Today, you’ll learn about why it's best to leave your shoes at the door when you come inside, how animals form and maintain their mesmerizing murmurations, and how certain food storage products release sub-microscopic, plastic particles when exposed to hot water.
Today, you’ll learn about why it's best to leave your shoes at the door when you come inside, how animals form and maintain their mesmerizing murmurations, and how certain food storage products release sub-microscopic, plastic particles when exposed to hot water.
Your mom was right about taking your shoes off inside.
Murmurations not murmuring.
The tiny side of plastic.
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Find episode transcripts here: https://curiosity-daily-4e53644e.simplecast.com/episodes/shoo-shoes-murmuration-information-nanoplastic-particles
[SFX: Intro Music]
NATE: Hi! You’re about to get smarter in just a few minutes with Curiosity Daily from Discovery. Time flies when you’re learnin’ super cool stuff. I’m Nate.
CALLI: And I’m Calli. If you’re dropping in for the first time, welcome to Curiosity, where we aim to blow your mind by helping you to grow your mind. If you’re a loyal listener, welcome back!
NATE: Today, you’ll learn about why it's best to leave your shoes at the door when you come inside, how animals form and maintain their mesmerizing murmurations, and how certain food storage products release sub-microscopic, plastic particles when exposed to hot water.
CALLI: Without further adieu, let’s satisfy some curiosity!
[SFX: Whoosh]
CALLI: Hey let me see your feet.
NATE: My…what? Uh…okay?
CALLI: I knew it, you're a shoes-on-inside type of guy.
NATE: Well I thought I’d spare you from any sock smells.
CALLI: Well, next time just bring some slippers! The science is in, and the verdict says we should all be taking our shoes off when we go inside.
NATE: I know a lot of cultures around the world do this already, but should we make it the norm everywhere?
CALLI: Absolutely! Our shoes can traipse in a lot of things we really don’t want to live with.
Environmental chemists did an exhaustive study and found that while most of us spend about ninety percent of our time inside, we spend far more time talking and worrying about outdoor air quality and contaminants than we do worrying about our inside biome.
NATE: How worried should I be?
CALLI: For this, I think we might need to play some horror music. Cause, honestly, you’re not going to like it.
[SFX: Thunder]
CALLI: Okay ... inside your home ... first, think dust, dirt, pet hair, and skin…
NATE: I mean Gross, but that is what I think of already…
CALLI: I’m just getting started. They tested homes and found a lot of stuff that we avoid in the outside world, but don’t notice when it comes inside with us on our feet, or on a stiff breeze through an open door.
NATE: What outdoor things we talkin’?
CALLI: Asphalt road residue, which is known to cause cancer, lawn chemicals that can screw with our endocrine system, major disinfectants, microplastics, and chemicals known as forever chemicals that stay in your body long term and never break down.
NATE: Calli, you’re scaring me!
CALLI: Even radioactive elements!
NATE: Okay, I’d settle for one radioactive spider if I got the positive side effects, like a neighbor named Mary Jane.
CALLI: Wishful thinking! They also found ...
NATE: There’s more?!
CALLI: There’s more! They found toxic metals including arsenic, cadmium, and lead. These are all colorless and odorless, so you may never know they’re in your house.
NATE: The toxic metals were coming from inside the house!
CALLI: They even found that testing what’s in your yard soil is a good indicator of what will be in your house, so leave it out there!
NATE: Metal is scary, but at least there aren’t any … living things.
CALLI: Wishful thinking again!!!
NATE: Nooooo!!!
CALLI: Oh yeah, they found antibiotic resistant bacteria like clostridium difficile, also known as c. Diff which attacks the lining of our intestines, as well as Klebsiella pneumoniae which, if you contract it, has a fifty percent death rate!
NATE: That is not a fun coin flip!
CALLI: Totally, and less scary but maybe (intensify horror/ghost story voice) more annoying ... studies also found that our shoes often track pollen in, and if you have allergies, these can really trigger your sneezes and sniffles!
[SFX: Thunder]
NATE: Ok, at this point you’re just naming every scary thing. And clearly, they’re only coming into my house in trace amounts. Am I going to be scared of every bad thing in the world? What about those studies showing that we have more allergies because we don’t interact with enough nasty stuff?
CALLI: Oh you're talking about sterile house syndrome? When kids develop more allergies after living in cleaner environments. Sure, some dirt is good, but it builds up and stagnates inside. Best to get it the classic way. Go outside! Get some fresh dirt air!
NATE: Okay fine. Wearing shoes in the house means I will track stuff in, that I’d rather keep out. But, what if I stub a toe? Or get cold feet?
CALLI: Have you heard of slippers? Or sandals?! You can protect your feet and your insides. Plus, you’ll have to clean your floors less often.
NATE: I know from a previous episode not to eat off the floor.
CALLI: I’m glad you’ve been paying attention, but the ones who are really susceptible are the ones who spend a lot of time crawling on the floor ...
