Dr. Shanna Swan reveals endocrine-disrupting chemicals—like phthalates in plastics (e.g., milking machines, wrappers)—reduce sperm counts by 1% annually, halving levels since 1973, with prenatal exposure linked to smaller male genitalia and 7x higher subfertility risk. Testosterone drops globally, while miscarriage rates rise, tied to factors like chlorinated tap water and pesticides (e.g., Missouri men had half the motile sperm of Minneapolis counterparts). Male infertility now accounts for 25–33% of cases, with combined poor sperm metrics making men 16x more likely infertile. U.S. lags Europe in chemical regulation, and untested replacements (e.g., BPF) may worsen harm, raising concerns about humanity’s reproductive future amid corporate resistance and societal inertia. [Automatically generated summary]
Your book, Countdown, says that the modern world is threatening sperm counts, altering male and female reproductive development, and imperiling the future of the human race.
But what I write about in this book is the problem with the decline of our reproductive health and the chemicals in the environment that we're surrounded with every day, all the time, that are playing a big part in it.
They interfere with our hormonal systems in various ways.
So they could increase production of a hormone, like a pro-estrogen.
They could decrease, say, an antiandrogen, decrease testosterone.
They could mess with our thyroid hormone, and so on and so forth.
So, they change levels, but they also change how they're transported and they interfere with making them available to other parts of the body, basically.
And you got it right.
I mean, that doesn't sound so scary to people, but the consequences sound really scary, which is that we're, you know, by every measure, our sperm count, Our miscarriage rates, our fertility rates, our testosterone levels, they're all going south, if you will, at the rate of about 1% per year.
And they sound weird, but they're very, very common.
And if you gave a urine sample today, And send it off to the Centers for Disease Control, you would see that you have, you know, not only phthalates, but other chemicals and plastics and other chemicals in your body right now.
So go into a hospital, into the neonatal intensive care nursery.
I'll come back to the food.
And there's a baby lying there, and that baby has a lot of lines coming into her body.
Okay?
And that's delivering food, nutrients, oxygen, whatever the baby needs.
Okay?
And the tubes are soft, squishy plastic.
Okay, so as the food nutrients comes through the tubes, goes into the baby, the baby metabolizes them, goes into the urine because they're water-soluble, and then we get the urine, we measure, and we can see what's in it.
And the amount of phthalate that's in that urine is exactly proportional to the number of lines coming into the baby.
So if you understand that, you understand how food could be contaminated with phthalates, because milking machines have this, and all kinds of processing machines have this soft plastic.
So this stuff is coming into the food somewhere between the time it's picked.
And by the way, phthalates could be in pesticides as well.
I'll tell you why in a minute.
And then they're introduced not only through those tubes, but also through the packaging.
They're wrapped in soft plastic sometimes.
And then in our homes, we might cook in microwave in plastic, for example.
All of that doesn't stick to the plastic.
It's not chemically bound.
Hops into the food, gets into us, gets into a pregnant woman's womb, affects the offspring.
And I hope to be able to tell you how it does that.
But that's what I've been studying for about 20 years.
So these plastic covers, like if you buy food and it's wrapped, like if you buy peppers or something like that, and they're wrapped in plastic, that plastic is leaching onto your food, a certain amount of these phthalates, no matter what.
Yeah, so it's a changing landscape as new things are introduced, but there's an old saying, which I think is pretty much still true, which is four, five, one, and two, all the rest are bad for you.
What does that mean?
It means that if you had a...
Plastic cup here, we could look at the bottom of it and you'd see a recycling code.
Before the phthalates, you know, early in pregnancy, the genitals are just a single ridge.
Same in males and females.
Undifferentiated.
Okay?
And then at a certain time, and in mice and rats it's 15 to 18 days of gestation, the testicles start making testosterone.
And then that gives the signal to produce the male typical genitals.
So If they don't have the testosterone, there will be ovaries and if there is testosterone, there'll be testicles and so on and so forth, right?
And that migration requires testosterone at exactly the right time and the right amount.
It's very delicately programmed, okay?
If that happens, if everything goes well, then the penis will develop, it'll have a certain size, and then there's something which is very key to my research, which is something you might know by the name of the taint.
So, you know, the females are masculinized, so they have a longer AGD, right?
