A major chemical disaster that occurred at a small chemical plant on 10 July 1976 near Milan, Italy. It involved a chemical runaway reaction in which the chemical 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) was released into the environment as a side reaction caused by a kettle heater being left on overnight. The release caused the death of many animals and the evacuation of local inhabitants. Following many studies, it has led to the standardization of industrial safety regulations aimed at improving the safety of sites containing large quantities of potentially dangerous substances. The Seveso II Directive is a European Union law formed as a result of the disaster and subsequent investigation. This is known as the COMAH regulations in the UK.