Medical marijuana smoke from neighbor is making my family sick.?

My neighbor uses pot medicinally. And each time he fires up in his apartment in gets into our shared ventilation system and ends up stinking up our apartment. My wife and kids are getting sick because of the stench(doctor verified). I'm not sure if I can do anything about it. We are currently in the middle of our lease and we like our landlord so moving isn't the first option(but it is being considered). We don't get along with them too well due to a dispute between our kids so talking to him about it won't do any good. And calling the cops is obviously not going to happen due to the medicinal marijuana laws in WA state. I don't know what to do.