I had a similar problem with a neighbor who smoked cigarettes. I had to buy an air purifier in order to live in the apartment.

If he's smoking weed, then you have a sure bet he doesn't want you to report it to the authorities. If he kicked you out for reporting, you'd have a nice lawsuit on your hands.

What I would do, is tell him to get an air purifier for both of your places or you will report him.