If you're sneezing right now, the cause may on the other side of the planet. In late June, winds began blowing what NASA describes as a "river of dust" from Africa across the Atlantic Ocean to North and South America.
Because of thermal expansion of the atmosphere around the equator, sand and dirt grains are suspended thousands of feet in the air, as a wind carries them westward.
Though Florida usually gets the heaviest dose of African dust, this year the dust seems to be spreading over a much wider swath of the south and southwest, according to Garrett Lewis, a meteorologist at TV News 5 in Fort Smith/Fayettsville, Ark.
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A study published in the Journal Environmental Science and Technology in 2008 found that the Saharan dust plume had the ability to double the atmospheric dust in Houston.
Dust events of this sort, which occur every year, can be a problem if you're an asthmatic or have respiratory problems. But the dust also can have some beneficial effects.