Real-time comparison of four particulate matter size fractions in personal breathing zone of Paris subway workers: A six-week prospective study

We developed a Bayesian spline model for the real-time mass concentrations of PM10, PM2.5, PM1, and PM0.3 measured simultaneously in personal breathing zone of Parisian subway workers. The measurements were performed by GRIMM, gravimetric method, and DiSCmini during the workers’ work-shifts over two consecutive weeks. The PM0.3 concentrations were more than an order of magnitude lower compared to the other PM and showed the highest temporal variation, followed by PM1. The PM2.5 raised the highest exposure concern: 15 stations out of 37 had higher mass concentrations compared to the reference. Twelve of these also had significantly higher PM1 mass concentration. Station PM levels were not correlated with the annual number of passengers entering the station, year of station opening or renovation, or the number of platforms and tracks. The correlation with the number of station entrances was con-sistently negative for all PM sizes. The number of correspondence concourses was negatively correlated with PM0.3 and PM10 and positively correlated with PM1 and PM2.5. Almost all studied environments had higher PM exposure compared to the study room, although the highest levels of PM were measured outdoors. The highest PM10 exposure was observed at the station platform, followed by the subway cabin and train, while ticket counters had the highest PM0.3, PM1, and PM2.5 mass concentrations. Compared with gravimetric and DiSCmini meas-urements, GRIMM results showed some discrepancies, with an underestimation of exposure levels. Therefore, we suggest to use GRIMM, calibrated by gravimetric methods, for PM sizes above 1μm, and a DiSCmini for sizes below 700nm.