Linda Birnbaum
Big Brains podcst

How PFAS ‘forever chemicals’ are harming our health, with Linda Birnbaum (Ep. 124)

From kitchen pans to drinking water, dangers hidden in everyday materials, scientist warns

Linda Birnbaum
Big Brains podcst

Show Notes

By now, you've probably heard about the dangers of PFAS “forever chemicals.” These chemicals are all around us—they're in waterproof hiking boots, electronics, nonstick pans and even our drinking water—but there's no way for them to break down in our environment. Epidemiological studies have linked to these chemicals to numerous diseases—from kidney cancer, liver cancer, obesity, decreased fertility and more.

American toxicologist Linda Birnbaum has been sounding the alarms about how PFAS are harming our health for the last few decades. She was previously the director of the National Institute for Environmental Health Sciences at the NIH and is currently an adjunct professor at the University of North Carolina, Chapel Hill. She explains that while we cannot completely avoid PFAS, there are steps we can take to limit our exposure.

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(Episode published November 16, 2023)

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There’s something dangerous lurking in your kitchenware. Your workout clothes, your hiking boots, your dental floss, and even the takeout boxes when you order food from your local restaurant.

Linda Birnbaum: They’re basically everywhere, in everything, and in all of us,

Tape: There’s a class of toxic chemicals so pervasive that they’re found in food, soil, water, and in the blood of most people in America.

Paul Rand: They’re called PFAS.

Linda Birnbaum: PFAS is a class of chemicals, which is the totality of more than 14 or 15,000 different chemicals.

Paul Rand: You may have heard them called by another name as well, forever chemicals.

Linda Birnbaum: There is no natural way that these chemicals break down, so if you make them, they continue to exist.

Paul Rand: That’s Linda Birnbaum, an adjunct professor at the University of North Carolina Chapel Hill. She was previously the director of the National Institute for Environmental Health Sciences at the NIH, and testified about the danger of PFAS in 2018.

Linda Birnbaum: We need to be aware that this is a huge class of chemicals that we’re all exposed, they’re everywhere. They exist in the soil, they exist in the sediment, they exist in the water, and some of them exist in the air. And they migrate all over the world, these are very mobile chemicals as well.

Paul Rand: How do these chemicals get everywhere? Well, it’s because they’ve been instrumental in making many of the consumer products in our lives.

Linda Birnbaum: PFAS are used as stain repellents, surface applicants, lubricants, used in lots of electronic equipment. Your new iPhone has PFAS in it. Your computer chips have PFAS in them.

Paul Rand: Even some pharmaceutical drugs have PFAS in them.

Linda Birnbaum: They’re pretty much in hundreds and hundreds and hundreds of consumer products.

Paul Rand: But even though these chemicals have made our lives better in so many ways, they could be harming the environment, wildlife, and even our health.

Linda Birnbaum: A couple of years ago I pulled off the numbers of papers that were published on PFAS in PubMed, and what you saw was essentially an exponential increase in publications. The ones that have been tested have all been shown to cause health problems. So the things that we’re seeing is a tremendous increase in what’s called chronic non-communicable diseases. Asthma, heart disease, cancer, stroke, preterm birth. We’re seeing tremendous decreases and problems with fertility.

Paul Rand: Welcome to Big Brains, where we translate the biggest ideas and complex discoveries into digestible brain food. Big brains, little bites, from the University of Chicago Podcast Network. On today’s episode, the science of PFAS and what they’re doing to our health. I’m your host, Paul Rand.

We often think positively of the word “forever.” It’s often associated with love songs, fairytale endings, or eternal life. But forever isn’t always a good thing. For instance, a toxic chemical that has been engineered to last forever.

Linda Birnbaum: PFAS have a lot of carbon fluorine bonds.

Paul Rand: This bond of carbon and fluorine atoms creates one of the strongest bonds that exist in chemistry. The bond doesn’t break.

Linda Birnbaum: If you have lots of them in a molecule, that is going to make the molecule forever in the environment because there is no natural way that has evolved to break that bond. So the carbon fluorine bond, for example, does not break down in the presence of sunlight. Other very persistent chemicals, things like dioxins, will actually break down in the presence of sunlight over time. It takes a long time, the estimate is about 10 years. No one has been able to demonstrate that these chemicals can break down with natural processes of light, heat, or even oxygen levels.

