Indoor particulate matter in urban residences of Alexandria, Egypt

Indoor particulate matter samples were collected in 17 homes in an urban area in Alexandria during the summer season. During air measurement in all selected homes, parallel outdoor air samples were taken in the balconies of the domestic residences. It was found that the mean indoor PM2.5 and PM10 (particulate matter with an aerodynamic diameter 2.5 and 10 m, respectively) concentrations were 53.5 +/- 15.2 and 77.2 +/- 15.1 mu g/m(3), respectively. The corresponding mean outdoor levels were 66.2 +/- 16.5 and 123.8 +/- 32.1 mu g/m(3), respectively. PM2.5 concentrations accounted, on average, for 68.8 +/- 12.8% of the total PM10 concentrations indoors, whereas PM2.5 contributed to 53.7 +/- 4.9% of the total outdoor PM10 concentrations. The median indoor/outdoor mass concentration (I/O) ratios were 0.81 (range: 0.43-1.45) and 0.65 (range: 0.4-1.07) for PM2.5 and PM10, respectively. Only four homes were found with I/O ratios above 1, indicating significant contribution from indoor sources. Poor correlation was seen between the indoor PM10 and PM2.5 levels and the corresponding outdoor concentrations. PM10 levels were significantly correlated with PM2.5 loadings indoors and outdoors and this might be related to PM10 and PM2.5 originating from similar particulate matter emission sources. Smoking, cooking using gas stoves, and cleaning were the major indoor sources contributed to elevated indoor levels of PM10 and PM2.5. Implications: The current study presents results of the first PM2.5 and PM10 study in homes located in the city of Alexandria, Egypt. Scarce data are available on indoor air quality in Egypt. Poor correlation was seen between the indoor and outdoor particulate matter concentrations. Indoor sources such as smoking, cooking, and cleaning were found to be the major contributors to elevated indoor levels of PM10 and PM2.5.