4 March 2019
Introduction
Why me
- Environmental Research Group
- PhD
- The London Hybrid Exposure Model
- A Game of Thrones
Why now
Exposure to particles on subway systems > important
- Seaton et al 2005, but …
- Tox. mechanisms
- Susceptible populations
- Analytical techniques
Aims
What we tried to do
- Measure variations in PM2.5 between lines and stations
- Characterise the chemical composition
- Calculate calibration factors for optical instruments
- Provide a spatially resolved dataset for future analysis
Method
Campaign One
- COPD Study
- 22 journeys alternating between Oxford Street / Hyde Park
- TSI AM510 SidePak for PM2.5
- Philips Aerasense for ultrafine particle number and mean particle diameter
Campaign Two
- Same equipment
- 31 hours
- All lines
- 89% of stations (NE Central, SW Piccadilly)
Characterisation & Calibration
- PM2.5 and total suspended particles collected on filters
- Filters, 4 hour intervals over 5 days, measuring:
- PM Mass, Elemental and Organic Carbon
- Elemental Analysis by ICP-MS ( ~ 32 elements characterised )
Characterisation & Calibration 2
- High time resolution
- Aethalometer
- TSI Dustrak
- 2 TSI Sidepaks
- Micro-aethalometer
Passenger-weighted stations
- 2015 tap in/tap out, Underground performance report
- Annual in/out for each station
- Mean PM2.5 measured at each station
- Passenger rank * air quality rank = passenger-weighted ranking
Spatial representation of the tube
Results
Calibration factors
The Victoria Line
Environment comparisons
Line averages
Station depth 1
Station depth 2
Depth on the Central Line
PM2.5 Map
Passenger-weighted stations
Origin-Destination matrix
Characterisation
Conclusions
Conclusions
- Particles tend to be larger in diameter than those at background or roadside environments
- More particles
- PM2.5 varied between lines & locations
- lowest Hammersmith & City (Mean 25 µg/m3), similar to roadside
- highest Victoria (381 µg/m3), 15 x higher than roadside
Conclusions 2
- General relationship between 'depth' and air quality
- Oxford Circus, Waterloo, London Bridge, Victoria and Vauxhall at top of passenger-exposure ranking
- 79% of PM2.5 characterised
- 47% iron oxide, 7% elemental carbon, 11% organic carbon, 14% metallic and mineral oxides
- Previous studies using light-scattering may under-report PM
What next
What next
- Characterise the remaining 11%
- More measurements accross the network to improve understanding
- train frequency
- passenger numbers
- time of year
- Interventions?
- Develop inclusion in exposure modelling
The end
Publication & Contact details
Public health risks from respirable particles on the 'London Underground' metro network
Smith, J.D., Green, D., Loxham, M. Priestman, M., Tremper, A., Mudway, I., Fuller, G., Nicolosi, E., Barratt, B.M.
