CSU's The Audit

HOST INTRO: With spring right around the corner, thoughts of spring cleaning aren’t far behind. There’s just something about throwing open the windows and doors to let fresh air in that makes you breathe a little bit easier – in theory.

In Germany, the practice of airing out one’s home is a daily one done year-round. Called “lüften,” it’s referred to as basically burping your house. But with new research around the chemical compositions released by everything from your carpet to your paint to your stove, is a daily luften enough? And what kind of pollutants might you be letting in?

Delphine Farmer is an atmospheric chemist at Colorado State University, researching indoor and outdoor air pollution and its impact on our health. Today, we’re speaking with Farmer to clear the air about how well traditional spring-cleaning remedies like lüften actually work.

HOST: A few years ago, you did a study on the potential impacts of different chemicals, such as cleaning products, on indoor air. It sounds like indoor pollutants hang out a lot longer than maybe we previously realized.

FARMER: Yes. Definitely. We did a study back in 2018 called HOMEChem. That was the house observations of microbial and environmental chemistry. We did all the normal activities. We cooked, we cleaned, we sat in the house and read books. The idea was that we brought about 20 different high-end pieces of instrumentation from about 15 different research groups from universities across Canada and the U.S.

We wanted to understand what the chemistry of indoor air was, and we encountered many surprises. One of them was just how much stuff was in the air. So, how many organic compounds were in the air we were breathing inside, orders of magnitude more than we have outdoors. That was really our first hint that indoor air is complicated.

Then we went back a few years ago to another test house with a similar group of people, lots more instruments from different universities, and we started to study how long these compounds lasted and how they interacted with indoor surfaces. What we found was really surprising. If you have something like a wildfire smoke event outside, and that smoke gets inside, those organic compounds – those air toxics associated with that smoke – attach to surfaces and then diffuse and bury themselves into all your building surfaces. So, carpets, ceiling tile, drywall – all the surfaces in your home – start to take up those compounds.

HOST: You're terrifying me right now.

FARMER: Absolutely, I'll keep you up all night.

Over time, those little compounds start to slowly evaporate back into the air. So, after a wildfire smoke event has passed, that's actually when all of those compounds that have stuck inside your home are going to start coming back out. Now your exposure to that smoke is actually extending for – it turns out – days, weeks, months, potentially even years for some of those components to remain in your home. Does that mean that they're toxic and are going to kill you? I don't know. But it does mean that what you're exposed to inside a building is really the past history of everything that happened to that house for certainly months, at least.

HOST: So, it's not just things like, was there a previous smoker in the house? There's a lot of things we have to think about when we're talking about the history of a house.

FARMER: Yes. I always classify them into things that we know are dangerous and things that we don't really know if they're dangerous. For example, just cooking a regular meal or applying personal care products that have a scent. Certainly, those scents, those compounds, are going to get onto the surfaces of a wall, but I'm not really concerned about lemon or lavender scents hurting me. But if someone smoked in a house, we know that nicotine if it gets onto surfaces, it can react over months and change into an even more toxic substance that then can release back out into air. So, the history of your house and your living space and your working space matters.

HOST: It feels almost like, I don't know if you remember this, but restaurants used to have smoking and non-smoking sections, and it was basically just one side of the room and then other side. But the air doesn’t know that and so it just all becomes the smoking section.

FARMER: Absolutely! I remember this. I remember getting on planes with the smoking and non-smoking sections, and it did not change. You could still smell it all. Absolutely that air is just moving around. Certainly, in commercial buildings there's an argument to be made they can have strong enough ventilation systems that you're not going to get exposed to all of those particles, but yeah that stuff just sticks around. I mean, it literally sticks to surfaces and then moves around on those surfaces.

The other thing to remember is that we also have a lot of dust in buildings. I mean, unless you're living in a clean room – you know bio-safety level really actively managed lab space –you're going to have dust in that house. Dust is really good at picking up chemical compounds. And we've all seen it in our houses. I mean, the dust collection under my couch is strong. Even though I don't push things under the couch, it still accumulates.

