Physicochemical and Toxicological Assessment of Commuter Exposure to Coarse and Fine Particulate Matter (PM) in Subway and Light-rail Systems of the Los Angeles Metro
Elevated concentrations of particulate matter (PM) have been found in a number of worldwide underground transit systems, with major implications regarding exposure of commuters to PM and its associated health effects. An extensive sampling campaign was conducted in May - August 2010 to assess personal exposure of coarse (2.5μm<dp <10μm) and fine (dp <2.5μm) particulate matter (PM) in two lines of the Los Angeles Metro system – an underground subway line (Metro red line) and a ground-level light-rail line (Metro gold line). Concurrent measurements were taken at downtown Los Angeles to represent urban ambient conditions. Considering that a commuter typically spent 75％ of time inside the train and 25％ of time waiting at a station, subway commuters were exposed on average to PM10 and PM2.5 concentrations that were 1.9 and 1.8 times greater than the light-rail commuters. The average PM10 concentrations for the subway line at station platforms and inside the train were 78.0 and 31.5 μg/m3, respectively; for the light-rail line, corresponding PM10 concentrations were 38.2 and 16.2 μg/m3 . A comprehensive chemical analysis was also performed including total and watersoluble metals, inorganic ions, and elemental and organic carbon. Mass balance showed that in coarse PM, iron makes up 27％, 6％, and 2％ of gravimetric mass for red line, gold line, and urban background, respectively; in fine PM, iron makes up 32％, 3％, and 1％. Ambient air is the primary source of inorganic ions for both lines. Non-crustal metals, particularly Cr, Mn, Co, Ni, Mo, Cd, and Eu were elevated for the red line and, to a lesser degree, the gold line. Mo exhibited the greatest crustal enrichment factors. The enriched species were less water-soluble on red line than corresponding species on gold line. Reactive oxygen species (ROS) activity results suggest that one unit of PM from gold line may be as toxic as one unit of PM from red line; however, PM from red line generates greater ROS activity per volume than PM from gold line and urban background.
Subway systems commuter exposure particulate matter PM2.5 PM10 reactive oxygen species
Zhi Ning Winnie Kam James J. Schauer Martin M. Shafer Constantinos Sioutas
University of Southern California,Los Angeles,CA,USA City University of Hong Kong,Hong Kong,China University of Southern California,Los Angeles,CA,USA University of Wisconsin,Madison,WI,USA
国际会议
西安
英文
347-353
2011-08-17（万方平台首次上网日期，不代表论文的发表时间）