[00:00:00] Aaron Goodman: You are listening to the Chemical Sensitivity Podcast. I'm Aaron Goodman, and I'm a journalist, documentary maker, and researcher—but I'm also someone who's lived with Multiple Chemical Sensitivity, or MCS, for years.

MCS—also called chemical intolerance, toxicant-induced loss of tolerance or TILT, and idiopathic environmental illness—affects millions around the world. It's a condition that makes everyday life extremely challenging and unpredictable. Fragrance, air fresheners, fresh paint, scented laundry products on someone’s clothing, and a lot more can trigger exhaustion, brain fog, muscle pain, rashes, and a wide range of symptoms.

And yet, for all its impacts, MCS remains largely invisible. Doctors dismiss it. Employers don’t accommodate it. Even friends and family struggle to understand. This podcast aims to change that. We dive into the latest research, share real stories, and explore how people navigate life with an illness that many refuse to see.

In this episode, we’re untangling how it is that fragrance products produce as much indoor air pollution as vehicles, according to two professors in civil engineering, they are Nusrat Jung, PhD, and Brandon Boor, PhD. Both are professors at Purdue University in Indiana in the U.S., and they specialize in indoor air quality and workplace air quality.

I ask them about what is actually in fragrance, which fragrance products they’re most concerned about, and if they have any hope that regulation can change.

Professor Jung and Professor Boor, thank you so much for joining me. Why did you choose indoor air quality as your field of specialty?

[00:02:20] Nusrat Jung: I’m really fascinated by things you cannot see—and in addition to that, things that affect us on a daily basis. Right? So air inside buildings is something that surrounds all of us every day.

All of the humans that are on this planet—if they have a safe home to stay in—this is our primary wish. We want to have a shelter. But within that shelter, we also have air that we breathe, and the quality of that air really matters, because we spend 90% of our time inside buildings. Right?

So the way I look at it is that you wake up in a building, then you go to another building, then you go to another building, and you ultimately return back to a building. So air that surrounds you really has a huge impact on your everyday exposure.

And of course, people who are listening—people with multiple chemical sensitivity—we’re aware of this, you know? And that really affects how we live our lives. It limits us in terms of where we can and cannot be. Your research is really important for folks like us with Multiple Chemical Sensitivity.

[00:03:12] Aaron Goodman: Professor Boor?

[00:03:14] Brandon Boor: I think I’m continually fascinated by the field. I think it’s a very dynamic field because I think there are many aspects to indoor air pollution that are linked to people—so, our own bodies.

I think a very obvious connection there is the COVID-19 pandemic, where the release of respiratory aerosol propagated the transmission of the SARS-CoV-2 virus.

And then we have our activities within buildings. We're responsible for the products we bring into our homes—the various chemical products, consumer products, and so forth. The dynamic operation of our ventilation systems has a profound impact on indoor air quality.

There are just many aspects that are quite interesting because things change so rapidly. And I believe that with studying indoor air quality, I’ve been focused on looking at what are the sources of air pollution, looking into ways to mitigate our exposures.

So, I think we have a lot of opportunities through the intelligent design and operation of buildings to protect ourselves from both outdoor and indoor air pollution. And I think that by understanding where the pollution is coming from—understanding the transformations of these pollutants and chemicals in the air around us—we can make better decisions to try to improve our health and well-being.

There are many aspects to the pollution that surrounds us, and it affects people all across the world. And I just think we need to be spending more time thinking about it moving forward.

So I have been thinking about this for a while, and about seven years ago, I moved to the United States. So I became a professor at Purdue University, and during the first one and a half years of my—

[00:05:03] Nusrat Jung: —living in the U.S., I started to experience hives, itching, extreme sensitivity to my surroundings. I was quite confused. Why is this happening?

And I think my first instinct was, “Is this the water I am drinking?” We had a filter at home, so we were using tap water. And in Finland, you drink tap water—it’s clean water. So for me, it never clicked that there could be anything wrong with the water.

I opened the water report for Finland, and then I opened the water report for my state and my county, and there was a drastic difference in the chemical loadings that were allowed. So it was quite clear to me that it may be the water.