So, all the gasses that are in the air are going to accumulate on that dust and then it moves around. That's where we do start to get a little concerned because floors are where infants spend time and children touch surfaces and can ingest things. So, it is something to think about in terms of the history of homes and how different compounds can move through that house and get taken up by people.

HOST: Those dust bunnies are dangerous.

FARMER: Yes. If only I vacuumed more.

HOST: I have a feeling I'm going to be doing a lot more cleaning after this conversation

FARMER: The more I've studied indoor air, the more I clean my house.

HOST: What are some of the dangerous chemical compounds that are typically found in indoor air? I know there's been a lot of talk about gas appliances.

FARMER: Yeah, so let me just clarify for a minute. There are two kinds of chemical compounds you can be exposed to in the air. One is particles. So, those are really, really tiny droplets. People think about aerosol spray, like hairspray. Think even smaller than those droplets. And they can actually hang out in the air for a really long time. Those are aerosol particles. And then the other components are gas particles. Those are really large numbers of molecules all put together. They're suspended, so liquids are solids, and then you have the gas component.

So, things to think about with the toxic chemical compounds – I often start by thinking of formaldehyde, which you might have heard of because of some of the really cheap building materials. After Hurricane Katrina many years ago, there was talk about formaldehyde off-gassing in the mobile homes that were given to people. A lot of manufactured materials can off-gas formaldehyde. It also just comes naturally off of some components. Formaldehydes are a known carcinogen and quite toxic. So, it's not something you want to be exposed to.

Particles are interesting because there's no known safe level of aerosol particles. They come in lots of different sizes. Depending on the size, that tells you how deep into your lungs they're going to penetrate, and then they get stuck there.

Everybody's heard about particles because that was how the COVID-19 virus transmits. Same with measles and tuberculosis. If you think about biological aerosol particles, those we’re exhaling all the time. But you can also think about other components. If you think about cigarette smoke, you're seeing the particles. Vehicle exhaust, you're seeing the particles. And of course, with wildfire smoke, too.

Anytime you burn something, you're generating particles. You're also generating gasses, and combustion. The act of burning, that's something I do get concerned about because we know that there are a lot of toxic compounds in smoke. It's not like cutting into a lemon and you can smell it. Those aren't toxic compounds.

Gas stoves are a whole different ballgame. They've gotten a lot of attention. I think that attention is deserved in terms of gas stoves can be a source of methane, and they're a release of natural gas, so that's releasing greenhouse gasses into the atmosphere. They certainly do release particles, and they release some known toxins like benzene. But I actually think we're maybe missing the big point with cook stoves, and that's the fact that when you cook, you're releasing huge numbers of particles. And again, we know that particles are damaging to human health. So, I actually get more concerned about the cooking side than I do about the gas stoves themselves, although I do think that changing out gas stoves if one has the opportunity to is a good idea.

But all of this can be solved, to a certain extent, if you have really good ventilation in your home. So, if your kitchen has a really good vent that pulls the air out of your kitchen and actually out of your house, that's a really good way to go. Otherwise, you want to start looking at opening a window any time you cook, no matter whether you're using a gas stove or not.

HOST: First of all, you just gave me a great excuse to not cook. I'm going to lean into that.

FARMER: Yeah, eat raw and order out. (laughs)

HOST: But also, one of the things we're going to talk about today is lüften, the German trend of opening doors and windows for 20 minutes every day. They refer to it as burping the house. Does that actually help with indoor air quality? Do our houses actually need to be burped?

FARMER: So, this is such an interesting idea. First off, you have to know what the air quality is outside. Because if you live next to a highway, or if there's a bad air pollution day here in the Front Range in Colorado – say high ozone in the summer, or a wildfire smoke event – then you don't want to open your windows, because you're actually just bringing known air pollutants inside. Ozone, in particular, I have grave concerns about.

