Exposure of cyclists to ultra fine particles

We present results from the Belgian SHAPES project, a policy oriented research project in which all major cycling related health risks are evaluated in an objective way. In this paper we present a methodology to estimate the exposure of ultra fine particulate matter (UFP numbers) to cyclists and results of measurements performed while cycling in real traffic. Methodology validation trials indicate that measured concentrations of UFP are independent of sampling direction (relative to cycling direction) and sampling height (between 0.9 and 1.6 m). Cyclists are exposed to frequent but short bursts of UFP, associated with motorized vehicles, even when cycling on the upwind side of the road. Concentrations range from below 10,000 to 500,000 cm−3. Peaks are related to the exhaust emissions of specific vehicles. UFP numbers quickly decrease with increasing distance from the road (approximately –6% m−1). There was no evidence for an effect of wind direction and dispersion at short range seems to be caused primarily by turbulence. Using this new methodology SHAPES will be able to determine the dose of UFP inhaled by cyclists compared to car users