Is oxygen toxic?

It turns apples brown. It helps corrode steel. It apparently causes aging in flesh.

So, is it toxic?

Yes - but at high concentrations and with prolonged exposure.

From the second last point on the American Lung Assoc Page


Thinking back to my scuba manual…

Oxygen toxicity became an important factor when divers were diving on pure oxygen and reached a depth of 33 feet. At this point, they would tend to convulse causing them to spit out the regulator and inhale a double lung full of water. Drowning ensued.

From this, we can see that oxygen becomes poisonous at 2 ATM of partial pressure. I surmise that breathing pure oxygen at the surface (would make one a bit light-headed, but would not have toxic effects.) Indeed, emergency first aid courses teach oxygen administration, which delivers pure oxygen to a resting diver on the surface.

      • What’s the difference between industrial-grade and respiratory-grade oxygen? Do they put something bad into the industrial stuff to prevent its respiratory use? I was wondering this today buying welding gas-- for nitrous oxide, they put a small percentage of something in it to make you gag if you try to inhale it, but you can’t do that with oxygen: you can’t add anything flammable to 200-bar Oxygen, it’ll combust. -So anything added would have to be inert,
        but then,
        it wouldn’t matter if you breathed it,
        but then there wouldn’t be two different “types” of oxygen…
        -so what’s the difference? - DougC

It’s certainly toxic to anaerobic bacteria. IIRC, the formation of an oxygen-rich atmosphere (oxygen being a waste product of certain metabolic processes) led to a major environmental crisis and a large-scale mass extinction early in Earth’s history. (We’re not talking dinosaurs, of course, but single-celled organisms, and so long ago they make dinosaurs look like day-old bread.)

If only I remembered my Biochem better…

Part of one of your metabolic processes (don’t remember which offhand and lent my notes to someone who had his stolen) creates an oxygen radical, which is highly reactive and toxic - you need to be able to convert that to something better pretty quickly. Lacking the appropriate substrates, or when given too much oxygen, it becomes toxic. In the presence of oxygen, your body will continue the process until it reaches the oxygen radical regardless of whether or not the previous radicals have been converted, and so it builds up and becomes a problem. Also, obviously, if the necessary enzymes or substrates for converting the radical are not available or non-functional, then the radical buildup will also occur.
I imagine it must be available online, and in most biochem texts. I have Stryer, don’t remember the edition (it’s the red cover).

Many thanks.

Doug C, I know part of the answer to the diff between welding and breathing oxygen or breathing air of any kind is how well it is filtered. I don’t know about additives; seems there wouldn’t be a point for O2. But just go to a dive shop some time and take a look at their air filters and tank filling equipment - very complicated and very expensive. If the air weren’t as “clean” and dry as it is, the tanks would rust and other bad things would happen when guys filled up their tanks from their home compressors (instead of paying $5 for air at the shop). I imagine medical oxygen like they’d have in an ambulance for breathing is filtered in a similar way, while industrial gases don’t have to be quite so spic and span if they’re just gonna get burned.