Wild boars in Bavaria are radioactive – but not for the reason many believe.
The hairy, tusked pigs, which can weigh up to 100kg, contain radioactive cesium levels that pose a risk to humans if eaten.
Previously this was thought to have been caused by the 1986 Chernobyl disaster, but a new study suggests the contamination primarily stems from nuclear weapons tests decades earlier.
Radioactive cesium is produced by nuclear weapons and nuclear fission, both producing the isotopes cesium-135 and cesium-137. However, the two decay at different rates depending on their origin, meaning the ratio between them can help determine the point at which contamination occurred – after Chernobyl, or earlier.
On April 26, 1986, reactor 4 at the Chernobyl power plant in Pripyat exploded, killing two workers. Pripyat was evacuated 36 hours after the accident as radiation spread across the European continent. In the three months that followed, 28 emergency workers and first responders died from acute radiation sickness.
The cloud spread as far as the UK, where heavy rain washed radioactive materials onto farms in the Lake District. Restrictions were put in place to prevent contaminated meat entering the market, only lifted in 2012.
For this reason it has long been assumed that high levels of radioactivity in Germany and Austria’s boar populations were also due to the Chernobyl disaster.
However, while cesium-137 has declined in most game animals, wild boars’ radioactivity levels haven’t changed substantially. Their meat continues to exceed regulatory limits for consumption, in some places leading to less hunting and consequently contributing to the overpopulation of the animals in Europe.
To investigate why this was the case, a team of researchers used a gamma-ray detector to measure meat samples from across southern Germany, and compared the amount of cesium-135 to cesium-137 with a sophisticated mass spectrometer.
The high ratios suggested that nuclear weapons testing supplied up to 68% of the contamination, and in some samples, the cesium from weapons alone exceeded regulatory limits, even without the radiation from Chernobyl on top.
During the Cold War, the Soviet Union carried out hundreds of nuclear weapons tests.
‘Some of our samples from 2019 to 2021 exceed the regulatory limits by a factor of up to 25,’ said lead author Dr Georg Steinhauser from Technische University.
‘The mid-20th century weapons tests were an underappreciated source of radioactive caesium to German soil, which was also unevenly impacted by the Chernobyl accident.
‘Contamination from both sources have been taken up by the wild boars’ food, such as underground truffles, contributing to their persistent radioactivity.’
The researchers said that future nuclear accidents or explosions could worsen these animals’ contamination, potentially impacting food safety for decades, as this study shows.
The study is published in the Environmental Science & Technology.
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