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New research suggests that microplastics could be affecting male fertility


They've been found all over the body, from the lungs to the brain to the blood - we're talking about microplastics. They're also all over the environment, including in our water and our food. Now, new research adds to concerns that they could be affecting male fertility. NPR's Will Stone reports.

WILL STONE, BYLINE: These ever-so-small fragments of plastic seemed to turn up every time scientists scour a new corner of the body. The male reproductive organs are no exception, specifically the testicles. That's what Dr. John Yu and his team at the University of New Mexico discovered in samples taken from about two dozen human autopsies.

JOHN YU: In this study, we found a huge different type of microplastic.

STONE: These particles had also accumulated in the testicles of about 50 dogs, although at lower concentrations than seen in humans. The research builds on a smaller study from China that recently detected microplastics in testicles for the first time.

YU: This is, you know, really surprising results for me.

STONE: Surprising because there's a very tight protective tissue barrier around these reproductive organs. Animal studies have shown exposure to microplastics can impact sperm quality and male fertility. But scientists are just in the early stages of translating this work to humans. The new study was published in the journal Toxicological Sciences. It did find a link between levels of a plastic called PVC and sperm count in the dog samples. They couldn't do the same analysis in the humans. There were also associations between several microplastics and testicle weight, which can be an indicator of damage. Matthew Campen at the University of New Mexico says polyethylene was the most abundant microplastic in the testicles. It's widely used in bags and other products.

MATTHEW CAMPEN: There are little shard-like stabby bits because of the way they've gotten old and brittle and fragmented. What they do in the body, we don't know. I mean, obviously little tiny particles can disrupt the way cells behave.

STONE: The study is a starting point. It can't prove microplastics cause lower sperm count. And there are still so many questions - which microplastics are most concerning? Exactly how much could be dangerous?

CAMPEN: We're just at the tip of the iceberg in trying to understand what these are doing. A lot of the problem is they're so ubiquitous - there are no proper controls anymore, right? Everybody's exposed.

STONE: However, the findings may be relevant to the global decline in sperm count and other problems related to male fertility. That trend has been linked to lifestyle and environmental factors, including certain chemicals in plastics. Richard Lea is a reproductive biologist at the University of Nottingham. His lab has shown these so-called endocrine-disrupting chemicals - one example are phthalates - are harmful for sperm in dogs, which can be a stand-in for humans.

RICHARD LEA: Microplastics will leach out chemicals, including the phthalates, and so having something unnatural like that in the testis is not particularly good news for good reproductive health.

STONE: Of course, testicles are just one part of the male reproductive system. Shanna Swan, a reproductive epidemiologist at Mount Sinai in New York, says microplastics in the testicles may not necessarily be more problematic than other parts of the body. She says there are still big issues with studies on microplastics in human tissue. It's hard to keep samples from being inadvertently exposed to these particles.

SHANNA SWAN: There have to be a lot of caveats. You know, it's suggestive. It's important. And it's preliminary.

STONE: Several years ago, Tracey Woodruff at the University of California, San Francisco, reviewed the evidence and concluded microplastics are suspected to harm sperm quality and testicular health in humans. But Woodruff thinks that may soon change from suspected to likely.

TRACEY WOODRUFF: You see these indicators of health harms. Those that have some type of evidence behind them just tend to grow. And I anticipate we're just going to see more health harms from these microplastics.

STONE: Even though research is not conclusive yet, Woodruff says it should still be a wake-up call.

Will Stone, NPR News. Transcript provided by NPR, Copyright NPR.

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Will Stone
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