Car users exposure to particulate matter and gaseous air pollutants in megacity Cairo

Cars are a dominant mode of transport in megacity Cairo, yet there is a scarcity of personal exposure data on air pollution. This is the first car users exposure study that investigates the underlying factors affecting particulate matter (PM); with aerodynamic diameter ≤2.5 μm (PM2.5) and ≤10 μm (PM10), nitrogen oxides (NO2) and carbon monoxide (CO) concentrations across Greater Cairo. Data is collected using a portable monitor during morning and evening peak hours for three car settings (open window; closed window; AC On). Open window consistently resulted in highest PM10 and PM2.5 concentrations (65 % and 48 % higher than AC On). However, most Cairo commuters do not have AC and are exposed to levels of PM10 and PM2.5 as high as 227 and 119 μg/m3. Evening peak hours experience higher pollution compared to morning peak. Zones with construction activities have 64 % higher PM10 concentrations. PM2.5 concentrations in cross-city routes are 3.6-times those in high-activity zones. The derived PM2.5/PM10 ratios are relatively low (