If your outdoor air is clean, opening windows is always a good idea because then you're going to reduce the level of air pollutants that you're experiencing inside. That said, you're only going to clean your air for the time that you have your windows and doors open. So, during the actual burping process, you're going to have much cleaner air. But once you close the windows and doors, the levels of all the indoor pollutants are just going to come right back up.

The problem is that all of these compounds – organic compounds, inorganic compounds, everything we exhale, everything we cook – it's all stuck on all the indoor surfaces. When we open our windows and doors, we don't actually remove those compounds. All we're doing is temporarily cleaning the air. Then we close it up, and then all those compounds start coming back off the surfaces. So, you're not giving yourself any long-term benefits. That said, if you were cooking with your gas stove or you burned some toast in a toaster oven, even if your smoke alarm didn't go off, by opening the windows and doors you're certainly clearing out all of those air toxins. Or, if you clean with bleach or something that you don't want to be inhaling, that you shouldn't be inhaling, then yes, absolutely, burp the house. Past that, if the air is clean outside, it's certainly not going to do anything bad to you. It will give you a few minutes of fresher, cleaner air, so that's a good thing. I don't think it's worth stressing over or requiring it as part of your daily schedule.

HOST: So, it's not a have to. But there's something about where it's a nice day and you just open the windows and doors because you just want to let the fresh air in. It just feels good.

FARMER: And that's something to not ignore, that feeling good, that enjoying that fresh air. To an extent, maybe that's our brains or our bodies telling us that outdoor air is indeed cleaner than the indoor air. That's a great indicator that you should be going and breathing outdoor air a little more often.

HOST: What about when you can’t do that? What can you do?

FARMER: So, other than living in a tent, great things you can do for your indoor air quality obviously include reducing the sources. Try to reduce burning candles or having wood fireplaces. Or if you do, make sure that the air is ventilated and clean. Avoid using toxic products if you can. If you don't need to use bleach, don't use bleach. If you do use bleach to clean, then clear out the air right away.

It also turns out that simple surface cleaning is actually a really effective way to remove a lot of those compounds. So, we did this study where we looked at wildfire smoke, we added wood smoke into a house, and then we tried various interventions. We vacuumed and swept and then mopped the floors. And that permanently removed those air toxics in an amount that was about proportional to the surface area that we cleaned. So, cleaning all the floors and all those horizontal surfaces – your tables, your shelves – that actually made a meaningful impact on the quality of air indoors.

The one caveat I'll say is that we did that within days of exposing the house to smoke. I don't know if that cleaning benefit is really true several months later, and so I think cleaning houses where, for example, there's been someone who's smoked a lot of cigarettes, that's maybe a little more complicated than simple surface cleaning. But if you have an outdoor air pollution event and you can kind of catch your house quickly and you clean it, then that's going to be really good. Every time there's a big wildfire smoke event here in the Front Range in Colorado, I clean my house, and that's just because of what I've learned.

HOST: I'm always thinking about closing up the house and turning on the air purifiers when there’s a wildfire event nearby. But I've never thought to maybe do a little extra cleaning, maybe wipe down the walls or the counters.

FARMER: Absolutely. Even just doing the counters and vacuuming and mopping your floors, that's going to actually make a difference. That said, what you just said is exactly the right thing. When there is a bad outdoor air pollution event, you want as little of that air to get inside as possible. So, closing up the windows and doors is important. If you have an HVAC system in your house, you should have a filter in it that you should change every year, and you can just circle the air through that filter. That filter will then catch particles, and if you have an air purifier, even better, because you're going to catch a lot of those particles. You're not going to stop the gasses from getting into your house and getting onto the floors and the walls, but you are going to at least help the air quality in your house.

HOST: We're talking a lot about stand-alone houses, but I'm wondering about apartments and condos where there are shared walls. You can kind of control that no one smokes in your home, but you can't control the next-door neighbor.

