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In the 1930's, the dust storms on America's Great Plains became legendary. Years of drought on the vast stretches of flat, grassy land stretching from Canada to Texas combined with years of deep plowing of deep topsoil led to dust storms that buried farms, houses, cars, and people, and a massive migration of Americans to California.
In the 1950's, even worse droughts led to a few even worse dust storms, without the migration of Americans and Canadians to the Pacific coast, because of the widespread use of better farming practices. For the next 40 years, dust storms became a very rare event, but since about 1990 they seem to many people in the American West to have become more frequent yet again. University of Colorado scientists set out to determine whether millions of Westerners weren't right in their sensation that their part of North America was becoming dusty once again.
Calcium as a Surrogate Measure for Dust
Meterologists don't typically measure the movement of dust over long periods of time. There aren't a lot of studies that could demonstrate whether or not dust storms, short of the kinds of catastrophic dust storms that led to the writing of The Grapes of Wrath, were really becoming more common in the Western U.S. Doctoral student Janice Brahney decided to look at the question of whether Western dust storms were becoming more common by taking a look at changes in calcium in rainwater.
Since scientists know that coal emissions, forest fires, and ocean spray haven't increased over the last 20 years, if there has been an increase in the amount of calcium coming back down to earth in rain and snow, chances are it's getting into the atmosphere in the form of dust. Conveniently, the US government's National Atmospheric Deposition Program has been measuring calcium in precipitation at 175 locations in the US since 1975. The now-Dr. Brahney took a close look at their data.
Calcium Dust Raining Down on the American West
Brahney found that at 116 out the 175 locations calcium levels have been increasing over the past 40 years. The reporting stations with the greatest increases in calcium, presumably from dust storms, have been in the Intermountain West, in Colorado and Utah, which is also where most people have been noticing "more dust storms than there used to be." Brahney and her dissertation supervisor Associate Professor Jason Neff are sure that there's more dust than there used to be. And that extra dust has significant consequences for human health.