavily disproportionate contributions of a few regions. Notably, the major producers/emitters, such as China, had several years of delay in ratifying the SCCP listing under the Stockholm Convention (Annex A, elimination since 2017 for congeners with > 48% chlorine content), and some countries have yet to ratify. Without the timely implementation of regulatory measures in these jurisdictions, global concentrations are expected to remain stagnant or even increase if emissions persist at current levels. These results further suggest that substantial time lags are likely before measurable declines in SCCP concentrations, and potentially in recently listed MCCPs, are observed even in regions where control measures are already in place. Hence, this global data set serves as a baseline for future assessments of temporal and spatial trends.

Antioxidants added to tires to prevent degradation have recently been recognized as emerging environmental contaminants. While their acute aquatic toxicity has raised concern, these compounds are also emitted to the atmosphere and can be associated with particulate matter (PM). On PM they can react heterogeneously with oxidants, producing a range of transformation products (TPs) with unknown impacts to human health via inhalation. Here, we show through laboratory experiments that many previously unrecognized TPs are formed in complex mixtures from both OH radical and ozone heterogeneous reactions of N-(1,3-dimethylbutyl)-N’-phenyl-p-phenylenediamine (6PPD) and N,N’-diphenyl-1,4-phenylenediamine (DPPD). In the presence of nitrogen oxides, 13 TPs incorporated additional nitrogen atoms in the form of potentially toxic nitrosamines and nitramines. Overall, >150 TPs were detected in oxidation experiments, with > 88 also identified in ambient near-road and urban PM samples. When tested in human macrophages, these TP mixtures induced potent inflammatory responses and rapid cell death. The effects consistently exceeded those caused by the parent antioxidants and by the single quinone compound (6PPD-Q), commonly assumed to trigger toxicity, even at total mixture concentrations comparable to those recently measured in human blood serum. These findings suggest that atmospheric processing of tire-wear chemicals produces PM-associated transformation products, which could potentially contribute to an elevated risk of inflammation-driven diseases near roads. The work highlights the importance of evaluating atmospherically derived tire-wear TPs as dynamic, interactive mixtures rather than isolated compounds, particularly as electric vehicles with higher tire wear emissions become more prevalent.

Airborne microbes significantly influence environmental processes and human exposure, yet they remain poorly characterized in Africa. This study presents a regional survey of airborne bacterial and fungal communities across 10 sites in five East African countries: Burundi, the Democratic Republic of the Congo, Kenya, Rwanda, and Tanzania. Polyurethane foam passive air samplers (PUF-PASs) were deployed concurrently, and airborne bacterial and fungal communities were characterized using 16S rRNA gene and ITS amplicon sequencing. Genus-level analyses identified both bacterial taxa (Massilia, Sphingomonas, Pseudomonas, Bacillus, and Kocuria) and fungal genera (Cladosporium, Alternaria, Aspergillus, Curvularia, and Penicillium) that are commonly detected in outdoor air and urban atmospheric environments. Beta-diversity analysis revealed no significant country-level differences in bacterial communities (ANOSIM (R = -0.045, p = 0.597)), while fungal communities exhibited significant differences among countries (ANOSIM (R = 0.652, p = 0.002)). Cross-border comparisons showed that nearby sites within 10 km did not consistently share similar microbial profiles. These findings indicate a broadly shared regional bacterial aerobiome, with more pronounced spatial structuring among fungal communities. This study serves as a proof-of-concept demonstration that PUF-PASs can be used to characterize airborne microbial communities in East Africa, while highlighting the need for future bioaerosol research with enhanced temporal replication and broader spatial coverage to support long-term public health surveillance in the African region.

