Alarming particle concentrations
According to Sophie Mazoué, head of air quality for the RATP, “the same pollutants that are found above ground are also found in the metro—with the exception of ozone—in addition to pollution particles specific to rail networks.” This means one can find aromatic hydrocarbon, and more particularly toluol, fluoranthene, as well as lead, nickel, cadmium, arsenic, chromium, iron, and manganese particles in the underground system. The monitored pollutants include fine airborne particles that are 2.5 µm to 10 µm in diameter (PM2.5 and PM10).
The RATP press report stated that “the measurements show a high level of particles emitted mainly by train equipment braking systems,” aggravated by poor ventilation and air conditioning. But this is nothing new since it occurs in all rail networks.
The majority of fine particles are created as the rails grind to prevent cars and train mechanical braking systems from screeching. With each passing train, the particles are stirred up and released back into the air, thus exposing passengers and employees.
Sophie Mazoué explained that fine particle concentration in the metro shows average rates of 150 to 300 µg/m3, peaking at 500 µg/m3 during rush hour in the metro and 40 µg/m3 in the RER A, which is the most affected. These figures should be compared to the 40 µg/m3 average measured in traffic pollution in the Ile-de-France region in 2005 and 20 µg/m3 in background pollution. Yet, according to the World Health Organization, average exposure over a 24-hour period and more than 3 days per year should not exceed 50 µg/m3 for PM10 and 25 µg/m3 for PM2.5. In other words, the underground rail network is not a nice place to live. The RATP points out however that today, there are no existing “regulation values regarding closed spaces […]. The work conducted by the Observatoire de la Qualité de l’Air Intérieur (French indoor air quality observatory) […] should, ultimately, lead to a set of standards.”
Yet, in 2001, the French higher council for public hygiene (CSHP) had reported that PM10 pollution peaks reached 1,000 µg/m3 in underground rail networks of the Ile-de-France region. As such, it recommended that a concentration average of 347 µg/m3 should not be exceeded for a two-hour commute. The RATP estimates however, that the average ride lasts 50 minutes. Therefore, the average content would be respected, except in the stations of the RER A line in the center of Paris.
La pollution de l’air dans le métro et le RER est très préoccupante
June 25, 2007