10th International Aerosol Conference
September 2 - September 7, 2018
America's Center Convention Complex
St. Louis, Missouri, USA

Abstract View


Global Long-range Transport and Lung Cancer Risk of Polycyclic Aromatic Hydrocarbons Shielded by Viscous Secondary Organic Aerosols

MANISHKUMAR SHRIVASTAVA, Sijia Lou, Alla Zelenyuk, Richard Easter, Richard Corley, Brian Thrall, Philip Rasch, Jerome Fast, Staci L. Simonich, Huizhong Shen, Shu Tao, Pacific Northwest National Laboratory

     Abstract Number: 898
     Working Group: Aerosols and Health - Connecting the Dots

Abstract
Polycyclic aromatic hydrocarbons (PAHs) have toxic impacts on humans and ecosystems. One of the most carcinogenic PAHs, benzo (a) pyrene (BaP), is efficiently partitioned to and transported with atmospheric particles. Laboratory measurements show that adsorbed BaP degrades in a few hours by heterogeneous reaction with ozone, yet field observations indicate BaP persists much longer in the atmosphere, and some previous chemical-transport modeling studies have ignored heterogeneous oxidation of BaP to bring model predictions into better agreement with field observations. We attribute this unexplained discrepancy to the shielding of BaP from oxidation by coatings of viscous organic aerosol (OA). Accounting for this OA viscosity-dependent shielding, which varies with temperature and humidity, in a global climate/chemistry model brings model predictions into much better agreement with BaP measurements, and demonstrates stronger long-range transport, greater deposition fluxes, and substantially elevated lung-cancer risk from PAHs. Model results indicate that the OA coating is more effective in shielding BaP in the mid/high latitudes compared to the tropics because of differences in OA properties (semi-solid when cool/dry vs. liquid-like when warm/humid). Faster chemical degradation of BaP in the tropics leads to higher concentrations of BaP oxidation products over the tropics compared to higher latitudes. This study has profound implications demonstrating that OA strongly modulates the atmospheric persistence of PAHs and their cancer risks.