Geologist William Hobbs divides a core into two-inch (five-centimeter) slices at Peru's Laguna Negrilla. The lake is several hundred miles from the mercury mine, but the team has found centuries-old evidence of mercury vapor at Laguna Negrilla. Each slice represents five to ten years of deposition.

Colin Cooke, author of the May 2009 study, is concerned that pollution from the mine may have left a widespread poisonous legacy in this region.