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Formation of Reactive Oxygen Species in Heated Cooking Oil Fumes and Real Cooking Emissions
LU LU, Vanessa Yan Zi Ng, Zheng Hao Melvyn Tan, Yue Qian Tan, Wei Jie Seow, Alex Lee, National University of Singapore
Abstract Number: 336
Working Group: Aerosol Chemistry
Abstract
Numerous studies have reported that the risk of lung cancer in people who never smoke is significantly associated with the exposure to cooking emissions, which is one of the major particulate sources in both indoor and outdoor environments. Studies have reported that cooking organic aerosols have the potential to generate reactive oxygen species (ROS, e.g., organic peroxides). The major component emitted from cooking is fatty acids with different degrees of unsaturation. Those unsaturated fatty acids have been shown to generate ROS through an oxidation process in the atmosphere, which may damage cell DNA and proteins and eventually lead to lung cancer.
In this study, we quantified water-soluble fraction of particle-bound ROS on per carbon basis (WS-ROS/C) using a 2’,7’-dichlorofluorescin (DCFH) fluorescence probe from cooking emissions in Singapore hawker centres, which are statistically higher than those observed in office spaces, lab-generated secondary organic aerosols, and diesel engine emissions. In particular, stir frying, a popular Chinese cooking style, can generate more WS-ROS/C than other cooking styles, such as deep frying, steaming and boiling. To evaluate what we observed from real cooking emissions, we investigated the formation of WS-ROS in fresh and aged lab-generated heated cooking oil fumes. The WS-ROS/C of fresh heated oil emissions is in the lower range of the real cooking emissions. In general, the WS-ROS/C increased continuously along with 3-days aging experiments, depending on ozone exposure levels and degree of unsaturation of cooking oils. Our observations indicate that the enhancement of WS-ROS/C in organic particles generated by poly- and mono-unsaturated fatty acids dominant cooking oils are more sensitive to low (~5 ppb) and high (~100 ppb) ozone concentrations under dark condition, respectively. Dark ozonolysis of real cooking emissions were also investigated in order to better understand ROS formation potential of cooking-related emissions in typical urban environments.