Concentrations and health effects of particulate matter on the London Underground
File(s)
Author(s)
Hedges, Michael
Type
Thesis
Abstract
Subway systems provide an important mode of sustainable urban transportation. However, there are increasing concerns over the elevated levels of particulate matter (PM) concentrations found in the subway and the potential health effects to passengers and staff. This thesis aimed to make high quality measurements of the concentrations and composition of PM, and other air pollutants, nitrogen dioxide and ozone (NO2, O3), that passengers travelling on the rail networks in London are exposed to. A small, wheeled measurement platform was developed – it made use of smaller, lower power technology which has enabled a long-term, exposure assessment of the spatial and temporal variability of air pollutants. A comprehensive set of laboratory and field experiments were undertaken to ensure the highest quality data from the different transport micro-environments. These measurements were used as part of a panel study examining the health impacts for participants with Cardiovascular Obstructive Pulmonary Disease (COPD) and healthy volunteers travelling on the subway and overground trains.
PM2.5 concentrations on the subway journey were 321 µg m-3 in the tunnelled sections (198 µg m-3 for the complete journey), with concentrations found to be affected by ventilation, tunnel depth and seasonality. These are far higher than the overground journey (4 ug m-3) and mean ambient concentrations in London over the same period (8 ug m-3). The oxidative potential of subway PM2.5 was found to be highly correlated to transition metals generated underground by train-related emission processes. A methodology for a multi-omics assessment of molecular and biochemical pathways affected by subway exposure was developed for use in a further cross-omics subway study. This work will provide a better understanding of the exposure in different transport microenvironments, the potential health impacts and encourage the application of mitigation strategies to reduce exposure in London and other subway systems worldwide.
PM2.5 concentrations on the subway journey were 321 µg m-3 in the tunnelled sections (198 µg m-3 for the complete journey), with concentrations found to be affected by ventilation, tunnel depth and seasonality. These are far higher than the overground journey (4 ug m-3) and mean ambient concentrations in London over the same period (8 ug m-3). The oxidative potential of subway PM2.5 was found to be highly correlated to transition metals generated underground by train-related emission processes. A methodology for a multi-omics assessment of molecular and biochemical pathways affected by subway exposure was developed for use in a further cross-omics subway study. This work will provide a better understanding of the exposure in different transport microenvironments, the potential health impacts and encourage the application of mitigation strategies to reduce exposure in London and other subway systems worldwide.
Version
Open Access
Date Issued
2023-11-30
Date Awarded
2024-07-01
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Green, David
Chadeau-Hyam, Marc
Sinharay, Rudy
Publisher Department
School of Public Health
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)
Rights Embargo Date
2026-06-30