Date Published: April 28, 2021
We’re in the midst of a fertility crisis. Worldwide fertility has dropped more than 50 percent in the past 50 years, and the decline shows no sign of slowing. Shanna H. Swan, PhD, a leading environmental and reproductive epidemiologist, has spent more than two decades studying the impact of environmental chemicals and pharmaceuticals on reproductive tract development and neurodevelopment. In this episode, she explains how endocrine-disrupting chemicals (EDCs), such as phthalates and BPA, are harming fertility and endangering the future of the human race. It’s scary stuff, but it’s too important to ignore. And, as Dr. Swan explains, there are steps we can take to protect ourselves and our children.
From the Mount Sinai Health System in New York City. This is Road to Resilience, a podcast about facing adversity. I'm Jon Earle. My guest today is Dr. Shanna Swan. She's a Professor of Environmental Medicine and Public Health at the Icahn School of Medicine at Mount Sinai. For over 20 years, Dr. Swan has been studying the impact of environmental chemicals on neuro- and sexual development. She's gathered her findings in a new book called "Count Down: How Our Modern World Is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperiling the Future of the Human Race." As the title suggests, this is scary stuff. But it's too important to ignore, and there's no wishing it away. Plus, as Dr. Swan explains, there are steps we can take to protect ourselves and our children from harmful endocrine-disrupting chemicals like BPA and phthalates. The future may literally depend on it. Dr. Swan, welcome to Road to Resilience.
Dr. Shanna Swan: 00:58
Thank you so much, Jonathan, for having me, and please do call me Shanna.
Will do. We are in a global fertility crisis, which is something that I didn't realize before I read your book. Worldwide fertility, the ability to conceive children, has dropped more than 50 percent over the past 50 years, at a rate of about 1 percent per year. And this affects both men and women. On the male side, men today have only half the number of sperm that their grandfathers had. And on the female side, in some parts of the world, a woman in her 20s is less fertile than her grandmother was at 35. You write in the book, "The current state of reproductive affairs can't continue much longer without threatening human survival." Without getting into the causes just yet, paint a picture of the fertility crisis as you see it.
Dr. Shanna Swan: 01:46
Well, overall, what we're seeing is that by any measure, male, female, we see a decline at about the same rate. So sperm counts have been declining at about 1 percent per year or even faster. Miscarriage rates have gone up at 1 percent per year. We have increases in women of diminished ovarian reserve. We have increases in men of problems with testosterone leading to the need for testosterone replacement, erectile dysfunction. All of these problems have been getting worse. And, by the way, also testicular cancer going up at about 1 percent per year in Western countries. Genital birth defects in males, also. So it's really an alarming picture when you put it all together and it's not slowing down.
I can't believe I'm saying this, but in its totality, this body of evidence that you and colleagues around the world have accumulated, this means, and this is no exaggeration, that the future of our species to reproduce, period, is actually at risk.
Dr. Shanna Swan: 02:55
That's correct. And the U.S. Fish and Wildlife Service, I forget what their technical name is, but they have criteria for an endangered species, and we go through that in countdown, and we meet the criteria for an endangered species.
It's one of the many, many places in this book where you have to put it down for a second and shake your head before picking it back up. It's really startling.
Dr. Shanna Swan: 03:20
So Jonathan, this is Western countries. Okay. And I have to stress that because while we try to look over the whole world and search the databases for every English-language publication, there was very little data from non-Western countries. So we really can't draw a conclusion about those. Although we hope to in future studies, for example, an update we're doing right now. But if you look at fertility, which is the number of children that a woman or a couple has, it's called birth rate or fertility rate, and you look at that over the whole world, and that's not my study that's World Bank data, you see that that has declined from 1960 from five children per woman, or couple to 2.4. So the same kind of 50 percent decrease in about 50 years, about 1 percent per year, which is the rate that sperm count has been declining.
2.1 being replacement. That's sort of the threshold.