Then I investigated detergents, what I’m eating, what type of foods am I purchasing...

[00:07:00] Aaron Goodman: Something I want to ask you about as we move a little bit forward—the study that you did, your conclusion that indoor air pollution is as significant as vehicle exhaust. I wonder if you want to talk to us about that a little bit?

[00:07:16] Brandon Boor: So in that particular study and a few other studies that we have conducted, we have been trying to compare indoor and outdoor sources of air pollution to better contextualize indoor air quality.

One of the things we have been looking at is the release of fragrance chemicals from consumer products. We have tested a wide variety of fragrance products. We have looked at scented candles, disinfectants that are fragranced, floor cleaning agents, personal care products, hair care products, essential oil diffusers, and air fresheners.

We have systematically looked at the chemical emissions from these products. I think there are two parts to this equation: the primary emissions of chemicals to the air, and then the transformations of these chemicals over time—and the secondary products that are produced.

So, the primary emissions include many volatile organic compounds—compounds that are often associated with the pleasant aroma that these products are intended to create, the "smellscape" of the indoor environment. Many of these products are very heavily fragranced with things like terpenes. Terpenes are naturally occurring; they’re found in vegetation. For example, a pine forest will emit pinene to the atmosphere.

These products contain very high concentrations of these fragrances because I think the manufacturers are deliberately trying to create a very strong aroma in the indoor environment. And we have used advanced instrumentation in our labs here at Purdue to measure these chemicals, and the concentrations—put in perspective—are orders of magnitude higher than what you would measure in a forest.

So, in a forest, you’re emitting terpenes to the air. They participate in a lot of atmospheric chemistry, which can lead to, for example, cloud formation. But the concentrations that we measure can be 1,000—sometimes even 1,000 times higher—than what you would have in a forested environment.

So even while these terpenes may be naturally occurring—and therefore people may believe them to be benign—the concentrations, and therefore the chemical exposures, accumulation, for sure, as well as potential dermal uptake, could be substantially more than what would occur outdoors.

And one unique aspect about a lot of these terpenes, which are found in fragrance products, is that they're highly reactive with ozone. Ozone is found outdoors. It can also be generated indoors through things like laser printers, bipolar ionization devices—things like that—but it primarily comes from outdoors to indoors through building ventilation.

Indoor levels are typically less than outdoors because ozone will react with skin oils, it reacts with our clothing, with surfaces, but there’s still some amount of ozone present indoors. Mingled together in the air, and then you’ll set forth a series of very complex chemical reactions.

So you can imagine that you’re using something like a wax warmer, or a plug-in air freshener, or a scented deodorant—these terpene molecules get into the air, they encounter the ozone molecules, and they trigger the formation of tiny particulate matter. Small particles that are suspended in the air are formed through these reactions.

So you end up with a situation where you’re exposed to these high levels of these fragrance chemicals and these secondary particles. These are very small particles, and they can penetrate very deep into your respiratory system. And we believe that it’s this kind of exposure—to both the terpenes and stuff in the particle phase, these small particles that are formed—that can be driving some of the adverse health outcomes associated with using these chemical products indoors.

So I think when we have a fragrance product, we have to be mindful that it’s not only emitting these fragrance chemicals in large abundance to the indoor environment, it’s also forming secondary particulate matter—and also at very high concentrations—and your body is exposed to all of that.

So we try to look at, for example, if you use a wax warmer or you’re cleaning your floor with a pine-scented cleaning agent, how does this particle production compare to vehicle exhaust?

Vehicle exhaust—there are regulations related to that. And we found that just by using a fragrance product that you can pick up at your local retail store, you can produce particles at the same rate—if not greater—than what is coming out of a car tailpipe.

And that may sound alarming, but that’s just how it is. These concentrations are just so high that these particle formation events are very intense. And this is something you cannot see—with these small particles forming around you, it’s not going to create visible smoke or smog or dust or anything like that—but it is occurring. And your body is receiving that exposure. And that may be driving a number of health outcomes that people are experiencing when using these products.

