Indoor and outdoor particulate matter concentrations at schools in the Athens area

Simultaneous indoor and outdoor PM10 and PM2.5 concentration measurements were conducted in seven primary schools in the Athens area during the winter of 2003-04 and 2004-05. The measurements were performed during school hours with the use of Harvard PEMs. Indoor PM10 and PM2.5 concentrations were also monitored continuously by a DustTrak monitor. Mean PM10 concentration was 236.13 mu g center dot m(-3) indoors and 162.89 mu g center dot m(-3) outdoors. The corresponding mean values for PM2.5 were 82.65 mu g center dot m(-3) indoors and 56.25 mu g center dot m(-3) outdoors. Indoor/Outdoor (I/O) ratios were close or above 1.00 at almost all sites. Indoor PM levels were greatly influenced by the presence of people and intensity of indoor activities. Moreover, PM concentrations exhibited significant short-term variability, underlying the need to include short-term measurements in children's exposure studies.