Bigger than the sperm they float beside: plastic particles found in human semen
Particles carrying traces of mercury have been found in samples from healthy men on three continents — the associations with sperm count keep accumulating
A human sperm head measures five micrometers across. Some of the plastic particles found floating alongside it measure five times that. Their surfaces show cracks and erosion, the result of years spent in the world before reaching a human body.
Researchers in Malaysia photographed the particles under an electron microscope and ran an elemental analysis. Iron, copper, mercury and titanium sat on the surfaces of some particles, picked up somewhere along the way. Every man in the study had them. All 115.
The result came in 2024 from forty men in Jinan, China. The men were all in their twenties and thirties, going through the medical checks required before marriage. None worked with plastics. Every sample contained plastic.
How plastic entered the fertility conversation
The starting point was ten men in Campania. In 2023, a group of researchers in Italy took semen samples from ten non-smokers in the region and put the samples under a Raman microscope. The device reads the chemical fingerprint of a particle by the way it scatters light. Sixteen fragments, spanning seven polymer types, came back across six of the samples: polypropylene, polyethylene, PET, polystyrene, PVC, polycarbonate, acrylic.
Ten men do not represent a population. What the study did was establish that the particles could be found in a place nobody had looked. By 2026, the question is being put to hundreds of samples across Italy, China and Malaysia — to semen, to testicular tissue collected at autopsy, to the seminal fluid of men going through IVF. The particles turn up in half the samples in some studies, in every sample in others. But, whether they do anything is the question that remains unanswered.
The plastics that show up: from food containers to non-stick pans
Polystyrene, polypropylene, polyethylene, PVC, PET, polycarbonate: the polymers used to make food containers, bottles, cling film, takeaway boxes, pipes. Most men carry several at once. In a study of 113 men across three regions in China, most had three to five polymer types in one sample. The more types a man carried, the lower his sperm count, concentration and motility ran. The pattern held after researchers accounted for age, weight, smoking and drinking.
One polymer stood out: polytetrafluoroethylene, the coating on non-stick frying pans and a material used across industry. But finding it in a sample doesn’t point to any specific pan or product. It just shows that the material gets in.
One finding involves behavior. Among two hundred men studied in 2025, those who reported daily use of plastic plates and cups carried more particles than those who used them only occasionally. Among men with lower body weight, higher exposure came with lower sperm concentration. Self-reported habits carry confounds — what men eat, where they work, how food gets packaged and heated before it reaches them. But, even accounting for these factors, the correlation held.
Testicular samples taken at autopsy contained a dozen polymers, with polyethylene the largest share by mass.
How microplastics get past the blood-testis barrier
Researchers propose two routes into the body: ingestion and inhalation. The particles are thought to travel from that point to seminal fluid by way of the epididymis or the seminal vesicles. Nobody has traced the route. It is simply an inference drawn from the fact that the particles turn up at the end of it.
The testicles sit behind one of the body’s checkpoints. The blood-testis barrier controls what reaches developing sperm. It screens out circulating substances and holds the immune system at a distance.
Animal experiments report that microplastics can disrupt the barrier, which would explain how a particle reaches a compartment the body works to seal. Once inside, sperm cells lack defenses against chemical stress. Their membranes contain polyunsaturated fats, which oxidize, and their capacity to repair damage approaches zero. What lands, stays.
What happens when sperm meets polystyrene in a dish
Ninety minutes: the time it takes, in a laboratory dish, for polystyrene microplastics to degrade a semen sample. Motility falls. Viability falls. Reactive oxygen species climb, oxidative stress rises, and the DNA inside the sperm fragments.
At 500 nanometers, the effects sharpen. Motility drops. The mitochondria that power the sperm’s movement lose membrane potential. DNA damage increases. In mice, offspring of males exposed to the particles showed altered embryonic development from the very first days.
These experiments demonstrate a mechanism with a basis in biology. They describe a situation nobody actually lives in. In a dish, sperm meets one polymer at one concentration for one measured span of time. A body meets mixtures of polymers, plus the additives inside them, plus metals, plus pollutants, across decades, at doses nobody can measure.
The IVF studies: where the association disappears
Evidence for this comes from fifty-one couples going through in vitro fertilization, whose reproductive fluids were measured for polyethylene and PVC. Both polymers turned up in both partners. Higher polyethylene in the woman’s follicular fluid came with lower fertilization rates. PVC in the man’s seminal fluid came with lower sperm motility.
But then the signal disappears. Neither partner’s particle levels showed a relationship with embryo implantation or pregnancy. This gap — between what’s measured and what happens — is where the field currently stands. A measurement can shift in the lab without the outcome that actually matters shifting with it. Motility drops, fertilization dips, and the pregnancy rate holds. A sample of fifty-one couples isn’t large enough to settle the question in either direction. That is the summary of what is known.
Why semen is collected in a plastic cup
Semen is collected in a plastic container. Fertility clinics run on plastic: pipettes, filters, tubes, storage vials. Researchers looking for plastic particles in the male reproductive tract work inside an environment built from the substance under study. Particles drift in from lab air, from synthetic clothing, from gloves.
Studies control for this with procedural blanks, filtered reagents, glass and metal instruments, covered samples, and records of what technicians wore. Separating what came from the body from what joined the sample on the way to the microscope requires judgment.
The instruments disagree with each other. One technique reads particles one at a time and identifies their color, shape and chemistry. Another operates within its own size limits and misses what the first one catches. A third burns the sample and weighs the plastic-related compounds by mass, producing a figure that could mean one large particle or ten thousand small ones. The results come out in units that do not compare; particles per sample, particles per milliliter, micrograms per gram of tissue.
