“Forever Chemicals,” Micro-Plastics, and More: How Do We Protect Ourselves from Modern Life? We Spoke to a Life-Course Epidemiologist and Got Answers

This interview will change the way you look at the products around your home. Meet Dr. Linda Kahn,one of the most important researchers on environmental exposures and women’s health working today. As an Assistant Professor in the Division of Environmental Pediatrics at the NYU Grossman School of Medicine, she is breaking ground on “forever chemicals” and their long-term effects on reproductive and overall health. We sat down with the researcher and epidemiologist to discuss the pervasiveness of toxic chemicals, such as PFAS, how it’s costing us (mentally, physically, and financially), and the surprising impacts these exposures have on pregnancy, postpartum maternal health, and long-term health outcomes for both women and children.

Amy Cohen Epstein: I've done a lot of these, and I'm a little star truck. I have a hundred questions. Leading up to this, I told a lot of people that I'm interviewing you. They're extremely jealous and asked me questions to ask you. I don't know if I'll get to them, but I'm just going to jump right in. Doctor Linda Kahn is an Assistant Professor in the Division of Environmental Pediatrics at the NYU Grossman School of Medicine. Your research interests span, really, three interrelated areas: the role of preconception and prenatal environmental exposures in pregnancy and postpartum maternal health, predictors of male and female reproductive development and fertility, and health outcomes of assisted reproduction in both women and children. You received your MPH in population and family health and your PhD in epidemiology from Columbia University's Mailman School of Public Health.

Doctor Lynda Roman at USC and Doctor Julia Smith at NYU, who I know well, have talked about you and mentioned you before. I've read about you. But one of the things that I couldn't put together was the connection between pediatrics and epidemiology until I started to dig into your research. So, the first question I just want to ask before you just dive in is which came first. How did those come together? Is that just because I'm not as smart as you and don't see the natural fit? Or is that just what happens?

Linda Kahn: Actually, my career trajectory is completely unconventional because I had a 20-year career as a book editor before I even went into public health. I was a pre-med in college, and then I got cold feet about going to medical school. Instead, I had double majored in English and biochemistry, so I decided to go the English track and become a book editor. Because I had this scientific literacy, I ended up being assigned a lot of health books. That was fine by me because I could talk to the doctors and understand what they were saying. So, I developed a specialty in women's health, being a good second-wave feminist. I did that for two decades. My kids were growing up, and it was great. It was a very flexible career. Then I decided, when they were in school full time, that I wanted to go back to science.

At that point, medical school wasn't an option, but then I discovered public health. I thought, "This is so cool. I really want to learn more about this." So, I went and got this MPH in population and family health because of my interest in women's health and reproductive health. My focus was on fertility. I wanted to learn more about the health effects of assisted reproduction. Then I just ended up getting apprenticed to a faculty member who had a strong interest in environmental chemicals. I had never focused on them at all, but the more I learned about them, the more I realized that they are hugely important because a lot of them have endocrine-disrupting properties. Obviously, the reproductive system is controlled by hormones, so a lot of the health effects that they can have affect fertility and reproduction.

Then I did my doctorate in epidemiology because I'm a data nerd. Epidemiologists just basically deal with a lot of data and study design. It's funny you ask about me being in the Department of Pediatrics because it has nothing to do with what I do. I don't study children at all. I ended up here because NYU's Division of Environmental Pediatrics is a research division within the Department of Pediatrics that runs a huge cohort study. What we do is enroll women in the first trimester of pregnancy. We get bio-specimens, blood, urine, saliva, hair, nails, and all this stuff. During three trimesters of pregnancy, we have the women do questionnaires. When their babies are born, we take cord blood, we take placenta samples, and then we follow the women and their children longitudinally. The oldest kids in our cohort now are just turning six. We have almost 4,000 participants in our cohort, and we're still enrolling.

“Something that we have learned over the past 40 years is that exposures can have long-term, distal effects. Back in most of the 20th century, people thought, ‘You're exposed to something. We expect to see the outcome in a matter of days, weeks, months, maybe 10 years.’ People didn't think that you could be exposed in utero and have that affect your health decades later.”

The study is funded to look at prenatal chemical exposures. We measure chemicals in these bio-samples that we collected in each trimester, and then the child health outcomes. But just as part of the study, we're also getting all this data on the moms. So, my PI, the guy who runs the study, Doctor Trasande, said, "We have all this data on the moms. You're interested in women's health. Why don't you look at the women's health side of things because it's just sitting here." So, I, as a women's and reproductive health expert, came in to the Department of Pediatrics. That's how I ended up there. Just being an epidemiologist in any department means that you are someone who focuses on designing studies and analyzing data. You could have epidemiologists in any department. Any department in the hospital can have an epidemiologist if they do clinical research.

