Hydrogen as a means for delivering energy to the point of need is most probably limited to its use in fuel cells. Fuel cells would convert hydrogen chemical energy into electricity; the only exhaust being water.
Evidence from:
Health and Safety Laboratory HSL/2006/59
“The Hydrogen Economy – Evaluation of the materials science and engineering issues”
Risks appear to be manageable. But uptake is likely to be low; it is not cost effective yet.
Further detail: