For any problem of lungs being dirty, NAC is helpful. This is N-acetyl L-cysteine. I recommend Bulk Supplements brand because it does not have any other ingredients.
This stimulates the process of the lungs producing mucous and flushing out dirt and contaminants. You need to make sure to drink water so your lungs don't become too dry, or don't have the humidity too dry in the room. If you take this supplement before you sleep, your lungs will be flushing themselves out all night. And when you wake up, you will cough out a big ball that contains the dirt and dust from your lungs.
Be careful and try only a small amount. But it works for me, and the few people I know who told me about this, it works for them too.