Hydroxyl Radical Production by Air Pollutants in Epithelial Lining Fluid Governed by Interconversion and Scavenging of Reactive Oxygen Species

Abstract

Air pollution is a major risk factor for human health. Chemical reactions in the epithelial lining fluid (ELF) of the human respiratory tract result in the formation of reactive oxygen species (ROS), which can lead to oxidative stress and adverse health effects. We use kinetic modeling to quantify the effects of fine particulate matter (PM2.5), ozone (O 3 ), and nitrogen dioxide (NO 2 ) on ROS formation, interconversion, and reactivity, and discuss different chemical metrics for oxidative stress, such as cumulative production of ROS and hydrogen peroxide (H 2 O 2 ) to hydroxyl radical (OH) conversion. All three air pollutants produce ROS that accumulate in the ELF as H 2 O 2 , which serves as reservoir for radical species. At low PM2.5 concentrations (<10 μg m −3 ), we find that less than 4% of all produced H 2 O 2 is converted into highly reactive OH, while the rest is intercepted by antioxidants and enzymes that serve as ROS buffering agents. At elevated PM2.5 concentrations (>10 μg m −3 ), however, Fenton chemistry overwhelms the ROS buffering effect and leads to a tipping point in H 2 O 2 fate, causing a strong nonlinear increase in OH production. This shift in ROS chemistry and the enhanced OH production provide a tentative mechanistic explanation for how the inhalation of PM2.5 induces oxidative stress and adverse health effects.

Ozonolysis of Oleic Acid Aerosol Revisited: Multiphase Chemical Kinetics and Reaction Mechanisms

“…The ozonolysis of alkenes is not only important for atmospheric chemistry but also for human health . Cell membranes and the lipid layer on top of the epithelial lining fluid contain unsaturated compounds and are exposed to ozone. − This study and other recent studies , point toward a large amount of reactive intermediates and radicals generated in alkene ozonolysis which might give rise to lipid peroxidation and in vivo production of hazardous reactive (oxygen) species. Thus, due to the wealth of data that are already available for oleic acid ozonolysis, it is a particularly useful reaction system to use in conjunction with kinetic modeling and draw conclusions regarding health effects of air pollution.…”

Stability of Terpenoid-Derived Secondary Ozonides in Aqueous Organic Media

“…The environmental implication is that inhalation of aerosols containing SOZs and transition metal ions may induce oxidation of antioxidants in the epithelial lining fluid. 6 , 57 This would result in disruption of the redox balance of the human respiration system. Furthermore, the present demonstration that terpenoid-derived SOZs can be stable in the aqueous phase hints at the potential use of rationally designed SOZs as antibacterial drugs.…”

Star fruit extract and C-glycosylated flavonoid components have potential to prevent air pollutant-induced skin inflammation and premature aging

“…3 A), which is attributable to the oxidizing action arising from the redox-active components nitrogen dioxide, sulfur dioxide, ozone, etc. in GEEG [ 24 , 25 ]. In the subsequent anti-GEEG activity evaluation by pretreating SC with the test samples, we found that SFE was also active against GEEG-induced protein carbonylation in the SC (Fig.…”