Six sacred objects (masks) of the Haudenosaunee were found to have high levels of arsenic and mercury contamination. Treatment with a surface-active displacement solution reduced the contamination in all of the objects, but only four reached the agreed-upon mitigation goal (nanograms). A chelating compound, dimercaptosuccinic acid (DMSA), was identified as a possible second treatment to further reduce the level of contamination. DMSA was subsequently applied to all painted and unpainted surfaces of all of the objects. Removal efficiencies for mercury ranged from 4 to 85%, with an average decrease of 48.5%. Arsenic residue removal efficiencies ranged from 2 to 33%, with an average of 15%. Although mercury and arsenic levels generally decreased, sacred objects 2 and 5 still did not meet the mitigation goal.