Tube dust: improving air quality on the Tube

Pollution on the London Underground is very different to pollution above ground. It is generally a mix of metal particles, organic matter and mineral dusts, caused by track and wheel wear and breaking. It is commonly known as Tube dust.

Air pollutants such as nitrogen dioxide and diesel exhaust  emissions, which have been found to be harmful to humans, are common above ground and are not produced inside the Tube network.

The International Agency for Research on Cancer has classified outdoor air pollution, especially particulate matter in outdoor air pollution, as carcinogenic to humans, causing lung cancer. That’s not true of Tube dust.

People are generally only exposed to Tube dust for relatively short periods of time during their journeys, and levels always meet the relevant regulatory standards for exposure. 

We are tackling Tube dust on our network not only by carrying out extensive cleaning but also monitoring and exploring the latest innovations, as well as commissioning world-leading research. 

We use an independent company to carry out annual air quality monitoring across the Underground network, and this has shown that dust levels on the Tube remain well below occupational limits set by the Health and Safety Executive (HSE) – the UK’s national regulator for health and safety. Levels on most of our network are also below the recommendations from the Institute of Occupational Medicine, which are set significantly lower. 

This monitoring is carried out using specialist, calibrated equipment, which is likely to achieve more accurate and detailed results than portable devices. Portable devices measure dust levels at a particulate matter (PM) level which isn’t accurate in an enclosed environment such as the London Underground network. High readings on these portable devices don’t necessarily indicate an impact on health.

However, we want to be certain on the nature and extent of any health risk to those travelling and working on the London Underground. That’s why we’ve commissioned further research to understand the potential health impacts better, while continuing to take precautionary action to reduce dust levels. The first of these studies is expected to be published later this year.

So far, we have taken these actions:

• we are reducing tube dust levels on the areas of the network which are most affected
• we have increased our annual Tube dust cleaning budget by a third, to £2 million
• we have put in place targeted cleaning at locations where our monitoring has shown higher dust levels
• we have introduced a number of innovative new cleaning methods, including mobile backpack vacuum cleaners.

This approach is getting results. We have reduced in-station dust levels on the Tube by 19 per cent and in-cab by 37 per cent between 2020 and 2021.