The lining of the respiratory system that is extending from the nose through the airway of the lungs is layered with mucus. Mucus functions in trapping foreign particles (junk in the air inhaled through the nose) to keep your lungs clean that it becomes very important with every breath that you take, and it also warms the air you breathe in. Black mucus can take its color from a number of factors. The most common cause is from environmental pollutants such as dirt and dust. Inhaling smoke is another source that can cause your mucus to be tinged black. The black coloration is likely due to a high aluminum content of tobacco smoke. Chronic exposure to environmental hazards such as inhalation of coal particles can result in black mucus that may lead to a black mucus disease called pneumoconiosis. The most dangerous cause of experiencing black mucus is specific types of chronic sinusitis and pneumonia
triggered by serious fungal infections. However, these fungal infections are very rare and affect only people with weakened immune systems. It is very important to investigate the actual cause of your developing black mucus and undergo appropriate treatment. I would recommend a consultation with a primary care physician
or ENT to have your condition evaluated. Good luck.