LAUSR

Transport for London (TfL) employed 36,506 staff between 2014 and 2019, 22,202 worked within the London Underground (LU). Employees were regularly exposed to PM2.5 concentrations 15-fold higher than those found above ground in London. However, PM2.5 in the LU differs in physical and chemical characteristics relative to outdoor air, and the health impacts are largely unquantified. This project aims to quantify LU PM exposure of staff and measure its impact on cardiorespiratory sickness absence. A job exposure matrix was developed to model TfL employee PM2.5 exposure based on their jobs. Measurement campaigns were deployed across the LU network to validate and revise staff PM2.5 exposure, which was then linked to sickness absence records. Poisson models were developed to explore the relationship with cardiorespiratory sickness absence. PM2.5 exposure of customer service staff varied depending on their grade and tasks they undertake. Concentrations ranged from 2 to 138 µg/m3 in the offices and 3 to 1,036 µg/m3 on the platforms. Drivers’ PM2.5 exposure was dependent on the line they worked on and the amount of time the train spent underground. Drivers have the highest PM2.5 exposure (median: 130 µg/m3) among all TfL staff and the highest mean number of all-cause (6.7) and respiratory (1.5) sickness absence episodes. This is the largest study to quantify LU PM exposure and the associated health effects within a London occupational cohort. It will contribute to a safer working environment for staff and to a better understanding of the potential health impact on the commuting population.