Does the reaction of hydrogen produce any products that negatively affect the environment?

The answer is NO. During combustion of hydrogen, water is produced as an end product. The chemical formulae for combustion of hydrogen are:

2H2 + O2 - ->2 H2O

another advantage is that the whole of the fuel load is combusted hence little wastage. This has made the fuel advantageous in its use as rocket fuel since there is no baggage fuel.