Each time I arrived in Hongjun village after a 12-hour journey by plane, bus, and motorbike, I took deep breaths of the crisp mountain air—as if that could clean out my Beijing-polluted lungs.

It did not take long for the irony to hit me. This alpine landscape in central China is home to hundreds—perhaps thousands—of men too sick to breathe normally.

Once farmers, these men left en masse in the late 1990s to work in gold mines—part of the army of migrant workers who powered China’s economic boom in recent decades. They dug deep into the mountains for treasures. Years later, they came back with the lung disease silicosis, and now wait in their homes for death.

For years, I’ve