40 years ago: When a chemical cloud passed over Basel

40 years ago When a chemical cloud passed over Basel As of: November 1st, 2026 • 12:06 p.m

40 years ago, a warehouse in which large quantities of dangerous chemicals were stored burned near Basel. A toxic cloud passed over the city and contaminated fire-fighting water flowed into the Rhine. What changed as a result of the disaster?

The Schweizerhalle industrial area is around eight kilometers from Basel city center. You can see chimneys, loading cranes, tanks and above-ground pipe landscapes that are typical of the chemical industry. The entire area is nestled directly on the Rhine.

On the night of November 1, 1986, it was the starting point of one of Europe's largest environmental disasters: the fire in a Sandoz chemical warehouse.

The fire department in Basel received the report shortly after midnight. First of all, there is talk of a smoldering fire. Soon, however, barrels of unknown contents explode, fireballs shoot into the night sky, and there is an acrid smell in the air.

While the fire brigade tries to get the fire under control, police cars drive through Basel in the middle of the night and people are asked to keep their windows and doors closed.

Many Basel residents still remember that night in minute detail. Matthias Nabholz is one of them. Nabholz was 16 years old at the time. His mother gave him and his three siblings wet washcloths. They should hold these in front of their mouths in the hope that they will not inhale toxic fumes.

The discoloration of the extinguishing water indicated that dangerous substances had been released in the Sandoz hall.

The full extent of the Sandoz disaster became apparent a few hours later. The Rhine, which flows through Basel, is blood red, with tons of dead fish floating on the surface. Both are a result of the toxins in the water.

It is a sight that deeply disturbs many people. It is also clear to laypeople: What the Sandoz management initially claims cannot be true: that nothing bad happened in the fire.

Bit by bit, the truth is coming to light: that 1,350 tons of toxic chemicals were stored in the hall, that several thousand cubic meters of contaminated fire-fighting water were discharged unfiltered into the Rhine, that there were almost no alarm and security precautions, that the Swiss authorities neither informed nor warned those responsible in France or Germany.

The effects of the catastrophe soon become apparent there too. With the current, the poisonous wave drifts down the Rhine to Rotterdam. In Baden-Württemberg, Rhineland-Palatinate and North Rhine-Westphalia, drinking water will no longer be taken from the Rhine for up to two weeks in order to protect the population. Downstream to Koblenz there is almost no life left in the Rhine.

At the time, Jo Kehm was a reporter at Südwestfunk in Lörrach. He reported on the disaster and its consequences for months. The now 79-year-old says that the people in the region were stunned with anger, especially because Sandoz must have known what risk the chemical warehouse posed in the event of a fire. In any case, there was already a corresponding report from an insurance company before the accident.

Kehm remembers an information event at the Basel Theater where the then Sandoz factory manager was pelted with dead fish. People from all walks of life suddenly took to the streets, says the former reporter.

40 years ago, reporter Jo Kehms experienced how anger over the catastrophe became the midwife of a movement.

Axel Mayer from the Mitwelt Foundation Upper Rhine is one of them. The environmental activist says that, of course, people had known about the risks that the chemical industry could pose at least since the explosion in a pesticide factory in Bhopal, India, two years earlier.

However, very few people would have believed that an environmental catastrophe like the one that followed the major fire at Sandoz was also possible in Switzerland. That's why fear has spread among many people: "Just a few months after the Chernobyl reactor disaster, nothing suddenly seemed impossible anymore."

As a result, environmental activists from Switzerland, Germany and France joined forces and organized protests together - including a human chain along the Rhine and a "Rhine Tribunal". Axel Mayer is certain: the pressure from the street has had an effect. It is thanks to the environmental movement that it is now possible to swim in the Rhine and other rivers again.

Images that disturbed and shocked the population: Only a few citizens in Switzerland would have thought such a catastrophe was possible.

Marc Daniel Heintz also sees it that way. Heintz is managing director of the International Commission for the Protection of the Rhine (ICPR) in Koblenz. He says: "Because of the great public pressure, not only the industry has invested a lot of money, but also the states in the Rhine catchment area."

They invested an estimated 13 billion euros between 1989 and 1995 to improve the water quality and ecology of the Rhine - nine billion euros of which went into the expansion of sewage treatment plants alone.

Heintz emphasizes: "This is also why we find 90 percent fewer heavy metals and up to 50 percent less nitrate and phosphorus in the Rhine today than before the chemical accident." Today the river is home to more than 70 species of fish.

Suddenly the water of the Rhine near Basel had different colors - this aerial photo shows the river on November 1st, 1986.

In addition, politicians made the industry responsible. Among other things, retention basins had to be built; laws now specify in detail which substances can be stored where and how the whole thing must be secured and documented.

There are also regular cross-country exercises so that in the event of a disaster, the different authorities know what to do.

Matthias Nabholz, who experienced the Sandoz disaster as a teenager in Basel, says that it still shapes his life today. The fear and helplessness he felt on the night of the fire forty years ago was one of the reasons why he later studied environmental sciences at ETH Zurich. Nabholz now heads the Office for Environment and Energy in the canton of Basel-Stadt.

This topic in the program: tagesschau.de | 40 years of the major fire at Sandoz - the disaster from which we learned | Oct 30, 2026 | 6:12 p.m