Howard Berkes

Rates are now the highest they've been in nearly 50 years among veteran coal miners. Mining experts blame toxic silica dust, now more common in mines.

Forty years after the Challenger disaster, NPR explores the engineers' last-minute efforts to stop the launch, their decades of guilt and the vital lessons that remain critical for NASA today.

Federal mine regulators have published a long-awaited rule that would limit the amount of toxic silica dust mine workers can legally be exposed to. For the first time, miners in all industries will get medical checks that coal workers have had for decades.

Addressing a problem first identified 50 years ago, federal regulators say stricter new rules to limit miners' exposure to silica dust are expected to finally go on the books on Tuesday.

For decades, miners have called for limits on highly toxic silica dust, which they're exposed to while mining. An investigation shows its impact and the weakness of proposed rules to protect them.