An interlaboratory comparison to quantify oxidative potential measurement in aerosol particles: challenges and recommendations for harmonisation

This paper presents the findings from a collaborative interlaboratory comparison exercise designed to assess oxidative potential (OP) measurements conducted by 20 laboratories worldwide. This study represents an innovative effort as the first exercise specifically aimed at harmonising this type of OP assay, setting a new benchmark in the field. Over the last decade, there has been a noticeable increase in OP studies, with numerous research groups investigating the effects of exposure to air pollution particles through the evaluation of OP levels. However, the absence of standardised methods for OP measurements has resulted in variability in results across different groups, rendering meaningful comparisons challenging. To address this issue, this study engages in an international effort to compare OP measurements using a simplified method (with a dithiothreitol (DTT) assay). Here, we quantify the OP in liquid samples to focus on the protocol measurement itself, while future international OP interlaboratory comparisons (ILCs) should aim to assess the whole chain process, including the sample extraction. We analyse the similarities and discrepancies observed in the results, identifying the critical parameters (such as the instrument used, the use of a simplified protocol, the delivery and analysis time) that could influence OP measurements and provide recommendations for future studies and interlaboratory comparisons even if other crucial aspects, such as sampling PM methods, sample storage, extraction methods and conditions, and the evaluation of other OP assays, still need to be standardised. This collaborative approach enhances the robustness of the OP DTT assay and paves the way for future studies to build on a unified framework. This pioneering work concludes that interlaboratory comparisons provide essential insights into the OP metric and are crucial to move toward the harmonisation of OP measurements.

The present work was supported by the European Union's Horizon 2020 research and innovation programme under grant agreement 101036245 (RI-URBANS), including the post-doc grant of Pamela A. Dominutti, and by a University Grenoble Alpes grant ACME IDEX (ANR-15-IDEX-02). Chemical analysis of the Air-O-Sol facility at IGE was made possible with the funding of some of the equipment by Labex OSUG@2020 (ANR10 LABX56). Despina Paraskevopoulou​​​​​​​, Aikaterini Bougiatioti and Nikolaos Mihalopoulos acknowledge support from the project REGENERATE funded by the Hellenic Foundation for Research and Innovation (HFRI) through the General Secretariat for Research and Technology (GSRT), project no. 3232. Hana Cigánková and Pavel Mikuška acknowledge support from project no. 24-10051S funded by the Czech Science Foundation. The analyses in Serbia were supported by the EC Horizon Europe research and innovation programme under grant agreement GA 101060170 (WeBaSOOP). Analyses at ISAC-CNR were supported by the project PER-ACTRIS-IT, funded by the Ministry of Education and Research (MIUR), Action II.1 of PON Research and Innovation 2014–2020. This study was also supported by the PROCOPE mobility programme (0185-DEU-23-0008 LG1) for grant 0185-DEU-23-0008 LG1 to Eduardo J. d. S. Souza (ACD, TROPOS). Pourya Shahpoury acknowledges support from the Hazardous Air Pollutant Laboratory of Environment and Climate Change Canada. Battist Utinger and Markus Kalberer acknowledge funding from the Swiss National Science Foundation, grant 200021_192192/1. Ian Mudway received funding from the National Institute for Health Research (NIHR) Health Protection Research Unit in Environmental Exposures and Health, a partnership between the UK Health Security Agency and Imperial College, with Ian Mudway receiving additional funding from the MRC Centre for Environment and Health, which is funded by the Medical Research Council (MR/S0196669/1, 2019–2024). IMT Nord Europe thanks the Région Hauts-de-France, the Ministère de l'Enseignement Supérieur et de la Recherche, and the European Fund for Regional Economic Development for their financial support to the CPER ECRIN programme. We also acknowledge Mark Diks (TNO), Alexandre Barth and Julian Resch (UNIBAS), Laurent Alleman (IMT Nord Europe), and Stephan Houdier (IGE) for providing help in the deployment of this ILC.

Peer reviewed