Amy Cohen Epstein: Even if you don't use it on a day-to-day basis, having access to, or being able to tap into, that data starting when the women are pregnant and in utero and then seeing it all the way through, doesn't that give you the fullest picture that you could ever have?

Linda Kahn: It could be even fuller because what we are learning is that exposures pre-conception are really important. We are just beginning to collect that, to start to enroll people before they conceive. Because what we're learning is that preconception exposure affects the quality of the gametes, the egg and the sperm, which eventually become the embryo that becomes the fetus. It becomes the child, but also can affect the pregnancy itself. That's why I would call what I do life course epidemiology, because it starts at the beginning of the beginning, and goes all the way through your life. Something that we have learned over the past probably 40 years is that exposures can have long-term, distal effects. Back in most of the 20th century, people thought, "You're exposed to something. We expect to see the outcome in a matter of days, weeks, months, maybe 10 years, whatever." People didn't think that you could be exposed in utero and have that affect your health decades later. But there started to be hints. First was with the DES catastrophe. I don't know if you're aware of diethylstilbestrol.

Amy Cohen Epstein: No.

Linda Kahn: It's a chemical. It's a synthetic estrogen that was prescribed to pregnant women during the middle part of the 20th century.

Amy Cohen Epstein: In the '70s, right?

Linda Kahn: Well, '50s, '60s, '70s. Yeah.

Amy Cohen Epstein: The '50s and '60s. Yes. In fact, I am aware of it. My mom was prescribed it.

Linda Kahn: Ah.

Amy Cohen Epstein: My dad to this day believes that's why she died of ovarian cancer.

Linda Kahn: It very well could be, but the red flag about DES was in the children. Particularly, it was in the daughters. These women were prescribed it to prevent nausea and morning sickness and miscarriage. It turns out it didn't necessarily have an effect. But everybody thought it did, so it was being dispensed liberally. The first sign was that a doctor, just a single doctor, noticed a case of a vaginal carcinoma, cancer of the vagina, in a ... I think she was 13 years old. This never happens. This is really unusual. It's a very rare cancer, period. Never in children.

Amy Cohen Epstein: Oh, my God.

Linda Kahn: It raised a red flag. He started to look for other studies. It turns out there was a small number that he could identify of young women, girls, really, who had been diagnosed with this. What did they all have in common? Their moms had been prescribed DES. That was the first sign that prenatal exposure could have an effect on a person years later.

Amy Cohen Epstein: 14 years later.

Linda Kahn: Right. That was the first sign of the fact that exposure-outcome can be separated by a long period of time, and that the prenatal period is critical. Something's going on in utero. These systems are developing. If you mess with them in utero, they can program disease later in life. The other thing that happened was in the early '80s, a doctor named David Barker in England showed a correlation between children who'd been born with low birth weight in the Depression and rates of cardiovascular disease, literally 50 years later. This was very unusual. There was an ecological study. He wasn't following individual people, but he would say, "In parts of England which had a lot of economic hardship and where there was a lot of low birth weight babies being born, 50 years later, we're seeing those regions have really high rates of cardiovascular disease. What's going on here?"

He formulated this hypothesis called the Barker hypothesis or the fetal origins hypothesis, which is saying that, again, this prenatal period is really critical. In his analysis, he was looking particularly at nutrition. He was speculating that low nutrition during pregnancy had programmed these fetuses to be very conservative metabolically. When they were born, they were expecting starvation because they had been deprived of nutrients, in utero. Then, what happens later in their lives, the Depression was over: Plenty of food. People ate normal amounts, but they had this thrifty phenotype. So, their metabolisms essentially predisposed them to cardiovascular disease, diabetes, and all these other metabolic problems. So again, it's this idea that something in utero can affect your adult health. That's life course epidemiology.

That's what we do in environmental health as well. We try to focus on what are these critical periods of exposure and look for outcomes, not just at the time of exposure, like in a chemical plant accident. If that happens, you're going to see immediate outcomes. But oftentimes, there's a low-level exposure, but at critical periods, that can have long-term health consequences. That's why children are so vulnerable, and fetuses even more so, because their systems are all developing. A little bit of exposure in a tiny, tiny, tiny little either fetus or child... Children are a lot of surface area, for example, per volume. If they're exposed to something on their skin, for example, they're going to get a lot more into them than you or I will.

