I don't think it is easy to predict what would happen to the pH of blood. Let me give you some help with the question I posed. To reduce oxygen to water takes four electrons, and molecular oxygen cannot ordinarily accept electrons in pairs, but only singly. Therefore, one produces the equivalent of the superoxide radical at the active site of cytochrome c oxidase. If that were to escape, it might cause mischief in the cell. Reactive oxygen species are a big topic. Here is a review to get you started:
http://www.sciencedirect.com/science/article/pii/S095528630600266XDuring normal cellular activities, various processes inside of cells produce reactive oxygen species (ROS). Some of the most common ROS are hydrogen peroxide (H2O2), superoxide ion (O2), and hydroxide radical (OH). These compounds, when present in a high enough concentration, can damage cellular proteins and lipids or form DNA adducts that may promote carcinogenic activity. The purpose of antioxidants in a physiological setting is to prevent ROS concentrations from reaching a high-enough level within a cell that damage may occur. Cellular antioxidants may be enzymatic (catalase, glutathione peroxidase, superoxide dismutase) or nonenzymatic (glutathione, thiols, some vitamins and metals, or phytochemicals such as isoflavones, polyphenols, and flavanoids).
Reactive oxygen species are a potential double-edged sword in disease prevention and promotion. Whereas generation of ROS once was viewed as detrimental to the overall health of the organism, advances in research have shown that ROS play crucial roles in normal physiological processes including response to growth factors, the immune response, and apoptotic elimination of damaged cells. Notwithstanding these beneficial functions, aberrant production or regulation of ROS activity has been demonstrated to contribute to the development of some prevalent diseases and conditions, including cancer and cardiovascular disease (CVD). The topic of antioxidant usage and ROS is currently receiving much attention because of studies linking the use of some antioxidants with increased mortality in primarily higher-risk populations and the lack of strong efficacy data for protection against cancer and heart disease, at least in populations with adequate baseline dietary consumption.
In normal physiological processes, antioxidants effect signal transduction and regulation of proliferation and the immune response. Reactive oxygen species have been linked to cancer and CVD, and antioxidants have been considered promising therapy for prevention and treatment of these diseases, especially given the tantalizing links observed between diets high in fruits and vegetables (and presumably antioxidants) and decreased risks for cancer.