Dr. Shanna Swan: 04:29
That's correct. At 2.1, a couple replaces themselves. Two people, a little bit extra. So worldwide we may still be, we don't have the latest data, we may be just at, or slightly above replacement, but most Western countries are below replacement. And in some countries, like Singapore and Korea, it's down to 1.0. And what's really scary is those countries are very concerned. And so they're trying to increase this rate and they're actually giving monetary incentives. For example, paid housing for couples that have a child in Singapore. It doesn't work. They can't get this up again. And this is what demographers predict, that when it goes down below two, it will not go back up. Who knows? That's the prediction. We'll see, but for now it looks very scary.
You argue in the book that a group of man-made chemicals called endocrine-disrupting chemicals, or EDCs, are largely to blame. What are EDCs and how are they used in commercial products?
Dr. Shanna Swan: 05:41
So endocrine-disrupting chemicals, or hormone disruptors, are chemicals that have the ability to interfere in some way with our body's endogenous hormones. And the ones that I'm particularly concerned about are those that can affect estrogen and testosterone, because those are so critical for reproduction. And that's what I study.
How did these chemicals get into our environment in the first place? What are they doing in our products?
Dr. Shanna Swan: 06:10
A lot of these chemicals are extremely valuable for us, enabling us to live the kinds of modern lives that we expect and want. And one key function is that they change the nature of plastic. Phthalates, in particular, make plastic soft and flexible, squishy. Think rubber duckies or shower curtains. And then on the other side are the bisphenols, which have the property to make plastic hard. So they're kind of twins, if you will.
The bisphenols are your BPA's. That's maybe a term people are familiar with, they've heard BPA-free this, BPA-free that.
Dr. Shanna Swan: 06:50
Or BPF more recently, or BPS. You can add various letters of the alphabet to that after the "B," and they are different kinds of bisphenols, and they have the property to make plastic hard. And they also are in linings of tin cans. They're also, surprisingly, in cash register receipts and pizza boxes, so paper products. And, yeah, so phthalates, they do make plastic soft and flexible, but they do a lot of other things. For example, they increase absorption of a product, like a personal care product, or a pesticide. They increase absorption. So for a pesticide, it helps the pesticide go up into the plant, for a personal care product or a cosmetic, it helps it go into the skin, which we want for the use of our cosmetics and our hand cream, but we don't want so much for our health.
What's the connection between the phthalates or the bisphenols and sex hormones. Do they mimic the hormones? How do they interfere with these systems?
Dr. Shanna Swan: 08:00
Yeah, so phthalates, certainly three of them that have been well-studied and in particular ones we found to be problematic, lower testosterone. The bisphenols are proestrogenic. So they increase estrogen. But what they do when they lower testosterone depends upon the age at which exposure occurs. So what I'd like to do is talk specifically about prenatal exposure.
That's something you focus on in the book a lot.
Dr. Shanna Swan: 08:32
Right. What I study is pregnant women and what they're exposed to and how it affects the development of their offspring. So of course I'm focused on fetal life. Early in fetal life, the genital tract is the same in males and females. And you can't tell by looking at it whether the child is a genetic male or a genetic female. And then early in pregnancy, and we're not sure exactly when but we know it's early in the first trimester, testosterone starts to be produced, and the presence of testosterone produced by the fetal testes starts the differentiation of the genital tract. So at that point, it starts to differ between what will become a boy and what will become a girl depending on the genetic makeup of the organism. So if testosterone is present, then this fetus will develop testicles. If not, it will develop ovaries and so on for the other organs.
Let me pause you for a second to make sure I understand before we get into this bit. So what you're saying so far is that there's a window when a fetus is developing in which sex differentiation takes place. And it's at that window in particular that the presence or lack of testosterone can make a huge difference into how the fetus develops sexually.
