A team of researchers from William & Mary University (USA) has found traces of the radioactive isotope cesium-137 in honey samples from different locations in the USA. Cesium-137 is a by-product of nuclear fission of uranium and plutonium coming , like other isotopes present in the atmosphere today, from nuclear tests carried out in the 1950s and 1960s in the framework of the Cold War.
The authors of the work, which is published in the journal Nature Communications , found traces of the radioactive isotope in 68 of the 122 samples analyzed. Furthermore, the proportion of cesium-137 was highly variable between samples. The reason for these differences is found, according to scientists, in the chemistry of the soil: honey with traces of cesium came from soils with low potassium content . “Potassium is a very important nutrient for plants,” explains Jim Kaste, associate professor of Geology and lead author of the work. “And it turns out that the cesium and potassium atoms are very similar.” According to his hypothesis, in soils with a low content of the precious nutrient, plants absorb what would be more similar, in this case cesium-137, which would reach the bees through the nectar of the flowers. Additionally, in the honey-making process, bees would biomagnify cesium, resulting in unusually high levels compared to traces found in other foods.
There is no health risk
The authors have insisted that the levels of cesium-137 found in honey are well below the limits established by health authorities to consider it dangerous to health and withdraw it from the market. ” We are not telling people not to eat honey, I actually eat more honey since I started this project, ” explains the researcher.
Cesium-137 has a half-life of around 30 years and remains the dominant form of ionizing radiation pollution in the environment even 60 years after the end of nuclear testing. The infiltration of cesium-137 into the human diet has long been a cause for concern, and many studies were done in the 1980s to determine safe levels. For example, much higher levels of cesium-137 were detected in many milk samples than those found in the honey samples of the present work, and they were never withdrawn from the market because they were considered safe limits.
A problem for insects?
Although the traces of radioactive isotopes that persist in the environment do not pose a risk to human health, insects could be another matter. “What we see today is only a small fraction of the radiation that was present during the 1960s and 1970s,” the scientists explain. ” And we can’t say for sure if cesium-137 has something to do with declining bee populations.”
Kaste hopes his work will serve as an example of the long life of environmental pollutants, particularly the often unpredictable ways in which pollutants can circulate in the environment. Cesium-137, he explains, is an “inherited pollutant,” which remains with us as nuclear decay halves its presence every three decades.
