What was done
The authors explored the effects of 28 dust clouds originating from the arid deserts of Mongolia and China on daily mortality in Seoul, South Korea, over the period 1995-1998, evaluating the association between daily death counts and dust events using Poisson regression analysis adjusted for time trends, weather variables and day of week.

What was learned
The estimated percentage increase in the rate of deaths due to Asian dust cloud exposure was determined to be 1.7% for all people due to all causes, 2.2% for deaths of persons aged 65 years and older due to all causes, and 4.1% among all people for deaths due to cardiovascular and respiratory causes.  These findings led the authors to conclude that "persons with advanced cardiovascular and respiratory disease may be susceptible to the Asian dust events."

What it means
How will the ongoing rise in the air's CO2 content impact this phenomenon?  First of all, the well-documented increase in plant water use efficiency that results from increases in atmospheric CO2 concentration [see Water Use Efficiency (Grassland Species) in our Subject Index] should allow more plants to grow in the arid source regions of the Asian dust clouds, which should help to stabilize the soil and decrease its susceptibility to wind erosion, thereby reducing the severity of these events.  Second, the propensity of elevated CO2 concentrations to increase soil moisture contents as a consequence of CO2-induced reductions in plant transpiration [see Water Status of Soil (Field Studies) in our Subject Index] should also enhance the ability of plants to do likewise.  Third, the ability of extra CO2 in the atmosphere to enhance the growth of cryptobiotic soil crusts [see Deserts (Algae and Lichens) in our Subject Index] should directly stabilize the surface of the soil.  Last of all, as noted by Zavaleta et al. (2003), global warming itself may increase soil moisture contents in water-limited regions by hastening plant senescence and thereby reducing the period of time over which transpiration-driven soil water losses occur.  All in all, therefore, if the air's CO2 content continues to rise, even in the face of further warming, we should see a gradual reduction in the intensity of Asian dust events that appear to have the potential to increase human death rates in Korea and other places around the world.

Reference
Zavaleta, E.S., Thomas, B.D., Chiariello, N.R., Asner, G.P., Shaw, M.R. and Field, C.B.  2003.  Plants reverse warming effect on ecosystem water balance.  Proceedings of the National Academy of Science USA 100: 9892-9893.