Dr. Shanna Swan: 10:00
Correct. So one of the most critical things that happens is the development of something which most people don't know about at all, but which I know about a lot, because I use it for the study of phthalates, and I was the first person to use it for human toxicity. The distance from the anus to the genitals is called the anogenital distance. And, by the way, there are street terms for this that people might know such as "taint" or "grundle." And what's really interesting about AGD is that it is 50-100 longer in genetic males than genetic females. And it increases under the influence of testosterone. And so it turns out that under the influence of phthalates, this distance in a genetic male is not as long as it would be if the mother had been exposed to less phthalates. That sort of the bottom line. But let me go back to when this was first asked. It was first asked around the late 1990s, and in 2000, toxicologists in the National Toxicology Program published a paper saying we have seen and replicated the phthalate syndrome. They named it the "phthalate syndrome." And a major part of it was that in phthalate-exposed rodents this distance was short, shorter than expected for their size. And they also showed that the penis was smaller, that the scrotum was smaller, that the testicles were less likely to be descended. And they also showed some internal problems that actually we couldn't follow up on because they're internal. But I asked, does this exist in humans? And we developed an exam to measure this in human infants. And then we did the study.
And what did you find?
Dr. Shanna Swan: 12:12
We found the phthalate syndrome in humans. And then we did another study. And that was a study in which I enrolled college students. And they volunteered for 75 dollars to let us measure their AGD. And they gave us a semen sample. And what we found was, as you might think, or as we hypothesized, that the shorter AGD was significantly associated with lower sperm count. It was linear. The bigger the AGD, the higher the sperm count.
So what you're saying is that exposure to phthalates in the womb has lifelong implications for fertility.
Dr. Shanna Swan: 13:02
That's pretty scary.
Dr. Shanna Swan: 13:06
And it probably has, and this we have less evidence of, but we know, for example, that worldwide testosterone has been decreasing at the same rate as sperm count and fertility have been decreasing, 1 percent per year, although it's not as well studied, of course, as sperm count. And since testosterone is lowered by phthalates, it's likely that that lowering in the womb has lifelong consequences for the men's testosterone.
I have a whole section in my interview notes called "WTF." But before we launch into WTF, because there's a lot of WTF, I want to ask one question that I know is very sensitive. Could EDC exposure influence gender identity and sexual preference? And how do we explore or even talk about this without further stigmatizing LGBTQ folks?
Dr. Shanna Swan: 14:07
Yeah, Jon, that's a hard one and a difficult one and a sensitive one, as you said. So what I like to do is break it into three parts. So we have disorders of sexual development. That is just physiological, for example, frogs with ovaries and testes in the same animal. That can be caused by EDCs and it's been caused in the laboratory. No question about that. So children with disorders of sexual development are possibly experiencing this because of exposures to their parents at the time of conception or during pregnancy. That's a relatively easy one. The next sort of complicated level is the question of homosexuality and partner preference. And this can be altered also in the laboratory and in the wild in other species by endocrine-disrupting chemicals. The pesticide atrazine, for example, changing the preference of frogs, and other chemicals, estrogens, changing the preference of fish and so on. Those are, arguably, in some people at least, maybe related to partner preference, although undoubtedly there's a genetic component as well, but there may be gene-environment interaction. Now the hardest question is gender choice, preference. First of all, I want to say, because people ask me this all the time, they say, well, this big increase in kids who want to transition, is that due to environmental chemicals? And I just say, I don't know that there has been a big increase. Because, of course, 40 years ago nobody would have talked about this. It wasn't recognized, it wasn't something you could report on our count. So if you're going to look at an increase, you have to be able to count, and we don't have those numbers. So certainly there's more awareness of it now. It's easier to talk about, there appears to be an increase, but whether there has been an increase, I don't think we know. And we may not know because those numbers haven't been recorded. Maybe we have to go from 2000 on and look at any trends that accrue. But as far as causes, I'm up against a wall here as well. Because you know from my talking to you that I rely very heavily on animal studies. I rely on animal studies to suggest a hypothesis, to suggest a mechanism, and I use those models to build human studies. If you look at animals, you cannot ask them what is their preference, their gender preference. Because we can't obviously communicate, and they don't have that concept of "self." At least we don't think they do, but that's another question for neuroscience. But honestly I would have to say, we don't know.
