PROJECT DESCRIPTION
BACKGROUND
Commuting by underground rail is a daily activity for over one hundred million people worldwide. In Europe alone, more than 60 cities use underground rail to facilitate commuter movement. With average return journey times lasting around one hour, these underground commuters can routinely be exposed to inhalable particulate matter (PM) levels that are higher than the normal legal limits for outdoor air quality in European cities (50 μg/m3 mean PM10 (PM <10 microns in size)). In fact, PM levels underground are typically much higher than those above ground.
Moreover, when compared to outdoor air, subway air is not only overly-rich in iron but can also contain high levels of trace metals such as Mn, Cr, Cu, Ni and Zn, as well as the toxic metalloids, Sb and As. The physical form of these metalliferous micro-particles is typically highly angular, with abundant fresh fracture surfaces available for bio-molecular interaction. Such a metalliferous cocktail, especially given the high mass loadings being breathed, is likely to be unusually bio-reactive.
From an environmental perspective, the subway system is relatively clean, with low emission electric trains and moving large numbers of passengers, which promotes less traffic congestion on the surface. However, in terms of air quality and personal exposure, breathing subway air is likely to present a greater respiratory health risk to the regular commuter.
OBJECTIVES
The overall aim of IMPROVE LIFE was to provide a benchmark study to lead to real improvement in subway air quality. The project was carried out in Barcelona, where the main pollutant sources were identified in order to inform the prioritisation of cost-effective and low energy air pollution mitigation strategies.
The project worked with public transport authorities in the city, improving their awareness of air quality and encouraging them to develop best practice policies for improving underground atmospheric conditions.
The project’s specific objectives included:
- Determining emission sources and their contribution to air pollution in both platforms and trains, identifying those that have a potentially higher health risk;
- Evaluating the effect of air quality mitigation measures already used in other subway systems worldwide (such as different types of break pad compositions, air filters, platform designs, as well as monitoring techniques, etc..);
- Developing proposals for helping local/national authorities to implement effective air mitigation measures in subway systems;
- Assisting Barcelona’s local transport services to implement a Strategic Plan designed to reduce air contamination in subways;
- Acting as a catalyst for the allocation of local/national funds, allowing for the implementation of air improvement strategies.
RESULTS
The IMPROVE LIFE project team performed a benchmark study that will lead to improved air quality in subways. The study was performed by CSIC (Spanish Research Council), in the Barcelona subway system, with the close collaboration of TMB (Transports Metropolitans de Barcelona) who manages the system.
As a first step, the beneficiaries selected the main air pollution sources in subway systems (i.e. mechanical abrasion of rail/wheel, brakes and catenaries, resuspension of material caused by air turbulence in stations and tunnels, night-time maintenance work, and ambient road traffic particles). After intensive campaigns carried out in the Barcelona subway system, they determined the contribution of these sources to air quality, both on platforms and in trains. Then the beneficiaries analysed the impact of air quality mitigation measures already used in some subway systems worldwide (e.g. change of ballast, sleepers, rails and brake shoes, change in the ventilation system, change of filters inside the trains, and isolation of platforms and rails by means of glass panels and automatic doors).
The project team developed a strategy and a methodology to improve the air quality in the subway systems. CSIC produced a Technical Guide "Improving air quality in the subway environment" (http://improve-life.eu/wp-content/uploads/2018/01/Technical-Guide_IMPROVE-final-version.pdf), which summarises all the mitigation measures analysed in the scope of the project and includes recommendations to improve subway air quality. This guide was distributed to subway managers worldwide, to assist them in reducing air contamination in their subway systems. The project approach and results have been presented to several relevant stakeholders, including the International Association of Public Transport (UITP).
The benefits of the project on policy effectiveness include:
- High visibility of methods for air quality improvement through the numerous communication activities carried out during the project;
- Strong partnership with other national and international subway bodies and institutions, for the development of efficient mitigation measures in subway systems;
- Creation of new scientific work, combined with a critical overview and analysis of previous publications on subway air quality, to help guide policymakers in their decisions (all the scientific papers are published in open-access scientific journals);
- The elaboration and dissemination of a detailed database with information on source apportionment results to stakeholders (transport and policymaking authorities) and to the general public, freely available through the project website and technical reports/pamphlets;
- Enhancement of public awareness of subway air quality issues, through the organisation of open meetings, the website, posters, and questionnaire surveys.