[00:12:27] Nusrat Jung: At Purdue University, we have a very sophisticated lab infrastructure. We created a house that has a very controlled building system, so we are able to very carefully create these controlled emission events and then measure everything about them over a period of time.

So your exposure is happening in two different ways. These are active things happening around you that are not visible to you at all. Another good way to explain this is: when you're peeling an orange, you smell that orangey scent. That's a terpene. But this is fine as an orange peel. It is not fine when you have injected the equivalent of 1,000 orange peels into a little bottle and then sprayed it around your whole house.

The concentrations are so high that we have to use instruments designed to measure tailpipe emissions. That’s really something serious to understand. We can’t measure them using small instrumentation.

What we need to actively think about is removing the sources of pollution in our environment. You are exposing yourself to a multi-phase source of pollutants on a continuous basis over many years. And if you continue to do that, it will, at some point, have a cumulative impact.

[00:14:07] Aaron Goodman: A couple more questions about what is in these toxic products that are sold. You mentioned terpenes, but let me please ask you about fragrance.

My understanding is that there are countless different chemical components in fragrance, right? And those can include terpenes—which you mentioned are natural—but we're also talking about VOCs, correct? And formaldehyde, and many other things. I don't want you to go through an exhaustive list, but what do you know about fragrance beyond terpenes?

[00:14:46] Brandon Boor: So, if you look at any scented product, there may be just the word “fragrance” or “fragrances.” And usually it’s not very descriptive. What does that mean?

Even in doing some of our research here using these fragrance products, it’s been a bit tricky to figure out what exactly is incorporated into these formulations.

So, terpenes are volatile organic compounds. And there are other non-terpene fragrance additives in these products, some of which we can measure using our instrumentation. But sometimes it’s tricky to figure out exactly what is present.

Often, if something is added in a small weight percentage, the manufacturer doesn’t necessarily need to list all the components of the fragrance. So it’s been a bit challenging to identify all the different VOCs that are creating the aroma.

Certainly, terpenes are a big part of that equation. But there are chemically manufactured fragrances as well that are incorporated, and they all have different purposes in terms of the olfactory experience—to create different “notes” in the fragrance.

I focus on terpenes because they are a particular component that is highly reactive with ozone. Because of that, they can form particulate matter—secondary products that could be quite harmful to our health.

Now, I’m not sure about some of the non-terpene fragrances and their contribution to particle formation, because I don’t know how reactive they are with ozone. But I think this tells us that we need to better investigate what’s being emitted.

And once these chemicals are in the air, how do they transform? Do they produce potentially more toxic products?

I think there are different elements to that.

One thing that we did look at was non-fragrance components of personal care products. So I’ll let Professor Jung talk about this from the perspective of hair care products. But there are components to these fragrance products that are not responsible for the fragrance themselves and are very concerning from a health perspective.

[00:17:12] Nusrat Jung: One of our papers that came out of our lab last year—it was a major discovery—comes from hair care products.

So, as you can see, I have curly hair, and I’ve struggled since I was a teenager to manage it. You always want to look professional, and that often involves straightening your hair. I always wondered, when I did that as a teenager, what am I seeing? What are these fumes?

So, once I became a professor and got more into emissions and sources of emissions and understanding my indoor environments, I thought: let me check out what I’m breathing.

I found a study—one of them coming from Sweden—that surprised me.

These hair care products and heat protectants, designed to protect your hair from being damaged by heat, contain a compound that is added to the product to help protect the hair. But at the same time, when you apply heat to it, it goes through a thermal degradation process that exacerbates the problem. It releases compounds into the air right next to your mouth.

These compounds have been found to have a profound impact on aquatic life and aquatic ecosystems. And if it’s having that kind of impact on aquatic life, it’s going to have a profound impact on humans too.

It’s bioaccumulative—which means, once you’ve inhaled it, it somehow enters your system and doesn’t leave.

So, if you’re conducting this activity every day for 30 years, what’s your cumulative exposure?

Again, this is not initiated by the product itself—it’s the process the product undergoes when a consumer uses it. So the consumer applies it, and it gets transformed.

