It doesn’t help matters for any budding hurricanes that the dust in the SAL is absorbing heat from the sun as it travels across the Atlantic, creating still more atmospheric stability. Even worse for hurricanes, they need a calm environment in order to start spinning, but the SAL is barrelling in with 50-mile-per-hour winds. “It tilts and it bends the tropical cyclone vortex as you go up in height, and it decouples and disrupts the storm’s internal ‘heat engine,’ as we call it,” says Miller. “What the storm wants is just a nice vertically-aligned vortex that it can transfer heat and moisture from the surface upward and out.”
Forecast models can predict where the dust might land in the Americas, just like scientists would do with an approaching hurricane. Miller reckons that the plume currently working through the southern US could eventually make it to him in Colorado, albeit in a diminished form. That’s because of gravity: As the plume makes its way across the Atlantic, the larger particles fall out first, leaving the smaller particles to make landfall.
Air sampling stations throughout the US gather this particulate material for scientists to study. “What we typically see is that the concentrations are highest in the southeast, more towards Florida,” says Jenny Hand, senior research scientist at the Cooperative Institute for Research in the Atmosphere. “And as it moves farther north, the concentrations will go down, just as it sort of settles out, diffuses, and gets moved around. But we do see those impacts up into the Ohio River Valley pretty regularly in our data.”
So what does that mean for respiratory health, especially with Covid-19 being a respiratory disease? “Yeah, it’s not good,” says Hand. “Especially now.”
When you inhale dust, it travels deep into your lungs, triggering an inflammatory immune response. If your lungs are healthy, maybe this will manifest as a mild cough. “But for others who have chronic inflammatory lung conditions, such as asthma or emphysema, this extra burden of inflammation can tip them over into severe breathing trouble,” says Dr. W. Graham Carlos of the Indiana University School of Medicine and Eskenazi Health. “We know, for example, that in many parts of the world that are afflicted with sand and dust storm events, such as the Middle East, we see more asthma and asthma attacks.” He advises that people with respiratory conditions stay indoors until the plume passes. If you have to go outside, he says, wear an N95 mask: “That type of mask filters those fine particles, fine enough to travel in the air across the Atlantic Ocean.”
Carlos adds that researchers can’t yet say whether inhaling the Saharan dust might predispose people to contracting Covid-19, or make the illness worse. “I would caution, though, that Covid is also an inflammatory condition in the lungs, and that’s in fact why people are needing ventilators and hospitals are surging,” he says. “So this could add insult to injury. In other words, you might have a low-grade inflammatory condition from the dust plume, and then if you were to get Covid on top of that, it may be worse.”
As the weather cools in Africa starting in mid-August, that temperature differential between the desert and the forests to the south will weaken, zapping the SAL conveyor belt. The dust clouds will stop rolling across the Atlantic. Then we can all go back to just worrying about Covid-19 and microplastics and a melting Arctic.
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