But for most mammals, it's this way, okay, including humans.
So here's this Little pup that's born and if he's unexposed, he'll have a good, you know, standard penal size and AGD and he won't have any malformations of his penis and so on.
You know, he'll be normal.
But if his mother was exposed to phthalates, everything can go south.
And what happens is the penis is smaller.
And the AGD is smaller.
And the scrotum is smaller.
And the testes are maybe not descended.
In other words, it didn't finish the process.
It was arrested, if you will.
So we say that that pup is incompletely masculinized.
Well, you would hope that you're not running experiments like you're running them on animals.
Right.
Are you measuring the blood of the people that are having children that have issues with development issues in the way the children look when they're born?
Phthalates have the property that they dissolve in water, water soluble.
And so they go into the urine.
So for this class of chemicals, if you want to know how much is in your body and my body, we've got to measure the urine.
Other chemicals, like flame returns, we would look in the blood.
So it depends what the chemical is.
But the right idea, look inside the body.
Okay.
Then, rather than looking at kids with problems, what I did was I just took a whole population of pregnant women and I got their urine, measured their phthalates, got their kids, measured their kids.
So then I had the problem of what to measure in the kids because nobody had made this translation from an animal genital developmental system to a human.
And so that was kind of a challenge, you know, figuring out how to do that.
But we did that.
And we developed this system for this exam for measuring all these things that you measure in a rat.
We measured it in our children.
And then we showed, and this was big news when it came out, that the mother's phthalates did alter the genitals of the boys.
So that was the first evidence.
That was 2005. And then we published some more in 2008. Fortunately, I got money to do it all again.
So the second time, I did it better because I really knew what I was looking for.
And I got urine actually in three points in pregnancy.
And I measured the kids exactly when they're born.
So everything was much more precise.
And I found it again.
So now there's no question, I don't think anyone questions, that at least this class of chemicals, which we know lower testosterone, alter the development of these boys.
And then I asked, well, what does that have to do with sperm count?
Because actually for a long time, we haven't talked yet about sperm count, but I've been studying, tracing, you know, what's happening with sperm count I'll tell you the history of that in a minute.
So then I thought, well, is this related to sperm count?
Well, these are babies.
They don't have a sperm count.
But in rats, it looked like the AGD was permanent.
So if you had a short, just like if you have a small hand, you know, your stature is set at birth, right?
So the AGD, if you're born small, and my friend Earl Gray, who was a toxicologist, said AGD is forever.
We don't know that for sure about humans, by the way, because we haven't had the 20 years yet.
But if you believe that, then a sensible thing to do was to take a group of adult men who could give you a sperm count and measure their AGD, right?
And then you could see whether those with a shorter AGD Had a lower sperm count.
And then you would have one pretty solid piece of evidence that chemicals in the environment lower sperm count.
If it was less than two, men who had less than two inches were seven times more likely to have a sperm count in the subfertile range, I can tell you what that is, as men who had an AGD longer than two inches.
So the growth of these chemicals tracks with the growth of the petrochemical industry because they're made from petrochemical byproducts.
So if you look at a curve, it starts around 1950. So back in 1950 you have people loving science, jumping on the science bandwagon, There's this better living through chemistry that everyone's talking about.
And everybody is just wanting everything made of plastic.
It's the new craze.
And it just took off.
It went faster than a straight line, exponentially up.
And so somewhere in there, it started having an effect.
But where...
We're not sure, but I did look at the decline in sperm count over time, so we could look at that as an indication that This is not the only thing that's affecting sperm count, by the way, these phthalates.
But that's one where I feel I can say this with confidence because I measured those babies and I did it.
I did the science and I did it again.
And other people have done it.
And so I believe it's solid.
And that's just one example of the many chemicals that can affect our hormone system.
The animal studies were earlier, but that was the first human one, and they've been going on ever since.
The problem is that we don't talk about the consequences of this.
We as a society, we don't talk about sperm counts are going down, testosterone is going down, you know, we're having more and more children by assisted reproduction.
I don't know about you, but do you know anybody who's had trouble having a child?
It's quite a few people, but in general, I notice it's usually older people that have had a career, and then when they get into their late 30s or their 40s, then they decide to have children.
