Neighbors smoking in out duplex and it's coming through our heaters?

I am 5 months pregnant and have a 18 month old, we moved here 2 months ago and have noticed that the neighbors cigarette smoke is coming through our heaters. I have already contacted our land lord but he is not clear if they own that side of the duplex or not. He did call them twice and tell them but was extremely rude to us and told us private owners(him) have more rights then we do. Is this even legally, is it not a health hazard? What can I do if anything.