Inflammatory responses to secondary organic aerosols (SOA) generated from biogenic and anthropogenic precursors
Wing Y. Tuet1, Yunle Chen2, Shierly Fok1, Julie A. Champion1, and Nga L. Ng1,31School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 2School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 3School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA
Received: 20 Mar 2017 – Accepted for review: 27 Mar 2017 – Discussion started: 28 Mar 2017
Abstract. Cardiopulmonary health implications resulting from exposure to secondary organic aerosols (SOA), which comprise a significant fraction of ambient particulate matter (PM), have received increasing interest in recent years. In this study, alveolar macrophages were exposed to SOA generated from the photooxidation of biogenic and anthropogenic precursors (isoprene, α-pinene, β-caryophyllene, pentadecane, m-xylene, and naphthalene) under different formation conditions (RO2 + HO2 vs. RO2 + NO dominant, dry vs. humid). Various cellular responses were measured, including reactive oxygen/nitrogen species (ROS/RNS) production and secreted levels of cytokines, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). SOA precursor identity and formation condition affected all measured responses in a hydrocarbon-specific manner. With the exception of naphthalene SOA, cellular responses followed a trend where TNF-α levels reached a plateau with increasing IL-6 levels. ROS/RNS levels were consistent with relative levels of TNF-α and IL-6, due to their respective inflammatory and anti-inflammatory effects. Exposure to naphthalene SOA, whose aromatic ring-containing products may trigger different cellular pathways, induced higher levels of TNF-α and ROS/RNS than suggested by the trend. Distinct cellular response patterns were identified for hydrocarbons whose photooxidation products shared similar chemical functionalities and structures, which suggests that the carbon backbone may be important for determining cellular effects. A positive nonlinear correlation was also detected between ROS/RNS levels and previously measured DTT activities for SOA samples. In the context of ambient samples collected during summer and winter in the greater Atlanta area, all laboratory-generated SOA produced similar or higher levels of ROS/RNS and DTT activities. These results suggest that the health effects of SOA are important considerations for understanding the health implications of ambient aerosols.
Tuet, W. Y., Chen, Y., Fok, S., Champion, J. A., and Ng, N. L.: Inflammatory responses to secondary organic aerosols (SOA) generated from biogenic and anthropogenic precursors, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2017-262, in review, 2017.