Mold issues are sometimes sufficient reason to break a lease. You must document the mold, and you must show that it is a safety hazard. You must also be able to prove that it is the landlord’s fault.
Start by taking pictures and video recordings to document the issue. Also have a local safety inspector document that mold is a serious issue. Medical records from your doctor will also go a long way if you have higher than normal sensitivity to mold and mildew issues. The sooner you document this after moving in to your apartment, the better. The longer you wait, the harder it is to prove that its the landlord’s fault.
Another option is to pay to have the mold taken care of. Then you can send the bill to your landlord. He may refuse to pay the bill, and you may have to sue him to enforce his legal responsibility. You should always review your lease agreement and look for any special clause pertaining to mold issues.