Every breath you take

Written by Lynne Featherstone and published in Parliamentary Health on Wed 30th Jul 2003

Every year dust on the London Underground hits the tabloid headlines. For a day or two passengers wonder whether it's true that travelling on the Tube for 40 minutes is as bad as smoking two cigarettes. Opposition politicians wonder whether the Government is playing Russian roulette with public safety. But eventually the dust settles again.

London Underground's seasoned professional on safety, Mike Strzelecki, insists that a good number of independent studies by a variety of specialists and institutions over the past 25 years have shown no evidence of a health risk from dust on the Tube. Even so, London Underground continue to reduce dust and seek to understand its effects.

Everyone seems to agree that our Tube has the highest dust levels of any Underground system in the world. They range from 1,000 to 2,500 micrograms per metre cube. The Stockholm underground is about 350 micrograms per metre cube at its highest; both the German systems and even the New York subway are much lower in terms of dust levels. Moreover the Tube compares badly with other London transport modes; Tube commuters tend to have double the dust exposure than people travelling by any other method.

This is because the London Underground is unique in having deep level small-walled tunnels with poor ventilation from vent shafts and fans - a Victorian legacy. However, the issue is not so much the levels of dust as whether the dust itself threatens the health of any of the Underground's passengers.

Professor Nick Priest of Middlesex University explains that there are concerns about the toxic silica levels. Although they are below Europe's existing occupational exposure limit, the limit itself may well soon be revised downwards from 300 micrograms per metre cube to 50. Asbestos fibres have been found (below the exposure limits), there is some enhanced level of ozone, which is an irritant, and there is a low exposure to radon. Professor Priest feels that there are valid health concerns that need to be addressed.

Everyone who travels by Tube knows the need for major upgrading of track and signalling so that delays and cancellations can be reduced. However, reconditioning the track can generate more dust. Metronet and Tube Lines, the two private consortia who maintain the Tube under the PPP contract, have a conflict between improving and cleaning the system. They are financially incentivised to clean the system and mandated to fulfil standards for cleaning dust.

It does not frankly seem from the evidence we have so far that there is any significant risk from dust on the Tube to fit and healthy passengers. We do have a duty of care, though, to vulnerable passengers - the very young, the very old, or people who have a chronic respiratory or circulatory disease. Transport for London, who recently took over the Tube, should in its own defence consider warning such passengers that there is the possibility of a risk.

In 1999 the Department of Heath contacted London Underground to suggest, among other things, that there was a case for an epidemicological study of the effects of particle dust. I can well believe that cash-strapped London Underground cannot afford such work. Four years on, perhaps the time has come for the Department of Health to fund the work it recommended.