I think there’s a need to think about the entire lifecycle of a product.

What happens once you purchase it, bring it home, and start using it?

So, it’s really complex. And we’re finding all of these chemicals finding their pathway into our breathing zone.

[00:19:39] Aaron Goodman: Could you put your finger on maybe a particular kind of product that piques your concern these days when it comes to fragrance—chemical fragrance? Because we know, anecdotally, people tell me all the time, and we know that companies are making products to smell stronger and last longer. Anything on your radar these days when it comes to fragrance products?

[00:20:03] Nusrat Jung: In terms of products particularly on our radar, I would urge people to actually just take a walk through their grocery store and look at all of the products. They are increasingly pumped with fragrances. So, it’s not one product—it’s hundreds of them. It’s hard to pinpoint just one because there’s simply an overwhelming number of them.

[00:20:32] Brandon Boor: As Professor Jung mentioned, at any retail store here in the United States, we just have aisles of scented products. For the average consumer, this information—about what’s in these fragrances—is not very clear. And also, a lot of people want to buy the product because of the fragrance.

Professor Jung and I try to tell people: clean air should not have any scent associated with it. Of course, the absence of scent doesn’t necessarily mean the air is clean. But this perception that if the air smells like a forest, or lavender, that it must be clean—that’s not the case.

We like to put scented products on our bodies to mask naturally occurring volatile organic compounds that are released from our skin, sweat, and breath. But these added scents can cause a number of problems, because many of them are very reactive molecules, and the concentrations can get very high during active use.

In our work—and the work of others—we’ve found that when people apply scented personal care products to their bodies, they become basically a walking, mobile source of these volatile chemicals. If someone’s getting ready in the morning and applies heavily fragranced deodorant, perfume, or cologne, then enters a shared space, other people will be exposed to the emissions coming off their body.

These chemicals are volatile, which means they want to evaporate—but they’ll continue off-gassing from the body for some period of time.

Another area Professor Jung and I are particularly interested in is laundry products. There’s been a big push to make laundry products even more heavily fragranced—not just the detergent, but things you add to the dryer so your clothes come out with a very strong smell.

I think people who are aware of these issues might stay away from those products. But if a lot of people are conditioning their clothes with these heavily fragranced products—and layering that on top of fragranced personal care products—you get residual chemical emissions coming from people throughout the day.

This idea that “if it smells good, it’s clean”—that’s a flawed assumption. And the same idea gets applied to cleaning products, disinfectants, and so on.

We need to rethink that. Because if we’re just adding large quantities of fragrances to products we put on our skin, hair, and clothes, people then become mobile sources of these chemicals.

So, even if you eliminate these products from your home, the moment you go to work or send your child to school, you can encounter secondary exposures from others who are using these products.

Also, if shared spaces like classrooms or offices are cleaned with fragranced floor or surface cleaners, you could walk in the next day and still be exposed to those chemicals. Of course, the exposure would be less than during active use, but those molecules can linger in the indoor environment.

Some of them are vented outdoors, but others get trapped on surfaces and can later re-enter the air. A good example is thirdhand tobacco smoke exposure. Some molecules stick to surfaces like walls and furniture, and then come back off into the air.

So, this is a real issue for people entering shared spaces. Even if you stay away from these products entirely, you can still be exposed.

[00:24:55] Aaron Goodman: Well, I'm so glad you mentioned these products, because they're definitely on our radar. Personally speaking—the laundry products, the dryer sheets, air fresheners, plug-ins, candles—these are huge kryptonites for me and for thousands, if not millions, of people with chronic chemical intolerance and Multiple Chemical Sensitivity.

And we struggle. Like myself—I'm a university educator. And because of my Multiple Chemical Sensitivity, I can't be in the classroom. Fortunately, I have a medical accommodation that allows me to teach and do my research online. Because the moment I walk into a shared space—whether it's commuting on public transit, or being in places where I'm breathing in emissions from laundry products, body sprays, cosmetics, and beauty products—I become extremely ill.

That leads to the next question: what can we do?

