WASHINGTON, D.C. -  Coal miners suffering from the debilitating black lung disease are demanding more from Congress.

On Tuesday, a group of miners suffering from the disease testified before members of the U.S. Senate, urging them to fully fund and extend the Black Lung Disability Trust Fund. Right now, that fund is running out of money. It’s reportedly more than $4 billion in debt.

Miners can get the disease from severe exposure to coal and silica dust, and it affects their breathing. The push comes after a 2018 report from the Centers for Disease Control and Prevention revealed nearly 1-in-10 coal miners suffers from black lung; and nearly 1 in 5 miners in Central Appalachia.

“I didn’t know I had the disease,” said former coal miner David Mullins, who worked 34 years in underground mines. “But the last ten years, it really has progressed. It just crippled me. I can’t do nothing.”

U.S. Senator Bob Casey (D-Pa.) chaired the hearing Tuesday alongside fellow coal-country Democrats Senators Tim Kaine (D-Va.) and Sherrod Brown (D-Ohio) among other labor and industry leaders. The hearing is not part of a formal U.S. Senate committee.

“This isn’t something extra our government is providing for them,” Casey said of the fund ahead of the hearing. “This is our government keeping their promise. These miners kept their promise.”

Last year, the coal excise tax that provides money to the fund was cut by 50 percent. Casey is proposing legislation that would make it easier for miners to access medical records related to black lung disease and subsequently access federal funds for treatment of the disease.