When did black lung disease occur at its worst in victims?

Black Lung: Coal workers' pneumoconiosis (cwp), colloquially referred to as black lung disease, is caused by long exposure to coal dust. It is a common affliction of coal miners and others who work with coal, similar to both silicosis from inhaling silica dust, and to the long-term effects of tobacco smoking. Inhaled coal dust progressively builds up in the lungs and is unable to be removed by the body.