- [Purnell] A constant rat problem.

- Very often you don't need pesticide.

- I think I've brought bedbugs home.

- The German cockroach, the bedbug are incredibly well adapted to the indoor environment, very much like us.

- It's us, we have our own little microbiome that we are just constantly shedding.

- [Announcer] "Home Diagnosis" is made possible by support from Broan-NuTone, Better Air, Better Life.

By the GOT MOLD?

Test Kits, Real Science, Real Simple.

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(creepy music) - Did you know we're never actually home alone?

- Every home is a party if you know where to look and you look hard enough.

- Whether you're fighting roaches and mice this week or not, (chuckles) there's a massive ecosystem at work around you.

- Investigations into this ecosystem of a home are just beginning.

- And the findings certainly make it seem like we all need to be a little more mindful with crowd control.

(dramatic music) It's the shields we build.

And the risks we take.

(dramatic music continues) It's the disasters that will test us.

And what will grow from them.

(dramatic music continues) It's real life.

And the physics, chemistry and microbiology of the science of homes.

(dramatic music continues) - Hi, this is Purnell, we're here at a home, which was built in the 1970s and they're dealing with a constant rat problem.

So we just started tearing down the deck just to get to the source of the problem.

Here's what we found.

And see this large opening?

You can see the leaves in the insulation that they gathered together, formed a little home.

And this was hiding right underneath the decking to where it provided easy access into the crawl space and into the flooring of the home.

(gentle music) - Oh, your- - Is this your boombox?

Cockroach, pulse of the planet, cockroach control, two programs, I love that you even have a mix tape.

- All insects are uniquely adapted to specific environments, so there are insects that live on ice in the Antarctic.

They've adapted for millions of years.

The German cockroach, the bedbug, are incredibly well adapted to the indoor environment.

The indoor environment is actually a very harsh environment.

It's very comfortable for us, but it's very harsh for insects, very harsh because of the low humidity in the indoor environment.

We use air conditioning, we use heating, which dries up the environment.

So it's only insects that are very well adapted to contend with desiccation.

Many ants, for example, they live outside, but they forage inside our home.

So they form these trails, but if you follow the trails, the colony is actually outside.

But what's unique about insects like the German cockroach and the bedbug, is that they spend their whole lifecycle indoors because they can withstand that low humidity of the home.

Different bugs that reside in our home have different costs to residents in the home.

Let's talk about cockroaches.

Cockroaches have a very rich bacterial community in their gut, very much like us, because we're both generalists, we eat all sorts of foods.

But the cockroaches constantly defecate these bacteria into the environment.

So the bacterial community in the home proliferates, and many of these bacteria can be pathogenic bacteria, first of all, which is a concern.

But a good fraction of the bacteria are gram-negative bacteria.

The cell wall of bacteria contains endotoxins and the word "toxins" should ring a bell.

They like cracks and crevices in a home, and they defecate in those cracks and crevices, and you can think of it as construction, right?

They're making a comfortable home for them, they like the texture of those areas.

So well, why don't you just clean up the home, eliminate all the food, and you'll get rid of the cockroaches.

That's incredibly difficult to do.

They can eat organic material that you can't even see.

So by eliminating the food, that's a good thing to do, you're curbing the infestation size.

But in order to eliminate them from the home, one has to take active measures and often use insecticides to eliminate them.

- I love my job, I never thought as a child that I would grow up to study house dust.

- Dust is really fascinating.

So on a speck of dust, we actually have so many different things.

There could be bacteria, fungus, maybe even some viruses, also different chemicals, we could have microplastics, our human skin cells and dust mites, and they're really different in everyone's home.

So the dust and the microbial communities that are in your home are very different than those that are in my home.

- If you think about a carpet, it's a really porous material.

And so, it actually serves as a reservoir where you can have dust deposit into the carpet more so than you would on a solid type of flooring, and also can get re-suspended at a higher rate when someone walks across the carpet.

Without the dust, there's no growth in your carpet.

I'm not saying that carpet is an awful thing to have, but if you're going to have carpet, just make sure to keep it clean and and vacuum.

(creepy music) - It's three o'clock in the morning, Grace is out of town, I have bug bites on one arm, woke up in the middle of the night with more bug bites on the other arm, and I just came back from a hotel that had all kinds of other problems that I was very interested in and laughing at, ha-ha.

And I think I brought bedbugs home.

The bites are in a zigzag pattern or in a line 'cause they just walk right over your body.

So the advice is to just go back to bed and deal with it in the morning, and not start moving yourself around and contaminating other areas.

So now I'm going back to sleep in a bed that I'm pretty sure has critters in it, gross.

- It's amazing that I've not had bedbugs.