Detection rates across the published work range from under half of participants to all of them. Most of that spread comes from the equipment, not the men. Labs have not agreed on one protocol. Until they do, the field will keep producing findings that resist being assembled into one picture.
Sperm counts have been falling since 1973 — plastic explains some
An analysis published in 2022 pooled data from more than two hundred studies. It reported a drop in sperm concentration and total count between 1973 and 2018, with the pace of the fall increasing after 2000.
The finding has been contested on grounds of geography, of laboratory methods that changed over fifty years, and of which men volunteered to be tested and where. Some reviews accept the trend by region. None extend it to every country. Nothing in the literature attributes the drop to plastic.
Male fertility responds to age, heat, weight, smoking, alcohol, inactivity, infection, varicocele, medication, workplace chemicals, pesticides and air pollution. Plastic may be one item on that list. Nobody knows its share.
Microplastics belong to one problem; the chemicals associated with plastic belong to another. Bisphenols and phthalates migrate out of materials on their own, without attaching to any particle you can see. Their effects on the endocrine system make up a field of study on its own, with its own literature.
The Trojan horse hypothesis
A plastic particle carries a surface that reacts with its surroundings. It leaves the factory carrying plasticizers, flame retardants, pigments, stabilizers, leftover monomers. Once it enters the environment, it collects metals and organic pollutants from whatever it passes through. This is how mercury and copper reach a fragment of polypropylene recovered from a semen sample.
The particle could work as a delivery vehicle, carrying substances into places they would not otherwise reach. Or it could concentrate substances on its surface until the dose in that location grows. Environmental chemistry supports this idea. Human reproductive biology has not confirmed it. Finding a particle and a chemical in one sample does not show whether one carried the other, or whether either was released at a dose that’s relevant.
What is established, and what remains unanswered
Groups with no connection to each other, on three separate continents, have found microplastics in human semen. The particles have turned up in testicular tissue and in seminal fluid. Studies report associations with sperm concentration, count and motility. Laboratory and animal work identifies oxidative stress, mitochondrial damage, inflammation and DNA fragmentation as the likely mechanism.
Nobody has demonstrated a cause. No dose has been identified at which particles impair fertility. No clinical test exists to tell a man what his exposure means for him. Nothing shows that reducing exposure clears particles from semen or reverses changes in sperm quality. No supplement, antioxidant regimen or detox protocol has been proven to remove microplastics from the reproductive system, whatever gets sold online.
The field needs studies with more men in each group, followed over years, with exposure and semen quality measured on a schedule, and endpoints that reach past the laboratory to fertilization, implantation, pregnancy, miscarriage and live birth.
Two facts sit side by side, with nothing connecting them. Plastic particles exist in the human male reproductive environment. Whether they affect fertility is a question yet to be answered.
Matteo Mammoli
The studies behind this article
2023, Italy. EcoFoodFertility project, published in Science of the Total Environment. Semen from ten non-smoking men in Campania; Raman microspectroscopy identified sixteen pigmented microplastic fragments in six samples, measuring 2–6 micrometers.
2023, China. Thirty semen samples and six testicular samples. Polyethylene and PVC predominant in semen, polystyrene in testicular tissue. Average abundance in semen: 0.23 particles per milliliter.
2024, Jinan, China. Forty men undergoing premarital health assessments, no known occupational exposure. Microplastics in every sample, averaging two particles each, 0.72–7.02 micrometers. Eight polymers identified, polystyrene most frequent.
2024, China. Multicenter study of 113 men, published in eBioMedicine. Paired semen and urine measurements for one hundred participants across eight polymers. More than 80 percent carried three to five types. Exposure to a greater number of polymers was associated with reduced total sperm count, concentration and progressive motility; PTFE showed one of the strongest associations.
2024, testicular tissue. Published in Toxicological Sciences. Twenty-three human autopsy samples and tissue from forty-seven dogs, analyzed by pyrolysis gas chromatography–mass spectrometry. Twelve polymers in all human samples, mean total concentration 328.44 micrograms per gram, polyethylene the largest component.
2025, fertility patients. Laser direct infrared microscopy on semen from forty-five men at a fertility center. Microplastics in thirty-four samples (75.6 percent), fifteen polymer types. Men with PET showed 20.6 percent progressive motility against 34.9 percent in those without; p = 0.056.
2025, plastic tableware. Two hundred men; microplastics in 111 samples (55.5 percent), 128 particles identified — PVC 36.72 percent, polystyrene 32.03 percent, polyethylene 23.44 percent. Daily plastic tableware users showed higher particle levels. Combined with mouse and spermatogonial cell experiments.
2025, IVF couples. Published in ACS Nano. Follicular fluid and seminal plasma from 51 couples, measured by pyrolysis gas chromatography–mass spectrometry. Higher polyethylene in follicular fluid associated with lower fertilization rates; PVC in seminal plasma with reduced motility. No significant relationship with implantation or clinical pregnancy.
2025, Italy, laboratory. Human semen exposed directly to polystyrene microplastics for up to ninety minutes: reduced motility and viability, increased reactive oxygen species, oxidative stress and DNA fragmentation.
2026, Malaysia. 115 men aged 18–45, Raman microspectroscopy. Microplastics in every sample, 0.2–3.3 particles per milliliter, sizes 4–27 micrometers. Polypropylene and PET predominant. Electron microscopy showed fractured and eroded surfaces; elemental analysis detected iron, copper, mercury and titanium.
2026, combined study. Human semen analysis with laboratory and animal experiments. Microplastics in all human samples. 500-nanometer polystyrene particles impaired motility, altered mitochondrial membrane potential, increased DNA fragmentation; paternal exposure associated with changes in early embryo development in mice.
