My father is coughing up hard chunks/ balls of Phelgm every morning, which is not like the normal saliva rather a greyish black cotton ball like. Occasionally it's yellow. As the day progresses, the phelgm remains thick but is not like the one in the morning. The phelgm also contains black particles, even though he is a non smoker. He has no fever. No diabetes, though he is taking medication for thyroid. This has been going in for a few months now. Other things are normal. Please suggest a remedy.