This SciShow video is supported by Brilliant.

You can visit Brilliant.org/SciShow to get 20% off an annual premium subscription and keep building your STEM skills day by day! [♪ INTRO] Take a deep breath. I hate to break it to you, but you just breathed in a bunch of dust with your air, because dust is all over the place.

Dust is just tiny particles of stuff, often broken off of bigger stuff, like rocks. But dust is not just rock in powder form. There are more kinds than you might think.

Some of it is poop from small animals, some of it is bacteria from the other side of the world, and some of it is rocks from beyond our world. And all of these different kinds of dust can take an extreme toll on your health. One place where lots of people encounter dangerous dust is in their own homes.

One study of homes in Ohio, US reported that the average house had 0.62 grams of dust in it per square meter. That’s about 1/130th the thickness of a sheet of paper. So yeah, it doesn’t sound like a huge threat.

But that dust might contain allergens that could have huge effects on you. Allergens are what trigger allergic reactions. But it’s not the allergens that pose a threat so much as the asthma that they can trigger.

If the allergen exposure or immune response is high enough, the results could be fatal. And two of the most common allergens in your house actually come from little animals, even if you don’t have a pet! One of them is the dust mite: a microscopic arachnid that looks kind of like a teeny tiny tick.

When you move stuff around in your house, like when you make your bed, the dust mites themselves can be tossed into the air and mix with the dust. And this could pose a problem, because their bodies make a protein with a carbohydrate on it that often triggers an allergic response. So the mites themselves can expose you to allergens, but it’s much more common for their poop to be at the root of your dust allergies.

One study found that a dust sample from someone’s house might have about 30 micrograms of dust mite allergen per gram of dust from over 250,000 balls of dust mite poop. But dust mites aren’t the only creepy crawlies that poop allergens all over your house. Cockroach poop also has allergens in it, in the form of proteins that come out of their digestive tract.

When they’re inhaled, those poop proteins cause allergic reactions, because they change the shape of little features in your immune cells called toll-like receptors. When these receptors change shape, they can’t do their jobs and send signals to other immune cells. But not everybody is affected by these allergens in the same way.

It might depend on where you live. For example, in the US, children in less affluent urban communities are disproportionately exposed to, and dying from, indoor allergens. And even in those communities, allergen exposure varies from city to city.

One study of kids with asthma who live in inner cities found that dust mite sensitivity was greatest in Dallas and Seattle, while cockroach sensitivity was greatest in New York City. Now we can’t say exactly what it is about these cities that led to these differences, because there’s more than one difference between Seattle and New York. But one correlation was the type of home that’s common in each city.

More houses in Dallas and Seattle are detached, and that’s where dust mite allergens are more prevalent, while New York City is full of apartments and cockroach allergens. Outside your home, one of the major contributors to the dust you’ll encounter is the Sahara! Believe it or not, dust storms from the Sahara are really well-traveled.

In 2020, dust from the Sahara made it all the way across the Atlantic Ocean and to the Americas. That happened, in large part, because of the weather. The air over the desert is hot and dry, while the air over the nearby Gulf of Guinea is colder and wetter.

So the transition between those different kinds of air produces a powerful air current that can flow westward. That’s what happened in 2020, when winds picked up Saharan dust and rushed it over the Atlantic. So people in the Americas and southwestern Europe were breathing in dust full of sand and, with it, bacteria.

Those bacteria can trigger allergic responses. Studies published in 2021 found that this dust decreased the air quality in Colombia and Spain during the COVID lockdown, which some researchers have linked to worse COVID outcomes. One of those studies found that during the lockdown, most particulate matter in Colombian air came from the Saraha.

And just after that dust storm there were up to three times more particles in the air. And the other study concluded that Saharan dust in Spain led to more hospitalizations during the pandemic. And that’s not the first time this has happened.

Similar dust storms have been reported since at least the 1970’s. OK, now look around. A lot of your home, and the stuff in it, like furniture, is made from the same material: wood.

And for people who work in the huge wood processing industry, breathing in wood dust is a serious problem. But how fresh the wood dust is makes a difference in how it affects you. People who breathe in dry wood dust can develop asthma, while people who breathe in so-called green wood dust are more likely to develop allergies.