Paul Rand: There are many chemical bonds that originate in nature, but combining carbon and fluorine is almost always a manmade process.

Linda Birnbaum: It barely exists in nature.

Paul Rand: And we’ve been able to use this simple carbon fluorine bond to make a plethora of different PFAS.

Linda Birnbaum: There is, I said, well over 10,000 PFAS. The latest dashboard from EPA ORD, at least in 2022, was over 14,000 different PFAS. Now people are saying over 15. It’s kind of if you look, you find more.

Paul Rand: Okay. When did the chemicals first come into existence?

Linda Birnbaum: The first PFAS was synthesized I believe actually in the 1930s or ‘40s.

Paul Rand: Chemists at a company called DuPont invented a new material that would change kitchens across America, Teflon.

Tape: Well, it coats the pots you cook with so the food doesn’t stick. It protects the carpet your baby crawls on. You may also have it in your winter jacket, your skin lotion, even your makeup. We’re talking about Teflon.

Paul Rand: Teflon was just one of the many PFAS that could be created. And once other companies saw the possibilities, well, they wanted in too.

Linda Birnbaum: I think real production and use got going in the ‘50s. Some of the major uses, other uses, started in the ‘60s.

Paul Rand: Another company they got heavily involved in the manufacturer of PFAS products was 3M.

Linda Birnbaum: You name their more than 200 use categories, and each of those categories has multiple uses.

Paul Rand: 3M manufactured PFAS like PFOS and PFOA, that were used to create many consumer products. We’ve all probably used at one point or another.

Linda Birnbaum: They are in all kinds of electronic and industry products. And I have to say, many of them are very useful. I mean, a major source of contamination has been the AFFF for the air film-forming foam, which was used to put out fires and to train firefighters and so on. And that has been a major source of water contamination throughout our country and throughout the world.

Paul Rand: Tell me how you started becoming really concerned about the PFAS.

Linda Birnbaum: Well, I would tell you, I actually published three papers on PFAS in the late 1980s, and then stopped working with them because at the time I didn’t know that there was exposure going on to all of us everywhere. I think I first began really concerned around 2000, 2001 or ‘02. 3M and then EPA announced that, oh, if you look at the general population, we all have some PFAS in us. And that I think raised a concern. And I was in EPA at the time. Some of my scientists started looking at the immune effects of some of the PFAS. And some of the other divisions, so some of my colleagues who were in charge, were looking at some of the developmental effects.

We also became aware of some of the rodent cancer studies with a couple of PFAS, which all showed that they were associated with an increase in tumors. I think as we began to see that, at least in our animal studies, there was a multitude of health effects, in several different animal models, including monkeys, I think my concern began to grow.

Paul Rand: In 2016, the Food and Drug Administration banned the use of substances called PFOA and PFOS in food packaging. And 3M has said they’ll stop making PFAS altogether by 2025. But many other companies are still using PFAS, yet none of that changes the fact that these forever chemicals are already everywhere, seeping into our bodies.

Linda Birnbaum: Okay, so how do they get into us? The PFAS are very well absorbed, whether you ingest them because they’re in your drinking water or they’re in their food. The estimates are that for most of us, the food that we eat is our major source of PFAS. If you inhale them, because some of them are quite volatile, those will be absorbed through your lungs and get into your blood. Skin is a pretty good barrier for PFAS, but not complete. So if you get it on your skin, some of it will get in, not all of it. But say orally, essentially anything you eat or drink for PFAS will get into your body and into your blood.

Now in our bodies, many of these chemicals have long half-lives, on the order of years. For a drug, think something like aspirin or Tylenol, you’re talking about a chemical with a half-life of a couple of hours at most. There are some drugs that have a half-life of a couple minutes. In our body some of these chemicals have half-lives as long as five to 10 years.

Paul Rand: And do they bioaccumulate?

