Studies have shown particles of Sahara sand in the air above France can cause respiratory and health problems, including transporting viruses such as avian flu, pathogens and pollution as they travel.
Skies above France have turned orange three times in the past month as weather patterns cause particles of sand from the Sahara desert to be picked up and blown over Europe.
The phenomenon happens every year, but it has been particularly noticeable recently.
It has caused peaks in pollution levels in several regions of France, including Corsica, Ile-de-France, Bourgogne, in the Alps, and Grand-Est.
Phénomène naturel garanti sans filtre.— Préfet de région Auvergne-Rhône-Alpes et du Rhône (@prefetrhone) February 6, 2021
Un puissant flux de sud transporte le sable du #sahara ce qui rend la couleur du #ciel particulière aujourd’hui à #Lyon et dans le reste du département. pic.twitter.com/g44FDzAeQd
This is because the phenomenon has been accompanied by anticyclone conditions and warm temperatures; and other sources of pollution including domestic heaters, road traffic, and the beginning of crop spreading by farmers.
A pollution alert was issued on March 3 for two days in three departments in the southwest: the Pyrénées-Atlantiques, Landes and Gironde.
Vincent Guidard, manager of the atmospheric pollution team at national meteorological research centre CNRS/Météo-France told newspaper Le Monde: “This phenomenon is quite normal but this time it was been particularly evident and noticed.”
The World Meteorological Organisation (WMO) estimates that between 1 billion and 3 billion tonnes of particles are thrown into the planet’s atmosphere every year. Of this, 500 million to 1 billion, come from the Sahara.
The World Health Organisation (WHO) is working with the WMO to publish a report on the health effects of these desert particles by the end of the year.
Dr Pierpaolo Mudu, statistician and specialist in air pollution at the WHO, said: “Epidemiological studies have shown evidence of an acute risk of cardiovascular mortality due to respiratory problems, as well as childhood asthma.
“But this risk has been identified in the short-term and there is a lack of studies into long-term effects.”
The sand particles are considered to be “large”, in that there are between 2.5 and 10 micrometres. They are more likely to be stopped by the respiratory airways, unlike fine particles (<2.5 micrometres) and ultra-fine (<0.1 micrometres).
Yet, Dr Thomas Bourdrel, radiologist and member of the Air Santé Climat group, explained: “Their initial composition is less toxic than particles from fossil fuel combustion.
“The problem is when they travel hundreds or even thousands of kilometres, they transport many pollutants and pathogenic agents that they come into contact with on the way.”
Studies have shown that the particles can also be themselves contaminated with dangerous heavy metals, phthalates, pesticides and pollen on their journey.
Dr Bourdrel, who is also a co-author of an analysis of articles exploring the links between air pollution and Covid-19, published in February in scientific journal European Respiratory, said: “This has shown, for example, that for avian flu, there was evidence of the virus spreading between two poultry that were several hundred metres apart.”