<prompt> Minimum duration of developing coal minor pneumoconiasis is24 years46 years810 yearsMore than 10 years  <response>: Coal worker pneumoconiosis Antracosis There are two general phases in coal miners pneumoconiosisThe first phase : Simple pneumoconiosis : This is associates with only little ventilatory impairment but requires 12 years of work exposure for its development.The second phase : Progressive massive fibrosis : This is associated with severe respiratory disability and takes much longer. 