Are we running out of clean air?
Completely ignorant on the subject, with pollution and deforestation, and 8+ billion people and animals breathing; at what point do we run out of clean air?
So it's not about running out of clean air on earth, but more so about specific locations and individual exposure.
It's uncanny how relevant this quote is 50 years later.
That being said, the air situation is generally improving because of people getting wealthier. Because air cleanliness is local, it matters much more where pollution is happening than how much pollution is happening, as e.g. indoor wood burning for cooking or warmth affects you much more than a much larger pollution through a power plant, and improved technology also makes a big difference even if you're burning the same quantity of the same thing.
In developed countries, air is cleaner than ever - London had notoriously unclean air, being the center of the industrial revolution, but looking at current data (e.g. https://en.wikipedia.org/wiki/Air_pollution_in_the_United_Ki...) 2000 London had immensely cleaner air than 1900 London, and 2024 London has much cleaner air than 2000 London. Similarly, while global deforestation matters for global issues like climate change, in developed countries there is no deforestation - Europe has reforested in the last century, increasing its forest cover, and USA has kept a rather stable forest area over the same time.
In developing countries, the industrialization does come at a cost of local air pollution until the country's wealth grows enough that they "choose to buy the luxury of clean air" by changing local laws to favor more expensive but cleaner ways to do the same thing. So currently the most polluted air is in places like Bangladesh and Pakistan, but there's a clear path for improving that when they come to prioritizing that - because it's inherently some tradeoff between the material welfare of your people and the physical welfare of air quality, because poverty can kill or hurt as much or more than polluted air. That being said, e.g. China seems to have peaked at its local air pollution and is expected to get cleaner air over the coming decades - it's not "running out" of clean air.