"It's hard to wear a mask and do a physical job," he says. "Just trying to do your job, you breathe so hard the dust will come in around the mask."

Stanton has been diagnosed with the most serious stage of PMF and is awaiting a lung transplant.

"The mining game is a numbers game," Branham says. "If you don't produce coal, they'll put somebody else in your spot that can. If I've got another man on the other side of the mines, he's cutting more coal than me, it's not going to look good on me. I just thought about my family to be honest with you."