Yeah, I was reading something about lowered testosterone counts and that lowered sperm counts is happening with people and they were trying to figure out why, but they had not made the connection to your work.
It was just an article about trying to recognize what's causing this trend.
So listening to what you're saying...
It really hits home.
That's terrifying because I'm thinking about how many people this affects and how many people consume things that are either wrapped in plastic or they microwave things in plastic or they drink bottled water.
We stopped drinking bottled water here a while back just because it was wasteful.
And I'd heard about plastic leaching into waters and how it could do something, add estrogen to your body or something like that.
I'm like, well, it just seems like a bad idea to just...
Drink out of plastic all the time.
And they said it was a bad idea when you leave, like we lived in California, it was hot.
And if you had a water bottle in your car, you should never drink it after it's been sitting in there.
It is a significant issue and hopefully more people are recognizing.
But look, people don't, if you have a problem with your cholesterol, I'm sure you don't, but suppose you had your cholesterol checked, you go to a cocktail party, you say, I went to the doctor, I had a high cholesterol, I'm going to not eat this and this.
You wouldn't say, I went to my doctor and have a low sperm count.
But that is why I asked because there's a gentleman that's a friend of mine named Dr. Mark Gordon and he's worked with a lot of people with traumatic brain injuries and one of the things that happens with damage to the pituitary gland is a decrease in the amount of testosterone that's produced by the brain.
And the testes and then what happens after that is severe depression and this connection between severe depression and lower testosterone is pretty significant.
He's done a lot of work with this group called the Warrior Angel Foundation with another friend of mine Andrew Marr and they have worked with these soldiers and now he's also done some work with football players and fighters and a lot of other people with head injuries and he's shown this direct correlation between severe depression and lower testosterone.
Anxiety, a lot of mental health issues.
I would imagine that these kids that are born with this disruption in their developmental cycle and they have lowered sperm count, I bet everything is decreased.
Have they measured this in different countries, like countries in the developmental world and the countries where they use less plastic versus countries where they use more plastics?
No, I don't know of a study like ours in a developing country, but we have studies in other countries for sure in Europe.
But one measure of where it's a problem, I would say, is where is sperm count declining?
I mean, the kickoff for this book, Countdown, was a paper that we wrote in 2017 in which we showed that sperm count in Western countries had declined kind of catastrophically.
It's really scary when you think about what you're saying about people having a hard time reproducing.
And where this could lead to, a dramatic drop-off in the population.
We're worried about overpopulation.
But if this is real, the children that are being born today, if they have this issue, and then we're looking at them 20 years from now, the reproductive cycle starts kicking in in terms of them having babies and raising families, what's the numbers going to be?
And here, another thing to think about, So a mother is exposed to some phthalates, other chemicals, the phenols, the line tin cans, and the flame retardants, and the pesticides.
They're all bad.
They all can do this in different ways.
But let's just talk about the phthalates.
So the mother is exposed to the phthalates, and she's carrying, let's just say, a son in the womb.
And then he has within him what's called the germ cells of his sperm, right?
So she's exposed, the child is exposed, and the next generation is exposed.
So from one person being exposed, you're exposing three generations.
So you're right to say, think about the later, you know, the kids coming and the kids coming after that.
But here's the good news.
Should be some good news, right?
The good news is that in a very elegant study in the University of Washington, Pat Hunt showed that if you...
Have a guy, mouse, who was exposed and had impaired fertility and sperm count.
And then you cleaned up everything about his environment and for his child's environment and his child's child's environment.
In three generations, we can recover reproductive health.
I'm sure there'll be a lot of pushback from your listeners, but first of all, We can do better.
One place...
Let me just say, we used to do terribly with drugs.
The regulation of drugs was terrible.
That's why we had thalidomide babies, you know, and other terrible breakthroughs.
And then the FDA got it together and learned how to regulate drugs.
And we're pretty safe now.
And we know, for example, how to test vaccines and so on and so forth.
So we can...
Work toward a viable regulatory system if we want to.
So I believe that.
In Europe, they're many steps ahead of us because they have instituted something called reach.
Now, under reach, if a guy manufacturer wants to put a chemical into commerce, into a plastic bottle, into a Personal care product, where they are also, by the way.
He has to show that it's not harmful before he does that.
