Tube particle pollution '30 times higher than by roads'
Particulate pollution on parts of the London Underground (LU) is up to 30 times higher than levels beside roads in the capital, a report has found.
The paper - by the Committee on the Medical Effects of Air Pollutants - found the Northern Line had the highest levels of particulate matter (PM).
Committee chairman Professor Frank Kelly said the committee were "uncertain about the health effects".
Transport for London (TfL) said they "closely monitor dust levels".
Tests were carried out over 10 days at Hampstead Station on the Northern Line, the deepest station on the network.
The average concentration of particulate pollution was found to be about 30 times higher than that found at monitoring sites close to a busy London road.
A similar length journey on a bus in the capital would expose passengers to about one third of the amount of particulates compared to the Tube, researchers discovered.
Particulate pollution was also found to be generally higher on London's Tube system compared to other subway systems.
Researchers said this was "likely due to the system's age and the fact that large parts of the network are in deep, poorly ventilated tunnels".
The Tube is the world's oldest underground railway network.
Prof Kelly said "further work" was required to look into the issue but commuters "shouldn't really change their attitude to using the Tube".
"These particles are of a different nature from the ones above ground so we are uncertain about their health effects," he said.
TfL, which commissioned the report, expanded cleaning regimes on the system in 2017 through the use of industrial vacuums and "magnetic wands".
Peter McNaught, director of asset operations, said TfL was "committed to maintaining the cleanest air possible".
"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," he said.