Nature Communications has published a study on radioactive substances left in the atmosphere by atomic experiments. The levels aren’t hazardous, but they are still there seven decades later.
Traces of the nuclear experiments carried out by the US, Russia, France and other nations who detonated hundreds of airborne atomic warheads during the 1950s and 1960s, can still be found in honey.
The disturbing announcement comes from researchers at the William & Mary University in Williamsburg, Virginia, who analysed 122 samples of honey from different areas in the US, before publishing the results of their work in the magazine Nature Communications. Science magazine has also covered the topic.
The concentrations of the radioactive isotopes found in American honey are low, far beneath safety thresholds for human health. Yet, this discovery once again underscores just how dangerous it is to conduct atmospheric tests with materials that take tens, if not hundreds, of years to decay.
Honey, in particular, revealed traces of Caesium-137, a radioactive isotope always left behind after the explosion of a nuclear bomb.
A chance discovery
The first sample of radioactive honey was virtually stumbled across in Raleigh, North Carolina, on the east coast of the USA.
Professor James Kaste, the lead author of the study published by Nature Communications, asked his students to collect foods used in their areas to conduct routine measurements of any radioactivity they might contain. Yet on examining a jar of honey in the laboratory, it was found to contain Caesium-137 in concentrations up to 100 times greater than those found in other types of food.
To study this in greater depth, Kaste decided to systematically collect and analyse a larger number of samples (122, as mentioned above) from different areas. In so doing he discovered 68 had Radiocaesium levels over 0.03 becquerels per kilo. One sample in particular, of unprocessed honey from Florida, reached 19 becquerels.
The concentration is far below the threshold safety limit (1,200 becquerels per kilo), but this study shows just how much nuclear fallout persists over time. It also demonstrates that it covers great distances, given that the tests were mostly conducted in the Pacific Ocean or in deserts thousands of kilometres away.
As with other isotopes, with the passing of decades, Caesium decays. The researchers checked data on two series of tests conducted on milk in the same areas in the ‘70s, leading them to calculate that levels of Caesium-137 at the time were around ten times higher than present-day levels.
Likely, the same thing happened with honey. “What we’re measuring today,” Kaste confirms, “is just a whiff of what was there before.”
Have bees been affected?
So, the contamination is still there, albeit at minimal levels. It comes from the fallout of elements that first disperse in the atmosphere, then fall to ground and water in the form of rain, before reaching plants and then bees.
Yet contrary to what one might first think, the fallout is not higher in the rainier areas, but instead in areas where soils contain little potassium, such as some parts of America’s east coast.
Why is this the case?
Researchers explain that plants need potassium to survive. But they can also make do with Radiocaesium, which is water-soluble and has some similar chemical properties.
Whilst there aren’t any consequences (at least, there shouldn’t be) for human health at this moment in time, the authors are wondering if there have been consequences for bees over the course of the decades; and if the radioactive Caesium might have played a part in their drastic decline (chiefly caused by pesticides used in farming), and to what extent. Bees suffered greatly in the wake of the accident at Chernobyl in 1986, although concentrations of radioactive elements then were thousands of times higher.
