Experts have raised alarms over the presence of trichlornitromethan, a toxic nerve and lung agent, found in the K-90 building in Basel, initially detected in 2021. This substance, historically used as a chemical weapon, poses health risks including irritation and severe lung damage. Despite previous warnings about potential contamination, Swisslife opened the facility for public events until recently, citing manageable risks. The building is now closed, necessitating protective gear for entry, while further investigations are ongoing regarding the safety of other structures in the area.