A viral clip from the Shawn Ryan Show, titled “Are Microplastics Causing the Fertility Crisis?” and posted August 15, has reignited public debate over whether tiny plastic particles found throughout the human body are contributing to falling sperm counts and rising infertility worldwide. The short-form video is part of a broader conversation on the podcast about environmental toxins, in which physician guests have discussed chemical exposure and its effects on modern health. The clip does not present new data itself, but it channels a growing body of scientific research examining a real and increasingly urgent question: is the microplastics fertility crisis actually happening, and if so, why?
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The scientific starting point for this debate is a series of meta-analyses led by epidemiologist Hagai Levine and colleagues, including reproductive researcher Shanna Swan. Their most recent 2023 analysis, published in Human Reproduction Update, examined data from 53 countries and found that sperm count is declining at an accelerated pace globally, extending earlier findings that had been limited mostly to North America, Europe and Australia.
Levine summarized the findings starkly at the time, noting that researchers were “seeing a significant worldwide decline in sperm counts of over 50% in the past 46 years, a decline that has accelerated in recent years.” That study, however, did not identify a specific cause, and Levine cautioned that the results serve as a warning sign rather than proof of any single culprit.
Not all researchers agree the decline is as dramatic or as uniform as the Levine team’s work suggests. A more recent analysis by researcher Kieran Lewis and colleagues has offered a more nuanced picture, with some datasets showing stable or even increasing sperm concentrations in certain fertile populations, underscoring that the underlying science remains contested and methodologically complex.
Microplastics Turning Up in Testicles and Semen
Separate from the sperm-count debate, a growing set of studies has directly detected plastic particles in human reproductive tissue. A 2023 study from Peking University researchers, published in Science of The Total Environment, found microplastics in six human testis samples and 30 semen samples, with
polystyrene composing 67.7% of microplastics in the testis, while polyethylene and polyvinyl chloride were the predominant polymers in semen
.
A separate 2024 study from the University of New Mexico examined tissue from both species and reported that researchers
tested 23 human testicles and 47 dog testicles and found microplastics in every sample, and dog testes with higher concentrations of certain microplastics tended to have lower sperm counts
. Because ethical constraints prevent researchers from directly manipulating human exposure, much of the strongest causal evidence linking microplastics to reduced sperm counts and testis weight still comes from animal studies rather than humans.
More recent work has tried to close that gap. A 2024 multi-site study in China published in eBioMedicine found that
each additional type of microplastic exposure was associated with a significant decrease in total sperm number, sperm concentration, and progressive motility
. That research specifically flagged PTFE, the non-stick coating material known as Teflon, as a microplastic of particular concern for male fertility.
Caution From Scientists Who Study Microplastics
Even researchers sympathetic to the microplastics hypothesis urge caution about overstating what’s been proven. Discussing the pilot testis-semen study, ecotoxicologist Dick Vethaak of Vrije Universiteit Amsterdam, who was not involved in the research, told Environmental Health News that while the presence of microplastics in testis and semen was unsurprising,
whether larger microplastics can truly penetrate the male reproductive organs “still presents ‘quite a question mark,'” calling the study “a pilot study that, in my opinion, provides preliminary evidence.”
He added that more data would be needed before drawing firm conclusions.
That distinction — between plastics simply being present in the body and plastics actively causing infertility — is central to how scientists are approaching the topic, even as public interest, fueled by podcasts, documentaries and social media, races ahead of the research. Netflix’s 2026 documentary “The Plastic Detox,” featuring Swan, follows six couples with unexplained infertility as they attempt to reduce household plastic exposure, reflecting how mainstream the microplastics fertility crisis conversation has become even as the underlying science is still developing.
Why the Debate Matters Beyond One Podcast Clip
As discussed in the Shawn Ryan Show segment, host Shawn Ryan’s guest framed environmental toxins, including microplastics, as a hidden and underappreciated threat to health — a framing that reflects genuine scientific concern even if some claims in popular media outpace what peer-reviewed data can currently confirm. Researchers broadly agree that declining fertility, where it is occurring, is likely driven by multiple overlapping factors, including delayed childbearing, obesity, smoking, heat exposure, pesticides and other endocrine-disrupting chemicals, not microplastics alone.
What is well established is that microplastics are now essentially ubiquitous in the human body, having been detected in blood, lungs, placentas, and reproductive organs. Whether that ubiquity is meaningfully driving the global fertility crisis, or is one contributing factor among many, remains an active and unresolved question that scientists say deserves continued, rigorous study rather than alarmist certainty in either direction.