Excess Oxygen isn't As Benign as Scientists Thought

We typically perceive oxygen as harmless, even the source of Life, but hyperoxia shows there is such a thing as breathing too much oxygen

Hiya!

Like many people, I thought oxygen is harmless. After all, it’s everywhere, and most living things on Earth utilize it. But then I saw a post on Reddit a while back that made me look at oxygen from a new perspective. It was a clip of a thread someone started by posing the question:

“What if oxygen is poisonous, and it just takes 75 to 100 years to kill us?”

Remarkably, some commenters said it’s true, so I did a little research and learned that, sure enough, oxygen isn’t as benign as I thought. We all know that too little oxygen hurts us and can even kill us, but now researchers are learning that receiving too much oxygen is also dangerous.

Hyperoxia

You’ve heard of hypoxia — It’s a fancy word for what happens when we receive less oxygen than our body requires. It causes symptoms like bluish skin, cognitive confusion, difficulty breathing, restlessness, rapid heart rate, and even death — aka suffocation.

Hypoxia is well known because it has affected our species — and countless others — probably for as long as we’ve depended on oxygen to survive. Air, like water, is synonymous with Life — and both contain oxygen. Maybe that’s why it was long thought that a person couldn’t have too much oxygen. But oxygen requirements are a spectrum, just like everything else in Life.

On the opposite side of the spectrum from hypoxia is hyperoxia, which occurs when we receive too much oxygen. Earth’s atmosphere is only 21 percent oxygen, and breathing air that contains higher levels of oxygen than that can result in hyperoxia, also known as oxygen toxicity, which can cause seizures, organ damage, and even death.

Understandably, hypoxia is more common, and scientists know a lot more about its effects on our tissues and cells than the effects of hyperoxia. Only a handful of situations result in a person breathing too much oxygen, which typically involves oxygen tanks, like while scuba diving or during a medical situation. So, understanding it was considered less urgent, and it remains understudied.

Alan Baik, a cardiologist at UC San Francisco (UCSF) and an assistant professor of biochemistry at UCSF, explained to Sarah C.P. Williams of Gladstone Institute that:

“For many years, the medical teaching was that, to a certain degree, more oxygen was better, or at least benign, when treating patients with conditions such as heart attacks. But there has now been a growing number of clinical studies showing that excess oxygen actually leads to worse outcomes. This motivated us to better understand why excess oxygen can be toxic.”

Baik is part of a team of Gladstone Institute scientists led by Gladstone Assistant Investigator Isha Jain, PhD, that has achieved precisely that with two studies published just months apart.

Study #1