Does Room Air Oxygen Cause Lung Cancer?

Your Question: You mentioned in your post "What is oxidative stress?" that inside the body oxygen breaks down into single molecules with unpaired electrons. They in turn become free radicals. Surely these free radicals can be neutralized with antioxidants. But you wrote that oxidative stress may cause lung cancer. So, does oxygen itself cause lung cancer?

My answer. To answer your question, under normal circumstances, oxygen by itself does not cause cancer. As it turns into free radicals, there are plenty of antioxidants available to neutralize it. So, under normal circumstances, the 21% oxygen in room air will not increase your risk for developing oxidative stress nor increase your risk for lung cancer.

However, inhaling supplemental oxygen can increase your risk of overwhelming antioxidants. In these situations, the risk of oxidative stress is increased along with the cancer risk. Things that might cause oxidative stress like this are abnormal circumstances, such as inhaling supplemental oxygen long-term or inhaling high doses of oxygen short-term. Certain disease processes (such as COPD) can cause it. Aging may change your internal environment in such a way as to cause oxidative stress.

So, to answer your question, inhaling room air oxygen should not increase your risk for developing cancer. And, I would surmise, as more is learned on this, only people with certain genetic predispositions at risk for developing cancers even in the presence of oxidative stress. So, there is so little known about this at the present time. It will be neat to see what researchers learn in the coming years.

References.

1. Reuter, et al., "Oxidative stress, inflammation, cancer: How are they linked?" Free Radical Biology & Medicine, 2011, December 1, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2990475/, accessed 8/19/19