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Dust storms in the Sahara are killing kids half a continent away

By Kelse Piper

It’s not news that air pollution is really bad for people’s health. A few recent studies have only hammered that point home.

One paper looked at the effects of diesel cars that were supposed to meet emissions guidelines — but in fact did not — and suggested that even the slight increase in air pollution from one cheating car meant more kids hospitalized and more babies born prematurely. Another study found that air pollution worsens dementia substantially.

Add a new NBER working paper from Stanford environmental researcher Sam Heft-Neal and colleagues to the pile of research sounding the alarm on air pollution. The paper looks at the health dangers of air pollution from a source we rarely think about: desert dust. Titled “Air Pollution and Infant Mortality: Evidence from Saharan Dust,” the study presents a stunning finding: Poor air quality in areas affected by dust from the Sahara desert leads to a 22 percent increase in infant mortality.

These numbers aren’t wildly out of line with research about the effects of air pollution on infant mortality from other studies conducted in richer countries. But their implications are enormous. If dust from the Sahara is killing as many kids as the working paper suggests, then we need to devote more attention to it. And perhaps extreme measures that have long been dismissed as excessive and extraordinarily expensive — measures like, as the paper proposes, watering the desert so it doesn’t get so dusty — would actually be a fairly cost-effective way to save kids’ lives.

At the very least, this latest study should bolster the case that air pollution is a high-impact and yet oddly neglected global problem.

Air pollution really, really matters.  Air pollution reduces life expectancy for everyone, but it’s particularly hard on children.

“Poor air quality is a known determinant of poor health outcomes, with even modest improvements in air quality likely to save millions of premature deaths annually,” the working paper notes.

But we’ve only recently learned more about air pollution, and so there are lots of important research questions that haven’t been answered yet. For example, how much sickness and death is caused by any specific source of pollution (like, say, Saharan dust)?

One good way to study that is with a “quasi-experimental” design that takes advantage of ways a specific source of pollution will vary in the environment (different states might have different regulations, or wind patterns might douse one half of a city in more pollution from a factory than the other half). With a good research design, these studies can isolate the effects of a specific pollution source. Research like this is being conducted in developed countries.

 This paper tries to take the same approach to estimate the effects of an unexpected air pollution source: dust from the Bodélé Depression, the area of the Sahara that is the single largest source of dust emissions in the world.

We might not usually think of dust when we think of air pollution. But what makes pollution so bad for us is the small particles that settle in our lungs when they’re not supposed to be there. And those particles are dangerous whether they’re from cigarettes, factory smoke, or dust (though of course some of the specific effects might be different). Dust is a form of air pollution — and, the study finds, a deadly one.

The researchers use satellite data to look at dust emission events in the desert — instances where weather patterns kicked up more dust than usual and swept it into the air. They combine that data with household survey data of about 1 million births across the continent of Africa.

The findings show that an increase of 10 micrograms per cubic meter in small particulate matter — for reference, an eyelash weighs about 40 micrograms and a cubic meter is about the space under your dining table — causes a 22 percent rise in infant mortality across Africa. Since in much of West Africa the amount of small particulate matter in the air is mostly a product of activity in the Bodélé Depression, that means somehow handling the dust from the Bodélé Depression could save a lot of lives. 

One idea to do so sounds outlandish on its face: watering the desert. Unrealistic though it may sound, the researchers conclude it could actually be a cost-effective intervention. They calculate that this could save lives for about $60 per year of life saved, and point out that even if they’re wrong by a factor of five, that’d still be impressive cost-effectiveness.

I’d take that with a grain of salt; my experience with development interventions is that they typically, for many complicated reasons, turn out to be much less cost-effective than they look in the first analysis. But as the authors observe, even if their estimate is too optimistic, the intervention would still appear to be in the range of cost-effectiveness that makes it worth pursuing.

This might become more urgent as time goes on, because climate change will affect rainfall patterns in the Sahara as well as how dust gets distributed. The researchers attempt to model the effects of climate change, but our significant uncertainty about how rainfall patterns in the region will be affected by climate change makes it hard to say what to expect: The dust problem could get better, or it could get much worse.

Now that we have reason to suspect many lives are at stake from these desert rainfall patterns, hopefully additional research can help reduce the uncertainty there — and further explore the possibility of environmental management to control dust, reduce air pollution, and save lives across West Africa.

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