Fine particle (PM2.5) personal exposure levels in transport microenvironments, London, UK

In order to investigate a specific area of short-term, non-occupational, hu man exposure to fine particulate air pollution, measurements of personal ex posure to PM2.5 in transport microenvironments were taken in two separate f ield studies in central London, UK. A high flow gravimetric personal sampli ng system was used, operating at 161 min(-1); the sampler thus allowed for sufficient sample mass collection for accurate gravimetric analysis of shor t-term travel exposure levels over typical single commute times. In total., samples were taken on 465 journeys and 61 volunteers participated. In a mu lti-transport mode study, carried out over 3-week periods in the winter and in the summer, exposure levels were assessed along three fixed routes at p eak and off-peak times of the day. Geometric means of personal exposure lev els were 34.5 mug m(-3) (G.S.D. = 1.7. n(s) = 40), 39.0 mug m(-3) (G.S.D. = 1.8, n(s) = 36) 37.7 mug m(-3) (G.S.D. = 1.5. n(s) = 42). and 247.2 mug m( -3) (G.S.D. = 1.3, n(s) 44) for bicycle, bus, car and Tube (underground rai l system) modes, respectively, in the July 1999 (summer) measurement campai gn. Corresponding levels in the February 2000 (winter) measurement campaign were 23.5 mug m(-3) (G.S.D. 1.8, n(s) 56), 38.9 mug m(-3) (G.S.D. 2.1, n(s ) = 32), 33.7 mug m(-3) (G.S.D. = 2.4, n(s) = 12), and 157.3 mug m(-3) (G.S .D 3.3, n(s) 12), respectively. In a second study, exposure levels were mea sured for a group of 24 commuters travelling by bicycle, during August 1999 , in order to assess how representative the fixed route studies were to a l arger commuter population. The geometric mean exposure level was 34.2 mug m (-3) (G.S.D. = 1.9, n(s) = 105). In the fixed-route study, the cyclists had the lowest exposure levels, bus and car were slightly higher, while mean e xposure levels on the London Underground rail system were 3-8 times higher than the surface transport modes. There was significant between-route varia tion, most notably between the central route and the other routes. The fixe d-route study exposure was similar in level and in variability to the 'real ' commuters study, suggesting that the routes chosen and the number of samp les taken provided a reasonably good estimate of the personal exposure leve ls in the transport microenvironments of Central London, This first compreh ensive PM2.5 multi-mode transport user exposure assessment study in the UK also showed that mean personal exposure levels in road transport modes were approximately double that of the PM2.5 concentration at an urban backgroun d fixed site monitor. (C) 2001 Elsevier Science B.V. All rights reserved.