Lungs clean themselves of small particulate matter pretty easy and regularly with the cilia (hairlike structures) that line the bronchioles and sweep it out. Unless you smoke. This knocks out the cilia, and prevents lung cleaning. That’s why ex-smokers can develop coughs that last for months: The cilia grow back and start catching up on their housework. But it a year or two they should be about as clean as they can get.
QtM, MD