Dioxins are complex chemicals containing chlorine. Some are toxic even at very low concentrations. Dioxins belong to the family of Persistent Organic Pollutants. They are characterised by their resistance to decomposition, their ability to concentrate through the food chain and their toxicity. The Seveso accident with the emissions of the dioxin (TDCC) in 1976 was the initiators for the EU Directive on the major-accident hazards – the Seveso Directive – in 1982.