[One in 8 couples in the U.S. struggles with infertility. In male
infertility, the issue is not only the declining number of sperm
produced, but the reduced motility (level of activity). Does
environmental toxicity contribute to male infertility? ]
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MALE FERTILITY IS DECLINING – STUDIES SHOW THAT ENVIRONMENTAL
TOXINS COULD BE A REASON  
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Ryan P. Smith
July 30, 2022
The Conversation
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_ One in 8 couples in the U.S. struggles with infertility. In male
infertility, the issue is not only the declining number of sperm
produced, but the reduced motility (level of activity). Does
environmental toxicity contribute to male infertility? _

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[An article published this week
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in Human Reproduction Update reviewed evidence of declining sperm
counts, using data collected globally over half a century. It
confirmed that sperm count has declined by more than half and that the
decline is accelerating. -- moderator]

In the U.S., nearly 1 in 8 couples struggles with infertility
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Unfortunately, physicians like me who specialize in reproductive
medicine are unable to determine the cause of male infertility around
30% to 50% of the time
[[link removed](20)32667-2]. There is almost
nothing more disheartening than telling a couple “I don’t know”
or “There’s nothing I can do to help.”

Upon getting this news, couple after couple asks me questions that all
follow a similar line of thinking. “What about his work, his
cellphone, our laptops, all these plastics? Do you think they could
have contributed to this?”

What my patients are really asking me is a big question in male
reproductive health: Does environmental toxicity contribute to male
infertility?

Male fertility decline

[A medical professional sitting with a couple.]
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If a couple is struggling to get pregnant, doctors will try to figure
out the cause. Philippe Roy/Cultura via Getty Images
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Infertility is defined as a couple’s inability to get pregnant for
one year despite regular intercourse. When this is the case, doctors
evaluate both partners to determine why.

For men, the cornerstone of the fertility evaluation is semen
analysis, and there are a number of ways to assess sperm. Sperm count
– the total number of sperm a man produces – and sperm
concentration – number of sperm per milliliter of semen – are
common measures, but they aren’t the best predictors of fertility
[[link removed]]. A more accurate measure looks
at the total motile sperm count
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of sperm that are able to swim and move.

A wide range of factors – from obesity to hormonal imbalances to
genetic diseases [[link removed](20)32667-2] –
can affect fertility. For many men, there are treatments
[[link removed](20)32667-2] that can help. But
starting in the 1990s, researchers noticed a concerning trend. Even
when controlling for many of the known risk factors, male fertility
appeared to have been declining for decades
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In 1992, a study found a global 50% decline in sperm counts in men
over the previous 60 years [[link removed]].
Multiple studies over subsequent years
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including a 2017 paper showing a 50% to 60% decline in sperm
concentration between 1973 and 2011
[[link removed]] in men from around the world.

These studies, though important, focused on sperm concentration or
total sperm count. So in 2019, a team of researchers decided to focus
on the more powerful total motile sperm count. They found that the
proportion of men with a normal total motile sperm count had declined
by approximately 10% over the previous 16 years
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The science is consistent: Men today produce fewer sperm than in the
past, and the sperm are less healthy. The question, then, is what
could be causing this decline in fertility.

[A stack of reddish plastic pipes.]
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Plasticizers are common endocrine-disrupting compounds, found in many
plastics – like PVC pipes – that come in contact with food or
water. Mm Zaletel/Wikimedia Commons
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CC BY-SA [[link removed]]

Environmental toxicity and reproduction

Scientists have known for years that, at least in animal models
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environmental toxic exposure can alter hormonal balance and throw off
reproduction. Researchers can’t intentionally expose human patients
to harmful compounds and measure outcomes, but we can try to assess
associations.

As the downward trend in male fertility emerged, I and other
researchers began looking more toward chemicals in the environment for
answers. This approach doesn’t allow us to definitively establish
which chemicals are causing the male fertility decline, but the weight
of the evidence is growing [[link removed]].

A lot of this research focuses on endocrine disrupters
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molecules that mimic the body’s hormones and throw off the fragile
hormonal balance of reproduction
[[link removed]]. These include substances like
phthalates – better known as plasticizers – as well as pesticides,
herbicides, heavy metals, toxic gases and other synthetic materials.

Plasticizers are found in most plastics – like water bottles and
food containers – and exposure is associated with negative impacts
on testosterone and semen health
[[link removed]]. Herbicides and
pesticides abound in the food supply and some – specifically those
with synthetic organic compounds that include phosphorus – are known
to negatively affect fertility
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Air pollution surrounds cities, subjecting residents to particulate
matter, sulfur dioxide, nitrogen oxide and other compounds that likely
contribute to abnormal sperm quality
[[link removed]]. Radiation exposure from
laptops, cellphones and modems has also been associated with declining
sperm counts, impaired sperm motility and abnormal sperm shape
[[link removed]]. Heavy metals such as
cadmium, lead and arsenic are also present in food, water and
cosmetics and are also known to harm sperm health
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Endocrine-disrupting compounds and the infertility problems they cause
are taking a significant toll on human physical and emotional
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these harms is costly [[link removed]].

[A sign warning of chemicals that cause cancer, birth defects or other
reproductive harm.]
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Thousands of new chemicals are introduced every year and government
agencies do their best to keep up. Stephen Osman/Los Angeles Times via
Getty Images
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The effects of unregulated chemicals

A lot of chemicals are in use today, and tracking them all is
incredibly difficult. More than 80,000 chemicals are registered in the
U.S. [[link removed]] and
nearly 2,000 new chemicals are introduced each year
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Many scientists believe that the safety testing for health and
environmental risks is not strong enough
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and that the rapid development and introduction of new chemicals
challenges the ability of organizations to test long-term risks to
human health
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Current U.S. regulations follow the principle of innocent until proved
guilty [[link removed]] and
are less comprehensive and restrictive
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Europe [[link removed]], for example. The World Health
Organization
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recently identified 800 compounds capable of disrupting hormones, only
a small fraction of which have been tested.

A trade group, the American Chemistry Council, says on its website
that manufacturers “have the regulatory certainty they need to
innovate, grow, create jobs and win in the global marketplace – at
the same time that public health and the environment benefit from
strong risk-based protections.”

But the reality of the current regulatory system in the U.S. is that
chemicals are introduced with minimal testing and taken off the market
only when harm is proved. And that can take decades
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Dr. Niels Skakkebaek, the lead researcher on one of the first
manuscripts
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on decreasing sperm counts, called the male fertility decline a
“wake-up call to all of us.” My patients have provided a wake–up
call for me that increased public awareness and advocacy are important
to protect global reproductive health now and in the future. I’m not
a toxicologist and can’t identify the cause of the infertility
trends I’m seeing, but as physician, I am concerned that too much of
the burden of proof is falling on the human body and people who become
my patients.

_This article was updated to more accurately represent the chemical
regulatory system in the U.S._[The Conversation]

Ryan P. Smith
[[link removed]], Associate
Professor of Urology, _University of Virginia
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This article is republished from The Conversation
[[link removed]] under a Creative Commons license. Read
the original article
[[link removed]].

* Science
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* biology
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* environmental pollution
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* reproduction
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