Pro-oxidants can originate from both endogenous and exogenous sources. Endogenously, they are generated as by-products of normal metabolic processes, such as mitochondrial respiration. Exogenously, they can be introduced through environmental pollutants, tobacco smoke, radiation, industrial chemicals, and certain pharmaceuticals. Diet can also be a source, including iron and copper, which can catalyze the formation of ROS through the Fenton reaction.