NATE: My roommates who like to party?
CALLI: Children. And we want to protect them. Though, we want to protect your roommates too. And on that note, Nate, I got you something.
NATE: Oh you shouldn't have.
CALLI: I shouldn’t have have had to, but I did.
NATE: Slippers! Thanks, Cal!
CALLI: You’re welcome. Now, we can both leave the outside, where it belongs.
NATE: Outside.
[SFX: Whoosh]
NATE: Calli, do you know what my favorite movie of all time is?
CALLI: Dude Where’s My Car? Obviously.
NATE: That’s definitely top ten. But my all time favorite is The Birds.
CALLI: Some would say you flock to the TV every time it’s on.
NATE: Guilty as charged. And, when all my friends join me it would be called a murmuration.
CALLI: Sounds like something you should call your doctor about ...
NATE: Nooo a murmuration is the word used to describe those giant flocks of starlings we see moving in unison in the sky.
CALLI: Or like a swarm of insects?
NATE: Or a school of fish, or any grouping of animals moving with a sort of hive mind.
CALLI: You know I always wondered how groups like that were able to move in such amazing patterns. They’re beautiful to watch. Mesmerizing.
NATE: Well all the way back in the 1930s a researcher named Edmund Selous theorized that birds were able to stay in sync with each other through some kind of shared telepathy.
CALLI: And now all I can picture is Professor X as a tiny bird.
NATE: As much as I would love an issue of X-Men where they’re all birds, that theory was disproved some twenty years later.
CALLI: Honestly? Kind of a bummer. Okay, so how do they do it? There’s no possible way they could be signaling each other all at once when there are thousands of them at a time.
NATE: Researchers found that the trick is not in the group as a whole, so it’s not some kind of top-down leader system. But instead, it’s a system of much smaller groups all communicating with each other.
CALLI: Team work makes the dream work.
NATE: In this case it really does.
CALLI: If there’s hundreds or thousands of participants in these murmurations, how small do these groups get?
NATE: In 2013 a team of aerospace engineers from Princeton and physicists from Italy set out to answer that exact question. Using more than four hundred photos of murmuration movement they were able to build a mathematical model that would determine the optimal group size for an individual bird to keep track of. (Puts on a performative voice) and the magic number was... Drum roll please…
NATE: Seven.
CALLI: Only seven!?
NATE: See, it sounds like a tiny number in the grand scheme of things. But when a group of seven all interact with another group of seven, and they interact with another group of seven - you can see how it fans out pretty big, pretty fast.
CALLI: Okay, fair enough. Now that I think about it, I can’t imagine getting seven people to all do one thing perfectly at the same time.
NATE: What about that breakdancing crew you used to be in? You guys were pretty coordinated on the video you showed me--
CALLI: Shhh. B-boy Calli is a life I’ve left behind.
NATE: Okay okay back to the murmurations.
CALLI: If the birds are only following along with that small of a group - how do they make such incredible shapes and movement patterns, all in unison?
NATE: The researchers found that not only do the birds keep their groups small, they keep their instructions small as well - identifying three simple parameters the birds pay attention to - an attraction zone, which is an area where they know they should get closer to the bird next to them.
CALLI: Like when K-Dog was hitting a sick windmill in the middle of a routine, I always knew to move right next to him for our tandem move...
NATE: I thought you said the B-boy life was behind you?
CALLI: You know what they say Nate: You don’t leave the dance floor. The dance floor leaves you.
NATE: We’ll have to unpack that someday. But the other two parameters of a murmuration are the repulsion zone: meaning a bird knows that it can’t fly within a certain distance of its neighbor, or they’ll both fall. And the final one is called angular alignment: when a bird knows to follow in their neighbor’s direction.
CALLI: And they make all those amazing patterns just by tweaking those three? That’s amazing.
NATE: It really is. You can get everything from loose swarms of insects, to those tornado looking fish groups, to very intricate and constantly changing bird patterns.
CALLI: Do we know why these groups form patterns in the first place?
NATE: While we don’t have evidence of any breakdancing competitions in the animal world, some believe it is in fact part of a performative display. The groups may come together to ward off predators and confuse them. And in birds in particular - there’s a theory that it helps keep them warm.
CALLI: Which would explain why we see it so commonly in the evenings.
NATE: Nothing beats a sunset starling murmuration. And the coolest part about all of it is that humans have already started applying murmuration principles to everything from self-driving cars, to swarm robotics, which can be used to help better identify and treat diseases!
CALLI: And now I can take the same principles back to the dance floor for another run at the world championship.
NATE: Let’s just hope you don’t run into a crew made of starlings or you won’t stand a chance…
[SFX: Whoosh]
CALLI: Nate, do you drink coffee?
NATE: You know, I actually don’t. Though, I do love a good cup of hot chocolate.
CALLI: And do you use a mug, or something else, like a single-use paper cup?
