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This photo from 1986 shows the Chernobyl nuclear power plant with the damage caused by the explosion and fire in reactor number four on April 26 of the same year.
archivio KEYSTONE
Shortly before the 40th anniversary of the Chernobyl reactor disaster, the authorities in Ticino are taking stock. The result: the contamination has decreased significantly - but traces are still measurable today.
On April 26, 1986, a reactor exploded in Chernobyl, Ukraine - the consequences were felt in large parts of Europe. Switzerland was also affected by the radioactive cloud, particularly Ticino and regions such as St. Gallen and Thurgau.
The reason lies in the weather conditions of those days. At the beginning of May 1986, rainfall caused radioactive particles to be washed out of the air and deposited in the ground. The long-lived isotope caesium-137, which can still be detected today, was particularly affected.
Four decades later, it is clear that the contamination has decreased significantly, but has not disappeared. As the Ticino authorities explain, around 40 percent of the originally deposited caesium is still present. The decrease is mainly due to natural radioactive decay.
Deposition of caesium-137 in Switzerland in 1986
ti.ch
However, this has hardly any practical consequences for the population today. Measurements show that only a very small amount of radioactivity enters the food chain. Foodstuffs such as milk, grass and soil samples show levels that are considered harmless.
Wild mushrooms, which are considered sensitive indicators of environmental pollution, continue to be a particular focus of attention. Here too, analyses of hundreds of samples show a clear decline in contamination over the past decades.
Organization of measurements: mobile resources and laboratories
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At the same time, monitoring has developed massively. More than 100 measurement campaigns have been carried out in Switzerland since 1986, and modern measurement networks now enable almost seamless monitoring. Thanks to precise weather models, authorities can also simulate how radioactive substances would spread in an emergency.
Switzerland is also closely networked internationally. Data is continuously exchanged with organizations such as the International Atomic Energy Agency via the national alarm center.
Despite the low level of contamination today, vigilance remains high. The authorities emphasize that the Chernobyl disaster was a turning point - and created the basis for a modern early warning system.
The assessment after 40 years is therefore twofold: The danger has largely been averted - the traces have not.