FARMER: Yeah, that's a really tough one. I've lived in apartments for many years of my life and some apartments, you know what your neighbor's doing. You know when they smoke a cigarette. You know when they cook some very strong-smelling food. You know that the air is getting from their apartment to your apartment. In that case, you might not have a lot of control over what's going on next door, but you still have control about what happens in your own apartment. So hopefully, if you've got windows that you can crack or you've got a ventilation system, again, that stovetop vent hood, bathroom fans, those should all be working to remove the air.

Sometimes older buildings are leakier, so more air gets out from inside and more clean air is going to come in. That can actually be better for your indoor air quality. It's a lot worse for your wallet in terms of heating and air conditioning costs, but it does have some benefits, too. There's a lot of factors to consider. If you're in a hotel room or if you are in an apartment, what happens next door can influence you. There I would say, you start to trust your nose.

HOST: The nose knows.

FARMER: Exactly. The nose knows.

HOST: You mentioned air purifiers. Is that something that everyone should have?

FARMER: Air purifiers, and when I say air purifiers, I really do mean a simple filter with a fan that pulls air across that filter. Nothing fancy, but those simple air purifiers work really well to get rid of particles. They're really effective if there is an air pollution event that has particles. Again, that wildfire smoke, that traffic exhaust. Or if you're concerned about airborne diseases. If you have someone in the house who has the flu and you don't want to get the flu, using an air purifier really helps because it reduces the number of particles in the room and hopefully starts to trap some of those particles that you don't want to inhale.

But they also only work on the particle component of air pollution. They don't work on gas phase components. So, it depends on what keeps you up at night. Is it the particulate matter or is it the gasses? There I really start to think about what is happening that's concerning me, and I think about what we know is a problem, because there's nothing I can do about all the stuff that we don't know about. So, I think, all right, if there is wildfire smoke, traffic, something where I know there's particles, then I can control that with an air purifier.

I will also say, I run an air purifier in my bedroom all night, actually 24 hours a day. And ever since I started doing that, my allergies started to get a lot better. That's because they catch a lot of dust and a lot pollen and any other sort of particulate matter, often the things that cause allergies. There's no real downside to having an air purifier, other than the fact that you have to pay for a little tiny bit of energy. But they should be pretty energy efficient, and they should pretty cheap. You can even build one from items at Home Depot, and they're really inexpensive and they work really well.

HOST: You mentioned that's for particles, so for gasses, what can we do?

FARMER: For gasses, I will say again that the first thing is controlling the sources – so, reducing the number of toxic components that come into your house, actively choosing what you use to clean, making sure that when you cook those emissions go straight out through vent hood. If you have a fireplace, really think about where that air is going and ensuring that as little of it is coming into your home as possible.

The last thing is actively thinking about what's in our outdoor air. I think that the simplest way to improve indoor air is to actually have clean outdoor air. In the United States, we have this incredible thing called the Clean Air Act. Of all the legislation in the United States, this is probably the single piece of legislation that has saved the most lives because it really does reduce particle pollution from various industries and some of those gas-phase pollutants that we also have. That's a really powerful tool that we have, and you can keep an eye on what that outdoor air quality is through the Environmental Protection Agency as well as state and local monitoring stations.

HOST: We also get ozone alerts, you can check on that as well.

FARMER: Exactly, and I take ozone really seriously. That's a well-known toxic compound. It can inflame airways. It's linked to cardio and respiratory problems. We see increases in hospital visits when there are bad ozone days. That's something that we know is problematic.

You also don't want to bring it inside because once it gets inside, all of those compounds on surfaces and all of those gasses in the air, they're just ready to react with ozone. The one that I find the most interesting is our skin oils has a compound called squalane and squalane has lots of double bonds. As a chemist, I look at it and know that it is so ready to react with ozone and indeed it does. Then it produces a variety of different compounds, some of which are known to be bad for human health. There are air cleaners that are marketed that will actually produce ozone, and that's something to be very wary of.

