Atmospheric Environment

Air quality in subway systems is of interest not only because particulate matter (PM) concentrations can be high, but also because of the peculiarly metalliferous chemical character of the particles, most of which differ radically from those of outdoor ambient air. We report on the oxidative potential (OP) of PM2.5 samples collected in the Barcelona subway system in different types of stations. The PM chemical composition of these samples showed typically high concentrations of Fe, Total Carbon, Ba, Cu, Mn, Zn and Cr sourced from rail tracks, wheels, catenaries, brake pads and pantographs. Two toxicological indicators of oxidative activity, ascorbic acid (AA) oxidation (expressed as OPAA μg−1 or OPAA m−3) and glutathione (GSH) oxidation (expressed as OPGSH μg−1 or OPGSH m−3), showed low OP for all samples (compared with outdoor air) but considerable variation between stations (0.9–2.4 OPAA μg−1; 0.4–1.9 OPGSH μg−1). Results indicate that subway PM toxicity is not related to variations in PM2.5 concentrations produced by ventilation changes, tunnel works, or station design, but may be affected more by the presence of metallic trace elements such as Cu and Sb sourced from brakes and pantographs. The OP assays employed do not reveal toxic effects from the highly ferruginous component present in subway dust. © 2016 The Authors

This study was supported by the Spanish Ministry of Economy and Competitiveness and FEDER funds (METRO CGL2012-33066 ), the I MPROVE LIFE Project ( LIFE13 ENV/ES/000263 ) and the European Union Seventh Framework Programme ( FP7/2007-2013 ) under grant agreement no. 315760 HEXACOMM. Support is also acknowledged to Generalitat de Catalunya 2014 SGR33 . Fulvio Amato is beneficiary of an AXA Research Fund postdoctoral grant . In the UK the research was funded by the National Institute for Health Research Health Protection Research Unit (NIHR HPRU) in Health Impact of Environmental Hazards at King's College London in partnership with Public Health England (PHE). The views expressed are those of the authors and not necessarily those of the NHS, the NIHR, the Department of Health or Public Health England. Special thanks to Wes Gibbons for improving an early draft of the manuscript. Appendix A

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