The legislation is intended to combat the rise in black lung disease, an irreversible and potentially fatal pulmonary disease caused by the inhalation of coal dust. After passage of the 1959 coal mine safety law, black lung disease rates declined. However in recent decades the rates have rebounded. Researchers are raising alarms over the fact that increasingly, younger miners (with fewer years of occupational exposure) are getting diagnosed with the disease – and with a particularly aggressive form of it.