HOST: That's a little scary. Now I'm like, OK, now I even have to wash myself more, too.

FARMER: I think it's more, if there's a bad ozone day, don't let that bad ozone come inside and react to things, whether it's on your skin or on the surfaces of your house.

HOST: You talked about reactions and I'm wondering about the idea of when indoor air meets outdoor air, do we have some collisions there, too?

FARMER: Yes, we do. When outdoor air meets indoor air, bad things happen. I think of indoor air as a big pile of dry kindling, and so there is all this chemical fuel that has the potential to do bad things. Most of it's not doing anything bad while we're inside, but if you let just one spark hit it, then you can have a whole series of reactions. One of the biggest sparks is again, ozone. When ozone comes inside, then you can get series of reactions and they produce quite a few toxic compounds, including, for example, formaldehyde. So, you don't want to have that collision happening. Indoor air, most of the time, is actually not that bad, as long as you don't bring in ozone and you keep the particulate sources.

Outdoor air we often think of as being pretty clean as long as you don't have an air pollution event. But yes, when you put those two together, you get a lot of chemical reactions. And as a chemist, the last thing I want happening in my home is a chemical reaction

HOST: Same.

FARMER: Right.

HOST: Are there instruments that homeowners can use to monitor their indoor air.

FARMER: Absolutely. There are two tools that you can think about as a homeowner. One is small particle sensors. So PurpleAir is one that's gotten a lot of attention, but there are a lot of other cheap sensors out there that will give you a PM2.5 number that's actually pretty good.

HOST: PM2.5?

FARMER: Particulate matter with a diameter of 2.5 microns or less. Those are the particles that we don't want to breathe into our lungs. There is a direct linear correlation between particulate matter of PM2.5 and mortality rates. The less PM2.5 you inhale, the better off you are.

It also reacts really quickly. So, if you cook and you release lots of particulate matter sometimes you can see it – I know I certainly can when I'm cooking – but sometimes you don't see it. Feedback from an indoor air quality monitor is going to tell you a lot about that. Something that measures PM2.5, is cheap, easy and really useful. It can also tell you when you should be opening your windows and doors or turning on your air purifier.

The other thing that's really nice for homeowners is a cheap little CO2, or carbon dioxide, monitor. Every single time we exhale, we're exhaling CO2. Outdoor CO2 is always about the same. It's about 480 parts per million. I should actually say it's about 420 parts per million. So, about 420 ppm outside, going up every year. But that CO2, you can go take a monitor, you can look at what your air is like outside your house. It'll change between the seasons. It'll change depending on where you're living and what your sources are nearby.

But if you have it inside, what you can watch is the combination of how many people are in your room and exhaling, plus how much ventilation there is. If that CO2 gets high – and when I say high, I mean above, I'd say 700 or 800 parts per million – then you know you've got a lot of people exhaling combined with really poor ventilation. That's a level where maybe if someone has a cold, flu, COVID, you want to start ventilating that air. You're basically breathing in kind of stale, used air. So, start breathing in fresher air from the outdoors. So, the CO2 monitors can be really useful as a monitor for ventilation, for how much indoor versus outdoor air you're breathing. But of course, that's a bit of a combination of people.

HOST: So, I feel like after this conversation, I'm going to be cleaning my house more, and cooking less, which is awesome. I love that.

FARMER: You're welcome.

HOST: And running my air purifier a little bit more.

FARMER: That would be a total win for your health. So, I totally agree with that.

HOST: All right, great. Well, thank you so much for your time. I appreciate it.

FARMER: You're very welcome.

OUTRO: That was CSU Assistant Professor of Chemistry Delphine Farmer, speaking about the effectiveness of airing out your home. I'm your host, Stacy Nick, and you're listening to CSU's The Audit.