The Sahara is the largest source of desert dust in the world, dust which is capable of travelling as far as Europe or the Caribbean. But the populations most exposed to this form of atmospheric pollution are those of West Africa, and almost nobody has looked into the subject.

The health of African populations could be seriously affected by the Saharan dust which, during certain seasons, climbs to altitudes of thousands of metres before subsequently depositing itself on European and American soil, but also on the majority of countries in West Africa. Such is the hypothesis of Florence de Longueville and Pierre Ozer, respectively researchers at the Department of Geography at the University of Namur and the ULg’s Department of Environmental Sciences and Management, at Arlon. With their colleagues Sabine Henry (Namur) and Yvon-Carmen Hountondji (Parakou Agronomy Faculty, Benin), they have just published an article (1) in Science of the Total Environment, based on a systematic review of the scientific literature devoted to the subject over the past ten years.

Despite scientific interest in this subject being pretty recent, it is known that immense clouds of dust, capable of carrying out journeys measuring thousands of kilometres, regularly form in nine of the planet’s regions: the Sahara (North Africa), South Africa, the Arabic Peninsula, Central Asia, West and East China, North America, South America and Australia. With a contribution estimated between 50 and 58% of the total, the Saharan zone comfortably appears in the lead of these dust ‘reservoirs.’ Even if particles specifically of anthropogenic origin (notably the ‘PM2.5s’ – Particulate Matter with a size smaller than 2.5 µm - with origins in particular in human activity in urban environments) eventually become part of this dust, the latter can be generally termed, at the start, ‘natural,’ and is the result of wind erosion.  In West Africa the dust is placed in suspension and carried by a dry wind (the Harmattan) which, from the end of November to March hauls this various particulate matter across a North East/South West axis from the Sahara desert to the Gulf of Guinea, passing through Benin, Nigeria, Togo, the Gabon, Ghana, the Ivory Coast, etc.

(1) de Longueville F., Hountondji Y.C, Henry S., Ozer P., 2010. What do we know about effects of desert dust on air quality and human health in West Africa compared to other regions? Science of the Total Environment, 409: 1-8.