Indoor and outdoor PM concenctration at a residential environment, in the Athens area

The aim of the present work was to study exposure to PM in the indoor and outdoor
microenvironment of a typical residence in the center of Athens. Simultaneous indoor and
outdoor measurements of PM10 and PM2.5 were conducted, by the use of gravimetric and
continuous samples, during October and November 2006. Moreover, air exchange rate was
monitored continuously during the entire measurement period.
The indoor and outdoor concentration levels were significant for both size fractions. Mean
daily PM10 outdoor concentrations exceeded the E.U. 24-hr limit value for 84 % of the
measured days, while the respective PM2.5 concentrations exceeded the 24-hr limit value set
by the C.A.F.E. working group for 69 % of the measured days. PM10 and PM2.5 concentrations
exhibited increased short-term variability with high peak concentrations during morning and
afternoon/night rush hours.
Indoor concentration levels seem to be mainly affected by PM of outdoor origin, since the
calculated indoor-to-outdoor concentrations ratios (I/O) were much lower than 1.00 during all
days and indoor and outdoor concentrations were highly correlated. This finding was also
supported by the pattern of their diurnal cycles, which followed the outdoor ones, with a delay
of approximately 1 hr.
The results indicate increased PM concentration levels in the center of Athens, even in indoor
microenvironments with no significant indoor sources and emphasize the need for a more
extensive investigation of the Athens population exposure, for the protection of public health.