IMPACT OF INDOOR HOUSHOLD ACTIVITIES ON THE SIZE DISTRIBUTION OF FINE AEROSOL NUMBER CONCENTRATION AND CASE SPECIFIC CALCULATED INHALED DOSE K. ELEFTHERIADIS 1 , S. VRATOLIS 1 , C. MITSAKOU 1,2 , I. COLBECK 3 C. HOUSIADAS 1 and M. LAZARIDIS 4 1 Institute of Nuclear Techn.-Radiation Protection, National Center for Scientific Research “Demokritos”, 15310 Ag. Paraskevi, Greece 2 Division of Applied Physics, Depart. of Physics, University of Athens, Building PHYS-5, University Campus, 157 84 Athens, Greece 3 Depart. of Biological Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, UK 4 Technical University of Crete, Department of Environmental Engineering, 73100 Chania, Greece Keywords: Indoor aerosol, number size distribution, household activity, inhaled dose. INTRODUCTION Indoor exposure of humans to fine particulate matter (< 1 µm) depends on a number of key parameters and processes. The most important are the indoor aerosol sources and sinks, the infiltrating outdoor aerosol, the ventilation rate and the indoor surface to volume ratio. Indoor aerosol concentration also depends on aerosol dynamics with respect to size and distribution moment of interest. Measurements performed in Athens, Greece for the characterisation of aerosol indoor exposure in typical residences have yielded a number of examples of fine aerosol number size distributions resulting during common household practices (cooking, vaccum cleaning) or occasions of little activity in the house (sleeping, unoccupied house). The results are compared to the equivalent outdoor number concentrations. In addition the inhaled dose in terms of number concentration is presented for two selected cases. INSTRUMENTATION AND METHODS The size resolved aerosol number concentration was obtained at five minutes intervals using a Scanning mobility particle sizer for the fine fraction expressed in mobility diameter (SMPS, DMA model 3071 and CPC 3022A, TSI Inc., USA). The size range measured varied between experiments due to changes in the sampling line configurations and was predominantly in the range 10-350 nm. Sampling of indoor and outdoor air was performed on a 15-minute cycle with 3 measurements per cycle. Other instruments for measurements of gaseous and aerosols parameters were also deployed and preliminary results have been already presented (Eleftheriadis et al., 2003). The respiratory deposition calculations were performed with an advanced numerical model, which solves the general dynamic equation in all generations of the respiratory tract, including inhalation dynamics (Mitsakou and Housiadas, 2003). For the present calculations, standard morphometric and physiological data for an adult male were used (ICRP, 1994). RESULTS AND DISCUSSION During the course of the study houshold activities were recorded in detail. The main indoor aerosol source was cooking, while other activities expected to have an effect on the particle size distribution and indoor concentration included vacuum cleaning, use of air-condition, opening doors/windows. Figure 1 displays two examples of the number size distribution normalised with respect to total number concentration (N t ) for the cases of cooking and vaccum cleaning. The outdoors size distribution is also displayed. Cooking produces number concentrations around one order of magnitude higher than usually observed, when the infiltrating outdoor aerosol is the main source. The event of vaccum cleaning took place after a period of airing the room by opening the window. In such cases the concentration indoors is found in general to be lower than Abstracts of the European Aerosol Conference 2004 S849