Linda Birnbaum: Okay, that’s a great question. Some of them do. Some of what we call the longer chains, which are things that have a row of, for example, carbons like eight or 10 or 12 or 14, many of those do bioaccumulate. Some of the shorter chain ones accumulate less, but less is not zero. And for most of them we have no information whether they will or not. We can have some predictive power, but we really don’t have the data.

People are beginning to use an additional approach, whereas you look for what we call the targeted ones, the ones we know a little about, and you measure what’s called total organic fluorine. And the total organic fluorine will also pick up things like certain drugs can be PFAS, certain pesticides can be PFAS. And the total organic fluorine will pick up those, as well as the ones you know about, and then it’ll pick up everything else that you don’t.

So estimates in our blood, the best estimate we have is a study that was done in Sweden about a year or two ago, and they found that measuring 61 different PFAS with the total organic fluorine, they accounted in some cases for over 30% of the total organic fluorine that was in somebody’s blood.

Paul Rand: Okay, so these chemicals are everywhere, and most likely in all of us. We’ve said they’re dangerous, but what exactly are they doing to us? And are there really zero ways to destroy these chemicals? That’s after the break.

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If PFAS are sitting around in our bloodstreams, unable to flush out every five or 10 years, then how are they impacting our health, and even worse, our risk of disease.

Linda Birnbaum: Most of the studies have looked at specific PFAS, like PFOA or PFOS. Some have tried to look at the mixture or the soup that we live in to a certain extent, but what we see there are pretty strong associations with testicular cancer and kidney cancer has increased. There’s that association. There’s also an indication of several other kinds of cancers that are associated with PFAS.

And then impacts on the liver. With elevated, especially LDL cholesterol, the bad cholesterol, goes up. And there are some studies now that are beginning to see associations, for example, with liver cancer as well. There are studies showing increased risks of overweight and obesity and associations with type II diabetes, so you have that metabolic change going on. And there are a couple studies that are beginning to see associations with heart disease as well. There’s evidence of impacts on the immune system, both an increase in autoimmunity and an increase in immune suppression.

The things I’m giving as examples, it’s not that we only see them in people, we also see them in our experimental animal models, and we see that human cells respond just like some of our animal cells. I think our species, our world, has not had an opportunity to evolve to deal with these things.

Paul Rand: If it’s not clear by now, the research on how PFAS impacts our health is still ongoing, and it’s going to take some time for us to fully grasp the effects these forever chemicals are having on us.

Linda Birnbaum: We have many studies that looked at a population of people at one point in time, and that kind of study is called cross-sectional. And those studies are very good for helping you form a hypothesis, but they’re not good for really looking at causation. If we want to look at causation, we want to especially do what we call our longitudinal studies. I mean, some of the best studies start before birth, and then you continue to follow the people for as long as you can follow. If you get a 10-year longitudinal study, that’s great.

Because some of these PFAS are very persistent in blood, there are, for example, stored blood samples from other studies that have been done, you can go back at and look at, “Well, what were the levels in these people at time 20 years ago?” And then you can look at what their health conditions are over time so that you’re seeing the association, if you see an association, with what was in their body. If you take someone who already has heart disease or someone who already has cancer and you look at their levels today, it becomes a little bit of a chicken and an egg, which came first, the high levels or their health condition.

So when you can follow a population before they have a health condition and then watch it develop, and we’re getting those kinds of studies. In fact, I’m seeing it, but certainly within the next 10 years we’re going to see many, many more adverse health conditions related to exposure to PFAS.

Paul Rand: The primary way most of us are exposed to PFAS is through our drinking water.

Tape: Nearly half of the nation’s drinking water contains potentially harmful forever chemicals.

Linda Birnbaum: I live in North Carolina. We have a major problem with PFAS contamination in the Cape Fear River because an industry, used to be DuPont and it’s now something called Chemours, and basically they’ve been polluting the Cape Fear River for decades.

Tape: A local water authority is urging the state to study health risks of toxic chemicals found in people’s drinking water. The Cape Fear Public Utility Authority asked the state to add a new compound to a group of forever chemicals the state has prioritized for study.

