Desert dust represents the largest source of aerosols in the atmosphere by mass. These fine terrestrial particles emitted by wind action can be transported over varying distances.
Thus, the Sahara and Sahel provide the majority of mineral dust emitted globally each year, some of which is transported to Europe, mainly in the form of sporadic episodes, usually in early spring.
These Saharan dust events darken the sky and impact air quality, which can cause respiratory problems. In March 2022, an exceptional event occurred, marked by significant ground-level dust deposits, covering much of Western Europe.
Cesium-137, an artificial radioactive substance emitted by atmospheric nuclear tests and nuclear accidents, was detected by an
association in dust deposits collected in France during this March 2022 event.
The origin of this substance was attributed to French nuclear tests conducted in the
Reggane region of southern Algeria in the early 1960s. However, results from a study conducted by CNRS Terre & Univers laboratories, the University of Oviedo, and the Swiss Federal Office for Civil Protection laboratory in Spiez, based on the analysis of samples (110 in total) obtained through a participatory science approach, show that this is not the case.
To achieve these results, various types of complementary analyses were performed: air mass back-trajectory analysis, elemental geochemistry, granulometry, clay mineralogy, and radionuclide activities and their isotopic signatures. These were conducted on all or part of the 110 samples collected from southern Spain to Austria following a call to collect dust deposits from the event via social networks during and after the event.
Example of a dust sample collected in northern France as part of the participatory science approach conducted in March 2022.
© LSCE
The results show that although the dust comes from a region that partly coincides with southern Algeria, where France conducted atmospheric nuclear tests in 1960 and 1961, it does not bear the expected radioactive signature of French nuclear tests. Instead, the dust carries the signature of global fallout, largely dominated by nuclear tests conducted by the United States and the Soviet Union in the late 1950s and early 1960s, which still mark soils worldwide today.
Moreover, the levels of radioactive cesium detected in all the dust samples collected (median of 14 Bq/kg) are much lower than those allowed in most foodstuffs in the European Union (generally 1000 Bq/kg). Additionally, inhaling this dust exposes populations to a negligible radioactive dose rate.
While the recurrence of such events reaching Europe is influenced by current climate change, these results are reassuring from a health perspective. Furthermore, this study highlights the unique opportunity offered by participatory science. Indeed, such a large number of spatially distributed samples across Europe could not have been collected by research teams alone.
Reference:
Yangjunjie Xu-Yang
et al.,
Radioactive contamination transported to Western Europe with Saharan dust.
Sci. Adv.11,eadr9192(2025).