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

Abstract

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 (<0.5) indicating a dominance of coarse particles fraction. AC On resulted in lowest average concentrations of NO2 and highest CO levels. This study provides preliminary air pollutants exposure mapping for car commuters that aims to feed into control strategies.