Removing a toxic air pollutant has unearthed a new health danger on Chicago’s Southeast Side. Federal and city officials discovered high levels of a type of heavy metal, known as manganese, while investigating piles of black dust known as petcoke. Officials say it was detected a few years ago and that the substance has since been removed. The Chicago Tribune reports officials believe S.H.Bell, a company along the Calumet River, is behind the manganese, but the company has denied that. Manganese can cause permanent damage to the nervous system and is linked to learning disabilities, memory loss, and anxiety.