US nuclear bombs still pollute several Pacific islands 60 years later | Science

It had not been a year since the bombs on Hiroshima and Nagasaki ended World War II, when the United States launched its nuclear test program in the Marshall Islands, then under US administration. Between 1946 and 1958, atomic weapons exploded in this archipelago in the middle of the Pacific. Sixty years later, an exhaustive independent study reminds us that the seabed, soils and even atoll fruits such as Bikini or Enewetak accumulate radioactive particles well above authorized levels and, locally, at high concentrations. higher than those measured in the Chernobyl or Fukushima disaster areas.

"Until now, no independent investigation has been conducted into the radioactive contamination and its consequences," says Spanish Monica Rouco, deputy project director K = 1, the center of the project. Nuclear studies from Columbia University (United States). They carried out a series of scientific missions to the Marshall Islands between 2015 and 2018. Until these works, the only studies conducted in the former Spanish colony on the effects of such a nuclear test had been carried out by government scientists and military, including the Lawrence National Laboratory. Livermore. "Previous data on the island population lack confidence and are unreliable," adds Rouco.

Scientists in the K = 1 project were able to badyze levels of gamma radiation in the environment during successive campaigns, the first results of which were published in 2016, and more recently, the concentration of several radioactive elements, such as plutonium 238, americium 241 or cesium 137. in samples of soil and seabed and fruits collected by all the atolls and islands supporting the bombs or their fallout.

But the worst is on the ground. Although they only detected the presence of plutonium 238, they found four other radioactive isotopes and very high concentrations. Let's take an example: the United States has established the maximum safety limit for one of them, americio-241, the figure of 1,110 Beckerels per kilogram of material, in this case land (the Beckerel is the unit of nuclear activity of a radioactive isotope). On the island of Naen they reached 3,090 Bq / kg. In Bikini, other elements, such as cesium 137, reached 7,140 Bq / kg. Although localized, they far exceed those recorded in areas near Chernobyl a decade after the explosion of reactor No. 2 or those measured after the tsunami that dismantled the Fukushima plant.

"For each radioisotope (Am-241, Cs-137, Pu-238 and Pu-239.240), we sought to compare the values ​​obtained with the standards and / or available concentrations measured in other regions of the world affected. by radiation by humans, "says Nikolic-Hughes. "In particular, comparison of Pu-239.240 concentrations with measured values ​​in Fukushima and Chernobyl-affected areas indicates that they are significantly higher in some of the northern parts of the Marshall Islands," he adds. -he. But the director of the K = 1 project specifies that in order to be able to compare, it would be necessary to have many more registers of the different sources and types of radiation of the zones to be compared.