Sandoz fire poisoned the Rhine and changed industrial safety
Sunday 1st November 2026 on 11:45 in
Switzerland
Forty years ago, a fire at a Sandoz chemical warehouse near Basel led to the release of contaminated firefighting water into the Rhine, killing hundreds of thousands of fish. The disaster prompted changes to emergency procedures and water monitoring, SRF reports.
The fire broke out on the night of November 1, 1986. Flames rose several metres above the warehouse as a large force of firefighters tackled the blaze. The building contained more than 1,000 tonnes of insecticides and crop protection products. By early morning, it had burned down, and pesticides had turned the firefighting water red.
The water was allowed to flow untreated into the Rhine. The river was left biologically dead in some stretches, and eel populations were wiped out in many places.
At the time, residents were also concerned about the smell and possible toxic gases in the air. Authorities said there was no longer a danger from gases, and pupils were told to go to school the day after the fire. Days later, students took to the streets to protest the decision and criticise the authorities’ communication.
The disaster also drew anger towards the chemical and pharmaceutical industries and their employees. Peter Marbet, who was a Sandoz plant chemist at the time, said he went from being a proud chemist to being seen as a villain harming the environment.
Since the disaster, companies have introduced firefighting water retention basins and emergency response teams, and have improved their communications. Switzerland also works with Germany and France to monitor the Rhine’s water quality. Patricia Holm, an emerita professor of ecology at the University of Basel, said samples can help investigators trace incidents, including cases that companies have not detected themselves.
The Rhine has since recovered. Eels and salmon now swim in the river in Basel, and people swim there on hot summer days. Schweizerhalle is remembered as a turning point in Swiss environmental and industrial history.