Rhine running red, fish dead – 20th anniversary of the Sandoz blaze

On 1 November 1986, a chemical warehouse at Schweizerhalle near Basel was destroyed by a fire. Aquatic life in the Rhine suffered catastrophic damage as a result of inflows of toxic, red-coloured firefighting water. The readily apparent impacts on river biology – images of dead fish were transmitted worldwide – led to major progress in the areas of chemical water quality monitoring, legal regulations and risk reduction measures in the chemical industry.

The blaze at the Sandoz plant shattered public confidence in the chemical industry’s self-inspection regime. Action taken by the authorities as a direct consequence of the disaster included the enactment of the Major Accidents Ordinance (StFV) and the establishment of chemical inspectorates. The anti-pollution efforts of the International Commission for the Protection of the Rhine (ICPR) were substantially intensified. Apart from the immediate damage caused, it can now be concluded, 20 years later, that the accident had positive effects overall from the viewpoint of water protection.

In 1986, Eawag experts were closely involved in efforts to analyse the chemical and biological state of the Rhine, and to document the effects of the accident. As they had correctly – although controversially – predicted, the dynamic river system and aquatic populations recovered relatively quickly, i.e. within a few months. This process was promoted by the migration of organisms from the upper reaches, tributaries and side channels and by the rapid cleansing of the contaminated river by floods. However, bottom-dwelling organisms have been found to be increasingly dominated by non-indigenous species. Researchers at Basel university assume that “Schweizerhalle” created vacant ecological niches, thereby facilitating colonization by exotic species.

While the risk of a new chemical accident on the scale of the Schweizerhalle disaster has decreased, attention is now being focused on chronic contamination – e.g. from continuous inputs of persistent household and agrochemicals. In recent years, for example, Eawag has studied the behaviour of benzotriazole, a compound that is not readily biodegradable. This substance, used as a corrosion inhibitor (e.g. in dishwasher detergents), is scarcely eliminated at wastewater treatment plants. Concentrations measured in water samples collected from the Rhine near Weil indicate loads of 100–220 kg per week – i.e. non-negligible levels.

Further information (only available in German):
NZZ article, 1 November 2006 (Walter Giger, Eawag) [pdf, 21 KB]
“20 years on from Schweizerhalle”, Swiss TV documentary (MTW), broadcast on 26 October 2006
“Taking stock”, Swiss TV report, originally broadcast on 27 November 1986