i initiative

Space and Development…Increasing Access to Space in Africa

Dust, Dry Days and Disease in Africa 3

Posted by Simon Adebola on August 14, 2009

Images from the Moderate Resolution Imaging Spectroradiometer (MODIS) on board the NASA Terra and Aqua satellites have been very useful in tracking the spread of dust on and away from the African continent. This has also helped in guiding researchers and scientists in observing the links between this spreading dust and various climatic and biological phenomena.
Saharan Dust Travels Over The Atlantic

The image above depicts the flow of dust off the west coast of Africa. The following description from the NASA Earth Observatory states that,

“The Sahara experiences extreme variations in land surface temperature—from freezing temperatures at night to more than 54.4°C (130°F) during the day. The extreme daytime heating in the Sahara Desert, especially during the summer, causes instability in the lowest level of the atmosphere. Dust-laden air rises and begins moving westward. As the air travels—a trip that often takes several days—it continues heating. When this Saharan Air Layer moves off the African coast and over the Atlantic Ocean, it is undercut by a cooler, wetter layer of air. Air normally cools with altitude, but the Saharan Air Layer passing over cooler air currents causes a temperature inversion, which suppresses mixing. As a result, Saharan dust often travels across the Atlantic, sometimes remaining visible throughout the trip.”

Dust moves freely across the continent and blows off the coast driven by the various winds and thus goes to contribute to the soil profile of other parts of the world. It also settles in the ocean along its way adding nutrients and thus embellishing oceanic ecological patterns.

But what effect does this have on human health and livelihood? In looking at that we would like to consider the amount of the earth’s surface that is potentially exposed to airborne dust. Airborne dust has been described, by the National Institute of Health (NIH) in the United States, as the primary source of allergic stress worldwide. Deserts (in this case referring to non-polar arid zones) are major sources of dust particles.

Global Distribution of Non-Polar Arid Land (Source: Meig, 1953 in Edwards, K. 2001)

Global Distribution of Non-Polar Arid Land (Source: Meig, 1953 in Edwards, K. 2001)

D. W. Griffin has worked on using satellites to monitor the global spread of dust and linking this with its effects on ecology and human health. His work (in this paper with C. A. Kellogg) identified these effects on life forms, both human and in the oceans, and on various continents. The identified effects include coral bleaching, algal blooms and allergenic effects on humans, including aggravating asthma. This may not be solely due to desert dust but the increased concentration of these dust particles, some as fine as 2.5 microns, in combination with other industrial and environmental pollutants may play a role in immunogenic responses that cause ill health. The human respiratory mucosa usually traps dust particles and tries to clear the respiratory passageways of these irritants. However, these very fine particles may exacerbate that response. This is of more serious concern in individuals with compromised respiratory and immunologic responses.

A lot of the research in this area has focused on the Trans-Atlantic effects of dust spread. This has had effects in the USA and the Carribeans. Griffin reported studies stating a 17 fold increase in paediatric asthma between 1976 and 1999. Other studies identified a relationship between dust events and hospital asthma visits. This however was not solely due to dust of African origin, which was said to have contributed (~50%) alongside other sources of dust activity. Also, the link between dust events and the epidemic prone disease, meninigitis, is already being investigated.

In strengthening the capacity to detect which dust events and sources are responsible for some disease events in Africa, the use of satellite technologies play a very important role. This occupies a relevant area of research alongside other initiatives to boost the monitoring and reporting capacity for Air Quality Indices. There are various aspects of using available resources for strengthening our awareness of the effects of inspired air on human health. The training of scientists and continued collaboration with the environmental sector, meteorologists, climatologists, public health researchers, and healthcare policy makers is a definite step towards developing a functional warning system with strong interventional capability. Academic research institutions can mobilize resources to develop training programmes in support of this crucial area of need. Ultimately such efforts may not go far without governmental support. The role of environmental and healthcare organizations in developing awareness and response capacity and acting to engage political leadership is also of importance. Hand in hand, individuals and associations can work to bring about a safer and securer environment to live and work in.

You can follow the progression of the Saharan Air Layer (SAL) on this site with frequently uploaded satellite images.

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One Response to “Dust, Dry Days and Disease in Africa 3”

  1. B umar said

    Thank u best dt u have been doing 4 us. Pls i need ur help 2 b sending me information on remote sensing. A student fr Fut minna. Thanks

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