On 1st November 1986 a stockroom of the chemical company SANDOZ near Basle (Switzerland) burned down; it contained 1,200 tons of pesticides, solvents and other toxic chemicals. 10,000–20,000 m³ water for fire fighting contaminated with approximately 30 tons of pesticides and 200kg of mercury flowed into the river Rhine. Unknown amounts of persistent organic pollutants infiltrated the groundwater. Three days later SANDOZ informed the drinking water companies along the River Rhine about the toxic flood. Approximately 150,000 eels died in the Upper Rhine. This also meant the extinction of all species in the water, as it was later reported by a speaker of the German Ministry of the Environment. On 5th November the pollution of the river had spread about 400 kilometres. Waterworks in the Middle and Lower Rhine began to close their water intakes. The President of SANDOZ announced intensified controls for chemical stockrooms. The German chemical industry worried about the tightening of environmental laws as a result of the SANDOZ catastrophe. About 25,000 inhabitants of a village in the Middle Rhine area were supplied with drinking water by tanker lorries after the closure of the (bank filtrate) fountains. On 8th November in Basle up to 1,000 people took part in a demonstration against the “Arrogance of Power”. On 18th November SANDOZ reported for the first time that the stock room also contained 1.9 tons of the highly toxic insecticide ENDOSULFAN.

The removal of the contaminated sludge started and the sludge was brought to a dumping site. Special “vacuum sludge cleaners” were used to prevent the highly contaminated sludge being dispersed during the next flood. It took eight months until they could find mussels, small cancers and insect larvae within the polluted stretch of the River Rhine. In the following years the colonisation by means of tributaries was completed and the situation of fauna and flora of the river has been normalised.

Lasting results of the SANDOZ disaster: improvement of international agreements and collaboration like ICPR (Improvement of Alarm System), River Rhine Action Programme and the programme “Salmon 2000”. Furthermore, technological requests emerged for enterprises like appropriate retention tanks for water for fire fighting and for cases of malfunctions.