The development of the Free State mines shifted investment and labour away from the Rand. By the early 1980s the new fields were employing two hundred thousand men. Most of the mines were operated by Anglo American, which built the nine-hundred-bed Ernest Oppenheimer Hospital at Welkom as its central facility. The largest and best-equipped hospital of its kind in Southern Africa, Ernest Oppenheimer was to become the site of the most influential medical research on gold miners. A second change during that period was the formation of the National Union of Mineworkers (NUM). Founded in 1982, the NUM was successful in gaining wage rises and soon had more than three hundred thousand members. The NUM was committed to improving mine safety and was instrumental in the establishment of the Commission of Inquiry into Safety and Health in the Mining Industry, usually known as the Leon Commission, which tabled its findings in 1995.

In the period leading up to majority rule, compensation payments under the Occupational Diseases in Mines Works Act No. 78 of 1973 (ODMWA) were based on race. Like its predecessors such as the Silicosis Medical Bureau, the Medical Bureau for Occupational Diseases (MBOD) delegated the examinations of black miners to mine medical officers. Over time the differences between the technologies used with white and black miners widened. Whites were given full-sized chest X-rays while miniature X-rays were used for blacks. The lack of pulmonary-function equipment at mine and rural hospitals contributed to the underreporting of chronic obstructive pulmonary disease among blacks.