Linda Birnbaum: And people living downstream or within close proximity to the plant, they are shown to have elevated blood levels of these chemicals. The City of Wilmington, which the municipal water is feeding about 300,000 people, had to completely put in a new water treatment plant to filter out the PFAS from their drinking water. And you can filter out the PFAS from drinking water, but what do you do with those contaminated filters? Put them in a landfill. We all know what happens with landfills. Eventually, the stuff leches out.

Paul Rand: In 2016, the EPA released a statement saying PFAS at low levels in our drinking water, 70 parts per trillion to be exact, were not a concern. But then just last year reversed course and said any level could cause harm, and officials said drinking water should contain no more than four parts per trillion. Birnbaum was the director of the National Toxicology Program when the overturned decision was made. So what exactly happened?

Linda Birnbaum: At EPA in 2016 I actually was called by the head of the Office of Water, which was the agency that made those advisory levels of 70 parts per trillion. And he said to me, “Linda, I know you’re not going to be happy about this.” And I said, “Well, Peter, I’m a pragmatist. Do I think 70 parts per trillion is where we should be? No. But 70 parts per trillion is a heck of a lot better than where we were in 2009, where you said the advisory was 400 parts per trillion.”

EPA, actually the head of the Office of Water, in June of ‘22 came out with exceedingly low levels for two of the PFAS, PFOA and PFOS. And last March EPA actually proposed regulatory limits in drinking water of four parts per trillion for PFOA and PFOS. And then they said if something called a hazard index, which relates to the toxicity and the concentration, of four other PFAS exceeds one, then they have to be regulated too. EPA was supposed to promulgate their regulations by the end of September, companies that are making and using PFAS that they have to respond to is huge. So I’m hearing through the grapevine that they’re going to try to finish it by December, but if not, the actual promulgation of values will come early next year.

Now the question is, is will EPA stick with these values? They did declare that PFOA and PFOS are likely human carcinogens, so their goal for limit would be zero. But EPA’s regulations, the law of the Safe Drinking Water Act, actually requires that they do something which is technologically feasible. And essentially all the laboratories that would be monitoring the levels in your drinking water can measure accurately four parts per trillion. There’s a huge new survey going on of municipal drinking water in the entire US from this year through ‘25, the EPA carries out with USGS. Many drinking water systems are going to find themselves out of compliance with the new EPA regulations when they come through. And so many, many water supplies are going to have to put in expensive filtration systems.

Paul Rand: If I understand this correctly, there was a long time where scientists like yourself couldn’t talk about these numbers or the consideration. And I wonder if that’s actually the case, and if so, why was it?

Linda Birnbaum: I think what you’re talking about is for if you’re a federal employee, you often have to get permission to speak to the press. As a long time, I’ve worked for the government for 40 years, and I will say that during the Trump administration, that became extremely difficult for many people dealing with environmental issues.

Paul Rand: They were not allowed to talk?

Linda Birnbaum: Let’s just say it became very difficult for them to talk to the press.

Paul Rand: Okay. And how is it today?

Linda Birnbaum: Well, I’m not a fed anymore. I retired at the end of 2019, so I’m having a good time talking to the press when I think it’s appropriate because I think, as scientists, we hold a responsibility to explain to people what it is that we do and why we do it and what the impact of that work may be. I think for certain topics there are still, let’s just say, some pretty tight controls that are exercised.

Paul Rand: This point where the US started phasing at, as you mentioned, the PFOAs and PFOSs in the 2000s, and some of the PFAS are still around, they’re still being imported, is it that the government and these different bodies know that these are damaging to people and the environment, but until there’s a public outcry, there’s enough pressure to keep them in? Is that kind of what’s going on?

Linda Birnbaum: I think that’s part of it. Yes, I mean, I think there’s a huge amount of lobbying that’s going on, both at the legislatures and at the level of the regulators. I think that is part of it, until the outcry grows. And it’s starting in certain areas, people are concerned and are trying to do something and working with their legislatures. I should say, again, in this country, as California goes, so goes the nation. I mean, California is the fifth or sixth-largest economy in the world. California has banned all PFAS in textiles. They’re looking at banning other kinds. New York State has banned them. We have many states that have regulated PFAS in drinking water or groundwater.

