Particle-bound reactive oxygen species in cooking emissions: Aging effects and cytotoxicity

Oil-based cooking (such as stir-and deep-frying) are large sources of particulate unsaturated fatty acids that can be further oxidized to form peroxidic products, a group of reactive oxygen species (ROS). Deposition of ROS on respiratory system can lead to adverse health impacts. In this work, we quantified the particle-bound ROS (PBROS), primarily peroxide species, in aqueous extracts of real cooking emissions at food stalls in Singapore. Stir frying has the highest potential to emit PB-ROS as compared to other cooking methods being investigated in this work. The PB-ROS contents in stir-frying emission can be comparable to those in secondary organic aerosol (SOA), which has been recognized as a potential large source of ambient PB-ROS. This work also demonstrates the complex effects of atmospheric processing. The PB-ROS contents in some stir-and deep-frying emissions with low initial values could increase by a factor of 2 or higher after dark ozonolysis at-100 ppb for 3 days, whereas substantial reduction of PB-ROS were observed for stir-frying emissions with high initial values regardless of ozone concentrations. The observations from the aging of laboratory-generated heated cooking oil droplets suggest that the bulk oil compositions, in particularly the fraction contribution of polyunsaturated fatty acids in cooking oils, and heating temperature can play an important role in affecting the degree of unsaturation (DoU) of fresh oil droplets and the subsequent production of PB-ROS during the aging process. The changes in cell viability and cellular ROS concentrations due to exposure of heated cooking oil droplet extracts indicate the possible relationship between the observed cytotoxicity and PB-ROS content, highlighting the potential impacts of inhaling cooking fumes on cellular ROS production and interconversion.