Hamilton, Ontario, an industrial city in Canada, can experience high air pollutant concentrations, which have been associated with adverse health outcomes. Using field-sampled data from 2009 and 2022-2023, this study examined the spatial and temporal dynamics of benzo[a]pyrene (BaP), a key toxic polycyclic aromatic hydrocarbon (PAH) in Hamilton, and its relation to environmental justice and gentrification. Average BaP concentrations and environmental injustices have both increased despite ongoing de-industrialization and gentrification. A review of regulatory monitoring site data showed a decreasing trend in PAH concentration from 2009 to 2018, followed by an increasing trend from 2018 to 2023. Sampled BaP concentrations showed a winter-higher seasonal trend. At the intraurban scale, land use regression (LUR) models showed that mean BaP concentrations increased from 0.04 ng/m³ (2009) to 0.07 ng/m³ (2022-2023). Linear Mixed-Effects regression analysis indicated worsening environmental injustice, with an increasing association between BaP concentrations and marginalization in the early period (2009-2011) compared to the recent period (2021-2023), driven by socioeconomic status rather than demographic variables. Moreover, gentrified areas experienced significantly greater increases in median BaP than non-gentrified areas between the early and late periods, with a comparably much greater number of gentrified areas seeing a 0.5 μg/m3 or greater increase over this time. In addition, gentrification was found to strengthen the relationship between BaP and marginalization. These findings enhance understanding of BaP-related environmental injustice in Hamilton from the past to the present, highlighting the interplay between pollution, socioeconomic factors, and urban form.

For the past quarter century, polyurethane foam (PUF) disk-based passive air samplers (PASs) have grown as a pivotal tool in research and monitoring of persistent organic pollutants and emerging chemicals in ambient air in both the gas phase and on ambient particulate matter. Their low cost and ease of use have facilitated deployment at the regional and global scales. Modifications to the PUF-PAS have expanded its use for more specific purposes, such as the sorbent-impregnated PUF-PAS (SIP-PAS), which improves sorptive capacity for more volatile chemicals, and the passive dry deposition (PAS-DD) sampler, which captures larger particles and enables estimation of gas and particle deposition. This review summarizes studies characterizing uptake rates and partition coefficients of PUF disks for a wide range of compounds and evaluations of sampler design and performance. It synthesizes applications of PUF-PAS, SIP-PAS, and PAS-DD from 2000 to 2024 across diverse topics: ambient air measurements, indoor air quality, source emissions, health, and, most recently, biodiversity. Approximately 650 publications employing PUF disk-based PASs are summarized herein, demonstrating their increasing use and diversification. On the horizon, we envisage that the PUF-PAS will continue to transform and integrate fields of science and inform policy.

Air pollution is associated with mortality and morbidity worldwide. The health effects are primarily associated with the inhalation of particulate matter (PM), which can lead to oxidative stress through the excessive production of reactive oxygen species (ROS) in the respiratory, cardiovascular, and neurological systems. The influence of PM size and gaseous oxidants on the production of ROS in the lung is understudied, as most studies to date have focused on assessing this aspect broadly in fine or coarse PM. In this work, we used a kinetic model of redox chemistry in the lung epithelial lining fluid (KM-SUB-ELF) to study the production of ROS (including hydroxyl radical; (OH)-O-center dot) from the inhalation of size-resolved PM (spanning eight size bins between 0.18 and 10 mu m), ozone (O-3), and nitrogen dioxide (NO2) at three sites located at different distances from roadways in Toronto. The highest ROS production was found at the site located next to a major highway, with particulate pollutants being the primary contributor. The total ROS production peaked in the PM accumulation mode at all sites (up to 41% associated with submicrometer PM), following closely the size distribution of trace metals, especially Cu. The (OH)-O-center dot production was more site-specific; it peaked in the accumulation mode with highway traffic emissions, and in quasi-ultrafine (<0.18 mu m) mode in areas with moderate traffic, following the trends of soluble Fe and PM (up to 60% associated with submicron PM). ROS production in the lung was also induced by gaseous oxidants. Ozone played the dominant role, particularly at sites with moderate traffic but high O-3 levels where up to 52% of ROS and 14% of (OH)-O-center dot produced in the lung were attributed to inhaled O-3. The results highlight the importance of traffic emissions, submicrometer PM, and gaseous oxidants in deriving the health effects of air pollutants in urban environments.

We present the first comprehensive comparison of polyurethane foam disk passive air samplers (PUF-PASs) and active high-volume air samplers (Hi-Vol) for bioaerosol monitoring in side-by-side deployments. Using qPCR, 16S rRNA gene sequencing, and multivariate analysis, we demonstrated that the PUF-PASs detected higher bacterial biomass, as evidenced by significantly elevated gene copy numbers and estimated bacterial cells per m3 of air volume, but exhibited lower diversity compared to Hi-Vol samplers. Hi-Vol samplers recovered a more taxonomically diverse community, including transient and rare taxa, during sampling periods of 1 day and 1 week. Hi-Vol detected genera not detected in long-term PUF-PAS sampling, while PUF-PAS detected species not observed in short-term Hi-Vol. PUF-PAS samples were enriched with environmental and spore-forming persistent genera. Hi-Vol samples were enriched with opportunistic and human-associated episodic spikes in a range of bacterial species. PCoA analysis confirmed a substantial divergence in bacterial community structure by sampler type and duration. Temporal analysis results showed a progressive shift in bacterial community composition with increasing sampling duration in PUF-PAS. The findings highlight the complementary benefits of both sampler types: active air sampling for capturing short-lived human-associated bioaerosols and taxonomic richness, while passive air samplers favor biomass accumulation and chronic exposure profiling, enabling exposure assessment and ecological surveillance.

