2015-09-09 10:31:50
The context
Since the early 2000s, air quality measurements have been carried out in underground railway enclosures (RER and metropolitan stations in Paris, Lille, Lyon, Marseille, Rennes, Toulouse). These notably revealed PM10 concentrations much higher than those measured in the outside air. The major constituents identified are different metals including iron, elemental carbon and organic carbon. Other chemical pollutants, present at concentrations sometimes higher than those measured outside, have been identified, such as aromatic hydrocarbons (toluene, phenanthrene, fluoranthene, anthracene and pyrene), and more rarely benzene, nitrogen and benzo(a)pyrene.
Knowledge of the toxicity of particles in suspension in underground railway enclosures appears to be much more limited than for particles from urban air pollution. In this context, ANSES received a request from the Directorate General for Labour, the Directorate General for Health and the Directorate General for Risk Prevention to carry out an expert appraisal relating to the chemical pollution of the air in the enclosures of underground rail transport and the associated health risks among workers.
Goals
First of all, the first objective is to carry out a state of knowledge on the chemical pollution of the air in the underground railway enclosures, on the toxicity associated with the pollutants, in particular the particles in suspension, on the individual exposure of the workers , on the health effects associated with this exposure and on the effectiveness of existing management policies.
On this basis, the second objective is to assess the health risks of workers exposed to this pollution.
And if necessary, the third objective is to propose lines of research and management avenues to reduce this pollution and the associated health risks among workers, by integrating a reflection on the methods of articulation with the management of exposure. transport users.
Air pollution in underground railway enclosures and health risks for workers
In underground railway enclosures, air pollution is dominated by the problem of suspended particles. The concentration of particles measured in the air is often expressed in PM10 and PM2.5: these are particles that penetrate the respiratory system, capable, for the finest (PM2.5) of being deposited at the level pulmonary alveoli.
The mass concentrations of PM10 and PM2.5 measured in underground railway enclosures in France and abroad are much higher than those measured in the air outside and in the air inside dwellings. The major source of these particles, which are rich in metals, mainly iron, and in carbon, is the wear of materials by the wheel-brake friction of passenger trains, followed by wheel-rail contact and contact between rolling stock and the power supply system.
The air particles in these enclosures have different physicochemical characteristics from the particles in the outside air. From an epidemiological point of view, the available data relating to workers in underground railway enclosures do not allow a decision to be made on the long-term risks. Although their toxicity has to date been little documented, the available toxicological data suggest that at an equivalent mass concentration, they are at least as toxic in the short term as the particles of the ambient outdoor air.
The Agency’s expert appraisal concludes that inflammation of the respiratory tract and the effects following this inflammation are probable in connection with chronic exposure to particles from underground railway enclosures. By analogy with the well-documented health risks of particles in outdoor ambient air, deleterious effects are expected on cardiovascular and respiratory health. This concerns workers working in particular in the areas of transport operation, organization of transport and services, businesses, police, security, prevention and social action. The health risks are probably higher for workers in charge of infrastructure maintenance, given the emissions from diesel engines and maintenance work.
The Agency’s recommendations
In this context, the Agency recommends the implementation and continuation of measures to prevent and reduce exposure for all of these categories of workers and in particular for those in charge of infrastructure maintenance.
In view of the absence of scientific data on the long-term toxicity of the particles present in the air of underground railway enclosures and the body of epidemiological studies which is still not very informative for assessing the health risks associated with chronic exposure of this population of workers, ANSES recommends that specific work be carried out to acquire new knowledge.
ANSES also suggests drawing up a management limit value and strengthening the air quality monitoring system for all the networks in order to be able to assess the effectiveness of the measures to improve the quality of the air and reducing worker exposure.
Reducing overall ambient air pollution remains the priority
The Agency recalls that the public health priority concerns the reduction of ambient air pollution as a whole. In this context, the use of less polluting means of transport than road transport, including rail transport, should be encouraged.
The air pollution suffered by road transport users appears to be more of a health concern than the air pollution of underground railway enclosures, given the high concentrations in road traffic for several pollutants whose toxicity has been proven, in particular : the number of fine particles, soot carbon, gases such as carbon monoxide, nitrogen dioxide, benzene and toluene.
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