We can try to stay away. We can make our homes as safe as possible. We can lobby for change. We can ask our employers to provide a fragrance-free or fragrance-aware policy. But, as you’ve mentioned, these policies are really hard to enforce. What can we do? Can regulation—or human resource departments—ever have any success in enforcing policies that will help?

[00:26:20] Brandon Boor: I think it may be difficult. Any regulations pertaining to indoor air quality are either non-existent or insufficient. There are some for occupational environments, but generally, they are not where they need to be.

After the COVID-19 pandemic, more and more people have become aware of indoor air quality issues. But when you’re looking at chemical exposure, it’s a little more complicated.

For example, we can wear a face mask that blocks out particulate matter, including particles that carry viruses and bacteria. But many of these fragrance compounds are in the gas phase. Unless they’ve formed particles, a simple face mask isn’t going to block your exposure. These compounds can penetrate a typical face mask very efficiently. And of course, wearing something like a respirator isn't really a viable long-term solution for most people.

It’s tricky. When we talk about buildings, ventilation is usually seen as a good thing. But that comes with some caveats.

As I mentioned earlier, ozone comes primarily from outdoors into indoor environments through ventilation. And we just published a study—Professor Jung and I—that showed when you increase outdoor air ventilation, you also increase indoor ozone levels. That ozone then reacts with fragrance chemicals like terpenes and forms fine particulate matter.

So, it’s a double-edged sword. Better ventilation brings in ozone, which reacts with indoor chemicals to create particles.

And then in some areas, like Los Angeles during wildfire season, you definitely don’t want to bring polluted air indoors. Or in low-income communities that are close to highways or industrial facilities—you may not want to bring that kind of outdoor air inside either.

So while ventilation is generally helpful, you need to scrub the incoming air. You can filter particulate matter with conventional HVAC filters, but volatile organic compounds and ozone are much harder to remove.

And because of that, it’s also difficult to remove those pollutants once they’re already indoors. So if you're in a classroom or an office where people have applied these fragranced products, the ventilation system won’t necessarily clean that air.

There are some air-cleaning products—like activated carbon filters—that can help remove volatile organic compounds. But they saturate quickly, so they’re not a perfect long-term solution.

That makes it hard to operate buildings in a way that protects people from chemical exposures in the gas phase. And that includes products that people wear on their skin, hair, and clothing.

So the best solution—as you said—is to help people become more aware. If you’re in a shared space and someone has sensitivities, maybe consider avoiding heavily fragranced products.

How to enforce that? I’m not sure. But raising awareness is a good place to start.

There could be regulations on the amount of fragrance added to products—but that would require better data on short- and long-term health effects across different demographics.

[00:30:37] Nusrat Jung: Thank you. I think the first thing we need to do is understand what these fragrances actually are. So many of them fall under the label of “proprietary information” because they're considered part of a company’s brand value.

Fragrances are of very high intensity, and we can’t measure them by weight percentage alone. Anything that falls below a certain weight percentage doesn’t legally have to be disclosed on the label.

Professor Boor mentioned gas-phase compounds and face masks earlier. A good example is this: if you're wearing a face mask and someone is smoking nearby, you can still smell the smoke—that's because it's in the gas phase. You’re only filtering out so much. That’s one way to understand the difference between particle-phase and gas-phase pollutants.

Third, I do have hope. We used to smoke indoors. There was a time when it was fashionable to smoke in your house or even in your bedroom. I have friends and family who now laugh about the ashtrays they used to have right next to their beds.

But things change. Society can evolve. We can create spaces for everyone—people who have sensitivities and people who don’t.

To the listeners who may not have sensitivities: you could become sensitive to certain chemicals at any point in time. You may not know how your body will react until you’ve been exposed repeatedly. So it’s not good to dismiss others—especially those already living with these sensitivities.

Yes, lobbying is important, but we also need to invest in research. That’s how we’re able to make these discoveries. Our labs are supported by the National Science Foundation, which has enabled us to do innovative work, and also by the Environmental Protection Agency. These are institutions that have really helped push our science forward.

