Large uncertainties exist in the methods determining the exposure of urban residents to atmospheric particles, thus making assessments of negative health effects, and eventual policy regulations questionable. The first uncertainty refers to the different health-related particle properties that may occur in an urban atmosphere, the second to the spatial and temporal variability of these properties. Aspects of spatial variability include both, variations within a city area, and between indoor and outdoor environments. These issues are scarcely understood, and have therefore prevented more efficient and sustainable particle monitoring strategies to be implemented in legislation. Currently, most particle exposure information is drawn from single point measurements of integrating mass based metrics (TSP, PM10, PM2.5) which allows only a crude characterisation of the health-related particle exposure and risks.
First, specially designed physical and chemical field measurements will be carried out to understand the difference between exposure in indoor and outdoor environments. The relevance is evident since urban residents spend up to 90 % of their time indoors.
Second, statistical investigations of both, high resolution time series, and spatially measured particle data will be used to characterise the fluctuations and variability of health-related particles properties in the urban atmosphere.
Third, the collection of an extended set of particle metrics in a panel health study will allow to determine which particle metrics are related with short term health effects in a susceptible sub-population. The combination of these analyses with known, toxic particle effects will provide guidelines for future exposure monitoring, in particular, about the particle properties to be measured, and the requirements for the measurement sites.