At the beginning of April, Respire obtained from the Paris public prosecutor’s office the opening of a preliminary investigation targeting the RATP for “deception and unintentional injury” due to poor air quality inside the metro. A month and a half later, Tuesday May 23, this same association presented, with the team of the program “Vert de rage”, broadcast on France 5 (1), new results confirming the seriousness of the situation.
In the viewfinder, PM2.5 particles, with a diameter of less than 2.5 microns (at least 20 times smaller than that of a hair) and which infiltrate deep into the lungs. The journalists measured five to ten minutes, at peak times, their concentration on the 435 platforms of the 332 metro and RER stations in Paris and the inner suburbs.
For each of them, they also carried out measurements on the surface, in order to distinguish the pollution “imported from outside” from the “excess pollution” generated by the trains, in particular due to the wear of the brakes and tires.
Line 5, the most polluted
Conducted with mobile sensors already used by around thirty European cities, this study shows that the excess pollution caused by metro and RER traffic is on average 10.5 µg/m3, i.e. twice as high as the threshold that the World Health Organization (WHO) tolerates outdoors (there is no standard for indoor spaces). If we add the external pollution that infiltrates the stations, in particular via ventilation, to the emissions linked to the circulation of trains, the average rate is five times higher than the WHO recommendations.
“Some lines, like the 5 or the RER A, are more polluted than others, says Mathilde Cusin, co-director of “Vert de rage”. Similarly, some stations have spectacular concentrations of PM2.5 particles, such as Belleville, where the rate is twelve times higher than the WHO standard. »
Iron and manganese, the main metals detected
The study was supplemented by the use of nose filters worn by 43 users (the average journey time, ie 36 minutes) and 12 RATP drivers (on a 6.5 hour service). Analysis of these filters revealed a high concentration of heavy metals. Rates were higher among users than among drivers, who however are exposed to these particles longer.
Main metals found: iron (with concentrations twenty times higher than those of control users using neither the metro nor the RER) and manganese. “The average manganese content is 2.6 times higher than the toxicological reference value (2), notes Joël Poupon, toxicologist at the Lariboisière hospital who carried out the analysis of the filters.
“Fine particles are likely to cause pathologies or irritation of the airways and lungs”, he continues. A study conducted in 2019 by the Regional Health Observatory and Airparif estimated the number of deaths linked to prolonged exposure to PM2.5 particles in Île-de-France at 6,220.
Ventilation, braking and particle filtering
The RATP, which conducts its own continuous measurements in five stations and which, on its website, mentions “generally good air quality”, dispute the reliability of these results. Even though the study was supervised by a member of the Respire association who happens to be a research director at the CNRS environmental physics and chemistry laboratory.
The transport authority also and above all highlights the efforts made to limit fine particle emissions: deployment of electrodynamic braking (using the electric motors of trains to slow down their speed), investment plan of 57 million euros to improve ventilation or even innovative devices to filter particles or fix them on the tracks.
Full Article (En) : Time.news