Short-term human exposure concentrations to PM2.5, ultrafine particle counts (particle range: 0.02-1 microm), and carbon monoxide (CO) were investigated at and around a street canyon intersection in Central London, UK. During a four week field campaign, groups of four volunteers collected samples at three timings (morning, lunch, and afternoon), along two different routes (a heavily trafficked route and a backstreet route) via five modes of transport (walking, cycling, bus, car, and taxi). This was followed by an investigation into the determinants of exposure using a regression technique which incorporated the site-specific traffic counts, meteorological variables (wind speed and temperature) and the mode of transport used. The analyses explained 9, 62, and 43% of the variability observed in the exposure concentrations to PM2.5, ultrafine particle counts, and CO in this study, respectively. The mode of transport was a statistically significant determinant of personal exposure to PM2.5, ultrafine particle counts, and CO, and for PM2.5 and ultrafine particle counts it was the most important determinant. Traffic count explained little of the variability in the PM2.5 concentrations, but it had a greater influence on ultrafine particle count and CO concentrations. The analyses showed that temperature had a statistically significant impact on ultrafine particle count and CO concentrations. Wind speed also had a statistically significant effect but smaller. The small proportion in variability explained in PM2.5 by the model compared to the largest proportion in ultrafine particle counts and CO may be due to the effect of long-range transboundary sources, whereas for ultrafine particle counts and CO, local traffic is the main source.

Personal exposure studies are crucial alongside microenvironment and ambient studies in order to get a better understanding of the health risks posed by fine particulate matter and carbon monoxide in the urban transport microenvironment and for making informed decisions to manage and reduce the health risks. Studies specifically assessing the PM2.5, ultrafine particle count and carbon monoxide personal exposure concentrations of adults in an urban transport microenvironment have steadily increased in number over the last decade. However, no recent collective summary is available, particularly one which also considers ultrafine particles; therefore, we present a review of the personal exposure concentration studies for the above named pollutants on different modes of surface transportation (walking, cycling, bus, car and taxi) in the urban transport microenvironment. Comparisons between personal exposure measurements and concentrations recorded at fixed monitoring sites are considered in addition to the factors influencing personal exposure in the transport microenvironment. In general, the exposure studies examined revealed pedestrians and cyclists to experience lower fine particulate matter and CO exposure concentrations in comparison to those inside vehicles-the vehicle shell provided no protection to the passengers. Proximity to the pollutant sources had a significant impact on exposure concentration levels experienced, consequently individuals should be encouraged to use back street routes. Fixed monitoring stations were found to be relatively poor predictors of CO and PM2.5 exposure concentration levels experienced by individuals in the urban transport microenvironment. Although the mode of transport, traffic and meteorology parameters were commonly identified as significant factors influencing exposure concentrations to the different pollutants under examination, a large amount of the exposure concentration variation in the exposure studies remained unexplained. (c) 2007 Elsevier Ltd. All rights reserved.

Short-term human exposure to PM2.5, ultrafine particle counts (particle range: 0.02–1μm) and carbon monoxide (CO) was investigated at and around a street canyon intersection in Central London, UK. During a four-week field campaign, groups of four volunteers collected samples at three timings (morning, lunch and afternoon), along two different routes (a heavily trafficked route and a backstreet route) via five modes of transport (walking, cycling, bus, car and taxi). PM2.5 was sampled using high-flow gravimetric personal samplers, ultrafine particle counts were measured using TSI P-TRAKs and Langans were used to measure CO exposure. Three hundred and ninety-four samples were collected—197 PM2.5, 86 ultrafine particle count and 111 CO. Arithmetic means of PM2.5 personal exposure were 27.5, 33.5, 34.5, 38.0 and 41.5μgm−3, ultrafine particle counts were 67773, 93968, 101364, 99736 and 87545ptcm−3 and CO levels were 0.9, 1.1, 0.8, 1.3 and 1.1ppm for walking, cycling, bus, car and taxi respectively. On the heavily trafficked route, personal exposure was 35.3μgm−3, 101142ptcm−3 and 1.3ppm, and on the backstreet route it was 31.8μgm−3, 71628ptcm−3 and 0.6ppm for PM2.5, ultrafine particle counts and CO, respectively. Personal exposure levels were high during the morning measurements for all three pollutants (34.6μgm−3, 106270ptcm−3 and 1.5ppm for PM2.5, ultrafine particle counts and CO, respectively).There was a moderately strong correlation between personal exposure of ultrafine particle counts and CO (r=0.7, N=67) but a weaker correlation between PM2.5 and ultrafine particle counts (r=0.5, N=83) and a low correlation between PM2.5 and CO exposure (r=0.2, N=105). The exposure assessment also revealed that the background and kerbside monitoring stations were not representative of the personal exposure of individuals to PM2.5 and CO at and around a street canyon intersection.

