The Microbes Among Us

11:48 minutes

You’re never truly alone indoors. Arthropods, like these tiny house dust mites (Dermatophagoides pteronyssinus) in carpet, and a plethora of microbes are keeping you company. Credit: Gilles San Martin/flickr/CC BY-SA 2.0

Many people are spending a lot more time in our homes than we’re used to. Thanks to the pandemic, some of us have found that cleaning all the nooks and crannies in our homes is a satisfying new hobby.

But compulsive cleaners might want to sit down for this next part: There’s a whole thriving, diverse microbiome that lives in your home. One 2010 study of North Carolina homes found an average of 2,000 types of microbes per house. And there’s likely a menagerie of arthropods living with you, too. Another study found that homes contain an average population of about a hundred invertebrate species, including spiders, mites, earwigs, cockroaches, and moths.

There’s no need to panic: These thriving ecosystems are doing us more good than we give them credit for. Children who grow up exposed to an abundance of microbes are less sensitive to allergens, and appear to have better developed immune systems throughout their lives. Science journalist Emily Anthes talks about the indoor microbiome in her new book, The Great Indoors: The Surprising Science of How Buildings Shape Our Behavior, Health, and Happiness. She joins Ira to discuss what she learned about the unique microbiome of her own home while writing the book, and the vast biodiversity of the indoors—a microbial place, with microbial charms.

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Further Reading

Segment Guests

Emily Anthes

Emily Anthes is a science journalist based in Brooklyn, New York and is author of The Great Indoors: The Surprising Science of How Buildings Shape our Behavior, Health, and Happiness.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. As you spend lots of time indoors now, do you find yourself incessantly cleaning? I know I have. It’s amazing what you can turn up. Right?

What’s even more amazing is the stuff you can’t see, tiny stuff like a whole microbiome that lives in your home. One study of North Carolina homes found an average of 2,000 types of microbes per house, and the dust we find all over surfaces and in our carpets, well the dust contains DNA from tens of thousands of bacteria and fungi. But there is no need to become germaphobic. This is completely normal and probably beneficial to our health.

Author Emily Anthes talks about the indoor microbiome in her new book The Great Indoors– The Surprising Science of How Buildings Shape Our Behavior, Health, and Happiness, and she joins us today from Brooklyn, New York, as we used to say it when I lived in Brooklyn. Thank you for joining us today.

EMILY ANTHES: Of course. Thanks so much for having me.

IRA FLATOW: Set the scene for us. What makes up the indoor microbiome?

EMILY ANTHES: So it is largely bacteria, and a little bit of fungi, and it comes from a few different sources. So in terms of bacteria, we ourselves are really the dominant sources of bacteria in our homes. So listeners may know that we all have our own microbiomes. These are bacteria that live in and on our bodies and are really critical to our health.

But as we move throughout the world, we’re constantly shedding these bacteria and releasing them into the air, and they then settle in the corners of our homes, on our pillowcases, on our kitchen counters. So that’s a big source of microbes in our home. Our pets also introduce microbes, dogs especially. They bring in soil microbes from outside, and then they shed their own microbes into the space.

Then there are microbes that just drift in from outside. So soil and leaves might come in through an open door or window. And then there’s another class of microbes that really live in and on our homes.

So mold is a big one. You might see on your shower curtain from time to time black splotches. Scientists have also found unique microbes in some of the extreme environments in our home. So when I say extreme, I’m thinking of dishwashers, which get really hot, and wet, and soapy, and it turns out there are some unique forms of life, some kinds of black yeasts, that live in our dishwashers.

IRA FLATOW: Wow, that’s cool. I mean, I see you like to really geek out about this


Which I really like because I understand that in geeking out you were looking at your shower head, and you found some interesting, really interesting, geeky stuff there.

EMILY ANTHES: I was, and so I– some of the researchers I interviewed were in the midst of a project to survey the microbes that lived in shower heads all around the world. So I was excited to participate, and I found a couple of things, or I should say the researchers found a couple of things. Some were not very surprising.

So there were bacteria living in there that are commonly found in soil and tap water, which is what you might expect, but there were also some more mysterious things. One of the organisms they found is called– it’s not a very evocative name. Right now it’s just called RB41, and it’s a not a well-understood microbe, but it has been found previously in both dog noses and in paleolithic cave paintings, and so it’s kind of amazing to me that this mysterious microbe that’s been found in such disparate places is also just hanging out my showerhead.

IRA FLATOW: It’s kind of cool that you could share that kind of history with them.

EMILY ANTHES: Yeah, it is. You know, you mentioned geeking out, and I think what’s interesting is the idea of our spaces and our homes, which are so familiar to us, as being these sort of rich ecosystems is really kind of cool.

IRA FLATOW: Yeah, and microbes aren’t the only things that make up indoor biodiversity because in your book, you talk about how many bugs can be found in your home.

EMILY ANTHES: Yeah, and again, here, I don’t mean to freak readers out. Most of the bugs and arthropods in our homes are totally benign, and some might be even beneficial, but researchers in one study found that on average each home has about 100 different species of arthropods. And that might seem improbable– you’re probably not seeing hundreds different kinds of insects scurrying around your home– but a lot of them are hidden, or they’re nocturnal, and they’re only coming out at night. Or they’re very tiny, and you might not normally see them, and they can live everywhere from the soil of your house plants to your plumbing.