Air pollution is a major environmental health risk and it has been associated with various diseases and mortality worldwide. The inhalation of fine particulate matter (PM) is an important cause of health effects from air pollution with one of underlaying mechanisms involving the induction of oxidative stress in the body. Oil sands mining is a major economic sector and a notable source of air pollution in northern Alberta, Canada. Despite this, studies investigating the potential health impacts associated with exposure to air pollutants in the region are rare. For the first time in this work, using an acellular •OH assay, we studied the oxidative potential (OP) of fine (<2.5 μm diameter) and coarse (2.5-10 μm diameter) PM from four community sites in the vicinity of oil sands production facilities. OPOH was found to be dominated by fine PM, which on average accounted for 70 % reactivity of the studied PM size range. The highest OPOH was found at the most populated sites located south of the open pit mines and with mixed emission sources, suggesting a cumulative effect of oil sands and non-oil sands sources. Nevertheless, OPOH was relatively small compared to values reported for urban sites influenced by traffic and industrial emissions in Canada. OPOH variation could not be linked with a statistical significance to changes in the concentrations of PM, trace metals, and secondary inorganic salts but, for a small set of samples, OPOH was associated with organic carbon and potassium, which suggests the influence of reactive organic species from biomass combustion. A larger sample size will be needed in order to examine more closely the links between various OP metrics and the aerosol composition and sources in the region. This work provides a proof of concept to support future studies aimed at assessing potential health impacts associated with exposure to air pollutants in the oil sands region.

Tire-derived chemicals (TDCs) are shown to be elevated in urban environments. In this study, we analyzed 6PPD-quinone, 2,2,4-trimethyl-1,2-dihydroquinoline (TMQ), hexa(methoxy)methylmelamine (HMMM), as well as selected benzothiazoles and benzotriazoles, in different urban source-sectors. The chemical analyses were conducted on archived extracts of polyurethane foam (PUF) disk passive air samplers deployed across eight locations (including residential, industrial, semiurban, and traffic areas) over successive 2-month periods in the Greater Toronto Area, Canada. Principal component analysis showed distinct profiles in traffic-heavy locations, where benzothiazole and 6PPD-quinone had maximal concentrations of 2100 pg/m3 and 3.4 pg/m3, and where several TDCs including 6PPD-quinone, benzotriazoles, and some benzothiazoles were elevated during winter months. HMMM had elevated concentrations in nontraffic sectors, suggesting anthropogenic sources other than tires. This study recognizes the unique challenges to accurately quantifying TDCs in ambient air and that results presented here should be considered semiquantitative. To reduce uncertainty, temperature-dependent PUF disk-air partition coefficients (KPUF-AIR) and gas-particle partitioning fractions of TDCs in ambient air are presented. These are calculated from KOA values derived from quantum chemical methods using COSMOtherm and show that TDCs span a wide range of volatilities and gas-particle partitioning behavior, with implications for atmospheric fate and exposure. Lastly, guidance is provided on future measures to evaluate and minimize degradation losses of TDCs during sampling, extraction, and storage.

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.

Bioaerosols are ubiquitous and play a significant role in global climate and human health due to inhalation exposure. Passive air sampling of bioaerosols, as a complementary method to active sampling using pumps, is increasingly valued due to its simplicity, electricity-free operations, and cost-effectiveness in providing time-integrated samples over weeks/months. In this study, polyurethane foam disk passive air samplers (PUF-PAS), passive dry deposition air samplers (PAS-DDs), and active high-volume (Hi-Vol) air samplers were deployed in Toronto and the Athabasca oil sands region (OSR) in the first stages of a proof-of-concept exercise for bioaerosols. Airborne bacterial and fungal communities were characterized using MiSeq DNA sequencing. All sampler types were shown to successfully collect bioaerosols. The dominant bacterial and fungal phyla observed by all samplers were qualitatively similar. Species richness and community structure of the airborne bacterial and fungal communities varied with sites and seasons. Principal coordination analysis indicated that bacterial and fungal communities differed between Toronto and OSR. Further work is required to calibrate and characterize the uptake of PUF-PAS and PAS-DD for bioaerosols to derive quantitative information on their abundance to better assess sources and potential exposure risks.

