Can I break my lease due to Mice?

You need to be in touch with the Allegheny County Health Department. They will probably send an inspector to look at the place. They may be willing, if they see a problem, to require the landlord to step up efforts to exterminate the mice. If you can prove the mice are in your food supply, I think you can terminate the lease. However, it would be a good idea for a lawyer to review the lease and assess the other facts before doing so. CLT