Por Redaccion 
A study conducted by the universities of Oviedo and Paris-Saclay examined the radioactivity of Saharan sandstorms and found that their radioactive material content is «much lower» at levels posing no significant risk to human health. It was also revealed that typically, the radioactive material transported during these Calima episodes was «not related to the evidence of nuclear bomb tests conducted by France in the Algerian desert in the 1960s.»
The research, led by Germán Orizola, a zoology professor at the University of Oviedo, and Olivier Evrard from Paris-Saclay, has just been published in the journal «Science Progress» of the American Academy for the Advancement of Sciences.
As explained in a press release by the University of Oviedo, Saharan sandstorms or Calimas reaching the European continent are becoming more frequent and intense. In mid-March 2022, Western Europe experienced an exceptionally warm period in terms of duration and the amount of material. The geochemical and mineralogical analysis, along with satellite image examination, has accurately determined that the radioactive material transported during Calima episodes was not linked to the nuclear bomb tests carried out by France in the Algerian desert in the 1960s.
Germán Orizola, a zoology professor at the University of Oviedo, emphasized, «These Calima phenomena generate significant and often unwarranted social alarm due to the amount of radioactive materials they contain, especially because one of the main source areas coincides with the area where France tested 17 nuclear bombs about 60 years ago.»
This study found average levels of radioactive cesium in these samples to be 14 Bq/kg, while authorized levels in food are set at 1000 Bq/kg and 400 Bq/kg for products consumed by children. By calculating the amount of radioactive cesium suspended in the air during these Calima events, the study estimated that in March 2022, these levels were a billion times lower than the limits set by the European Union. «Our findings show that the radioactive material transported during this Calima episode posed no risk to human health,» he added.
The researchers analyzed the mineralogical and geochemical composition of all samples, as well as a detailed analysis of 31 chemical elements and lead isotopes in a selection of locations. These analyses, combined with satellite imagery taken in March 2022 and existing data from air quality monitoring stations, were used to accurately identify the origin of this Calima episode. The abundance of the clay mineral Claygorskite, along with the analysis of lead isotopes and rare earth elements proportions, revealed a characteristic sediment pattern located in Southern Algeria, which was also confirmed by satellite images.
French nuclear tests in the Sahara
The Southern area of Algeria identified as the origin of the March 2022 event includes the Reggane region, where the first French nuclear bomb tests were conducted in 1960. France conducted a total of 17 nuclear tests in the Algerian desert, 4 atmospheric between 1960 and 1961, and 13 underground between 1961 and 1966.
A common concern during Saharan Calima events is the possibility of these episodes transporting remnants of these nuclear tests scattered across the Algerian desert to Europe. This study examined this possibility through a detailed analysis of the concentrations of different plutonium isotopes (240Pu, 239Pu) and Cesium (137Cs).
The analysis of the proportions of these radioactive elements did not match the signal generated by French atomic tests. Instead, it aligned with the global radiation signal detected worldwide, dominated by nuclear tests conducted by the Soviet Union and the United States in the 1950s and 1960s.
Citizen participation
This study was organized around a call through social networks to promote citizen collaboration in collecting samples from different European countries. The sample collection, coordinated by Ana Elisa Valdés, a researcher at the Joint Biodiversity Research Institute (University of Oviedo-CSIC-Asturias), gathered a total of 110 Saharan dust samples collected by 69 key contributors from Spain (83), France (14), and Austria (12).
The significant involvement of citizens in this project, along with the interaction between various international public institutions and the use of data generated and maintained by climate and environmental agencies, offer valuable insights into societal interest in science and the importance of preserving scientific structures.