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Table 4 Studies using in vitro-in vivo extrapolation for risk assessment of exposure to underground railway air pollution

From: Health effects of particulate matter air pollution in underground railway systems – a critical review of the evidence

First Author Year Location [Airborne PM] (μg/m3) PM Composition Comparator PM Model Findings
Kam [85] 2011 (sampling May–August 2010) Los Angeles, USA PM10–2.5 = 11 ± 2; PM2.5 = 33 ± 1 PM10–2.5: Fe = 27%; PM2.5: Fe = 32% PM10–2.5 and PM2.5: overground train journey; ambient Alveolar macrophage Underground PM enriched in Fe, Mn, Cr, Co, Ni, Cu, Ba, Mo, Cd, Eu, especially in PM2.5–0.1. In terms of water-soluble elements, only Fe and Ba were higher in underground PM. For ROS generation, underground>overground>ambient, but difference small.
Kam [86] 2013 (sampling May–August 2010) PM2.5: overground railway; HGV-heavy and HGV-light freeways; stop-go road N/A On the basis of airborne PAH concentration, lung cancer risk was: HGV-heavy road>HGV-freeway>stop-go road>overground railway>underground railway
Lovett [87] 2018 (sampling May–August 2010) N/A Extending [86] to also take metals into account, total hazard quotient from PM exposure greatest on the underground, mainly due to Cr(VI). Overground railway has lowest hazard.
Cao [92] 2017 (measurement March–August 2015) Suzhou, China PM2.5 regular hours: underground platform = 198 (range 86–351); carriages = 60 (45–121); PM2.5 rush hours: platform = 265 (112–365); carriages = 79 (75–145) Not stated 4 underground stations, 1 above ground station N/A PM2.5 underground stations>overground, especially in urban vs. green areas. Underground PM2.5 summer>spring. Underground exposure associated with 6390 DALYs = 375 premature deaths = 1% total deaths in the city.