SAHARA SAND. As last February, the sky turned orange in several regions of France this Monday, September 4. In question, a cloud of sand from the Sahara. The phenomenon could persist all week over a large part of the country.
[Mise à jour le 04 septembre à 14h51] The sand of the Sahara invites itself again in France. After flying over Portugal and Spain, the sand particles from the Sahara reached France on September 4th. This phenomenon, which occurs several times a year, has already been observed throughout France last February.
The clouds of sand, carried by the winds from the south, give the sky a yellow-orange tint. They can also cause eye and respiratory tract irritation.
Although the term “cloud” is commonly used to refer to this phenomenon, it is actually a “mist”. This distinction is important because mists are denser than clouds and can therefore have a greater impact on visibility.
According to meteorologist Guillaume Séchet, the arrival of this sand is linked to the high temperatures that will rage throughout the week. An interactive NASA map shows that only part of the east of the country will not be affected by the phenomenon. The sand should not land on French soil due to the fine dry weather which is expected until Sunday. The sky could however have a milky appearance in places depending on the concentration of sand.
This situation is rather frequently observed in winter. Indeed, the depression, with the strong winds it generates, lifts the sand of the Sahara desert. And with a southerly flow that extends from the Maghreb to Europe, the sand particles transported will then give this particular color to the sky and come to settle on the ground because of the rains. The phenomenon is more often visible in the south of France, because the sand is deposited on the side of the Pyrenees or the Alps, and does not rise in the North of France.
Experts agree that the fallout from nuclear tests carried out in the 1960s left a lasting mark on the Sahara desert, as the Institute for Radiation Protection and Nuclear Safety reminds us. These fallouts come from a hundred atmospheric tests carried out by several great powers: in the final score, the USSR and the United States are neck and neck with 219 shots, then comes the United Kingdom with 23 shots, China with 22 and France with only 4 in the Sahara (but 46 in Polynesia).
The sand indeed contains cesium 137, a radioactive element which has a half-life of 30 years and which can therefore act on these particles. However, radioactivity specialists want to be reassuring since the phenomenon had already occurred in February 2021, without major consequences on air quality. Indeed, if, during this month of February, the activity concentrations of cesium 137 had been higher than the average of the activities measured in February 2019 and 2020 (measurements taken by IRSN as part of its mission to monitor the radioactivity of the air), the concentration of cesium 137 present in the fine particles of Saharan sands was “in February 2021 extremely low in the atmosphere and at ground level” recalls Jean-Christophe Gariel, deputy director general in charge of the health- environment at IRSN (comments reported by the Parisian).
The health impact of these meteorological episodes is therefore considered negligible by IRSN. If health risks exist, they are no worse than those of classic air pollution: in the same way as in March, Météo-France did not communicate an operational color forecast, because this phenomenon will not have normally no real impact on the safety of people.
Why shouldn’t you wash your car?
This phenomenon of depositing dirt on cars leads to a great temptation to wash your vehicle so as not to keep these particles on the bodywork. However, grains of sand can cause scratches, if only by running your finger over them. It is therefore strongly recommended not to clean it with a roller from a car wash, but rather to wait for the time to do its work for the cleaning. For those in a hurry, it is better to rinse it by hand and possibly apply a cleaning product with a sponge.