Although scientists have long known that flora and fauna in Central Europe still carry traces of radiation from the 1986 meltdown at the Chernobyl nuclear power plant in Ukraine, a new study of wild boars that roam the Bavarian forest in southern Germany showed unexpected findings. about the radiation present in their tissue.
The peer-reviewed study, was published this past week in the journal Environmental Science & Technology, found in the boars high levels of radiation that researchers believe came from atmospheric nuclear weapons tests that were conducted before the fall of Chernobyl. It also answers a question that has puzzled researchers and hunters: Why is radiation relatively high in the wild boar population, when most other wildlife is not contaminated, many generations after the accident? (Spoiler: It’s because they eat deer truffles.)
The findings were so unexpected that when Georg Steinhauser, the paper’s lead researcher, and a colleague first saw the results, they thought there had been a mistake. “That can’t be right – that’s not possible,” Professor Steinhauser recalled his colleague exclaiming.
Because radiation from the Chernobyl accident temporarily contaminated large parts of Ukraine, Belarus, Russia and Central Europe, the flora and fauna there were regularly tested to determine if they were safe for human consumption. And Martin Steiner, a scientist at the German Federal Office for Radiation Protection who was not involved in the study, said in an interview that he and his colleagues have long known that significant radiation from the mid-20th century nuclear weapons testing remained in the environment. .
But the newly published study, by researchers from Leibniz University in Hanover and the Vienna University of Technology, provides a more concrete way of quantifying the extent to which the radiation from the test persists in the boars. now.
The research used a method involving the ratio of two cesium isotopes to analyze the carcasses of wild boars killed by hunters across Bavaria from 2019 to 2021. That relatively new method of analysis allowed the team to better understand what is behind higher levels of contamination in the wild. wild boar in Central Europe.
In Bavaria, pork caught in certain areas must be tested for radioactivity, and German health regulations allow human consumption of such meat if the radiation is below 600 becquerels per kilogram. Torsten Reinwald, a spokesman for German Hunting Associationsaid in an interview that, in general, “We have no indication that meat from wild boar in Germany is contaminated with significant radioactivity.”
But some of the boars tested in the new study carried higher levels of radioactivity, with contamination ranging from 370 to 15,000 becquerels per kilogram of meat.
And because nuclear reactors and nuclear weapons leave slightly different contamination signatures — with distinct ratios of cesium-135 to cesium-137 isotopes — the researchers determined that a surprising amount of radiation present in the tested boars came from nuclear testing in the 1950s and 1960s.
After the first nuclear weapons test in New Mexico in 1945, the United States, its allies, China and the Soviet Union continued to test atomic weapons by detonating them above ground, leading to heavy nuclear pollution in the atmosphere spread around the world.
All in all, the world’s nuclear powers are in action more than 500 atmospheric tests before moving them underground to try to limit the spread of radioactivity. The new study’s findings indicate how decades of above-ground detonations continue to have consequences.
“The fact that the radiation from the nuclear tests is still there, even compared to Chernobyl, is remarkable,” said Michael Fiederle, a professor at the University of Freiburg who studies radiation and was not involved. in research, in an interview. He also described the method of sourcing radiation by viewing cesium isotopes as promising.
As for why wild boars in southern Germany have more traces of such radiation than other animals, Professor Steinhauser says that an important element in the mystery is a fungus – elaphomyces, or deer truffles – that is dug up and eaten. by wild boars but ignored by other wildlife.
While many other edible fauna are less contaminated, truffles, which grow inches below the Earth’s surface, particularly store radiation. (According to Germany’s Federal Office for Radiation Protection, some wild mushrooms can reach more than 1,000 becquerels per kilogram, although it still considers wild mushrooms safe to eat in small quantities.)
Depending on the composition of the soil and how deep the truffles are dug, the fungi can be exposed to water containing decades-old radiation from nuclear tests and the Chernobyl disaster, making them a particularly rich source. of radiation.
Mr. Steiner, of the Federal Office for Radiation Protection, said that regardless of the source of the radiation, it still poses a risk to people if the levels are high enough.
“When it comes to the radiation exposure of people, it doesn’t matter whether the cesium comes from the global fallout of weapons tests or from the fallout after the Chernobyl reactor accident,” he said, adding, “What is relevant is the total intake of cesium -137 that a person only takes in food from the forest.”