Assessment of road users’ elemental carbon personal exposure levels, London, UK

Abstract

Little is known about particulate elemental carbon (EC) personal exposure levels, a key component of diesel exhaust, specifically in transport microenvironments. A method utilizing the optical properties of EC particles has been applied to personal exposure measurement filter samples. In a series of field studies carried out in London, UK, during 1999–2000 over 400 fine particle (PM 2.5) personal exposure level measurements were taken for journeys in bicycle, bus, car and underground rail transport microenvironments, along three main fixed routes. The particulate EC contribution to the PM 2.5 personal exposure was assessed indirectly by means of an optical technique and with the development and use of a size fraction specific and site-specific calibration curve. In this first EC personal exposure study of transport users geometric mean exposure levels in the summer field campaign were 11.2 μg m −3 (GSD=2.7) for cyclists, 13.6 μg m −3 (GSD=1.9) for bus passengers and 21.6 μg m −3 (GSD=2.1) for car drivers; corresponding exposure levels in the winter were 16.4 μg m −3 (GSD=1.8), 18.6 μg m −3 (GSD=2.3) and 27.3 μg m −3 (GSD=2.0), respectively. EC/PM 2.5 ratios were approximately 0.5–0.6 for bicycle and bus modes and 0.7–0.8 for the car mode. EC/PM 2.5 ratios for different routes ranged from approximately 0.7 for Route 1 to 0.4 for Route 3. Cyclists had the lowest exposure to EC, and car occupants the highest exposure. A large difference in exposure levels between a central high traffic density route and the other less central routes was observed. Particulate EC was a very significant proportion of the total PM 2.5 personal exposure and EC personal exposure levels were considerably higher than reported fixed site monitor EC concentrations.