What was done
The authors review what is known about the long-range transport of windborne dust throughout the world and the biological characters that hitch a ride on it.

What was learned
Shinn et al. report that "dust from the African desert can affect air quality in Africa, Europe, the Middle East, and the Americas," and that "Asian desert dust can affect air quality in Asia, the Arctic, North America, and Europe."  During large Asian dust storms, for example, they say that "an estimated 4,000 metric tons of soil per hour can affect the Arctic environment (Rahn et al., 1977)."  Likewise, they state that "Perry et al. (1997) found African dust as far north as Maine and as far west as Carlsbad, New Mexico," where "approximately half of the dust collected in Carlsbad originated in Africa."

Typically riding on this dust are a number of biological entities, including "many species of fungi (commonly known as molds) and bacteria - including some that are human pathogens."  In African dust collected in the Caribbean, for example, Griffin et al. (2001) discovered, in the words of Shinn et al., that "approximately 30% of the microbes cultured and identified thus far are capable of causing disease in plants and animals, and 10% are opportunistic human pathogens."

What it means
Shinn et al. conclude that "atmospheric exposure to mold-carrying desert dust may affect human health directly through allergic induction of respiratory stress," and that "mold spores within these dust clouds may seed downwind ecosystems in both outdoor and indoor environments."  We concur in this assessment and merely add that the ongoing rise in the air's CO2 content may help to reduce the seriousness of the situation by promoting plant growth [see Deserts (Expanding or Shrinking?)] and the spread of cryptobiotic soil crusts [see Deserts (Algae and Lichens)] in desert areas, which can help stabilize desert soils and reduce wind erosion.

Reference
Griffin, D.W., Garrison, V.H., Herman, J.R. et al.  2001.  African desert dust in the Caribbean atmosphere: microbiology and public health.  Aerobiologia 17: 203-213.

Rahn, K.A., Boyrs, R.D., Shaw, G.E. et al.  1977.  Long-range impact of desert aerosol on atmospheric chemistry: two examples.  In: Fenner, F. (Ed.), Saharan Dust: Mobilization Transport, and Deposition. John Wiley & Sons, Chichester, United Kingdom, pp. 243-266.

Perry, K.D., Cahill, T.A., Eldred, R.A. et al.  1997.  Long-range transport of North African dust to the eastern United States.  Journal of Geophysical Research 102: 11,225-11, 238.