Estradiol hemihydrate is just plain old estradiol like the human body produces. This is used in pills for sure (I have one under my tongue as I'm typing) but far less often in injections.
Estradiol valerate is a drug which is structurally the same as plain old estradiol except one hydrogen atom is replaced by a chain of five carbons, one oxygen, and nine hydrogens (this whole mess is known as an ester in chem geek talk due to how it connects to the estradiol part.) But that's nothing to worry about as enzymes in your body are quite good at lopping off that extra chain and slapping a hydrogen back in its place leaving good old estradiol but it does take time.
That delay is good for injection use as it slows down how quickly your body can use the resulting estradiol. If you injected plain old estradiol your levels would be insanely high for a few hours and crash. With your body having to work to free estradiol from the valerate ester, it makes for a longer lasting dose.
As for the safety concern, that I don't know about. But in any case, this is about as good a reason to quit smoking as any.