Researchers think that this difference could be related to acids in the wood’s resin. Wood is more saturated with acids when it’s freshly sawed, so those acids play a larger role in how green dust affects you than dry dust does. This green dust contains acids, like levopimaric acid and neoabietic acid, that oxidize easily, triggering allergic reactions as a result.

And other studies found that this is particularly true of people who breathed in pine wood. Pine wood contains abietic acid. And studies in rats showed that this acid kills lung cells by busting them open and destroying the lung’s outer lining.

So scientists think this could be part of why woodworkers develop asthma and lung disease. Now that we know this, measures are being taken in some places to help protect workers. One study found that while cleaning up wood dust increased exposure, working in booths or cabs that separate workers from the dust can keep exposure up to 6 times lower.

But woodworkers don’t have the only dusty job. Coal miners who inhale coal dust are at risk of diseases like pneumoconiosis, a condition that can cause scarred lung tissue, inflammation, and the formation of masses called fibroids. Back in the 1970’s, 30% of coal miners in the US with 25 years or more experience had this illness The US had passed the Coal Act, which required the adoption of preventative measures to keep them safe.

So once those measures were adopted in mines, it seemed to work! But since then, people started noticing a troubling trend. Pneumoconiosis started making a comeback, especially in Appalachia.

By 2015, it was back above 20%. So researchers dug into the problem and found that it might have to do with how coal miners are mining. These days, miners in Appalachia are cutting thinner and thinner coal seams, which introduces more of the surrounding rock into the mix.

And when they cut rock along with the coal, not only are they introducing different minerals to the dust, but they’re also grinding it up finer because they’re using more powerful equipment. And smaller particles can cause more damage. One study in rats found that smaller particles stick around longer in the lungs, produce larger immune responses, and reduce the effectiveness of those immune responses more than larger particles.

And any of those particles can cause pneumoconiosis, but there’s another threat posed by that surrounding rock: Much of it contains silicates – a really common kind of mineral that can lead to a type of pneumoconiosis called silicosis. See, when silicate particles are inhaled, the immune system starts to attack them, causing inflammation in the lung tissue. Eventually, this can lead to swelling and scarring that makes it hard to breathe.

If you want to learn more about the effects of coal on our lungs, check out the SciShow video about the London Fog. But while working in a wood mill or as a coal miner are generally dusty jobs, one job that seems like it would keep you away from dust is astronaut. But!

Starting in 1969, the Apollo astronauts were exposed to lots of lunar dust from activities like driving and walking on the Moon’s surface. It got everywhere. They couldn’t even seal their suits back up after their encounters with the dust because it got in every crack.

And it was so abrasive that it scratched up their helmets so they couldn’t see in certain directions. At some points, it obscured the astronauts’ vision completely. The dust even made its way through their suits and onto their skin.

But even if it hadn’t, it absolutely coated their space suits. And then they ended up tracking it into the landing module, where they breathed it in, and it got it in their eyes. This resulted in a condition with a funny name: lunar hay fever, which is basically just the eye and lung irritation caused by the dust.

To see just how big of an effect space dust can have on astronauts, researchers have conducted experiments that involve grinding up samples of various space rocks for rodents to inhale. In those studies, the effect of breathing in the dust depended on what planet the dust was from. Like, one study found that dust from both the moon and a Martian meteorite cause significant inflammation.

Another study concluded that Martian samples inflamed the lungs more than samples from Earth and the moon. And the moon dust led rats to develop thick and fibrous lung tissue, but not as severe as the lungs exposed to ground-up quartz from Earth. So Martian dust seems to impact lungs the most, then Earth dust, then moon dust.

And moon dust is less toxic and less inflammatory than quartz. So there’s a lot going on in that thin layer of dust that’s probably on your desk right now. It could have little arachnids in it or have come from another part of the world.

So, remember that the next time you … breathe. If we’ve learned anything from this video, it’s that not all dust is the same. So different dust particles probably look different too.

If you wanted to compare the shape and angles of a particle of lunar dust with a particle of ground up quartz, you might need a foundation of geometry. And Brilliant can help you out with that. Brilliant is an interactive platform that keeps you learning on the go and at your own pace.

Their course “Geometry Fundamentals” takes you through the essentials in practical, bite-sized segments. You’ll get to put your knowledge to the test with shape puzzles and angle hunting games. And if you’re traveling this summer, you can still keep learning while you’re on the road.

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Thank you to Brilliant for supporting this SciShow video and thank you for watching. [♪ OUTRO]