Description: Atmosphere, Vol. 9, Pages 368: Particle-Bound Polycyclic Aromatic Hydrocarbon in the Atmosphere of Heavy Traffic Areas in Greater Cairo, Egypt: Status, Source, and Human Health Risk Assessment Atmosphere doi: 10.3390/atmos9100368 Authors: Salwa Kamal Hassan Airborne particulate samples were collected from three main squares (Ramsis, El Giza, and Sphinx) representing heavy traffic areas in Greater Cairo during the period of December 2015–February 2016, and analysed for polycyclic aromatic hydrocarbon (PAHs). The maximum concentrations of particle-bound PAHs were observed at El Giza, while the minimum levels were recorded at Sphinx. The levels of particle-bound PAHs in the square areas of Greater Cairo are higher than those found in many different locations in Egypt and around the world.The distribution of individual particle-bound PAHs as well as PAH categories, depending on the ring number in Ramsis, El Giza, and Sphinx, wasquite similar. This similarity implies similar emission sources of PAHs in the three square areas, with vehicle exhaust emissions being the dominant one. Benzo[b]fluoranthene (BbF), benzo[ghi]perylene (BGP), and indeno[1,2,3-cd]pyrene(IND) were the most abundant PAH compounds. Diagnostic concentration ratios of PAH compounds in the three square locations suggest that both petrogenic and pyrogenic sources emit these compounds. Moreover, they originate mainly from traffic emissions in the study areas. Based on the calculated benzo[a]pyrene equivalent (BaPeq) for the individual particle-bound PAH compounds, health risks associated with the inhalation of these compounds were assessed. Total carcinogenic activity (TCA) for all measured PAHs represented 20.03% (El Giza), 20.40% (Ramsis), and 20.60% (Sphinx) of the total PAH concentrations. Benzo[a]pyrene (BaP) and dibenz[a,h]anthracene (DBA) were the highest contributors to the total health risks; these accounted for 42.72% and 38.50% (El Giza), 41.79% and 39.17% (Ramsis), and 42.92% and 37.78% (Sphinx) of the TCA of all PAH compounds, respectively. These results indicate the importance of BaP and DBA as surrogate compounds for PAHs in the atmosphere of square areas of Greater Cairo.