So he has to pass a series of tests.
In this country, we don't have that regulation.
In this country, it's put it in and we'll see if it's harmful.
No prior regulation required.
You see?
So it's really, really different.
The bottom line is like, we have only like 11 chemicals that are not allowed in our personal care products.
unidentified
In Europe, they have 1100. They also don't allow commercials for drugs.
So this delicate testosterone balance that I talked about can go the other way for females, but that's not through something like phthalates.
It's through other chemicals possibly.
We just published a paper that, and this is early, I'm not going to, you know, this is not the same weight of evidence at all as I have for the phthalates, but we just published two papers in which we showed that when Mothers were exposed to higher levels of a certain pesticide, which is in Roundup, which is—have you heard of Roundup?
So there are, you know, there's the chemicals that are in coatings, just to say, you know, coatings of can, Teflon frying pans, coatings of your jacket that you wear in the rain, you know, repellent.
Those coatings, they're also on paper, you know, keeps the grease from going through to the box when you buy a pizza.
Those coatings are also hormonally active and very, very prevalent.
I haven't studied those myself, so I don't want to talk a lot about their effects, but I know they have reproductive effects.
Anything that puts a barrier, any barrier, a chemical barrier, they're called the PFOS. Sometimes they're called PFOS and PFOA. They're different classes of chemicals, but perfluorinated compounds.
Then there are the phenols, the bisphenols.
Which, by the way, you probably, did you ever try to buy a BPA-free bottle?
So what happened was people got really upset about BPA. It had a lot of reproductive effects.
And so they took it out.
And that's good.
But what happened was, and this happens over and over and over again in chemical cycles, they put something else in.
They put in BPF like Frank and S like Sam.
And BPF and BPS are, particularly BPF is equally if not more risky than BPA. And the bottle says BPA-free, that's true, but it doesn't say bisphenol-free, right?
Think about walking through your kitchen and looking for plastics and trying to swap out ceramic and glass or metal, not for the microwave, of course, and in your bathroom to look at your personal care products.
And that would be if you're trying to eat organic.
Even in that sense, if you're having milk and it's coming through tubes, if you're having anything that's wrapped in plastic, even if it's grass-fed, organic, you're wrapping it in a plastic.
I don't think most people have any idea that this is that big of an issue.
And when you're saying all this stuff, and I'm terrified of this because I feel like, and I'm glad you wrote this book, and I'm glad you did these studies, but I feel like this has caught people completely off guard.
And then I'm picturing a supermarket and just going down the road looking at, like, packages of lettuce and things wrapped in plastic and meat wrapped in plastic and chicken and, like, wow.
We haven't studied the effect of adult exposures of somebody my age, but if it's a couple who's grown up but wants to go to, say, assisted reproduction, a beautiful series of studies at Harvard showed that the amount of chemicals in their urine and blood when they come in for their assisted reproductive procedure influences how that procedure comes out.
So how many eggs can be retrieved, How many are implanted?
How many actually progress to a live birth?
Is related to the chemicals in their body at the time they start the procedure.
So that's an effect of an adult, to an adult, of an adult exposure, you know, that I know of for sure.
I don't It's very possible that these are related to aging and diseases of aging.
They certainly affect the brain.
We know that from our studies.
But, you know, every one of these questions requires, like I said, $5 million.
And you got a lot of chemicals and you got a lot of questions.
And you also have a lot of companies that have a vested interest in continuing business as usual and they want to deny as much responsibility for having these chemicals in our bodies as they can.
And what you're talking about too is that to turn this around, in general, you're talking about multiple generations in order to bring the developmental cycle back to normal.
I mean, but really that has been the response that some people have, that this is probably...
Maybe they look at it in terms of, like, nature has a way of working itself out, whether or not it's voluntary or whether or not it's just an incidental part of the system.
But it's really the responsibility of the people that are packaging food.
It's really the responsibility of the people that are involved in getting the stuff to us and how are they getting it to us and how are the phthalates getting to us.
If there was any other thing that someone was doing that turned out was affecting the entire human race because of their business, just fill in the blank, like if we found out that, you know, whatever it is, cell phone use or driving a car, looking at your dashboard was somehow or another affecting the reproductive cycle of the human race, there would be drastic consequences.