Pedestrian exposure to PM2.5, the loss of reflectance (‘blackness’) of the PM2.5 filters, ultrafine particle counts (particle range: 0.02–1μm) and carbon monoxide (CO) was investigated along a major road running through the DAPPLE study site in Central London, UK. During an intensive 12-day exposure measurement campaign, groups of four volunteers sampled twice in the morning and twice in the afternoon along Marylebone Road. They were randomly designated a walking direction, walking position (kerbside or buildingside) and a side of the major road to walk along. PM2.5 was sampled using high-flow gravimetric personal samplers, ultrafine particle counts were measured using TSI P-TRAKs and Langans were used to measure CO exposure. PM2.5 samples were analysed gravimetrically and reflectance was measured using a smoke stain reflectometer to obtain a measure of ‘black smoke’. In total 603 acceptable samples were obtained—155 PM2.5 and reflectance, 120 ultrafine particle count and 173 CO. The average pedestrian exposure along the road was 37.7μg/m3, 12.1m−1×10−5, 80009pt/cm3 and 1.3ppm for PM2.5, loss of reflectance, ultrafine particle counts and CO, respectively. PM2.5 exposure in the morning was significantly higher than in the afternoon, and there was a significant difference in exposure on the different sides of the road. For both reflectance and ultrafine particle counts, the exposure was significantly different both between the two walking positions on the pavement and the two sides of the street canyon. However there was no significant difference in CO exposure based on walking position, walking direction, canyon side or timing. Filter reflectance was significantly but weakly correlated with PM2.5 exposure (r=0.3, N=155), CO exposure (r=0.2, N=154) and ultrafine particle count exposure (r=0.7, N=108). PM2.5 and CO personal exposure measurements were much higher than those recorded at both the local background fixed monitoring station (FMS) and a kerbside FMS, but PM2.5 personal exposure was significantly correlated with the PM2.5 concentrations at the background FMS (r=0.6, N=155).

An increasing number of studies indicate that short-term peak exposures, such as those seen in the transport microenvironment, pose particular health threats. Short-term exposure can only be sufficiently characterised using portable, fast-response monitoring instrumentation with detailed summaries of individual activity. In this paper, we present an exposure visualisation system that addresses this issue—it allows the simultaneous presentation of mobile video imagery synchronised with measured real-time ultrafine particle count exposure of an individual. The combined data can be examined in detail for the contribution of the surrounding environment and the individual's activities to their peak and overall exposure. The exposure visualisation system is demonstrated and evaluated around the DAPPLE study site in Central London using different modes of transport (walking, cycling, bus, car and taxi). The video images, synchronised with the exposure profile, highlight the extent to which ultrafine particle exposure is associated with traffic density and proximity to pollutant source. The extremely rapid decline in concentration with increasing distance away from the pollutant source, such as from the main street to the backstreets, is clearly evident. The visualisation technique allows these data to be presented to both technical audiences and laypersons thus making it an effective environmental risk communication tool. Some exposure peaks however are not obviously associated with any event recorded on video—in these cases it will be necessary to use advanced dispersion modelling techniques to investigate meteorological conditions and other variables influencing in-street conditions to identify their possible causes.

DAPPLE (Dispersion of Air Pollution and Penetration into the Local Environment, http://www.dapple.org.uk) is a major research project that will provide the understanding necessary to assess the sustainability of urban road transport in terms of exposure to traffic-related air pollution as an alternative to current indicators based on emissions, roadside, or far-from-road air pollution levels. The methodology is described, which combines on-street and laboratory measurement with modelling of the movement of air, vehicles, and vehicle exhaust emissions. The relationship between this kind of assessment and more realistic indicators of sustainability is discussed. The value of large-scale interdisciplinary research in this area is thus demonstrated.

The Dispersion of Air Pollution and its Penetration into the Local Environment (DAPPLE) project brings together a multidisciplinary research group that is undertaking field measurements, wind tunnel modelling and computer simulations in order to provide better understanding of the physical processes affecting street and neighbourhood-scale flow of air, traffic and people, and their corresponding interactions with the dispersion of pollutants at street canyon intersections. The street canyon intersection is of interest as it provides the basic case study to demonstrate most of the factors that will apply in a wide range of urban situations. The aims of this paper are to introduce the background of the DAPPLE project, the study design and methodology for data collection, some preliminary results from the first field campaign in central London (28 April–24 May 2003) and the future for this work. Updated information and contact details are available on the web site at http://www.dapple.org.uk.

Background: Evidence for an association between exposure of pregnant women to chlorination disinfection by-products and adverse birth outcomes is inconsistent and inconclusive.Aims: To evaluate the use of a questionnaire in a population of pregnant women to assess their exposure to water, examine the validity of the questionnaire by a seven day diary, and to obtain a better understanding of the exposure of pregnant women to water in Central London.Methods: A total of 147 pregnant women were asked to complete a questionnaire. Information was requested on their exposure to water from cooking and washing up, showering and bathing, food and drink, and swimming. Demographic and socioeconomic information were also recorded. For validation purposes, women were asked to complete a seven day diary at home.Results: The average exposure duration was 338.5 min/week for cooking and washing up, 172.2 min/ week for bathing and showering, and 67.9 min/ month for swimming. The total fluid intake was 18.9 l/ week of which, on average, 18% was cold tap water; 30% of this tap water was consumed outside the home. The correlation between questionnaire and diary data was generally good to very good, although women tended to overestimate their exposure in the questionnaire compared to the diary.Conclusions: Information was obtained on the daily exposure of pregnant women in Central London to chlorinated water at home, work, and elsewhere. The questionnaire was found to be a valid method to assess the exposure of pregnant women to water and the response rate was higher than for diaries.

R.N. Colvile, S. Kaur, S. Belcher, M. Bell, R. Britter, M. Nieuwenhuijsen, A. Robins, A. Tomlin, D. Shallcross Imperial College London, Department of Environmental Science & Technology, London, UK University of Reading Department of Meteorology, Reading, UK University of Leeds Institute for Transport Studies, Leeds, UK University of Cambridge, Department of Engineering, Cambridge, UK University of Surrey, School of Mechanical Engineering, Guildford, UK University of Leeds Department of Fuel & Energy, Leeds, UK University of Bristol Department of Chemistry Bristol, UK