The European Union is considering a ban on all PFAS, and that ban is kind of taking the Montreal Protocol approach, which is what’s called essentiality. If you don’t really need something, then you don’t use it. You don’t have PFAS in it. I don’t really need my clothes stain-proof. If it’s really necessary, but there’s an existing alternative, and it doesn’t have to be a chemical alternative, it could be a different way of achieving a solution, then you move to that alternative. And if you really need something and there is no alternative, you keep using it until you can develop an alternative. And certain, I would say, drugs might fall into that category. Maybe certain uses for chips, computer chips, would fall into that case. Again, and you keep looking for alternatives.

Paul Rand: We’ve come a long way in terms of understanding these chemicals and trying to remediate the damage that’s been done. This year 3M agreed to pay out $10.3 billion to cities and counties across the country to allow them to test and cleanup PFAS in their water systems.

Tape: Minnesota-based 3M will pay more than $10 billion to settle lawsuits surrounding forever chemicals in drinking water. PFAS were manufactured by 3M for decades and legally dumped in different sites in the East Metro. Some got into the drinking water in the area. The company says that this settlement will help detect and remove those chemicals.

Paul Rand: But none of that changes the fact that these substances are everywhere. So is this just a hopeless cause? Well, not quite.

Linda Birnbaum: There’s a lot of money right now appropriately being spent to develop ways to how do we get rid of this stuff. And there are some experimental laboratory-based approaches that have been shown that can break those carbon fluorine bonds. Some of the conditions are not that extreme, some of them are very extreme. Incineration, if you go to about 1,200 degrees, you can break that bond, but much of this stuff has not been tried in a major sense. In other words, how do you clean up a whole river system? How do you break it down when it’s everywhere?

I think the remediation and the destruction technologies, there are some ways that people are trying to develop, but unless we turn off the pump, I guess would be the way, unless we stop making, we’re not going to get rid of it. I’ve been pushing and talking to people, research people, about the need to how can, say, we recover some of these PFAS that have already been made, say from those filters that you get from removing up from water. And if you absolutely need to still have PFAS, use it from the stuff you already made, instead of making more and more and more carbon fluorine bonds.

Paul Rand: I was curious when we were going to have our interview, of were you going to be in a clean room and how are you living your life? And you’re in a very comfortable, well decorated room, with a couch and pillows and carpeting and a rug, and it looks like a blanket on the back of a chair. Knowing what you know and how you’re living with it, am I supposed to be worried about this or not? And what do you tell people as this gets more attention?

Linda Birnbaum: Well, let me say, Paul, I’m a pragmatist. The rug on this floor is about 50-some years old, which was before they were putting PFAS on. This was a Scandinavian rug. But for example, I got rid of my Teflon pans because the Teflon non-stick pans were made with PFAS. There are other kinds of non-stick pans that have no PFAS in them, like some of the ceramic, and those I have. I recently recovered some of my dining room chairs and they asked me did I want them to be treated with the stain repellent, and I said no. Frankly, club soda and salt work very well at getting out your stains.

Again, I do the things that are easy. If I go to the store and I’m looking for, say, a pair of new hiking boots, I choose not to get the ones that are labeled stain or waterproof. But for example, I remember there were studies that came out maybe two years ago that showed a lot of PFAS in, for example, waterproof mascara. And I was shopping with my daughter and she needed new mascara, and the salesperson was encouraging her to buy the waterproof. And basically I said, “Honey, you don’t want to get that because that’s going to be loaded with PFAS.” Why? Because that makes it waterproof. If you cry, your mascara won’t run.

We may need to start thinking about what makes sense. There are two websites I know of. Green Science Policy Institute has a whole section on PFAS and what does and doesn’t have it. And the Environmental Working Group, which has lots of lists for lots of chemicals, is another good source to go. So I do what I can do, and I try not to drive myself too crazy.

Matthew Hodapp: Big Brains is a production of the University of Chicago Podcast Network. We’re sponsored by the Graham School. Are you a lifelong learner with an insatiable curiosity? Access more than 50 open enrollment courses every quarter. Learn more at If you like what you heard on our podcast, please leave us a rating and review. The show is hosted by Paul M. Rand and produced by Lea Ceasrine and me, Matt Hodapp. Thanks for listening.

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