And lastly, it’s not just one person. It’s not just one product. It’s the cumulative effect. And that cumulative exposure is what will have an impact. We need to be thinking about that—and acting with care.

[00:33:34] Aaron Goodman: I realize you're not experts in Multiple Chemical Sensitivity, but knowing what you know about chemicals, the harms, and the potential impact on human health and the environment—we experience a lot of dismissal.

Medical providers often tell us it's not real, that it's in our heads. Even loved ones can be dismissive. What would you say to a doctor who dismisses people with Multiple Chemical Sensitivity, based on what you’ve learned in your research?

[00:34:07] Nusrat Jung: I would say that medical professionals are trained to make decisions based on evidence—and often on very specific types of evidence. They're looking at what they can measure directly in your body: your organs, your temperature, your blood pressure.

But exposure to environmental chemicals—especially over time—is more complex. It’s cumulative. Multiple exposures to different chemicals might eventually manifest in the body as illness, but it’s not always immediate or obvious.

So there’s a gap. There's a disconnect between what we’ve discovered in our labs and what’s available to clinicians when they evaluate a patient. That information—the environmental data—needs to reach the medical community.

And I want to say I am very supportive of doctors. I've had my own health challenges, and medical professionals have saved my life. I have deep appreciation for their work.

But I also encourage them to keep an open mind about what’s happening in people’s homes and environments. Some exposures may not show immediate physical symptoms, but they could still be harming people in invisible ways over time.

[00:35:39] Brandon Boor: I would add that most fragrance chemicals aren’t widely monitored indoors. So it’s hard to make clear associations between exposure and health outcomes—especially for groups like people with chemical sensitivities.

A lot of what we know about air pollution and health is based on outdoor air monitoring. We’ve studied things like ozone and particulate matter outdoors and linked them to health risks.

But indoors, it’s different. These fragrance chemicals are far more prevalent inside than out. Yet we don’t have strong indoor air monitoring networks. That’s a big limitation.

So I think we need to invest more in measuring what’s actually in indoor air—in schools, offices, homes—especially where people are reporting symptoms. We need better data: where the chemicals are coming from, how much people are exposed to, and what the cumulative intake is.

Once we have that kind of data, we’ll be in a better position to make those connections to health outcomes—especially for populations that are more sensitive to these exposures.

[00:38:14] Aaron Goodman: You mentioned more research needs to be done and that there isn’t enough. How much research is actually happening about toxic chemicals and fragrance? Are you isolated in your work?

[00:38:28] Brandon Boor: It’s far from where it needs to be. There is some growing interest in what are now called volatile chemical products, which include many fragrance products that are used primarily indoors.

But it’s a big challenge. As Professor Jung mentioned earlier, just walk into a store—there are aisles and aisles of these products. And they come in so many different forms: sprays, gels, creams. The way each product is used affects how it emits chemicals.

So there’s a lot of complexity. It’s going to take a lot of different simulations and lab-based studies to even begin to understand what’s being released and how it behaves in indoor air.

The hair care products, for example—that’s a really unique use case. And it’s one we had to simulate very specifically to understand the emissions and exposure pathways.

There’s a long way to go. And we’re just getting started.

[00:39:24] Aaron Goodman: You’ve been listening to the Chemical Sensitivity Podcast. I’m the host and podcast creator, Aaron Goodman.

The Chemical Sensitivity Podcast is by and for the MCS community. The podcast is generously supported by the Marilyn Brachman Hoffman Foundation and listeners like you. If you’d like to support the podcast, please visit chemicalsensitivitypodcast.org. Your support helps keep the show going and helps us raise awareness about Multiple Chemical Sensitivity.

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Thanks for listening.

The Chemical Sensitivity Podcast and its associated website are the work of Aaron Goodman, made possible with funds from the Marilyn Brachman Hoffman Foundation, supporting efforts to educate and inform physicians, scientists, and the public about Multiple Chemical Sensitivity. The content, opinions, findings, statements, and recommendations expressed in this podcast and on the associated website do not necessarily reflect the views or opinions of its sponsors.