Can I break my lease because of a rodent infestation?

I live in a house in Massachusetts that has 3 apartments. We noticed mice droppings and saw a few mice when we moved in. The land lord bought a few traps for us. When the rodents persisted, the landlord hired an exterminator. It has been over a month since then and we continue to catch mice daily. We have caught over 20 in less than 6 weeks. We find them crawling in the sinks, the bathroom, and on the furniture. I understand that the landlord is making an effort to exterminate the rodents but there is clearly a serious health issue. Am I allowed to break my lease on these grounds?