The Seveso disaster was a chemical accident on 10 July 1976, at the small Italian town of Meda, 20 km from Milan in Lombardy. There was an explosion at a chemical factory which released a lot of the toxic poison dioxin, "TCDD", into the air. The cloud of poison gas covered an area 6 km long and 1 km wide. It was named after the municipality of Seveso. It resulted in the highest known exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in residential populations There were many studies and new regulations after the accident. The European Union directive covering the protection against such accidents is known as Seveso-II-directive today. 