But, you know, you can find a female cause about a third of the time, a male cause about a third of the time, and a third of the time, it could be both, or you don't know.
So that's kind of 50-50.
And then you go, if they manage to conceive, then a high percent of pregnancies have miscarriage.
Well, I can't say that off the top of my head, all of them, but the ones that I've studied, when I studied that, those were the chlorination byproducts.
So when you chlorinate water, the high levels of certain chlorination byproducts, and also solvents that are used to clean chips and other, you know, certain high...
So here, the big picture is that we have these thousands of chemicals that we can't get a handle on.
There was a law, it was called the Toxic Substances Control Act, and it was published in 76. And at that point, when they put that in, they said, okay, here are thousands of chemicals that have been out there for a long time.
Nobody seems to worry about them.
They're all okay.
They were called grandfathered in.
They were not regulated.
We have that legacy on top of the lack of testing of new chemicals.
So there's very little regulation of all of these chemicals that are circling in our environment and entering our bodies.
And I and my colleagues, you know, are few compared to the problem and we need more resources and we need more people worrying about this.
And I think the first step is to just have people like you and your listeners and people I talk to on all these shows I've gone on, you know, recognizing, thinking about it, just thinking about it, you know.
worry about bringing this and this and this into my house.
Maybe I should read these labels.
Maybe I should, you know, because it hasn't been in our consciousness.
There's a decrease in lifespan that's associated with large population centers, whether it's, you know, Los Angeles or New York or living, but living in urban areas, there's a decrease in lifespan.
They think it's somewhere in the neighborhood of 10 years.
And they don't know if it's because of breakdust or pollutants or particulates in the atmosphere.
They don't know what it is.
But has there been a study on, well, I'm sure there probably hasn't, on sperm counts in rural areas as opposed to sperm counts in high population areas?
Is it like we're talking about enormous cornfields and glyphosate and all these other different chemicals, or they work their way into the air itself because they spray?
But I don't know, when you talk about monocrop agriculture on large scale, like these enormous cornfields, I don't know how they do that without pesticides.
When you see the amount of manipulation that's required to grow a thousand acres of corn or whatever in one spot, you don't see that anywhere in nature.
Like what we've done to the environment in such a short time.
What's crazy to me is if you go back to, you know, 1820, 200 years ago, there's none of this.
There's none.
Zero.
So in 200 years, we've completely ruined the ground.
We've completely changed the way we cultivate food.
We've added all these chemicals to our environment, to our water, to our air, changed sperm counts, changed reproductive cycles and reproductive quantity.
What's your fertility IQ? Many men and women feel fairly confident about their fertility intel, but research shows a surprisingly high percentage of people don't know as much as they think they do.
Are you one of them?
Answer these six questions and find out.
Well, I've reproduced, so I'm pretty sure my sperm works.
But I could be wrong.
As far as sperm go, which of the following can contribute to whether a man is likely to be considered infertile?
Answer D. Aside from a total absence of sperm, total bummer we know, no single sperm parameter can predict that a man will be completely infertile.
Turns out When the sperm concentration, motility, the sperm's movement or swimming ability, and morphology, the size and shape of the sperm, are measured, each one matters in identifying infertile men, but there is an additive effect.
When one of these measures is in the infertile range, a man is two times more likely to be infertile as a man with none of these measures in the infertile range.
When two measures are in the infertile range, a man is five to seven times more likely to be infertile.
And when all three fall are subpar, his odds of being infertile are 16 times higher.
While the official term for taint, people that are listening, it was like 40% said no.
Or 40% said yes, 60% said it didn't matter.
But it does matter.
While the official term for taint or gooch is anogenital distance, ACD, size really does matter.
The length of the guy's ACD will reflect his exposure.
We talked about this.
Okay, we already know this one.
Let's go next.
Number three, what proportion of infertility cases can be attributed solely to the man?
A, less than 10 percent.
B, about 11 to 24 percent.
C, 25 to 33 percent.
D, 34 to 45 percent.
I'm saying D. We can't click on it.
Won't let you.
Let's go.
Answer C. Interesting.
Less than I thought.
Infertility used to be considered mostly a woman's problem.
That seems so sexist.
Yeah.
In recent decades, it has become increasingly recognized that male reproductive issues can cause approximately one-half to one-third of infertility cases.
