How Common Household Products Pollute Our Indoor Air

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Today on the show–

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–what are you breathing in when you do your hair?

NUSRAT JUNG: When we think about air pollution, we think of smoke, we think of smog, we think of wildfires. But we don’t think of everyday haircare products to be causing indoor air pollution.

FLORA LICHTMAN: You’ve probably given some thought to outdoor air pollution. Whether it’s smog from traffic or wildfire smoke, I suspect that many of us are checking AQI measurements on our phone more than we used to. But what about the air inside your house? Today we’re talking to a researcher who thinks a lot about indoor air pollution and how we create toxic air without even knowing it and how to avoid it.

Dr. Nusrat Jung is a civil and environmental engineer at Purdue University in West Lafayette, Indiana, and she has a new study out on the toxins released during basic hair care. Nusrat, welcome to Science Friday.

NUSRAT JUNG: Thank you, Flora. How are you?

FLORA LICHTMAN: I’m well. Let’s brush up on your recent findings. This is where haircare products meet heat. What did you find?

NUSRAT JUNG: Our study shows that routine hair-based styling can release billions of nanoparticles into the air just within 10-to-20-minute routine. These particles are small enough to penetrate deep into the lungs. So when we think about air pollution, we think of smoke, we think of smog, we think of wildfires. But we don’t think of everyday haircare products to be causing indoor air pollution.

FLORA LICHTMAN: When you talk about basic haircare routines, what do you mean? Is it hair spray? Is it using a blow dryer? What are we talking about here?

NUSRAT JUNG: Right. So haircare routine means utilizing haircare products that are categorized as leave-on haircare products, which means you do not wash them off. So we are not talking about shampoo and conditioner, because that is something you would use when you are taking a shower. We are talking about gels, creams, hair sprays, oils, any kind of liquids that you would leave on your hair.

FLORA LICHTMAN: And are they releasing these nanoparticles only when they’re heated? Or if you’re spraying hairspray, you know, if you’re doing Aqua Net all over your hair, are you also getting that same dose of nanoparticles?

NUSRAT JUNG: So we found that heat tends to exacerbate the sheer number of nanoparticles released from everyday haircare products, and this is far greater than what we have ever expected to see.

FLORA LICHTMAN: When you say far greater, what do you mean?

NUSRAT JUNG: The concentrations are about 10,000, 200,000 nanoparticles per cubic centimeter. So it is not just about concentration, Flora. This is important to understand because we studied not just the concentration, but what are you going to receive in terms of dose when you inhale.

So our study shows that the exposures can rival highway traffic, which means that highway traffic exposure occurs outdoors, where pollutants are diluted in much larger air volume. In contrast, the hair styling takes place just inches away from the nose and mouth in an enclosed indoor space where nanoparticle concentrations can build up quickly. But especially this closed proximity and confinement gives airborne nanoparticles a more direct pathway into the lungs, and the doses can be surprisingly high, even during a short styling routine.

The heat-based hair styling can release billions of nanoparticles into the air within just 10 to 20 minutes, and they deposit and penetrate deep into the lungs. And the exposure from a single session can rival those from sitting in heavy traffic.

FLORA LICHTMAN: Wow. And you’re doing it every day.

NUSRAT JUNG: Yes.

FLORA LICHTMAN: So do you know what nanoparticles are being generated by these processes? And do if they’re harmful?

NUSRAT JUNG: Yes. So our research shows that some of the tiny particles released during heat styling come from the chemical ingredients, particularly siloxanes. Siloxanes have been found to lead to adverse effects on the respiratory tract, liver, and nervous system of laboratory animals. And when these ingredients are heated, they can break down and form airborne nanoparticles that people breathe in.

So these are really the reactions or the secondary mechanism that occurs where they are being formed because they’re exposed to heat.

FLORA LICHTMAN: It’s a chemical reaction, basically.

NUSRAT JUNG: Yes. They become something else than what is listed on the list of ingredients. So I think this is quite serious, because breathing them in can irritate the lungs and worsen conditions like asthma. Over time, you have potential for more serious impacts because they can pass from lungs into the bloodstream, they can spread to other organs. And long-term exposure to these kind of particles with chronic respiratory and heart disease, and they have possible effects on the brain. So these are serious things.

FLORA LICHTMAN: Are these products regulated for their aerosol effects and these chemicals that they can generate?

NUSRAT JUNG: So our study is the first to have actually discovered what is happening during the process of application of a haircare product. So we can only regulate something if we understand that there is a problem. So none of these products are tested for their emissions, for what happens to them when they are being used. They are formulated only to do certain things. But no, we have never seen that information on any packaged material. I have never come across it.

