Exposure Assessment

The exposure assessment measurements were centred on the intersection of Marylebone Road and Gloucester Place in Central London, and incorporating the surrounding area of approximately 250m in radius. During the four week DAPPLE field campaign, groups of four volunteers 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 via five modes of transport (walking, cycling, bus, car and taxi). The first route on Marylebone Road was circular and included the heavily trafficked area between Marylebone and Baker Street stations. The second route was a figure-of-eight circuit centred on Westminster City 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.

Exposure measurements to three pollutants were measured with detailed transcripts for time-activity:

• PM2.5 (using gravimetric high flow personal samplers developed by Adams et al (2001))
• ultrafine particle counts (particle size range: 0.02 to > 1um) at 1s resolution using TSI P-Traks
• CO exposure with a Langan T15 CO personal monitor equipped with a Langan DataBear data logger (Langan Products, San Francisco, CA, USA) at 10s resolution

In addition, collaborative work with the Health and Safety Laboratory resulted in the application of an exposure visualisation technique in an urban pollution context that had previously been 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 (ELVis) displayed the synchronous video and exposure profile, allowing main factors effecting personal exposure to be identified. An example of the output from ELVis is shown below, Apple QuickTime required:

Exposure Album

Exposure Team	Cyclist Equipped for Exposure Measurements	Ptrak Setup on Bicycle
Setting off...	Pedestrian Equipped for Exposure Measurements	PM2.5 HFPS Pump in Rucksack
PM2.5 HFPS Equipment Set	Gilibrator	Bike Mounted Exposure Visualisation