Be Aware of the Indoor Air. Physicochemical Characterization of Airborne Fine Particles in Occupied Homes : Physicochemical Characterization of Airborne Fine Particles in Occupied Homes

Negative health effects of exposure to particles of outdoor origin have been confirmed by epidemiological studies. In developed countries, we spend on average 65% of our time in our homes. Thus, the properties of airborne particles indoors need to be understood. The aim of this PhD thesis was to investigate the differences in physicochemical and toxicological characteristics of fine particles (PM2.5) inside and outside occupied homes, as well as to understand the contribution of indoor sources to exposure indoors. The effects of energy renovation and of the occupants' activities on indoor concentrations were assessed.Indoor and outdoor differences in physicochemical and toxicological characteristics of PM2.5 were studied in 15 homes in urban and rural areas of southern Sweden. PM2.5 characterization was performed with online state-of-the-art techniques, simpler portable instruments, and with offline methods. The occupants’ self-reported activities were used to identify the contribution of indoor sources and for interpretation of the results. Measurements in homes were supported by a laboratory study focused on the characterization of particle emissions from candles under stressed burning conditions. An in-vivo toxicity study in mice was performed to assess the differences in toxicological properties of PM2.5 collected indoors and outdoors by evaluating inflammation in bronchoalveolar lavage cells. To understand if the energy renovation affect particle concentrations, measurements were performed inside and outside of seven occupied apartments over three consecutive years, before renovation, after renovation and at a follow-up. High number of ultrafine particles (UFP) were observed mainly due to the presence of indoor sources such as cooking, and candle burning in homes. Some of the indoor sources additionally contributed to elevated PM2.5 and black carbon (eBC) mass concentrations. In one apartment, a detailed online characterization using a mass spectrometric technique