Air quality evaluation of London Paddington train station

Enclosed railway stations hosting diesel trains are at risk of reduced air quality as a result of exhaust emissions that may endanger passengers and workers. Air quality measurements were conducted inside London Paddington Station, a semi-enclosed railway station where 70% of trains are powered by diesel engines. Particulate matter (PM_2.5) mass was measured at five station locations. PM size, PM number, oxides of nitrogen (NO_x), and sulphur dioxide (SO₂) were measured at two station locations. Paddington Station's hourly mean PM_2.5 mass concentrations averaged 16 μg m^-3 [min 2, max 68]. Paddington Station's hourly mean NO₂ concentrations averaged 73 ppb [49, 120] and SO₂ concentrations averaged 25 ppb [15, 37]. While UK train stations are not required to comply with air quality standards, there were five instances where the hourly mean NO₂ concentrations exceeded the EU hourly mean limits (106 ppb) for outdoor air quality. PM_2.5, SO₂, and NO₂ concentrations were compared against Marylebone, a busy London roadside 1.2 km from the station. The comparisons indicated that train station air quality was more polluted than the nearby roadside. PM_2.5 for at least one measurement location within Paddington Station was shown to be statistically higher (P-value <0.05) than Marylebone on 3 out of 4 days. Measured NO₂ within Paddington Station was statistically higher than Marylebone on 3 out of 5 days, while measured SO₂ within Paddington Station was statistically higher than Marylebone on all 3 days.