In this July 31, 2012 photo, workers at the Antamina copper mine, wearing white uniforms, clean the river in Cajacay, Peru. A pipeline carrying copper concentrate laced with volatile compounds burst open on July 25. Three weeks after the leak spilled 45 tons of slurry into the town of Cajacay, spreading toxic dust that left 42 people hospitalized for up to 11 days, the copper mine’s owner, Antamina, has said little about the accident, and been silent about the slurry's chemistry. (AP Photo/La Republica Newspaper)