Ozone Generation Method Impacts Lung Toxicity and Oxidant Signaling.

Ozone (O3) is a criteria pollutant that is anticipated to rise over the next decade due to climate-related activity. Varying amounts of nitrogen oxides (NOx) are produced as by-products during O3 generation from oxygen depending on the method of production including the source and oxygen purity. A review of the current literature confirms a lack of consistent monitoring and reporting of potential nitrogen species produced with different methods of experimental O3 generation. The lack of consistent monitoring and reporting is potentially a factor that can explain divergence of reported experimental O3 exposure outcomes from different research groups. In the present report, we compare the effects of O3 source generation from either filtered air (FA-ozone) or a pure oxygen (Oxy-ozone) source on NOx generation and measures of O3-induced lung injury. We also consider if this also impacts mixed exposures with O3 and ultrafine carbon black (CB) based on if the O3 was generated from a filtered air (FA-ozone-CB) versus a pure oxygen (Oxy-ozone-CB) source. Comparing FA-ozone vs. Oxy-ozone we observed increased lung inflammation and injury in the FA-ozone group. In the FA-ozone-CB group, compared to the Oxy-ozone-CB group, the FA-ozone-CB inhalation exposure resulted in the formation of a greater amount of NOx and induced protein nitrotyrosine in the lungs. Moreover, the FA-ozone-CB group had evidence of eosinophil recruitment not observed in the Oxy-ozone-CB group. Overall, this suggests that the source of oxygen for O3 generation impacts experimental outcomes. Furthermore, measurement and reporting of nitrogen species in O3 exposure should be considered.