NATE: I’ll take a cup of cocoa in whatever I can get it in.
CALLI: Okay, then you’ll probably want to hear this. A new study found that when exposed to hot water, many everyday plastic products that meet all our safety standards can still release trillions of nanoplastics.
NATE: Whoa, that doesn’t sound good. And what’s a nanoplastic? Is that different from a microplastic?
CALLI: Right, we’ve known about the problem of microplastics, these are those pieces of plastic smaller than 5 millimeters that are visible to the naked eye. Those little bits of styrofoam broken off a food container, or the microbeads from some beauty products. Well, nanoplastics are even smaller, so small in fact that we can’t see them. Many microscopes can’t even see them.
NATE: Wow, not even a microscope?
CALLI: Well these particles are smaller than a micrometer, which is one millionth of a meter. They’re often 20 or 30 nanometers across, really small.
NATE: I’m having a hard time understanding just how small that is.
CALL: Think of this, it would take 1,000 particles 100 nanometers long, to be as wide as a single human hair.
NATE: That’s incredibly small. A thousand of them to get to the width of a hair?! So how do you even track those?
CALLI: That was a huge hurdle for this study, but let’s set the stage first. The researchers used two types of widely-used plastics. Food-grade nylon, which is used in storage bags and liners for baking sheets, and ... I dunno if you know this, but those single-use coffee cups you’re drinking the occasional cocoa out of are lined with plastic!
NATE: Really?!
CALLI: Yep! Low-density polyethylene, also known as LDPE.
NATE: I guess I never thought about it, but that makes sense! Paper on its own would soak through. It had to be lined with something.
CALLI: Right! So, they simulated a pretty common real-world circumstance for these plastics. They exposed them to hot water, up to two hundred and twelve degrees Fahrenheit, for 20 minutes.
NATE: So, boiling temperature, for twenty minutes.
CALLI: You got it. But researchers had to find a way to find the nanoplastics in the billions of particles of water. So, researchers took the water they had exposed to these plastics, and sprayed it as a mist that they then let dry. And that exposed the particles.
NATE: Oh, haven't we done that to test for what is in the atmosphere?
CALLI: Yes! Researchers borrowed that same technique. They exposed these particles to hot butane vapor, then rapidly cooled it. As the alcohol condensed, the particles swelled, which made them easier to count with an automated computer particle counter.
NATE: So, what did they find?
CALLI: Well the average nanoparticle size was 30 to 80 nanometers, with some outliers around 200 nanometers. But incredibly, they found that the plastic lining of that coffee cup released 5 trillion plastic nanoparticles per liter of hot water.
NATE: Trillion?!
CALLI: And the concentration for the food-grade nylon was seven times higher.
NATE: So what does this mean?
CALLI: Well the researchers were quick to point out that we don’t yet know what this means, we have just confirmed that it's happening. All the products were still within acceptable FDA levels for plastics.
NATE: But did we even know about these nanoplastics before this? Like, did the FDA know about them and say they were fine, or now we need to research these nanoparticles?
CALLI: Well we’ve found bigger particles before, but this is such a big deal in part because of how small they are. We can’t be sure yet but some of these plastics are small enough that they could actually make their way inside cells, and possibly disrupt their function.
NATE: And we need our cells to function!
CALLI: Absolutely. And while we don’t yet know the specific side effects of nanoplastics in our bodies, we do know that other types of disruptions like radiation, or unwanted buildup of certain materials—like in the case of asbestos or lead—have historically had serious, or even deadly consequences. This study will likely be the foundation for researchers and studies that look into how exactly these nanoplastics might affect us.
NATE: Hmm, I don’t like fear mongering at all, but I’m not sure I like hearing this.
CALLI: I hear you. There is no sense getting spooked when we haven’t confirmed any negative effects, but if you want to avoid the nanoplastics, you could start making small changes like bringing your own mug to the coffee shop.
NATE: For my hot chocolate.
CALLI: Yes, of course, for your hot chocolate.
[SFX: Whoosh]
NATE: Let’s recap what we learned today to wrap up. The debate on whether or not to take your shoes off at the door is over. Ditch the sneakers! Wearing your outside shoes inside can bring bacteria, heavy metals, and even radioactive chemicals into your living space. Swap them out for a pair of house slippers, and keep that nasty stuff outside.
CALLI: One of nature’s most awe-inspiring occurrences - a starling murmuration - not only strikes us with wonder at the world around us but also inspires us with its efficiency. So much so that the principles of these flocking groups are already being applied to everyday life in the worlds of logistics and medicine, helping us take lessons from nature to better enhance the human experience.
NATE: A new study is finding that many commonly-used food and drink storage products release trillions of plastic nanoparticles when exposed to boiling water. Even though these numbers fall within FDA standards, the findings are raising questions, and laying the groundwork for future research into the effects of these miniscule particles on the human body.