Pollution: the air in the metro three times more loaded with fine particles than outside

The observation had been made seven years ago, in 2015. At the time already, ANSES noted that the air in the metro was “more polluted than the ambient air and the air of the dwellings“. His observation made on June 8, 2022 therefore only reinforces the conclusions made seven years ago.

Fine particle concentrations are three times higher in the metro than in urban air. Based on these conclusions, ANSES confirms “the need to continue actions to limit user exposure, by reducing the concentrations of particles suspended in the air”.

A study in seven major cities in France

The analyzes carried out relate to seven major cities in France with a metro, six major conurbations – Paris, Lyon, Marseille, Lille, Toulouse and Rennes – but also Rouen in part, which has a tram running partly underground. These “underground railway enclosures“welcome several million passengers every day, including about five million for the Ile-de-France network.

Effects on cardio-respiratory health

The ANSES report also reports the composition of the fine particles detected in these underground corridors, which counts “a high content of metallic elements, including iron in particular, and also elemental and organic carbon“.

But according to ANSES, “the body of studies remains too limited to be able to draw firm conclusions”. It is therefore impossible to know with certainty the effects of these particles on health, even if the Agency specifies that the epidemiological and toxicological data “suggest the possibility of cardio-respiratory effects, inflammation and oxidative stress and effects on autonomic cardiac function”.

It therefore calls for the continuation of the actions already undertaken, such as the renewal of rolling stock, the use of braking systems with less particle emissions as well as the improvement of the ventilation of these places, and insists on the importance of reducing the pollution in the subways.

A public health priority

Given the number of people using these galleries every day, ANSES recalls that this issue must be a “public health priority”.

It therefore pleads for the establishment of indicators “to characterize the air quality in these environments”taking into accountexposure over a day in different environments (at home, at work and in transport) and the regulatory limit values, in daily concentrations, not to be exceeded“.

Finally, ANSES recommends “strengthen the air pollution monitoring systems in the various enclosure environments: platforms, stations, trains” and to further study the effects of this pollution on the body.