1. Surbjit Kaur, Mark Nieuwenhuijsen & Roy Colvile
Exposure of Road Users to Air Pollution at a Street Canyon Intersection
Surbjit Kaur, Mark Nieuwenhuijsen & Roy Colvile
Department of Environmental Science & Technology, Faculty of Life Sciences, Imperial College London, London, UK
Introduction & Background
DAPPLE is a 4-year UK Engineering and Physical Science Research Council funded project that brings together a multidisciplinary research group, from six universities (Bristol, Cambridge, Imperial, Leeds, Reading & Surrey), whose aim is to enhance understanding of events from emission to exposure for air pollution in the urban environment. The work also intends to quantify the determinants of human exposure to air pollution as sources and people move together through the urban environment, and thereby contribute to better planning and management of urban air quality that takes account of requirements and opportunities to minimise exposure. The wider aim is to assist in the evaluation and development of appropriate decision support tools, to permit the development of sustainable, safer, and more pleasant cities worldwide. 
This poster introduces the preliminary results for the PM2.5 personal exposure measurements made during the first field campaign in Central London between 28 April and 24 May For the most recent information please refer to the web site at
Supersite outside Westminster University
Fig. 1 Map of field site, intersection of Marylebone Road and Gloucester Place, London, NW1.
KEY:
Automatic Weather Station
Route 1: Marylebone Road circuit
Route 2: Gloucester Place & backstreet circuit
Ref. AWS
WCC
Start point/Endpoint
Fig. 2
a. Marylebone Road and
Gloucester Place Intersection
b. Study participants a b
Sampling Location
The measurements were centred at Westminster Council House on the intersection of Marylebone Road and Gloucester Place in Central London, with a surrounding study area approximately 250 m in radius (Figs. 1 and 2a). Marylebone Road is a busy dual carriageway (A501) and forms the northern boundary of the London Congestion-Charging Zone. Gloucester Place is 3 lanes, one-way north (Baker Street is southbound one block to the East). The roads intersect perpendicularly and Marylebone Road is at a 20 ˚ angle north of due east, approximately WSW-ENE.
Study Description
During the four week DAPPLE field campaign, groups of four volunteers (Fig. 2b) collected data at each of the three timings (morning, lunch and afternoon), with the exception of the first week when additional early evening measurements were made at a fourth timing. They travelled along two routes (shown in Fig. 1) via four modes of transport: walking; cycling; car/taxi and bus.
The first route on Marylebone Road was circular and included the heavily trafficked area between the stations of Marylebone and Baker Street. The second route was a figure-of-eight circuit centred on Westminster Council House using Gloucester Place and back-streets to the North and South of Marylebone Road. The mode of transport and route followed by each volunteer at each timing was randomly designated.
Fig. 6 Exposure Visualization - synchronous video and exposure profile
Personal exposure to three pollutants were measured, this included PM2.5 (using gravimetric high flow personal samplers developed by Adams et al, 2001), ultra-fine particle counts at 1s resolution using TSI P-Traks, and 10s CO exposure with Langan T15 CO personal monitors equipped with a Langan DataBear data logger.
Results
Results for PM2.5 personal exposure are now becoming available. Preliminary data analysis indicates mean personal exposure varies through the day, lowest at lunchtime and similar in the morning and afternoon (Fig. 3).
Mean personal exposure was found to be higher on the Marylebone Road circuit in comparison to the Gloucester Place and back-street route (Fig. 4).
Examination of the mean personal exposures for the different modes of transport indicates mean personal exposure to be the lowest when walking, similar when cycling or using the bus, and highest when using the car/taxi (Fig. 5).
In addition, collaborative work with the Health and Safety Laboratory resulted in the application of an exposure visualisation technique in an urban pollution context, previously used in an occupational environment (Walsh et al, 2000). Individuals were videoed as they moved through the field study area while simultaneously measuring their personal exposure to pollutants. The HSL-developed software displayed the synchronous video and exposure profile, allowing main factors affecting personal exposure to be visually identified (Fig. 6).
Conclusions
At this early stage of analysis, the PM2.5 personal exposure results indicate a variation in personal exposure within and between transport modes, sample timings and routes. Some of these are likely to depend more strongly than others on the traffic flow and the weather conditions. The full data set when completed, for carbon monoxide and ultrafine particle number counts as well as for PM2.5 , will be analysed in more detail to identify the determinants of exposure in a street canyon intersection environment.
References
Adams H S, Kenny L C, Nieuwenhuijsen M J, Colvile R N & Gussman R A (2001), Design and validation of a high flow personal sampler for PM2.5, J Exposure Environ Epidemiol (11) 5 – 11
Walsh P, Clark R, Flaherty S, Gentry S (2000) Computer-aided video exposure monitoring, Appl Occup Environ Hyg 15 (1)
Background photograph and Fig 2a by Dominic Edsall and Fig 2b by Surbjit Kaur