Did you know that hydrogen will destroy the ozone layer?
Yes, if we ever move to hydrogen as a major transportation fuel or an energy carrier the consequences for the ozone layer in the stratosphere will be dire - far worse than what CFC have done to deplete the ozone layer.
Hydrogen leaks like crazy. It is a very small molecule. It is buoyant with a density one fourteenth of air. Hydrogen will not react with oxygen in the air unless there is a spark or it is above 4% by volume.
Hence, the hydrogen that will leak in vast quantities if we move to a hydrogen economy will move unreacted from earth's surface to stratosphere. In the stratosphere, it will react vigorously with ozone causing major depletion of the ozone layer.
I explore this topic in-depth in my book: Hydrogen - Hope or Hype?