Amy Cohen Epstein: Right. What about what a mom does before she gets pregnant? What about this idea that you can do whatever you want until the day you find out you get pregnant? Then you're “clean,” whatever that means per person. What's that theory about? What can you say to a woman who comes to you and says, "I'm good, now"?

Linda Kahn: Right. I mean, not to make people nuts, but you have all the eggs you're ever going to have by the time you're born. Essentially, anything you've ever done your entire life is going to potentially affect those eggs. Men have a little more leeway. Sperm are constantly being produced, but the cells that produce the sperm have been around since they were born, too. But yeah. The truth of the matter is your whole life is affecting the quality of your eggs. You can't just change on a dime. Certainly, it doesn't hurt to stop smoking or drinking, or doing what we know to be adverse behaviors when you're pregnant, but it’s even better to do it before you become pregnant. A big one is obesity. It's an epidemic in our country, and now, more and more, in our world. We know that's not good. It increases your risk of so many different conditions and increases oxidative stress, which can contribute to a lot of pregnancy complications. So yeah. The healthier you can be, the sooner, the better.

Amy Cohen Epstein: Absolutely. Let's just pivot a teeny bit, which is we know what we can control. I've talked about that a lot. Obviously, this entire conversation is about preventive care in the fullest sense of the topic. But what about those things that we can't control? What's out there? Some of the work that you've done is what's in our water, and what's in the environment. What’s seeping into our bodies that has potentially a lifelong effect? What is that? What do we do? How do we help? How do we fix it? How do we live our life knowing that we've ingested things that are going to stick with us forever? I just cooked eggs and my pan is giving off disgusting toxins that I've given to my children.

Linda Kahn: I know. The guilt. The guilt. The guilt.

Amy Cohen Epstein: The guilt. I'm from Santa Monica. I think I'm buying the best BPA-free everything, but I'm sure there's something in there. What do we do? How do we, as I say, take control of our health and wellness and be proactive and knowledgeable?

“The first thing is not to beat yourself up because I think the stress of doing that is probably worse than a lot of these chemicals. There's got to be a reasonable balance.”

Linda Kahn: Yeah. Well, the first thing is not to beat yourself up because I think the stress of doing that is probably worse than a lot of these chemicals. There's got to be a reasonable balance. We don't live in a cave in the middle of nowhere. We all live in society. There are unavoidable things that we're going to be exposed to. It's a fact of life. I would say do what you can. Do what you can afford. But there are certain things where it is probably best practices to try to avoid. For example, we know there's a lot of evidence that phthalates, which is a class of chemicals that are used in fragranced products, are highly endocrine disrupting. If you have a choice between, say, a fragranced laundry detergent or an un-fragranced laundry detergent, pick the un-fragranced. Simple things like that. Don't use those plugin air fresheners that spew all kinds of fragrance into your home. Just look on the packaging of your personal care products, and try to choose things that don't have added fragrances. That's a very simple thing that you can do.

In terms of organic food, I think the Environmental Working... I mean, that's just a phenomenal resource in general, but they have a list of the dirty dozen. So, if you can't afford to buy 100% of your produce organic, because it is expensive, focus on these ones because they're the most highly contaminated, things like strawberries. In terms of plastics, obviously, you look for your BPA-free plastics. Sadly, the manufacturers have mostly just replaced BPA with BPS, which they can still say, "It's BPA-free," but BPS, we are discovering, is just as bad. Ideally, just use metal water containers, if you can, or metal food containers, or glass food containers. Even better. If you do use a plastic container, don't microwave it. A lot of common sense stuff can go a long, long way. Just minimize the number of personal care products that you use, if possible.

Amy Cohen Epstein: What about things like what's in our water that you've recently read about?

Linda Kahn: Compared to what's in your water, some regions do have contaminated water. Obviously, we've heard a lot in the news about lead. Certainly, you must be very careful if you live in one of those areas to try to avoid consuming the water. A lot of this country has water contaminated by PFAS. These are the forever chemicals that are also in Teflon and all kinds of non-stick, non-stain products. Places with contaminated water supplies tend to be nearby places where those chemicals were or are produced. A lot of Teflon plants, the DuPont plants down in the Carolinas that produced all that stuff that goes into non-stain carpets. I think 3M plants do contaminate a lot of water in the upper Midwest.

