Sidewalk pollution flows caused by vehicular traffic place children at a higher acute exposure risk

The objective of this work is to study the immediate transport flows of PM_2.5 diesel exhaust emissions on a city sidewalk. Under calm conditions largest direct exhaust PM_2.5 diesel concentrations tend to accumulate at two preferred heights: higher ones at 200-225 cm due to truck and buses aerodynamics, and lower ones at 130-160 cm due to light vehicles. Obtained flows indicate that exhaust emissions are transported to these heights via vortices generated by vehicular traffic. The lower height vortices transporting PM_2.5 direct diesel emissions place children aged between 7 and 15 at a higher acute exposure risk due to their stature. Also, the hourly averaged PM_2.5 concentrations tend to accumulate nearer to the roadside. This information was obtained using a specially designed electromechanical near-surface atmospheric profiler equipped with a PM_2.5 measurement instrument, a thermistor and a sonic anemometer installed on a sidewalk. Using signal analysis techniques, coherent flows of direct PM_2.5 emissions and thermal information were obtained. The proposed methodology can be used to evaluate before and after urban interventions, obtain full-scale sidewalk data for exposure studies and provides criteria on where to place sidewalk measurement instruments.