I would quickly run the whole thing through my mind, because the mold is entering your mind at the same time. The longer you stay in the apartment, the more likely it is that you will get sick.
So I think you can definitely request a rent reduction...ask a lawyer. I also think that the landlord is obligated to hire a company that eradicates the mold.
Mold is really nasty. And I also think that you shouldn't demand a rent reduction, but that the landlord should somehow get rid of the mold. And if that doesn't work, then move out.
Yuck... mold... I had that too... however, my landlord didn't care either. Well, after my lawyer visited him, he thought it would be a good idea to do something about it.