Everyone knows we've got air quality problems in London, but it might surprise you to hear that the air on the underground is even worse.
A new report by the Committee on the Medical Effects of Air Pollutants (COMEAP) has found that breathing the air on the tube for just an hour on your way to work is as bad for your lungs as standing outside and breathing the polluted city air for an entire 24-hour period.
The Northern line is among the worst offenders, partly because its tunnels go so deep. Some sections of the line had air five times worse than the 'healthy' level dictated by the Air Quality Index.
The most concerning findings in the report relate to particulate matter (PM) – dust, essentially. It states that PM in ambient air (i.e. outside) contributes to death and disease, and that the Underground has significantly higher concentrations of PM than outdoor air. It does also mention that the specific makeup of PM on the tube is different from outside, though, which might make a difference -- the particle size distribution and the chemical composition is different from outdoor pollution.
The conclusion the study comes to is that while it's hard to be sure pollutants on the tube are harmful to breathe in, it seems likely:
"We cannot rule out the possibility that there is a health risk from exposure to underground PM. Given that there is strong evidence that both long- and short-term exposure to particle pollutants in ambient air are harmful to health, it is likely that there is some health risk associated with exposure to underground PM."
The study was commissioned by Transport for London, whose Director of Asset Operations Peter McNaught comments:
"It is vital that we operate with the very latest understanding of the risks arising from particles in the air, which is why we commissioned COMEAP to undertake this research.
Although the report emphasises further monitoring and research is needed, it is an important contribution to the study of health effects associated with dust exposure.
We are committed to maintaining the cleanest air possible for our staff and customers when using the Tube.
We closely monitor dust levels on the Tube and, through a wide range of measures, ensure that particle levels are well within Health & Safety Executive guidelines.
We have already enhanced our sampling regime by including tests for additional metals and we will continue to investigate ways we can keep dust and particles to an absolute minimum."
In the meantime, maybe we need to take Japan's approach and start wearing filter masks on the tube. [Evening Standard]