Assessment of fine particulate matters in the subway system of Istanbul

The purpose of this study was to determine the concentrations of fine particulate matter (PM 2.5 ) at six subway stations. The PM 2.5 levels were compared at the platforms, inside the trains’ cabin and at the train driver’s cabin in the first section of the train. The measurements were grouped into three sections: (1) six underground platforms, (2) trains’ cabin and (3) train driver’s cabin in the Aksaray-Airport light metro line (M1) and the Taksim-4.Levent metro line (M2). On average, the highest PM 2.5 concentrations were recorded in the underground platforms. The average daytime PM 2.5 concentrations varied from 49.3 to 181.7 µg·m −3 at the two subway line platforms. The PM 2.5 levels measured at five stations were higher than the ambient air PM 2.5 standard declared by US-EPA, given as 35 µg·m −3 for a 24-h arithmetic mean. The second highest PM 2.5 concentration was recorded inside the trains (61 to 73 µg·m −3 ), followed by train driver’s cabin (50 to 74 µg·m −3 ) of the M1 and M2 lines. When the train was in the subway tunnels, the PM 2.5 concentrations increased. The correlation ( R 2 ) between the PM 2.5 level on the platform and the depth of the underground stations was 0.88 ( p<0.01). The highest PM 2.5 levels were recorded in the morning and evenings.