I too have had black flecks in my sputum, and I'm a smoker. I also have chronic post nasal drip. The flecks were pronounced in the morning but as the day went on I guess I hacked it all out because there'd be none til the next morning. I searched extensively on the net seeking for an answer (found nothing other than a fungus called Asperilligus) so I went to the dr about this but he wasn't the least bit concerned. I also smoke pot (didn't tell him this though) so am thinking this might have something to do with it.

Anyway, oddly enough, the flecks disappeared after about a year, but I can't figure out why. Might have been after a nasty bout of viral bronchitis where I probably coughed it all out....?