I mean, we raise 'em and you would think that one of us would take bedbugs home.

The history of bedbugs, 200,000 years ago, bedbugs were associated with bats in caves.

As humans evolved, the humans entered the cave.

The more recent history, my parents grew up in Europe and they remember bedbugs and they remember the smell of bedbugs.

My mother, for example, hated guavas because guavas and bedbugs have a similar smell.

Even though bedbugs developed resistance to DDT and the following insecticides, bedbugs were essentially eliminated from developed countries.

Back in the mid 1990s, something has happened, we don't know exactly what, but bedbugs came back on a global scale.

Bedbugs are really difficult to control.

Pretty much all the populations of bedbugs that we find in the United States with very few exceptions are resistant to pyrethroid insecticides.

There is good evidence that they're becoming very, very resistant to our newest insecticides.

A very effective way to control bedbugs is to use heat.

- [Corbett] Wow, that is a lot more equipment than I thought it was gonna be.

Let's do this.

(heater whooshing) That is an 80 amp heater that's made it about 120 degrees in here, all over the place.

- So bedbugs can't escape to little cracks and crevices, and then you have to maintain that temperature for at least four hours.

It doesn't leave a residual behind.

And so, if there are bedbugs next door in your neighbor's home, they can come right back.

For single family homes, it's incredibly effective.

But it's interesting, insects have relationships with microbes that live inside them.

There's a bacteria that lives inside the bedbug, and the bedbug would die without this bacteria.

(soft music) - Microbes is a broad term that can include a lot of different organisms, such as bacteria, fungi, some people include viruses in microbes, it might include some types of protist, and it's really microscopic organisms that you can't see with your eye that you need a microscope to look at.

(birds chirping) - Think about when you walk out into a forest and you have that smell of the forest, those are those microbial VOCs that are being produced by microbes in the forest, and that's something that we all associate with a good feeling, a healthy feeling of being outdoors.

We are exposed to microbes all the time that are not germs, that are not going to make us sick, and that we actually need to be around.

They connect us to this microbial ecology that humans have evolved with for millions of years.

- People think with microbes in their home that they need to sterilize everything, they need to get rid of all those microbial communities.

That's not true, but it's also kind of impossible.

The minute you put people in a space or pets or have open windows with ventilation, you're going to have a microbial community in a home.

So it's okay to have microbes in your home, in fact, you need to, you have to as a person.

You really want to just make sure that you're maintaining a healthy indoor microbial environment by controlling the moisture in the different parts of your home.

- It's really the people who are driving the microbiology of our built environments.

And there's been studies where we actually see someone sampled their home, they moved to a new home, and within three days, the microbiome of their new home was very similar to their old home.

So it's really all about us and what we're doing, your habits, what are you using to cook?

You know, how many animals do you have?

Dogs, cats, which types?

It's us, we have our own little microbiome that we are just constantly shedding, and that's really shaping this built environment.

- [Purnell] So we're about to show you a squirrel's nest from the outside.

If I lift up the shingles, you can see how the squirrels use insulation in your attic as a nesting material.

It's all sealed.

- So when we were uncovering things in our home, removing the insulation and everything, we found rodent nests that that existed in the house and they were abandoned, they hadn't been there for a long time.

But one of the things is just the grossness that they leave behind, even though it's been vacuumed out, there's certain things that stuck to the top side of that drywall.

And so, you know, it's not bad enough where we have to replace the drywall, we just need to wipe it up.

But it's a diluted bleach solution, and, obviously, wearing a respirator and all those things to make sure we're not smelling that and vacuuming up other pieces with a HEPA filter vacuum.

That's some of the things that we've done to try to mitigate some of that and remove it.

(bright music) - I would say if we took any vertebrate animal that's a pest, you know, it's mice, rats, raccoons, you name it, and any insect that's a pest, say cockroaches, bedbugs, the big difference between those two is when the mouse researcher says, "Oh, we have a big population," they mean, oh, there may be a couple dozen or maybe a hundred mice.

Whereas when we talk about cockroaches and we say, "We have a big population," there may be hundreds of thousands in a single home.

So the numeric difference between these types of pests, it's quite astounding.

And the reproductive potential, how rapidly evolution occurs is dependent on the transmission of that DNA material from one generation to the next.

So humans evolve very, very slowly.

Insects not quite on the order of bacteria, but they evolve very rapidly.

And one of my biggest fears is that the rate of development of new technology cannot keep up with the evolution of resistance to things that we're throwing at these insects.

- If you're spraying pesticides again and again in your house, you kind of start this treadmill or what you're left with after you use the pesticide are resistant strains of species, and the species that were helping you to control those are now gone.

And so, your only solution is then more pesticide, new pesticides.

