Oxidative potential of PM2.5 and PM10 in an urban background site in Lecce: influence of combustion sources and Saharan dust advection

Exposure to atmospheric particulate matter (PM) leads to adverse health effects and the exact mechanisms of toxicity are still not completely understood. Recent studies suggested that a large number of PM health effects could be due to the oxidative potential (OP) of ambient particles leading to high concentrations of reactive oxygen species (ROS). However, information about the OP of natural sources are scarce and no data is available regarding the OP during Saharan dust outbreaks (SDO) in Mediterranean regions. This work uses the a-cellular DTT (dithiothreitol) assay to evaluate OP of the water-soluble fraction of PM2.5 and PM10 collected at an urban background site in Southern Italy. DTT activity normalised by sampled air volume (DTTV), representative of personal exposure, and normalised by collected aerosol mass (DTTM), representing source-specific characteristics, were investigated. DTTV was larger for high carbon content samples but during SDO events was statistically comparable with that of samples representative of typical conditions for this area. DTTM was larger for PM2.5 compared to PM10 and the relative difference between the two size fractions was maximised during SDO events. This suggests that Saharan dust is a natural source of particles with low OP and that DTTV could be a useful indicator in epidemiological studies, especially in regions frequently affected by Saharan dust advection.