Higher particle concentrations inside railway enclosures than outside
The networks of underground railway enclosures are distributed in 7 urban agglomerations (Paris, Marseille, Lyon, Lille, Toulouse, Rennes and Rouen). The Ile-de-France network is by far the largest in France and one of the busiest in the world.
Since the beginning of the 2000s, air quality measurements in railway enclosures in France have highlighted airborne particle concentrations (PM10, PM2.5 in µg.m-3) on average three times higher than in urban outdoor air. Their composition is however different with a high content of metallic elements, including iron in particular, and also of elemental and organic carbon.
Specific to underground railway activity, this pollution is caused by the wear of materials due to the braking of trains, by contact between the rolling stock and the railway or even by the resuspension of dust due to the movement of oars.
Preventive actions to be continued
ANSES has updated its inventory of knowledge on the health effects of exposure to particles in the air of underground railway enclosures made in its 2015 opinion. It emerges from its analysis that the body of studies remains too limited to be able to draw firm conclusions on such health effects.
However, epidemiological and toxicological data suggest the possibility of cardiorespiratory effects given the biological changes observed in relation to inflammation, oxidative stress and autonomic cardiac function.
In view of these observations, the Agency confirms the need to reduce particulate pollution in railway enclosures underground and therefore to continue actions in this direction, such as the renewal of rolling stock, the use of braking systems with less particle emissions and the improvement of the ventilation of these enclosures.
New indicators for monitoring air quality inside railway enclosures
The Agency proposes indicators to characterize the air quality in these environments.
« The proposed indicators correspond to suspended particle concentrations (PM10 and PM2.5) to be targeted in underground railway enclosures. They have been determined in order to be applicable on each network according to a characteristic duration of the journeys of their users. The calculation of these indicators integrates the exposures over a day in different environments (at home, at work and in transport) and the regulatory limit values or the guide values in daily concentrations not to be exceeded, which are defined for the particles of Ambiant air. explains Matteo Redaelli, Expertise Coordinator at ANSES.
These indicators are intended to be used as benchmarks to locate the levels of pollution in particles measured or modeled in the air of each network present on the national territory. They will help to assess the effectiveness of source reduction actions.