Do you rank this up with thalidomide, asbestos, cigarette smoking? Is it on that level of urgency?
Dr. Shanna Swan: 17:19
I think it's higher than that. I think it's at a higher level because it's much broader. Those were specific exposures, very bad for a certain class of workers, also bad for people who have these things in their home, but that wasn't everywhere. But this is everywhere. This is global. This is not just humans, it's other species, which we see all the time are endangered or going extinct. And I think this is a much larger problem than any one of those chemicals.
Well, I think it's time for WTF. How is this even possible? Doesn't the government protect us against EDCs?
Dr. Shanna Swan: 18:03
It doesn't protect us and it could. It could do better. And I just want to point to what happened in the EU—
Well, say what happens here so that we can compare the two.
Dr. Shanna Swan: 18:17
Yeah. Okay. So what happens in the U.S. is that there is no requirement that a chemical be proven safe before it's put into commerce. It's put out there, it goes into products, and the way it's tested is on us. We are guinea pigs, and it takes somebody like me and my fellow scientists to recognize there might be a problem, to do a study that takes 5-10 years and costs 5-10 million dollars to identify the risk associated with a single, or maybe multiple chemicals in a class, and a single outcome or system outcome. So very long, very hard, very difficult. And, by the way, once we do that, they often remove the chemical that we've identified as harmful and replace it with another one with a slightly different name, which causes the same harm. We call that "regrettable substitution." It's been done with BPA being replaced with BPS and BPF. It's been done with phthalates. So it's a terrible rollercoaster ride that we're on—.
It's Whac-A-Mole. You're playing Whac-A-Mole with these chemicals.
Dr. Shanna Swan: 19:27
It's Whac-A-Mole. And they can do that because a chemical is not required to be tested before it's put into the market. But under REACH, which is in Europe, they actually are required to, the manufacturers are required to test before it's put into market. So the consequence is pretty big. If you look at the number of chemicals that are not allowed in cosmetics in our country, there's 11. And in the EU, there's 1,100. So it's quite a different scene. That's not to say that the EU is home free, or that everything has been removed or anything like that. There's a lot, lot more work to be done, but at least that's on the right track.
Clearly this is something that needs to be handled on a government or inter-governmental level. For the listener, who is by now freaked out beyond freaked out, what are some things that they can do to reduce their exposure?
Dr. Shanna Swan: 20:27
There are many things we can do to reduce our exposure. If we're pregnant, if we're planning a pregnancy, it's the most important time to do that. I would suggest, of course, that people read "Count Down," my book, because we go in for several chapters in detail, lots of detail, about things people can do. But here are some things I can say quickly. I would say start with your kitchen. And to the extent possible try to replace plastics with glass and ceramic. And I guess the number one thing I would say is do not microwave in plastic. Because what happens is that the phthalates and the phenols are not chemically bound to the plastic. That means they leave easily, and they leave most quickly in the presence of heat. So when the plastic is warmed, they come out of the plastic, they go into the material, whether it's food, whether it's milk, whether it's any thing in a plastic container. And then we absorb them very easily and we absorb them through ingestion, through dermal absorption, through inhalation. We get them through the air, we get them through the dust, and this is true not just about phthalates, it's also the phenols, it's also the flame retardants, it's also the perfluorinated compounds that are in our frying pans and so on and so forth. So there's so many, we can't do this all in this interview, but there's obviously a huge problem that we have to address. And I think the first step is to say, let me think about what I'm bringing into my house. Let me think about what's in the food I'm feeding my baby or my family. Let me be aware of what I'm putting on my body. And that awareness is the first step. Just say, "Ah, this could be a problem. Let's not use this product." Or you can go online. There are many websites, and we go through resources in Count Down, but a simple one is the Environmental Working Group. You can put in the name of a product, and it can tell you it's safety rating, if you will. So I think just stop closing our eyes to the problem, recognizing the problem, and we can do a lot.
You can definitely go crazy with this stuff. You can become extremely obsessive about banishing every plastic, every—because there's so much we still don't know. So how can somebody take this on without losing themselves to the panic?
