Hi, Forming of dust like particles on the tongue and back of throat can be due to a number of causes, however it depends on many factors like the color of the particles, it is small bits or coating / layer. Another factor is that whether the particles can be removed or are scrapable or not? So in case if there is white coating or particles that are scrapable with nail or tongue cleaner then it can probably be fungal infection or thrush. As you said you are recovering from COPD and in case if you are taking antibiotics then it can possibly be Thrush. In case if the tongue looks like tiny brush like projections and it is brownish black then it can be Black Hairy tongue. This is harmless overgrowth of tongue papilla that causes debris and bacteria accumulation giving it black appearances. So you need to first get checked what exactly it is. You can also send me pictures of the same so that I can have a look and advise you accordingly. For now you should do warm saline gargles, use a tongue scraper to clean your tongue. Drink plenty of fluids and chew on hard foods like hard fruits and salads. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Honey Arora, Dentist