Is oxygen toxic/poisonous?


I read somewhere that oxygen is, in fact, poisonous, and it “oxidises” your cells, burning you slowly, which is why anti-oxidants are important.

Is there any truth to this?


p.s. not a debate or anything, just want info on the negative/positive effects of oxygen on organic matter and properties of oxygen

p.p.s will this go in chemistry or biology???

In: Chemistry

2 things here: Is oxygen toxic, and what are antioxidants?

Everything is toxic/poisonous to something at some amount.

Oxygen is not toxic to mammals at our atmospheric amount. 100% is toxic to humans, but not immediately. Our lungs like the amount of oxygen in the air, but they can function with different amounts. It takes time for our lungs to be saturated and do harm. People do breathe 100% in certain situations.

Now, the act of using oxygen, our fuel, does cause free radicals. Free radicals are what is harmful. Using anything would produce free radicals, so there is no way around that. Antioxidants protect against free radicals.

We need oxygen to live, but oxygen being very reactive has the side effect that it also sometimes oxidizes things it isn’t supposed to. This is where anti-oxidants come in: Your body has a few different mechanisms to prevent oxygen/reactive oxygen species from doing (too much) damage but in simple terms it creates chemicals that ‘sacrifice’ themselves reacting with the oxygen.

Eating more food that is rich in’anti-oxidants’ is not proven to be effective in improving health compared to a normal healthy balanced diet, and certainly no amount of anti-oxidants can protect us from the serious effects of oxygen at high pressures which is the only situation where oxygen really becomes toxic to us and ‘burns you slowly from the inside’.

Oxygen is like love

Too less and we suffocate and die
Too much and we slowly get destroyed from within
Just the right amount to keep us well and good

Under general circumstances, oxygen doesn’t do much to you. If you SCUBA dive, you have the possibility of encountering it when you go deep enough, Oxygen at a high pressure will result in [oxygen toxicity]( This can cause brain/nerve damage, lung issues, and eye issues. You can avoid this by not diving that deep (most of the interesting stuff is in the top 10-15 meters anyways), or by breathing a different mixture in your tank (Usually tanks are filled with air which is about 20% oxygen, for deep diving you will be breathing something with less oxygen and more helium).

First of all, oxygen as we depend on it occurs not in single molecules (O) but in the diatomic molecule O2.

And it can in fact have toxic effects depending upon pressure and concentration. In normal air, there is 21% 02, so in pure oxygen at atmospheric pressure there is 5X more oxygen than human body is adapted to. This can cause body problems, so to avoid them and to save weight, NASA used a one-fifth cabin pressure of pure 02 in the Apollo block 2 capsule, and 21%-O2 Earth air at normal pressure in the Shuttle.