Hanyuan County in China's southwest Sichuan province is rich in lead-zinc deposits and dozens of mines are scattered along the Dadu River to extract the ore. The arrival of the mines offered well-paying jobs to locals, many of whom had been poor farmers who jumped at a chance to lift their families out of poverty.  But years of work in the mines without proper protection gear has taken a deadly toll in the form of silicosis. Former miners say thousands from their ranks have contracted the…