Elizabeth Herndon, PhD candidate in Geosciences, and co-authors have determined that iron furnaces in operation during the 1700s and 1800s may have left toxic levels of manganese in Pennsylvania soils. Researchers identified the manganese enrichment after sampling various sites within the Susquehanna Shale Hills CZO. By examining soil chemistry from around the world, the team concluded the increased manganese levels were the result of industrialization.