I've given it some more thought. I won't deny that it would meet with huge resistance, but it's not as far fetched as it first seems. Look...there was a point in history where government officials said "okay...we have to draw a line. From now on, you can't just claim land and do what you want with it anymore. It'll become a good that can be bought and sold, and will be taxed accordingly". To us, this makes perfect sense, but I can imagine the general population didn't like being taxed for simply using what was already there to begin with.
And...it might just be Belgium, but I assume this goes for most countries: there are already huge amounts of taxes that make little to no sense (anymore). Most often, a tax is created in times of need or to change a certain behavior (festivals playing too loud? Introduce a local tax on loud noises) and then quietly remains dormant, sometimes years after the origin is taken away. When I learned about taxes in...2000, I think...there was this Belgian thing called "crisisbelasting". It was a tax to help out in a crisis that was then introduced somewhere years before that. And I just checked: it still exists to this day.
Compared to that, at least a tax on clean air makes SOME sense. Yes, everyone who breathes has to pay that tax. And those who drive cars as well (hint: cars pollute). Airline and shipyard companies as well. Farmers will have to pay for their animals as well. And so on. And while this certainly sounds increasingly scary (is the government just going to tax EVERYONE?????), you have to look more to the global picture.
First and foremost: the more people getting taxed, the lower the total amount will be (taxes are usually drawn up so they bring in a certain amount of money. Usually because they already have plans to use said income on other projects).
Second: even small taxes have huge effects on people's behavior. Over time, it will lead to things that now have 'air pollution' as side product to become more expensive. This will simulate companies to search for alternative means of production that have less air pollution. Which isn't so much "tax evasion" as the probable intention of the tax. Because in case you haven't noticed: no one is in favor of pollution, but companies (and even individuals) generally don't mind it if it means it's the cheapest way of production. If a tax means that a non-polluting way of production becomes cheaper...then who is really against it?