Dr. Shanna Swan: 22:58
Right. Panic doesn't help. Actually panic is bad for your reproductive health. We don't want to panic. But I think just like we've learned to shop better. We've learned to, just kind of add it to the list of things you want to do besides comparing how well something works, how expensive it is, what kind of reviews it gets. Look at what's in it if you can. If you don't know you can look that up online. And as I say, you can look in our book, but I would just make this one of the things that people consider when they bring things into their lives.
I know that there are certain EDCs that are persistent. They're going to stay in the environment for a long, long time. But phthalates and other EDCs, if I'm not mistaken, there are some that are water-soluble, which means that if you've reduced your exposure, you can make a difference in your body and your health. It's not like you're a lost cause. I think that's good for people to know, that they think, "Oh, well, shoot, I'm not ruined because I didn't know about this earlier." No. It's not too late to make a difference for yourself, for your health and the health of your family.
Dr. Shanna Swan: 24:14
Yeah, so unlike the persistent chemicals, the legacy chemicals, which stuck around forever in fat, in our bodies, and in the environment, the good thing is the phthalates and the bisphenols and other modern chemicals are going in and out very quickly. So they're non-persistent, they're water-soluble. We take them in and we excrete them with a half-life of 4-6 hours, many of them, and then they're gone. The bad news is that they keep coming back. So they're forever chemicals, but if we change our habits, then they're gone.
And do you have any thoughts on how to become active in truly creating meaningful legislation or regulations or anything? Because again, this needs to be on a larger level. The personal level is not effective enough.
Dr. Shanna Swan: 25:03
I honestly can't pick out my favorite environmental group for people to join. If you're interested in doing this, you could maybe talk to some people at Mount Sinai in the community engagement group in our department, Environmental Medicine and Public Health. There are wonderful people there that can lead you to specific resources in the community that could help. I think the more communities get involved, the better. And we would love to bring in a diverse set of voices to address this problem. Because we haven't talked about environmental equity here, but these are problems that actually impact underserved communities more than wealthier communities. The exposures are higher, and we're showing in one of our studies just being published, that the impact of these chemicals are greater on underserved communities. So it's a double whammy.
And there's a huge privilege associated with buying organic, taking these other steps to reduce your exposure. These are not accessible to everybody.
Dr. Shanna Swan: 26:11
A question I like to ask my guests, and I think we're going to close on this one, is what's the biggest unanswered question that you are looking at, thinking about, hoping to get clarity on in the next few years?
Dr. Shanna Swan: 26:27
I think the biggest question is how to bring about the kind of regulatory change that's necessary to fix this. That has a lot of ramifications, of course. How do you get people engaged so they put pressure on the government to make these changes? And you also have to have alternatives in the manufacturing sphere and in the chemical manufacturing sphere so that they can say, "Well, don't use this, use this. Right now we don't have a lot of good alternatives for plastics. And so I think that we need to lean on the system, if you will, to say, we demand safer products. That means the chemical manufacturers have to make the chemicals. The plastics manufacturers have to use them. And the government has to regulate them.
In other words, we have the science, we know what we need to know to make change. We just need to make change.
Dr. Shanna Swan: 27:31
We know enough to demand change.
Thank you, Dr. Swan.
Dr. Shanna Swan: 27:37
So much. And thanks for doing all this. This is wonderful.
Dr. Shanna Swan is a Professor of Environmental Medicine and Public Health here at the Icahn School of Medicine at Mount Sinai. Her book is called "Count Down." That's all for this episode of Road to Resilience. If you liked it, please head over to Apple Podcasts, leave us a five-star rating and a nice review. We've also got a listener survey going. We'd love to hear from you, as always. And we're always looking for guest suggestions. So follow the link in the show notes for that. Road to Resilience is a production of the Mount Sinai Health System in New York City. It's made by Nicci Cheatham, me, Jon Earle, and our executive producer, Lucia Lee. From all of us here, as always, thanks for listening. And we'll see you next time.