Sperm Decline Is Global and Significant, New Study Warns

Are plastic and fire-resistant furniture worth it? Accelerating rates of impaired male fertility and genital malformation portend a male health crisis – but experts say humanity isn’t about to go extinct

Ruth Schuster
Ruth Schuster
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Illustration of abnormal, deformed human sperm
Illustration of abnormal, deformed human spermCredit: Shutterstock
Ruth Schuster
Ruth Schuster

Human fertility is in crisis. Sperm counts worldwide have plunged by more than 50 percent in less than half a century. Moreover, the decline in quantity and quality of the male seed has been accelerating, as have abnormalities in male reproductive systems – even as the planetary population continued to increase, hitting 8 billion this week.

Despite that dubious milestone, natural reproduction faces emerging disaster, according to two meta-studies: one published in 2017 reporting on the decline of sperm in the West; and the second published Tuesday in the Oxford journal Human Reproduction Update, by an international research team led by Hebrew University’s Hagai Levine and Shanna Swan at Mount Sinai, New York, with researchers in Denmark, Brazil, Spain, Israel and the United States.

The first meta-study, in 2017, reported declining sperm counts in North America, Europe and Australia, based on data from 1981 to 2013. The new paper by the same team encompasses 53 more countries – in Latin America, Asia and Africa – and is based on data up to 2018. In other words, now the whole world has been checked and sperm count is declining everywhere, generally by more than 50 percent in the last 46 years.

The green-stained sperm is chemically abnormalCredit: REUTERS

Genital abnormalities

Testosterone concentrations and sperm quality have also been dramatically diminishing. In parallel, the rates of males being born with genital abnormalities such as micro-penis, hypospadia (the urethra culminating on the side of the penis, not the tip), malformed testicles and rates of intersexuality (aka hermaphroditism) are rising.

Nor is the problem confined to humans. The discovery that Florida alligators living in swampland contaminated by fertilizers and pesticides had micro-penises too small for them to mate was made in 1996.

A similar problem was found in panthers, as Swan – a professor of environmental medicine – describes in her 2021 book “Count Down.” Animals around the world are evincing signs of reproductive crisis. “They are all signs that something very wrong is happening,” she says.

An American alligator in a Florida swamp. Might like a word with you about his penis.Credit: Michael Fitzsimmons / Shutterstock

And the problem is gaining momentum. The meta-studies show counts of “good” sperm decreasing by 1 to 2 percent a year. The trend line of these statistics implies that human sperm will approaching zero by roughly 2045. Also, make no mistake: female fertility is being affected too. Girls are experiencing earlier puberty and women’s eggs are losing viability at younger ages, Swan says.

Does this imply that it is infertility that will doom us to extinction in or around 2045? Probably not: statistics are bare while life is fuzzy, and as “good” sperm become rarer, assisted reproduction can be a lifeline, Swan points out. Also, while the situation is already dire, there are things that can be done.

But even though men with low sperm count can still naturally conceive – albeit possibly with more effort – we need not face extinction to experience catastrophe, Levine points out.

He too doesn’t see humankind reaching a mean of zero viable sperm, though acknowledges it could be a failure of imagination; at the least, there ought to be statistical outliers (though nobody survives rabies). In the longer run, the proportion of men with viable sperm will shrink. Or, alternatively, we could be heading for a tipping point from which the problem becomes irreversible, he says. We simply don’t know; we only know that modern civilization cannot persist in its trajectories without paying a horrendous price.

“It sounds unbelievable. Now we have the terrific responsibility to deliver this message to study the causes, and do something about them,” Levine says. “The issue isn’t the inability to conceive – a problem many men already had. The main problem is that we have a clear indicator that we are living in a sick system, a sick environment, and the sperm is a barometer of the problem.”

Prof. Hagai Levine from Hebrew University. "We have a serious problem on our hands that, if not mitigated, could threaten mankind’s survival."Credit: Avi Hayon / Hadassah

Poor sperm, poor health

The problem isn’t just procreation. Various studies show association between poor semen quality and poor health outcomes for men in later life, Levine explains: heightened risk of chronic illness and testicular cancer, for instance. Why sperm quality is an indicator for male health is a mystery. The point is that declining sperm quality portends a male health crisis, the researchers stress.

It bears adding that there is a lot more research on male infertility than female, which could also be for the pragmatic reason that male genitalia are “easy to access,” Swan says. Nor is it rocket science to lay hands on a man’s sex cells for examination under a microscope for counting and diagnosis. The female reproductive system is hidden and immensely harder to study, and the reasons for increasing incidence of female reproductive difficulty need not necessarily be the same as for men.

Levine also points out the difference between potential and realizing potential: If one plans to have two children, even at low sperm counts that dream can come true. But if one aspires to be fruitful and multiply as much as possible, the impaired fertility will clearly impact family size. “The point at which we see decline in number of children is a very late stage. If you plan for one to three kids, you don’t see a big difference,” he says. But globally, the emerging difference is very big.

The causes for this looming multifaceted threat to reproduction have not been nailed down and the meta-studies do not address them at all. But since the problem is also appearing in wild animals, clearly the root evil doesn’t lie in human evolution or in the sedentary lifestyle.