I would assume it was more than that.
Same proportion as female reproductive challenges do.
The rest are believed to stem from a combo of male and female factors.
It takes two to make things go right.
Oh, it takes two to make things go right.
Here we go.
Testosterone replacement therapy can increase sperm count in men with low testosterone levels.
This means that if a man cleans up his lifestyle, gives up cigarettes, heavy alcohol use, sugar-sweetened drinks, and couch potato habits and takes steps, literally, to slim down and be physically active, his sperm count and his sperm integrity may increase significantly.
Next.
A man's age can affect his female partner's miscarriage risk.
True.
82% agree.
True.
Research suggests that for men ages 40 and older, their female partners have a 60% increased risk of miscarriage compared to the aspiring dads under 30. This may be largely because with advancing age, there is an increase in the presence of abnormal genetic material Within the sperm at any age, a pregnant woman is more likely to miscarry when sperm is faulty, but neither partner may realize this.
That's a miscarriage of reproductive justice.
That's a big thing with men who drink heavily, correct?
That actually there are physiologically the way the woman is shaped and her vagina is shaped and is to make it easier for the earlier sperm to kill off the later ones that are coming in after them.
Male masturbation is said to discard old dying sperm so that ejaculate contains younger sperm so that it will stay active inside the cervix longer with more of a chance of being present during the window of ovulation.
Yeah, I don't know that I've heard there's been a different kind, but I've heard that maybe the timing of the sperm and, you know, the place in the, you know...
In the race, so to speak, might affect the survival of the later ones.
Men with low sperm counts and infertile men have a shorter life expectancy.
That makes sense.
Yeah, that makes sense.
It just means...
It makes sense that you're less...
There's less vitality.
There's also...
There was something about...
Something I read recently about the immune system and muscle quality, like the amount of muscle mass a man carries on his body is a direct correlation to the health of his immune system.
That also makes sense that if a woman is not ovulating, but a man has sex with her before she's ovulating, and then all of a sudden she gets pregnant, that's what it is.
The sperm stuck around.
The sperm was like, look, I'm not giving up yet.
I'm telling you, this door's going to open.
Men who take testosterone supplements can suffer from reduced sperm counts.
We already went over that one.
The riskiest period for a man's reproductive development is while he's in the womb.
So, some scientists suggest that it's hard to fathom, but an argument could be made that Homo sapiens already fit the standard for an endangered species based on U.S. Fish and Wildlife Service's requirements, okay?
How would that be?
Well, of the five possible criteria for what makes a species endangered, only one needs to be met to be called endangered, okay?
So, the first is that we're arguably experiencing destructive modification or curtailment of our habits.
This is wording from the Fish and Wildlife.
Well, this means that we're messing up our air, our food, our water in a way that modifies or destroys our habitat.
And last but not least, declines in sperm count and testosterone levels and increases in testicular cancer and miscarriage rates are all occurring at the same rate, 1% per year.
I mean, they're just small things, but we got an hour off of apples.
So when people...
If you multiply that by hundreds of times having people go after specific problems that they're concerned about, I think we can do this.
We've done amazing things.
We produced this vaccine in a year when people said it wasn't possible.
We put the lander on Mars.
I have a lot of faith that technologies that I haven't thought of You know, chemicals that haven't been designed yet will come in and take the place of these chemicals.
I'm just skeptical because I think so many industries would have to make a big change and it would cost them so much money that they're going to deny this as long as they can.
Well, I'm actually glad you're disturbed because you have a lot of followers and maybe they will listen to this and think about this and, you know, help to turn this around.
By the way, I ask people to use the hashtag count me in.
I think it's the next problem, you know, I just say in closing that we had Denial of climate change, and then some recognition of climate change, and then finally people saying there's things we can do about it.
And I see the same pattern happening here.
Initially there was a study saying sperm count had declined in 1992, which was dismissed.
I was actually skeptical of it myself at first.
And then when my paper came out in 2017, it went viral.
It was the 27th most cited paper in the world that year.
It was on the cover of Time and you name it.
And then people didn't say, sperm count has not declined.
They said, yes, we do have a problem.
But they didn't make the next step, which is doing something about it.
And I think the same progression will happen here as has been happening with climate change.