For centuries, men who work as coal miners have had many health problems. The
worst of these problems is a disease called "Black Lung," which is caused by the coal
dust in the mines. Until very recently, about one in every five miners in the United
States got this disease. For these men, it meant poor health and a shorter life. Then, in
1969, a new law forced the coal companies to improve the working conditions for
miners. Since then,