Normal, abnormal and defective spermCredit: Pikovit/Shutterstock

No question, disease and poor choices such as chronic overeating (or self-starving), choosing processed and ultra-processed foods, smoking and indolence contribute to personal human infertility. But even if everybody on Earth lived on reconstituted potato chips and beer consumed out of plastic bags with artificial Cheez on top, that wouldn’t apply to wild animals. Or dogs, in which sperm decline has also been observed.

Like in the case of climate change, when it comes to cause and effect, everything is connected. But two culprits stand out, Swan says: our passion for plastic; and use of chemicals to which we are exposed and, crucially, to which our mothers were exposed. Or grannies.

That is because apparently, damage may accumulate over generations. Research has found that when subsequent generations of men were exposed to endocrine-disrupting chemicals, the effects of the originally reported damage to sperm-producing cells were amplified, and increasing reproductive tract abnormalities were observed, Swan says – such as kinking or collapse of the vas deferens tubule that leads sperm to the outside world.

Let’s explain. Women are born with all the eggs they will ever produce; if they’re born with “bad eggs” or none because of their mother’s exposure, there is nothing to be done about it. Men are born with the tissue that will produce sperm from puberty to death, though sperm quality indeed diminishes with age, Levine says. So a man with essentially healthy sperm-production tissue may experience a temporary slump, but his output can rebound.

But a man may be born with impaired spermatogenic tissue because of his mother’s or even his grandmother’s exposure – and probably both. A sort of cumulative multigenerational inheritance is possible: a pregnant woman is exposed to a chemical that impacts the fetus but it survives and grows up and is exposed some more (because we keep polluting). Now we already have a two-hit model and, if he has children, they will be exposed yet more.

This may cast on the observed acceleration of sperm decline, Levine notes: Maybe multiple factors coming together and accumulating over generations are having a greater impact. In any case, proper development of the testes in utero is easily derailed by hormone disruptors, stress, smoking, and so on. Observing crocodilians who can’t have sex, wild frogs living in chemical soup who develop eggs in their testicles, and sex-changing fish is horrifying; and animal research in the lab has proven the connections between certain chemicals and hormonal disruption.

This is the state of affairs. What can be done?

A worker at Keio University Hospital in Tokyo monitoring the movement of a sperm donation.Credit: YUICHI YAMAZAKI - AFP

Forever yours

Among the dangerous chemicals marinating our environment are chemicals that enter our bodies and are passed out quickly, in a matter of hours. Research has shown these lose all effect within three generations if exposure stops, Swan says. But “forever” chemicals have become as ubiquitous as microplastics, which is no coincidence.

Among them are endocrine-disrupting chemicals such as pesticides and flame retardants, and they’re barely regulated, if at all.

In the United States, for instance, the default position is that a chemical must be shown to cause harm to be regulated, which has resulted in a tsunami of inadequately tested chemicals. Moreover, some endocrine-disrupting chemicals can have harmful impacts on all our systems, not just our reproductive ones, even in very low amounts, Swan says; there is no such thing as permissible exposure. You don’t need a chemical accident like at Bhopal in 1984: putting on unregulated makeup or body lotion, or even using plastic bags, can do the trick, she says.

At the personal level, you can’t live in a pristine bubble. But you can clean up your act – and your shopping list. “The same factors that harm our health also harm sperm production, and sperm is produced all the time. Your sperm now was manufactured 80 days ago, so what you did 80 days ago will affect it,” Levine explains.

Specifically, get off the couch, stop drinking sodas and eating processed foods, and ditch the cigarettes. Secondhand smoke does you no favors either. Healthy body, healthy mind, healthy sperm. You know what to do. And, Swan stresses, buy hygienic household products that do not state “deadly” on the packaging and do not contain forever chemicals.

As for the non-forever chemicals, the problem here is that they may pass from your body, causing no harm after a few hours but if our environment is saturated with the stuff, we just pick up some more, so they effectively become sort of forever chemicals, she says.

Which leads to what can be done at the planetary level. At least the non-forever chemicals can simply be banned. But key sources of chemicals monkeying with our chemistry are plastics and, let’s get real, plastic isn’t going anywhere.

One can, however, replace plastic boxes with glass or metal; use textile bags instead of plastic ones; and, at the planetary level, cast one’s faith in ... business? Yes, companies can be motivated to invent plastic-like materials that won’t counter reproduction, because people want it and will pay for it, Swan suggests. You can count on that.

Is it too late?

The world has known about climate change for over a century, yet done nothing concrete about it. Similarly, plastic contamination is ubiquitous and the few stabs at reducing its use haven’t had much of a global impact.

To draw a parallel with climate change: even if we stop all emissions this second, temperatures will continue to climb because of the carbon dioxide already in the atmosphere. Even if we were to stop using plastics, pesticides and flame retardants, the world is saturated with them, and with bad chemicals.

Is it too late? "I would say – not yet,” Swan responds. But that is based partly on urging better education, including for doctors, and the availability of in vitro fertilization, which in Israel is subsidized by the state. IVF is, however, is both expensive and also, no long-term solution for the human race.

More hearteningly, awareness of the problems is developing and the hope must be that better research, regulation and enforcement ensue. The non-forever chemicals can vanish in a poof, theoretically speaking. The forever ones are more of a problem, but it isn’t game-over yet.

That said, time is running out, Levine cautions. “Our findings serve as a canary in the coal mine. We have a serious problem on our hands that, if not mitigated, could threaten mankind’s survival. We urgently call for global action to promote healthier environments for all species, and reduce exposures and behaviors that threaten our reproductive health.”

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