Domestic use of pesticides, it's gone up and up as we've used it as the only way to control species, and I think a better solution is that very often you don't need pesticide, that there really aren't any problem species in your house.

But if you do find a problem species, in that moment, you can then use it to control what's happening in that moment, and so use it selectively, I think becomes a much more sustainable solution.

- There are several things to consider when eliminating cockroaches from the home.

Number one is, what species do you have?

If it's a species that's coming from the outside into the home, they'll eliminate themselves because they cannot live inside the home.

So the critical thing to do is not to use insecticides, but to seal the entry points from the outside.

They're probably coming in through a crack in the window or a gap in the door, or maybe the crawl space, maybe the attic, in many cases, they come in through the eaves and they're looking for water.

So they'll end up in a bathtub, they'll end up in the sink, looking for water.

So that's one situation when no insecticides are needed at all.

On the other hand, if you have the German cockroach, which lives indoors, absolutely does not live outside, we don't know of any natural populations of the German cockroach worldwide.

- So the German cockroaches have their own hotel.

- Yes, their own dedicated room with two incubators.

- And I can really smell their pheromones, or is it?

- This is actually their feces.

Some of smells that you smell are actually used as pheromones.

Nowhere in the world does it live outside of human-built structures.

But there, the decision of what type of insecticide to use, what formulation of insecticide to use is very critical.

So many people go to the hardware store and buy these bug bombs.

We went into homes where they were heavily infested with cockroaches and tried four different types of bug bombs, not a single one of them worked.

But when we took swabs of the kitchen counters and the floors and the walls, we recovered large amounts of insecticides that people would contact, children would contact.

So no bug bombs.

The next formulation that people like to use a lot are sprays.

Those are called residual insecticide.

You spray the environment and you hope that, at night, when the cockroach comes out looking for food, it will walk over the insecticide.

Those are fairly effective, but again, they deposit residual insecticide in environments that people contact.

What's incredibly effective in residential settings is baits.

Cockroaches love to eat, they must eat in order to molt from one stage to the next, and they must eat in order to reproduce.

Female cannot produce an egg case and babies without eating.

Because they're so dependent on eating, we can feed them a bait containing an insecticide.

Put little dabs of the bait in out of the way places where your pets can't get to it, children can't get to it, inside cabinets where cockroaches tend to be.

If we can see cockroach poop, we put the bait very close to the cockroaches.

So when the cockroaches come out at night to forage, they find that bait right away.

- The worry is that we develop a culture around managing our homes in which we try to kill everything.

We have simple monkey brains, and they really like the idea that if a little bit is good, a lot is better.

And how do we get out of that?

Our brains are really conducive to making this kind of mistake over and over again.

I mean, the one that I think is really interesting in this regard is antiperspirant.

Antiperspirant closes up these apocrine glands in the armpit.

Apocrine glands evolved with one function, they're not sweat glands, they're a different kind of gland entirely, their only function is to feed specific bacteria on the skin.

And so, 40, 50 years ago, it started to become sort of culturally normal that everybody used antiperspirant.

Major shift, largely unnoticed.

That was a massive cultural experiment in body microbes, and we still don't understand what the consequences of it are, but it looks like it may have shifted the normal microbes of Americans in a relatively few decades.

And I worry the same sort of thing may happen in the coming decades in sort of the tail end response to COVID, with regard to microbes in our house, - There are several ways that we use one type of insect to control another type of insect.

One very obvious one is to use wasps and flies that parasitize other insects or predators.

The ladybug is a good example.

You can release them in your garden and these ladybugs go after caterpillars that are eating your tomato plant.

So there are many wasps around that seek specific insects to lay their eggs in.

- And people have been introducing those into homes and barns for a long time, they're teeny.

If they're in your house, you won't see them.

In Raleigh, North Carolina, we found them in most houses and nobody had ever noticed them before.

And so, they fly around, they lay their eggs inside the baby cockroaches and they eat the cockroaches.

And so, that's one model for that.

But another model for that is bacteria.

And so, MRSA, methicillin-resistant staphylococcus aureus is a problem in households now.

And one of the ways that people talk about treating it is by giving people specific viruses that attack individual strains of that bacteria species.

And so, that's also a pest control, same approach.

- We use fungi very effectively in some cases to control insects.

So there are some what are called entomopathogenic fungi.

One is Beauveria bassiana, it's a fungus that has been exploited to kill bedbugs.

So there's a formulation of an insecticide that instead of containing a chemical, it contains a biological agent, and that biological agent is the fungus.

We've shown in laboratory studies, this fungus is incredibly effective against bedbugs, it's totally ineffective against cockroaches, but there are not enough studies of how this fungus behaves in the field, in real life situations.