IRA FLATOW: You know, when people hear that there are so many bugs, many times their first reaction is going to be to get the bug spray, but you say, don’t do that because so much biodiversity in our home is a good thing. Right?

IRA FLATOW: Yeah, but some of these bugs, especially when you start thinking about things like spiders, are actually doing you a favor and they’re a natural form of pest control. And there are some cultures around the world that sort of deliberately introduce spiders into their home because they help control populations of maybe mosquitoes that could carry disease. So a lot of these bugs are really nothing to be worried about, even though they might seem creepy.

IRA FLATOW: Yeah, your book isn’t just about the microbiome indoors. Its titled, The Surprising Science of How Buildings Shape Our Behavior, Health, and Happiness. It’s more broadly about how buildings can be designed to influence how we feel. I found that part very fascinating.

EMILY ANTHES: Yeah, almost everything about our indoor environments, from how spaces are laid out to the ventilation to even the indoor air temperature affects us in ways that we might not really appreciate, and it can affect our mood, our stress level. It can affect how quickly patients recover when they’re in the hospital, how well students do on standardized tests. So it really plays a hidden but profound role in our lives.

IRA FLATOW: Do architects take that into account? Do they specifically shaped buildings and indoors because they know it’s going to be a mood changer?

EMILY ANTHES: Increasingly, yes. So there is a field, which much of my book is about, known as evidence-based design, which really was founded in the mid 1980s but has really gained steam since then. And so there is an increasing attention that architects are paying to creating buildings that make us feel good or are healthier. There are now– listeners may have heard of LEED certification, which a building can get if it’s sustainable, but there is also now a WELL certification that a building can get if it incorporates enough design features that are good for occupants.

IRA FLATOW: Oh, I didn’t know that. That’s kind of interesting. There’s this fascinating Japanese building you talk about in the introduction of the book, where the creators believe that the residents could cheat death by this special kind of architecture.

EMILY ANTHES: Yeah, so this was a couple. They were married artists, Arakawa and Gins, and they devoted their careers to this concept that they called reversible destiny, and they really believed that death did not have to be inevitable and that the best way to fight death was through architecture, through creating buildings they believed that really challenged us. So their buildings are really wild. They have floors that are bumpy and misshapen. They might have 30 or 40 different interior paint colors, rooms of different shapes, and their idea at least was that these kinds of environments would keep us on our toes, and strengthen our immune systems, and really keep us vigorous and vibrant throughout our lives.

IRA FLATOW: Are there buildings like that still in existence?

EMILY ANTHES: Their buildings do still exist. They– I say in the book, “If they discovered the secret of immortality, they did not take advantage of it themselves because they have both passed away.” But their buildings stand, and one of their homes is actually out on Long Island.

IRA FLATOW: Well, obviously, since they’ve passed away, it’s not working for a lot of people.

EMILY ANTHES: Right, well, and so I think the idea of immortality is obviously a bit farfetched, but I think they are onto something a little bit because scientists have known for a long time about what they sometimes call environmental enrichment, and that’s that living in engaging, stimulating environments is good for our physical and mental health. So in that way, they were onto something.

IRA FLATOW: So are we missing that, that engagement while we’re staying at home? I know that you say in your book, you call yourself, “unapologetically indoorsy.”

EMILY ANTHES: I am, yeah. I’m the kid that would bring a book to sleepovers, and I enjoy being outside, but really, inside in my home is my safe place. But I do think that now that we’re all confined to our homes, there are some things we’re missing. And obviously it’s not complete sensory deprivation, but there is sort of a sameness to our lives and our environments right now, some boredom that may be creeping. And there’s research that shows that this kind of sensory sameness can be stressful and can actually cause our cortisol levels to rise, so it’s not great to not have stimulating environments.

IRA FLATOW: You also make the point that modern humans are basically an indoor species now.

EMILY ANTHES: Yeah, in North America and in Europe, I think the statistic that you often hear is that we spend about 90% of our lives indoors. And I would guess that in the last few months it might be more like 95% or 98%.

IRA FLATOW: And of course, your book really is especially timely right now with all of us staying inside more than usual. Do you think people will pay more attention to their indoor environments now?

EMILY ANTHES: Well, I hope so, and I would say that I think in certain ways that’s already beginning to happen. I’m hearing a lot more interest in and concern about indoor air quality, which is something that scientists have been trying to sound the alarm about for the last few years but now is something that people are thinking a lot more about.

IRA FLATOW: And I would imagine, being a plant person, I’d love to bring plants indoors or keep my house plants indoors, and I find that they actually change my mood also.

EMILY ANTHES: That is one of the most well-validated findings in all of the literature, is that plants and nature are good for us in almost every way you can think about. They boost our mood. They reduce stress. They can boost our attention and cognitive performance.

And one thing that might be reassuring for people is real plants are great. If you can bring house plants in, that’s wonderful. But if that’s not your thing, or you’re worried about a black thumb, that even quote, unquote “fake nature” has some of the same benefits. So a big photo of nature on the wall, or even nature sounds, can have some of the same stress-relieving effects.

IRA FLATOW: Yeah, well, I’m trying to do some of that in my home, and it’s a learning experience, but being a geek, I love this stuff.



IRA FLATOW: All right, Emily, thank you for taking time to be with us today, fascinating book. Emily Anthes, author of The Great Indoors– the Surprising Science of How Buildings Shape Our Behavior, Health and Happiness, and a great read. Thanks for taking time, as I say, for joining us today.

EMILY ANTHES: It was a pleasure to be here.

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