FLORA LICHTMAN: As I was reading about this, it occurred to me that there’s just tons of things that we spray on a daily basis. There are things that we heat up on a daily basis, our cookware. What is your top concern for indoor air pollutants? Or what are you most interested in studying?

NUSRAT JUNG: So I have been fascinated, Flora, with our everyday life and what can we be exposed to. So our discoveries have come from basically observing and then really using cutting-edge instrumentation to measure these everyday activities, to understand what is not visible to us.

So air pollution in indoor environments is very, very important because we spend more than 90% of our time indoors. I mean, if you want to think about it, we all go to sleep in a building. We wake up, we leave our building to go to some other building that may be work or may be coffee shop. Then we go to lunch, we are in another building. Then we go back home, and that is another building. Maybe we go to a gym later in the evening. That’s another building.

So as humans, we keep rotating from one building to another. We spend 90% of our time inside buildings. And what happens within these buildings is really important to capture in terms of emissions. Cooking activities are sources of air pollution. Using scented products, candles are sources of air pollution. Using heavily centered cleaning products in your enclosed home environment is a source of air pollution.

So we are inadvertently causing all of these chemical reactions in these. Really, we live in boxes that are mechanically ventilated. And if the ventilation conditions are good, even then you are not able to remove all of these pollutants. For example, the pollutants we are talking about today are coming from haircare products. The sheer number of nanoparticles are so many that ventilation alone is not able to get rid of it.

So honestly, that’s a lot about problems in internal environments. I think I’d like to make it a little lighter and maybe think about solutions.

FLORA LICHTMAN: Well, yeah, I was going to ask. I mean, what are the solutions, do you think?

NUSRAT JUNG: So my number one recommendation is, if there is any way you can get rid of your chemical mixtures that you are introducing next to your nose and your mouth would be like the best thing you can do. The second best thing you can do is simply reduce the frequency of them. Try to limit it to once in a week, once in three days. Third would be limit the use of the amount of the product you are applying. Fourth would be to, yes, have ventilation on. I mean, ventilation does help.

But then we have other problems, like what you are exhausting from your bathroom exhaust, maybe someone else’s air intake in a city like New York. So these nanoparticles, these volatile chemical mixtures, they are cycling through our buildings. So honestly, the best way would be to ideally remove the source of them.

FLORA LICHTMAN: Has your own hair routine changed since you started studying this?

NUSRAT JUNG: Yes. So I am blessed with quite many curly wavy hair, and I have enjoyed being in these aisles and aisles of so many kinds of haircare products. And believe me when I say I have used so many of them. And then our team started measuring what is being released, and I think it was one surprise after another surprise. And that surprise turned into a shock. And then that shock resulted in simply coming back home and getting rid of every single bottle of spray, cream, heat protectant that I had.

FLORA LICHTMAN: Really?

NUSRAT JUNG: Yes. I have decided now to be totally natural. So I’m very, very pleased with having changed my haircare routine and simply removed all chemical mixtures from my everyday routine.

FLORA LICHTMAN: That says a lot, I think.

NUSRAT JUNG: Yeah, because if you think about it, Flora, your body is not filtering these things out. When people choose to smoke, it’s like it’s their choice, right? It’s like, OK, I am smoking because I want to smoke, and you kind of have your own will. But in case of a haircare routine, I mean, I never thought that I’m being exposed to anything at all.

FLORA LICHTMAN: Yes. I think that’s the fascinating thing about this, that it is a window into how little we really probably know about these kind of exposures, that we didn’t even think to wonder about this kind of exposure.

NUSRAT JUNG: Yeah. Heat-based hairstyling should be recognized as an emerging and serious public health concern. And these exposures occur right where people live, where they breathe, they spend most of their time, and yet they remain invisible and unregulated. We have worked on indoor smoking bans, and we have now come up with volatile organic compound, VOC labeling for our building materials. This represents another blind spot that deserves attention.

FLORA LICHTMAN: Thank you for taking the time to talk to us.

NUSRAT JUNG: Thank you, Flora.

FLORA LICHTMAN: Dr. Nusrat Jung is a civil and environmental engineer at Purdue University in West Lafayette, Indiana.

Thanks for listening. Don’t forget to rate and review us wherever you listen. It really does help us get the word out and get the show in front of new listeners. Today’s episode was produced by Dee Peterschmidt. I’m Flora Lichtman. Thanks for listening.

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