Man has been steadily polluting the world for millenia. It's just that there are more of us, with the better technology, to do it more effectively.
Hydrogen as a fuel is not necessarily the way to remove pollution.
Burning anything in air, can produce high enough temperatures to oxidise the Nitrogen, so it may not just be water leaving the tail[pipe.
And the Hydrogen will have been produced by electrolysis; so burning fossil fuels, solar, hydro, wave, wind power, or nuclear, as the initial power source?
And currently, in UK we transport goods by road that are too large to fit into the loading gauge of all the railways.
So vast expenditure on infrastructure to enlarge the loading gauge, and to electrify every inch of railway, (so that we don't have to use internal combustion or steam power, ANYWHERE) ?
And maritime transport presumably will rely either on sail or nuclear power? The Galley may not be the place to cook, just to row!
But cheer up! Public road transport will be clean and cheap, there will be bicycle pedals and cranks at every seat; but just don't get on an empty bus!
At least I shan't be around to see the mess made by the technically ignorant ideologues running (did I omit an i from that word?) the country.
Howard