In those regions, people are aware of it. Really, the only way to take it out of your water is a system that they install into your basement to filter the water. A Brita won't do it. For the rest of us who don't have contaminated water, again, it's about trying to just avoid exposure. Better not to use non-stick coated surfaces on your pans. Or if you use them, just don't use them if they get scratched. Try to use waxed dental floss instead of the other kind because that's coded in PFAS. Unfortunately, it's not labeled. PFAS is in a lot of our personal care products that we're not aware of, pretty much slippery stuff and non-stick stuff.

Amy Cohen Epstein: Wow. Are your children experts on this?

Linda Kahn: No, no, no, no. They're not. They're experts on reproductive health. We talk a lot about sperm at the dinner table.

Amy Cohen Epstein: I'm interested in that because I think it's a hard conversation in general. I think there are so many barriers that have been broken down amongst women and about talking about reproductive health and about talking about how to healthfully have those conversations. Talking about miscarriage now, which was something women didn't talk about before. It was very shameful. I think reproductive health is incredibly important. I think talking about our ovaries is important. I think talking about our fallopian tubes, all these things are what I talk about. It's in my everyday conversations. But what do you talk about, and what do they talk about? I think it's fascinating. I mean, you have college-aged children.

Linda Kahn: Oh, I started talking about it long before they were college-age. I used to embarrass them in front of all their friends. I mean, I just have always been very, very open about it. It's super important. I think it has to be normalized. It's part of their everyday health. They have to be thinking about it. Certainly, denying that your kids have sexual impulses or that they're going to have sexual experiences is putting your head in the sand. Better to be open about it and talk to them about it so that they're prepared. They did an ad campaign in New York where they had ads on the bus shelters for dual protection, meaning two kinds of birth controls. You use the oral contraceptives plus a condom. You have both because the oral contraceptives are not going to prevent sexually transmitted infections.

Amy Cohen Epstein: Right.

Linda Kahn: You want to prevent the pregnancy and the infection. They're two separate things. I think my son was 10 or 11 when this campaign was running. I'm walking down the streets, and I point it out. I said, "Do you know what that means, Elliot?" He's like ... When you start having sex, you should always use full protection. I mean, my kids know me. They weren't bad. But, I mean, everybody around me thought it was weird that I was talking to him about this stuff. But I just have always been very open about it, and it has served me well, I think. They talk to me about things.

They talk to me about close calls. My girls, certainly, any kind of menstrual irregularities, we talk about it because it's important. Our middle child, she was a ballet dancer.

Amy Cohen Epstein: It messes with your menstrual cycle.

Linda Kahn: Totally, totally, totally. It's secondary amenorrhea. Basically, she got her period and then stopped for a long, long, long time. I mean, that's something you have to pay attention to. You can't say, "Oh, yeah. Whatever. She's a dancer. They don't get their periods." I need to share this. I'm on balance. These are things that I think it's health. Reproductive health is health. It just drives me nuts that women have to go to two separate doctors. Why is this, that our GPs, our regular primary care physicians, won't touch our reproductive organs? They've been so silo-ed and so segregated and so like, "Ooh, that's not my realm. I don't know anything about that." Well, you should know something about it because it's not like it exists in some separate compartment of our body. It's all connected.

Amy Cohen Epstein: Well, also, why doesn't your gynecologist just give you a full exam?

Linda Kahn: Vice versa. Exactly the same thing. What drives me really crazy — because my current research is on pregnancy complications, particularly hypertensive disorders of pregnancy, like preeclampsia and their connection with cardiovascular disease — is that it turns out that women who have preeclampsia are two to five times more likely to die of cardiovascular disease compared to women who don't. Yet does your primary care physician ... I've been to many because of insurance changes over the years. I've been to so many doctors. Not even one of my internists has ever asked me about my reproductive history.

Amy Cohen Epstein: Oh, no.

Linda Kahn: They're taking my blood pressure. They're measuring my cholesterol. They think that they're screening me for cardiovascular disease. They're not asking me about something that is so highly predictive of cardiovascular disease.

Amy Cohen Epstein: Well, I can tell you the number of women that have told me that their doctors ... And I've talked to many women who don't live in New York and Los Angeles, so let's put that out there, whose doctors really didn't either know or tell them that their annual pap smear doesn't screen them for ovarian cancer, that it has nothing to do with ovarian cancer. They thought that it was a screening for ovarian cancer. No idea whatsoever.

Linda Kahn: The other thing that people don't understand is a lot of people think that mammograms somehow prevent breast cancer.

Amy Cohen Epstein: Oh, many do.

Linda Kahn: Yeah. If they get a regular mammograms, they're preventing breast cancer. Mammograms are not a preventive tool. They're a screening tool.

