There are several environmental concerns when driving a hybrid.
One is the rare earth metals used in permanent magnet motors such as neodymium. However, it has been already established that electric cars end up being more sustainable than gasoline cars, and also the electric motors in hybrid vehicles aren't bigger than those in electric cars (actually in ...
Here is a report from Union of Concerned Scientists on the total benefits of hybrid vehicles:
It was quoted in this general interest article:
It discusses a full range of aspects of this question, ...