East St. Louis: Two persons have died after exposure to a dangerous chemical at a storage and mixing plant, a city official said today. At least eight people were sickened by exposure to the chemical yesterday, and emergency rooms were quarantined at two St. Louis hospitals where those people sought treatment. In a statement issued early today, East St. Louis City Manager Robert Betts said two people had died. The chemical was released when a barrel was dropped at the Ro-Corp. plant. The lid popped off the barrel and a white powder came out, said Fire Chief Jim Silvernail from Mehlville, Missouri.