African Dust in the United States? Impacts on the Environment
Did you know that dust from North Africa can travel west by air currents and reach the eastern United States? Dust clouds move through the Caribbean into portions of North, Central and South America. This phenomenon happens every year and it is estimated that arid regions of North Africa can generate up to 800 teragrams of dust per year (one teragram weighs as much as three Empire State Buildings), making it the largest dust source in the world – six times larger than the next largest source, Asia. African dust can also travel east towards the Middle East and Arabian Sea, and north over the Mediterranean to Europe. Charles Darwin even documented this phenomenon during his trip in the 1830s on the HMS Beagle, while navigating near the west coast of North Africa.
African dust in the United States has been detected in southern states, across the northeast as far as Maine, and westwards as far as Texas. As dust particles travel across the Atlantic, large particles are lost in transit and smaller particles remain. Occasionally, swarms of African grasshoppers travel along in the cloud of dust and land in the Caribbean.
African dust can impact the environment in a number of ways:
- African dust is a significant contributor to soil formation in the Caribbean and the Bahamas. It also supplies critical nutrients to the Amazon basin.
- African dust contains particles such as phosphorus, which contributes to soil fertility. Deep ocean supplies of iron and phosphorus from African dust are essential nutrients for the oceanic food chain.
- Particles in African dust can be smaller than 2.5 micrometers – for comparison, the average human hair is about 70 micrometers in diameter – and are easy to inhale. African dust can impact air quality and constitute a major health threat. It is a potential asthma trigger and poses a risk for people with other respiratory problems.
- Scientists believe that African dust could be a contributing factor to Caribbean coral reef decline because it transports pathogens to the area. African dust contains spores of fungus that can be destructive to corals such as sea fans.
- Bacteria and viruses have also been detected in African dust clouds, as well as pesticides banned in the United States. More research is needed to determine the impact on human health.
- African dust can produce haze and reduce airplane visibility, affecting the aviation industry.
Thanks to satellite imagery, scientists can watch and study African dust clouds. This technology aided scientists in detecting that African dust is transported mainly into the Caribbean and to South America during North American winters, and then shifts northwards to the southeastern United States during the summer. Watch this video of an African dust cloud traveling over the Atlantic, from NOAA’s Environmental Visualization Laboratory:
(Source: Prospero, J.M. and O.L. Mayol-Bracero. 2013. Understanding the Transport and Impact of African Dust on the Caribbean Basin. Bulletin of the American Meteorological Society. 94(9):1329-1335. and Huang, J., C. Zhang, and J.M. Prospero. 2010. African Dust Outbreaks: A Satellite Perspective of Temporal and Spatial Variability over the Tropical Atlantic Ocean. Journal of Geophysical Research. 115, D05202, doi:10.1029/2009JD012516. and Prospero, J.M. 1999. Long-range Transport of Mineral Dust in the Global Atmosphere: Impact of African Dust on the Environment of the Southeastern United States. Proc. Natl. Acad. Sci. 96:3396–3403 and Prospero, J.M. 2013. African Dust in America. Geotimes. Accessed online 24 October 2013. http://www.geotimes.org/nov01/feature_dust.html and Kellogg, C. 2002. African Dust Microbiology in the Caribbean. United States Geological Survey. Accessed online 24 October 2013. http://soundwaves.usgs.gov/2002/09/research2.html and Schmidt, L.J. 2001. When the Dust Settles. National Aeronautics and Space Administration. Accessed online 24 October 2013. http://earthobservatory.nasa.gov/Features/Dust/ and Science Daily. 2013. African Dust Storms in Our Air: Dust Storms in Africa Affect U.S. and the Caribbean’s Air Quality. Accessed online 24 October 2013. http://www.sciencedaily.com/releases/2013/09/130918180934.htm)