Amy Cohen Epstein: It's completely different.

Linda Kahn: Right. There's a lot of shock, like, "How could I have breast cancer? I've been having regular mammograms."

Amy Cohen Epstein: By the way, you might have dense breasts, and a mammogram is basically doing not much of anything.

Linda Kahn: You have to have a sonogram at the same time.

Amy Cohen Epstein: You might have to have a sonogram, and you might have to have an MRI, which your doctor might never have told you. I mean, the list is long. I am in awe of your work. I am a complete layperson, but I do know more than most, just because, for the last 25 years, I've done so much in the world of breast and gynecological oncology, and know so many of the most incredible people in that field. So smart. Amazing gynecologists and oncologists and genetic counselors and all these incredible people, many of whom are at NYU and SC in LA and all over.

But I have to say, the most fascinating are the epidemiologists… It's fascinating… The only other thing I wanted to ask was where do you see this moving forward in the future? In the terms of your research, what would you like to do and keep doing that you think you can make the greatest impact?

“Well, I'm very, very interested in putting my research into action. I feel, as an epidemiologist, that I have access to all this data, but if the results of the studies stay within the academic community, it's not doing anybody any good”

Linda Kahn: That's hard to say. Well, I'm very, very interested in putting my research into action. I feel, as an epidemiologist, that I have access to all this data, but if the results of the studies stay within the academic community, it's not doing anybody any good. That's one of the reasons why the paper that I think originally you responded to, the one that was published on these forever chemicals, PFAS, and the economic cost, exposure to PFAS.

Basically, we did this analysis where we looked at what we know PFAS to be associated with, which health conditions we know there's a lot of certainty that they're associated with. Some of the other ones, we don't have enough data yet, but it's looking likely. The list includes adult obesity, child obesity, several different kinds of cancer, low birth weight, endometriosis, polycystic ovarian syndrome, a whole bunch of different endocrinological diseases because they're endocrine disruptors. So what's the price tag? Infertility is on there, too. What's the price tag? How much is this costing society? A lot of times policymakers are like, "Oh, yeah. Well, we know PFAS are all over, and they're contaminating people's water systems, but it's so expensive to go and clean all these water systems and remediate."

Amy Cohen Epstein: Not compared to the alternative,

Linda Kahn: That's the thing. I don't think they know the alternative. I don't think they know what it's costing on the other side. They're only thinking about the cost of remediation. It's like, "Well, if you don't remediate, let's tell you how much this is costing." How much is this costing in terms of healthcare costs? How much is it costing in terms of lost productivity? How much is it costing for those kids that are born low birth weight in terms of IQ points, which is long-term earning potential, which has a dollar amount associated with it? I think trying to translate the research that I do, whether it's in terms of the environmental chemical exposure, whether it's in terms of women's cardiovascular disease risk, whatever it is, trying to translate it into language and outcomes that matter to people.

“Sadly, we don't live in a society with universal healthcare, so this is all coming out of everybody's pockets. It's a huge source of strain for Americans and for women in particular.”

Amy Cohen Epstein: I think you should work with an economist. I think teaming up with an economist would be really, really fascinating.

Linda Kahn: Yeah, I think that would be fascinating, absolutely fascinating. And making it practical for people because-

Amy Cohen Epstein: The long-term disease, I mean, the long-term probability of disease and then what that costs in the hospital system and medication… It's like when your insurance company won't pay for physical therapy, yet if you don't do physical therapy, your chances of ending up in surgery are up by 90%. It doesn't make any sense. It just literally doesn't make any sense to a rational person.

Linda Kahn: Right. None of this is counting the costs which you can't put a price tag on: the stress, sacrifices that you have to make if you have health conditions.

Amy Cohen Epstein: Of course.

Linda Kahn: Sadly, we don't live in a society with universal healthcare, so this is all coming out of everybody's pockets. It's a huge source of strain for Americans and for women in particular. I mean, a lot of this is burdening women in terms of these health outcomes. It's just a lot. My focus has been on women's reproductive health, but we just happen to be seeing a lot of associations with conditions that we know are really debilitating, both physically, things like endometriosis, and psychologically, like infertility. I think that we can't always put a price tag on that. People suffer in silence. We don't hear about it a lot of the time. As you say with miscarriage, we need to destigmatize a lot of these conditions and talk about them because we're half the population.

Linda G. Kahn, MPH, PhD. Assistant Professor, Department of Pediatrics. Assistant Professor, Department of Population Health.