Inadequate management of mine tailings at Cerro de Pasco, one of Peru’s largest mining complexes, has resulted in elevated concentrations of Pb, As, Cu, Zn, and Ag in surface soil horizons across the Junín Plain, central Peru. During June 2016, in response to local concern over mine contamination, teams of local citizens armed with sample bags, plastic trowels, and GPS receivers acquired 385 surface soil samples and 9 plant samples from agricultural lands from an area ∼1000 km2 on the Junín Plain. Metal concentrations were determined by acid digestion and inductively coupled plasma–mass spectrometry, and results revealed elevated levels of Pb, As, Cu, Zn, and Ag in all samples within a 10 km radius of the center of mining activities, and measurable contamination at least 30 km to the south-southwest, in the direction of prevailing winds. Dust traps emplaced for a 12 month period confirmed that contamination is ongoing. High metal concentrations in grasses growing on contaminated soils revealed that a portion of the total metal contamination is removed from the soil and held in grass tissue, where it can be ingested by graminivores, especially llama, alpaca, and sheep, thereby entering the human food supply.