The mass concentration of atmospheric particulate matter (PM) has been systematically used in epidemiological studies as an indicator of exposure to air pollutants, connecting PM concentrations with a wide variety of human health effects. However, these effects can be hardly explained by using one single parameter, especially because PM is formed by a complex mixture of chemicals. Current research has shown that many of these adverse health effects can be derived from the oxidative stress caused by the deposition of PM in the lungs. The oxidative potential (OP) of the PM, related to the presence of transition metals and organic compounds that can induce the production of reactive oxygen and nitrogen species (ROS/RNS), could be a parameter to evaluate these effects. Therefore, estimating the OP of atmospheric PM would allow us to evaluate and integrate the toxic potential of PM into a unique parameter, which is related to emission sources, size distribution and/or chemical composition. However, the association between PM and particle-induced toxicity is still largely unknown. In this commentary article, we analyze how this new paradigm could help to deal with some unanswered questions related to the impact of atmospheric PM over human health.

The mass concentration of particulate matter (PM) has been systematically used in epidemiological studies as exposure indicator, to relate airborne concentrations with a wide variety of human health effects, which can be hardly explained by using this single parameter. In fact, PM is a “particle cocktail” that includes a complex mixture of compounds with a wide range of sizes, chemical compositions and emission sources. Current research hypothesizes that many of the adverse health effects are derived from oxidative stress in biological systems caused by the deposition of PM into the lungs. This emerging hypothesis is called the oxidative stress paradigm. In this commentary article we analize how this new paradigm could help to answer the as-of-yet unanswered questions related to the mechanism of action of PM pollution on human health. Acellular oxidative potential (OP) assays have been emerged as a promising approach to quantify the PM potential to induce oxidative stress and to relate it with the chemical composition and size distribution of PM. Recent researches have shown that the OP is related to the presence of metals, organic carbon, polyaromatic hydrocarbons and quinones. However, the association between PM and particle-induced toxicity is still largely unknown. Therefore, additional research is needed to identify the specific PM characteristic(s), such as its specific size, emission source or chemical content, which contribute the most to its redox activity. Thus, the OP measurements provide information that allows us to evaluate and integrate the toxic potential of PM in a unique parameter, whose relationships with emission sources, size distribution and/or chemical composition should be faced in the near future.

Health effects associated with aerosol exposure have been widely studied, demonstrating a positive association with mortality and poor health from a diversity of ailments. Emissions from vehicular traffic have been a major source of air pollutants, especially in urban and highly-populated environments, and emissions controls have considerably reduced the amount of aerosol from these sources. Nevertheless, policy based on mass concentration alone overlooks the possibility that certain aerosol sources may be more toxic than others. To address this, oxidative potential (OP) has been used as a metric that incorporates these properties, and ties in together mass and toxicity into a single metric that is a proxy of oxidative stress – thought to be a mechanism associated with adverse health effects from particulate matter exposure.In this work, we focus on evaluating the oxidative potential of vehicular emissions using the dithiothreitol assay (DTT) during various field observations conducted as part of the EASOLEE project. Emissions from controlled environmental and driving conditions were characterized to compare diverse types of vehicles. Real driving conditions for large vehicle fleets inside a 12 km underground tunnel connecting France with Italy, as well as emissions from an underground parking lot were characterized. Our results showed a lower OP mass normalized (OPm) for fresh particles compared to aged particles. Diesel vehicles (47±67 pmol DTT min-1 μg-1) also exhibited a lower OPm when compared to scooters and gasoline vehicles (142±193 pmol DTT min-1 μg-1 and 130±75 pmol DTT min-1 μg-1 respectively). Measurements in the tunnel also revealed a lower OPm on average than previous studies (below 6 pmol DTT min-1 μg-1), possibly from the usage of a more modern ventilation system; in all cases, aging of the primary emissions led to more OP-active aerosol, with an enhancement of up to a factor of 10 in some cases. The implications therefore are that health impacts of particles away from their sources, especially certain types of vehicles, may be affected by increases of their toxicity from atmospheric aging.

With over 1.6 billion vehicles worldwide, the combustion of fossil fuels is a major source of particulate matter (PM) and trace gases, which significantly contribute to air pollution, climate change and cause health burden. Heavy-duty vehicles (HDVs) constitute a small fraction of the global vehicle population but account for a disproportionately large share of total emissions when compared with light-duty vehicles (LDVs). However, uncertainty remains about which vehicle type contribute most to the emission factors (EFs) of various pollutants, particularly in Europe, where diesel technology has historically been favored for LDVs.Because traditional engine emission tests may not accurately reflect the real-world emissions, there is a need for on-road, real-world emission assessments. In this study, we conducted a three-week measurement campaign in the Fréjus Road Tunnel using MIRO MGA-10, aethalometer and SMPS. We developed a practical method to determine the EFs of primary pollutants, including trace gases (NOx, CO2, CO, N2O, NH3, CH4), black carbon (BC), and ultrafine particles (UFP). The calculated EFs will be reported, and selected pollutant species will be compared with previously published data from Asia and America in equivalent units.Figure 1 shows the results for the species mentioned, where HDV* indicates the proportion of HDVs to the total number of vehicles, taking into account the CO2 emissions from a single HDV and LDV. The results indicated that for most pollutant species, LDVs exhibited higher EFs than HDVs. However, HDVs emitted a higher fraction of N2O compared to LDVs. The EFs of NOx, CO, BC, and NH3 were consistent with previous studies conducted in Europe but lower than data reported from Asia and America. This study’s findings will raise public awareness and provide valuable insights for policymakers to develop strategies to mitigate emissions. Figure 1. Emission Factors (g/kg fuel)

