The correct answer is pneumoconiosis.
The occupational disease is the disease, which is acquired through the occupation.
The coal workers, especially those who work in mines are regularly in contact with the coal dust, which is also called as black dust. This black dust can accumulate inside the lungs of the coal workers.
The accumulation of the black dust causes the pneumoconiosis. It can lead to coughing, shortness of breath and fibrosis of lungs.