Black sputum

I cough up this black stuff in my sputum.  I'm not sure what it is.  I have not been exposed to asbestos.  I did smoke pretty heavy for several years.  In the last year I smoked the damiana leaves, now called incense.  I quit smoking the damiana about 2 months ago and i have been coughing up this tar like substance.  The black and sometimes brownish in color spots in the sputum does not have a texture.  I notice it comes up in large quantities after eating.  At any time I can force it to come up.  I'm not sure if this is just my body cleaning out all the tar from the smoking.  I do not have any other symptoms at all other than just the nasty sputum.  I also exercise in the mornings and after I'm done it really come up in larger amounts.  My Dr had no idea what it was and recommended me to wait and see.  Of course Im worried....who wouldn't be.  There has been no visible blood in it at all either.

[leillani]

As far as I know, black sputum can be caused when people are exposed to dusty environments or when they inhale smoke. It may be due to your heavy smoking. Sorry, I have no better or more profound explanation.