Atmospheric biological particles, including pollen and other plant-derived materials, constitute a substantial fraction of coarse particulate matter, particularly during flowering seasons. Olive trees represent one of the most widespread crops in southern Europe, and olive oil is a major economic resource for the region. Approximately 95% of global olive cultivation is concentrated in the Mediterranean basin (Sofiev et al., 2017). Pollen production from an area with complete olive coverage can reach up to 10¹⁰ pollen grains m⁻² season⁻¹, with an average grain diameter of 20.1 ± 4.0 μm. Olive pollen is considered among the most allergenic tree pollens in Europe, inducing respiratory symptoms such as rhinitis and asthma in humans (Liccardi et al., 1996), while also acting as a significant atmospheric source of organic matter and nutrients to terrestrial and aquatic ecosystems (Rösel et al., 2012; Violaki et al., 2021).In this study, a series of chamber experiments was conducted to investigate the response of olive pollen to atmospheric stressors, with a particular focus on NOx pollution. Olive pollen (Olea europaea L.) was collected between 5 and 7 May 2024 from Puglia, southern Italy (https://www.bonapol.com/). Prior to chamber exposure, comprehensive lipidomic, biological, and chemical characterizations were performed, including analyses of metals, major ions, and carbon content.A robust analytical workflow for pollen lipidomics was developed and applied before and after chamber aging. Using LC-Q-TOF/MS with ESI in both positive and negative ionization modes, approximately 480 lipid species spanning 41 lipid classes were identified. Phosphatidylcholines (PC) were the dominant class (66%), followed by diacylglyceryl carboxyhydroxymethylcholine (DGCC, 19%), and ether monogalactosyldiacylglycerols (MGDG, 8%). A significant decrease in major membrane lipids (PC, PG, SM, DGDG, and MGDG) was observed after aging, indicating lipid degradation processes. In contrast, oxidized lipid species, including oxidized triacylglycerols (OxTG), oxidized phosphatidylcholines (OxPC), and ether-linked lipids, showed a pronounced increase, highlighting oxidative transformations induced by atmospheric aging. Overall, these results highlight the sensitivity of lipids in pollen grains to atmospheric aging and emphasize the importance of considering oxidative processing when assessing the chemical evolution of primary biological aerosol particles. ReferencesLiccardi et al., Int Arch Allergy Immunol. Nov;111(3):210-7, 1996.Rösel, et al., Aquatic Sciences, 74, 87–99, 2012.Sofiev, et al., Atmos. Chem. Phys., 17, 12341–12360, 2017.Violaki, et al., npj Clim Atmos Sci 4, 63, 2021.

The Cleancloud Helmos OrograPhic site experimeNt (CHOPIN) campaign took place in autumn 2024 at a unique high-altitude location at Mount Helmos, Greece (38.0oN, 22.2oE) ideal for targeted studies of aerosol-cloud interactions (ACI) due to its strategic location, serving as a crossroad for different aerosol transport paths. This unique position allows the detection of a wide range of particles like wildfire smoke, continental polluted, marine and mineral dust from Sahara, as well as bioparticles (pollen, bacteria, fungal spores) from near- and long-range sources. State-of-the-art laser remote sensing and in situ instrumentation was implemented at Mount Helmos at two level heights: 1700 m (remote sensing instrumentation) and 2314 m a.s.l. (in situ instrumentation) to characterize the incoming air masses in terms of their bioparticle content and study the role of bioparticles in cloud formation. In this study we will focus on data obtained by two lidar systems: the two-wavelength (532 -parallel and cross depolarization and 1064 nm) depolarization aerosol lidar system (AIAS), and the NTUA/EPFL/FORTH 4-wavelength elastic-Raman-laser induced fluorescence (LIF) lidar system (ATLAS-NEF) to provide vertical profiles of aerosol optical properties (extinction and backscatter coefficients and lidar ratio at 355 nm, backscatter Ångström exponents at 355/532nm, 532/1064 nm, particle depolarisation lidar ratio at 532 nm), water vapor mixing ratio, fluorescence capacity and fluorescence backscatter coefficients at 470 nm. We present cases of Saharan dust intrusions with increased values of the aerosol backscatter coefficient and high particle depolarization ratios (δ532 ~0.20-0.25) and increased values of lidar ratios (LR~40-55 sr), high numbers of ice-nucleation particles (INPs) obtained with a PINE instrument and strong signals obtained at the 3 channels of the Wideband Integrated Bioparticles Sensor (WIBS) operating at the (HAC)2 station indicate the presence of bioparticles able to enhance cloud formation.