Miners chat as they wait to descend into Wangpingcun Coal Mine, Mentougou District, Beijing, 1990

Miners working for Shandong Yankuang Group take a break inside a coal mine in Yanhzou, Shandong Province, in the 1980s. Their faces are smeared with soot, which takes time to wash off

Miners take a short break in the sun near the mine entrance as they wait to change shifts, Shanxi Lu’an Mining Group, Changzhi, Shanxi Province, 1992

Shigejie Coalmine in Shanxi Province was a model mine in the 1980s. Pictured is an artist drawing a poster of the miners

Miners drink in a bar after work, Shandong Yankuang Group, Yanzhou, Shandong Province, 2013

After work, young miners exercise in the gym at Xinglongzhuang Coal Mine, Shandong Yankuang Group, Yanzhou, Shandong Province, March 20, 2013

To keep the mines tidy above and below the surface, Shandong Energy Group requires its workers to clean their shoes whenever they enter and exit the mines at Liangbaosi Coal Mine in Jiaxiang County in Shandong Province, October 2013

Many miners with Shandong Longkou Mining Group have developed rheumatism, an occupational disease associated with long periods underground, Longkou, Shandong Province, 2005