Will earths oxygen ever become impaired and a threat to human civilization?

It depends on how old you are now. If you are young IMO the Earth will burn and that will change the oxygen and IMO it will be in your lifetime.

Oxygen is one of the most abundant elements on the planet. The problem is with all the other junk in the air. The tropical rain forests are where most of the worlds gasious oxygen is removed from carbon dioxide and returned to the atmosphere. So if we continue to cut down the rainforests, then yes, we will run out of oxygen. There are plenty of ways to artificially restore oxygen to the atmosphere, but I don’t believe (although I have not researched it) that any are practical on a global scale.

There has been a huge drop in atmospheric oxygen content from prehistoric levels of 35% (as measured from air bubbles trapped in amber 10,000 years ago) to an average of 21% today. In major cities, the content can be more like 15%. That’s low enough to start having health effects. It would have to drop to around 6–7% to make Earth unlivable at sea level.

Most of the oxygen is in Earth’s crust, I believe (oxygen readily forms compounds with other elements—think water or rusty iron).

The reason there is so much oxygen in the air is because early life forms started using metabolic processes that spat out oxygen as a waste gas. This actually caused a massive extinction when it happened, sometimes called the “Oxygen holocaust.”

In any case, the oxygen doesn’t escape into outer space. I’m not sure what process would cause Earth to somehow lose its oxygen supply. Do you mean, some as yet unknown process that would drive large amounts of oxygen in the air back into rocks and water?

It’s not so much oxygen running out but carbon dioxide reaching alarming levels. It carbon dioxide reaches 1% of all atmospheric gases we will all suffocate

Here’s my data-free answer. Oxygen content will slowly decrease but with enough time life will slowly adapt to the challenge. We might develop larger lung capacity or increase our hemoglobin like the Sherpa of Nepal.
If our air is ever to become impaired it would more than likely be due to some chemical or radioactive dump that happened to quickly for humankind to adapt.

According to National Geographic, half of the world’s oxygen is produced via phytoplankton photosynthesis. The other half is produced via photosynthesis on land by trees, shrubs, grasses, and other plants.

Nope not in my life time. By that time when if happens I hope we as humans will have a plan.

No worries. Capitalism and the market economy will provide an answer at $50 a cylinder, face mask included.

The only way this would occur in our lifetime is if there is some impact from a comet or asteroid that burns up a huge area of the Earth’s surface, and then what is likely to happen is that plants won’t grow, but we’ll be ok, left to freeze to death, starve to death or resort to cannibalism. Plants and algae in the ocean are the earth’s lungs. As long as they are well enough, they will keep the air at a sustainable level.

The earth’s oxygen level has changed dramatically since there has been life on the planet. Remember the evidence of the giant flying insects? Those wonderful dragonflies? Their existence was made possible by a very oxygen enriched atmosphere back millions of years ago. We live now with much less oxygen than there was then. If the decline is gradual enough for evolution to adapt, then @worriedguy ‘s scenario of a race of humans adapted for their environment may come to pass, otherwise, we go the way of the dinosaur.

The other, long term situation is that the sun will go through phases that will cause more radiation on Earth, burning out the atmosphere and destroying our life-giving bubble. But scientists estimate that is millions and millions of years away.

The good news is that, as CO2 levels increase, the total amount of plant mass on the planet (in the oceans and on land) increase proportionately. It’s a self-balancing system.

The bad news is that as we clear cut rainforests and poison the oceans with oil spills, it’s questionable how much plant mass the planet can carry.

When that balance tips, oh well…

Many people today do not know that atmospheric O2 levels have been dropping continually ever since the Scripps Institute began annual measurements in 1990.
http://scrippso2.ucsd.edu/
It not falling as fast as CO2 is rising, but it is falling. BTW, this is probably the main reason why CCS (carbon capture + storage) will fail. You can pump CO2 in the ground (I seem to recall that it is naturally in liquid state below 700 meters) but you will still be using atmospheric oxygen when you burn the fossil fuel)