Final answer:
Excessive oxygen exposure may cause toxicity, free radicals, and coma but does not typically lead to increased mental function.
Step-by-step explanation:
Breathing excessively high concentrations of oxygen for a long period can lead to several health issues. Among the possible consequences, oxygen toxicity, the production of large amounts of free radicals, and coma are notable side effects; however, increased mental function is not typically associated with high oxygen concentration exposure and could in fact be impaired. While the body needs oxygen to maintain energy homeostasis, there is a very narrow range of environmental oxygen tolerance, with both deprivation and excess being harmful.