So we'll have to wait a while for those studies to come out.

Most of the insects that are well adapted to live inside the home are flightless.

And so, the only way they can get from one home to another or one city to another is through human transport.

We are really good at moving insects from one place to another.

So it's very common for us to go into a thrift shop, for example, pick up a piece of furniture that we really like, bring it home, and we have just brought a whole colony of bedbugs into the home.

Used furniture is great, but before bringing it into a home, very carefully look at that chair, look at that sofa, almost dismantle it to see if there's bedbugs in there.

If you catch the infestation early on when there's just a few individuals, you can actually grab that table, put it in a bag, put it outside in the sun to heat it up and fry the bedbugs or put it in the freezer for a few days and get rid of them.

But once they've spread in a home, it's really quite difficult to get rid of them.

If you live in a multi-family apartment building, it's very easy for them, for both cockroaches and bedbugs, to move through the walls, to move through pipes that are connected between apartments.

Oftentimes, kitchens abut each other between apartments or bathrooms abut each other.

There's some really affluent multi-family housing, high rises in New York City and other cities.

They have cockroaches as well, but not the high level infestations that we find in disadvantaged communities, low income communities.

Maybe a better way to state that is, these are resource-poor communities, right?

They're not necessarily filthy, they're not necessarily less sanitary, but they don't have the resources, the money to control cockroaches.

It requires either a professional coming in to eliminate the cockroaches or it requires taking the time to learn how to do it yourself.

Because oftentimes, people make these mistakes of using bug bombs or other types of pest control products.

- There are lots of animals besides humans that build their own places to dwell, that provide shelter from the uncontrollable surrounding environment.

And I've always felt that we can learn a lot about the dwellings that we built, in terms of the microbes that we live with, how we can manage them,, how we can manage things like moisture in a way that prevents or at least limits biodeterioration by studying the homes that other organisms build.

- When you talk about social insects, obviously honeybees and wasps, they can build elaborate structures, and leaf-cutting ants, for example, build these huge galleries in the ground.

They farm leaves, they cut leaves from trees, they bring 'em into their gardens and they grow fungi on these gardens, much like we grow mushrooms.

But in order to grow fungi, you have to make sure that you don't grow bacteria, right?

You wanna grow fungi only.

So they also produce all sorts of antibiotics, natural antibiotics, to prevent the growth of bacteria so the fungi can grow.

Termites grow these amazing galleries that extend upwards and and are climate controlled, using physical concepts that we discovered much later.

- How do they build their environment so that they're healthy?

In the case of nest building wasps and hornets, there are some that dwell underground that dig out burrows, there are others that make aerial nests, and their aerial nests are made of paper.

The paper is scraped from wood fibers that they collect from rotting trees or fence boards, and then they carry that little blob of pulp up to where they're building the nest, they mix it with their saliva and they flatten it up into paper.

- Termites, on the other hand, termites eat the wood.

When they decompose wood in a natural setting in the forest, they're clearly not pests, but the same species, the same subterranean termite, when it's eating your house, it's obviously a pest.

- Obviously, there are aspects of the environments that we live in that can increase our risk to developing certain diseases, especially in childhood, things like allergies and asthma, but also other kinds of illnesses do have, as we learn, increasing links to exposures that occur in the built environment.

But what about these other organisms that build dwellings?

What about the underground dwelling rodents?

And there are lots of those.

They sometimes line their nests with roots and stems, plant materials, not unlike the kinds of plant materials that we build with in our environments, but we know in our environments when those materials are subject to superfluous moisture, they grow mold.

So what happens in these underground burrows of rodents?

Do they have these really enormous inhalation exposures to molds?

And if they do, how do they manage it?

Do they ever develop any of the diseases that have their analogs in humans?

We don't really know an awful lot about that.

Do they have ways that we don't know about that manage the negative effects of uncontrollable moisture in their homes?

We don't know about that either.

I think there are lots of interesting parallels that we could learn from studying the built environments of other organisms and then draw analogies to our own environments.

- Now that we've driven way deeper into the science of critters than you've probably hoped, let's back up to the practical again.

Keep your home reasonably clean, seal any hole that seems like an open door.

- And when you use the right pesticides for the job, use them sparingly.

The home is a system, and that includes everybody living inside.

- Learn more about using this science in your own home at homediagnosis.tv, till next time.

(creepy music) (creepy music continues) (creepy music continues) - [Announcer] "Home Diagnosis" is made possible by support from Broan-NuTone, Better Air, Better Life.

By the GOT MOLD?

Test Kits, Real Science, Real Simple.

By AirCycler, Retrotec, Rockwool, and RenewAire.

By generous support from these underwriters, and by viewers like you.