It also follows a string of apologies from various U.S. cities over historically racist policies or wrongdoing in the wake of the nationwide racial reckoning after the killing of George Floyd by a Minneapolis police officer.The city allowed University of Pennsylvania researcher Dr. Albert Kligman to conduct the dermatological, biochemical and pharmaceutical experiments that intentionally exposed about 300 inmates to viruses, fungus, asbestos and chemical agents including dioxin - a component of Agent Orange.A group of the inmates filed a lawsuit against the university and Kligman in 2000 that was ultimately thrown out because of a statute of limitations.Philadelphia Mayor Jim Kenney said in the apology that the experiments exploited a vulnerable population and the impact of that medical racism has extended for generations."Without excuse, we formally and officially extend a sincere apology to those who were subjected to this inhumane and horrific abuse."