Oil sands process-affected water (OSPW) is a source of atmospheric emission for polycyclic aromatic compounds (PACs), compounds known to have toxic effects on humans. Estimating emissions and assessing the chemical fate of PACs requires measured or predicted physical-chemical properties such as Henry’s law constants (H), that can be used to predict chemical transfer into the atmosphere. OSPW is a complex water-based mixture that is highly variable in composition and nature and contains both organic and inorganic ions. This study uses COSMO-RS solvation theory to estimate and compare Henry’s law constants for a set of PACs in both water and theoretically modelled OSPW, to assess the expected deviation that occurs from pure water H values due to the ionic content within OSPW. Experimental measurements of Henry’s law constants for PACs in pure water and OSPW using EVA-coated passive dosing and sampler beads were also made in support of our theoretical predictions. For the theory work, OSPW composition data for the Athabasca oil sands in Alberta were used to model a simulated OSPW environment with realistic sodium, chloride, fluoride, sulfate, potassium, bicarbonate, and naphthenic acid concentrations. Theory results indicate that the combined presence of these ions at OSPW concentrations has a negligible effect on H values, causing on average a 3% or 0.014 log unit deviation. By comparison, temperature has a much larger influence on H values, with estimations showing an average 0.20 log unit increase for a 5°C increase in temperature. The experimental results demonstrate that Henry’s law constants can be accurately and precisely measured with this technique in pure water but with less precision in OSPW. Nevertheless, the experimental results support the conclusion that Henry’s law constants for OSPW can be accurately estimated assuming a pure water phase.

The global increase in electronic waste (e-waste) has led to a rise in informal recycling, emitting hazardous heavy metals (HMs) that threaten human health and ecosystems. This study presents the first comprehensive assessment of HM levels in dry deposition and soils at proximity of forty (40) informal e-waste recycling sites across Pakistan, between September 2020 to December 2021. Findings reveal that Zn (1410), Pb (410) and Mn (231) exhibited the higher mean deposition fluxes (μg/m2.day), derived from air samples, particularly in Karachi. Similarly, soils showed higher mean concentrations (μg/g dw) of Mn (477), Cu (514) and Pb (172) in Faisalabad, Lahore, and Karachi, respectively. HMs concentrations were found higher in winter or autumn and lower in summer. In addition, HM levels were significantly (p = 0.05) higher at recycling sites compared to background sites year-round, highlighting the e-waste recycling operations as the major source of their emissions. The Igeo index indicated moderate to extremely contaminated levels of Cu, Pb, Cd, and Ni in Karachi, Lahore and Gujranwala. Ingestion was found as a leading human exposure route, followed by dermal and inhalation exposure, with Pb posing the greatest health risk. The Cumulative Incremental Lifetime Cancer Risk (ILCR) model suggested moderate to low cancer risks for workers. Strategic interventions recommend mitigating health and environmental risks, prioritizing human health and ecosystem integrity in Pakistan's e-waste management.

The GAPs networks are engaging in cross-cutting studies across fields of science and policy to address future challenges.

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.

We investigated the trophic magnification potential of perfluoroalkyl substances (PFAS) in a terrestrial food web by using a chemical activity-based approach, which involved normalizing concentrations of PFAS in biota to their relative biochemical composition in order to provide a thermodynamically accurate basis for comparing concentrations of PFAS in biota. Samples of hawk eggs, songbird tissues, and invertebrates were collected and analyzed for concentrations of 18 perfluoroalkyl acids (PFAAs) and for polar lipid, neutral lipid, total protein, albumin, and water content. Estimated mass fractions of PFCA C8-C11 and PFSA C4-C8 predominantly occurred in albumin within biota samples from the food web with smaller estimated fractions in polar lipids > structural proteins > neutral lipids and insignificant amounts in water. Estimated mass fractions of longer-chained PFAS (i.e., C12-C16) mainly occurred in polar lipids with smaller estimated fractions in albumin > structural proteins > neutral lipids > and water. Chemical activity-based TMFs indicated that PFNA, PFDA, PFUdA, PFDoA, PFTrDA, PFTeDA, PFOS, and PFDS biomagnified in the food web; PFOA, PFHxDA, and PFHxS did not appear to biomagnify; and PFBS biodiluted. Chemical activity-based TMFs for PFCA C8-C11 and PFSA C4-C8 were in good agreement with corresponding TMFs derived with concentrations normalized to only total protein in biota, suggesting that concentrations normalized to total protein may be appropriate proxies of chemical activity-based TMFs for PFAS, which predominantly partition to albumin. Similarly, TMFs derived with concentrations normalized to albumin may be suitable proxies of chemical activity-based TMFs for longer-chained PFAS, which predominantly partition to polar lipids.

Data presented in the manuscript "Oxidation of a commercial antioxidant is driving increasing atmospheric abundance of a novel organophosphate ester: Implication for global regulation" by Liu et al. (2023).

Given the considerable financial and logistical resources supporting long-term monitoring for air pollutants, and the use of these data for performance evaluation of mitigation measures, it is important to account for contributions from primary versus secondary sources. We demonstrate a simple approach for using open source Global land cover raster data from the National Mapping Organization from the Geospatial Information Authority of Japan to assess local source inputs for air measurements of legacy persistent organic pollutants (POPs)-polychlorinated biphenyls (PCBs) and organochlorine pesticides-reported under the Global atmospheric passive sampling (GAPS) Network at 119 locations for the time period 2005-2014. The land cover composition within a 10 km radius around the GAPS sites was identified to create source impact indicator (SII) vectors to quantify and rank the remoteness of the sites from human infrastructure. Using principal component analysis, three SII vectors were established to rank sites by impact of (i) general infrastructure/remoteness, (ii) urban infrastructure, and (iii) agricultural infrastructure. General infrastructure describes the combined effects of settlements and agricultural infrastructure. We found significant correlations (p < 0.05) between POP concentrations in air and specific SIIs. PCB levels in air had a statistically significant correlation to the SII ranking urban impacts around the sampling sites, while Endosulfan I, Endosulfan II, and Endosulfan sulfate had a statistically significant correlation with SII ranking agricultural impacts. The complete GAPS data set from 2004-2014 (1040 samples at 119 locations) was standardized based on the SII rankings to assess the global temporal trends of legacy POPs. SIIs were incorporated in the multiple regression analysis to determine global halving times. This includes short-term monitoring data from 79 locations that were previously excluded. Furthermore, the SII approach allows the integration of global monitoring data from different studies for broader global temporal trend analysis. This ability to link the results of independent and small-scale studies can enhance temporal trend analysis in support of the larger scale initiatives, such as inter alia, the Global Monitoring Plan and Effectiveness Evaluation of the Stockholm Convention in the case of POPs. This simple approach using open source data has a broad potential for application for other classes of air pollutants.

The adverse health effects of air pollution around the world have been associated with the inhalation of fine particulate matter (PM2.5). Such outcomes are thought to be related to the induction of oxidative stress due to the excess formation of reactive oxygen species (ROS) in the respiratory and cardiovascular systems. The ability of airborne chemicals to deplete antioxidants and to form ROS is known as oxidative potential (OP). Here we studied the influence of aerosol acidity and organic ligands on the solubility of transition metals, in particular iron (Fe) and copper (Cu), and on the OP of PM2.5 from Canadian National Air Pollution Surveillance urban sites in Toronto, Vancouver, and Hamilton. Using chemical assays and model simulations of the lung redox chemistry, we quantified ROS formation in the lung lining fluid, targeting superoxide anion (O2•-), hydrogen peroxide (H2O2), and hydroxyl radical (•OH), as well as the PM2.5 redox potential (RP). Experimental •OH formation (OPOH) showed high correlations with RP and model-predicted ROS metrics. Both aerosol acidity and oxalate content enhanced the solubility of transition metals, with oxalate showing a stronger association. While experimental OP metrics were primarily associated with species of primary origin such as elemental carbon, Fe, and Cu, model-predicted ROS were associated with secondary processes including proton- and ligand-mediated dissolution of Fe. Model simulations showed that water-soluble Cu was the main contributor to O2•- formation, while water-soluble Fe dominated the formation of highly reactive •OH radical, particularly at study sites with highly acidic aerosol and elevated levels of oxalate. This study underscores the importance of reducing transition metal emissions in urban environments to improve population health.