Spanish researchers have identified different types of plastics in seminal plasma and ovarian follicular fluid

As a consequence of decades of living in a plastic-filled society, plastic is now everywhere. Once degraded to the size of microplastics (particles smaller than five millimeters), plastic has reached the Arctic, the Mariana Trench, the Himalayas, the atmosphere, our food, and even our bodies. Now, Spanish researchers have confirmed that it has also made its way into human reproductive fluids: where the egg develops and in semen. They were able to identify up to a dozen different types of plastic, albeit in low concentrations. It is still not known what impact they might have on sperm or oocytes and their ability to create life.

Researchers and doctors from the University of Murcia and the assisted reproduction clinics Next Fertility analyzed seminal plasma samples from 22 donors and follicular fluid from 29 women undergoing fertility treatment. The results of this work were presented by the study’s lead author, Spanish researcher Emilio Gómez Sánchez, at the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE), held in Paris.

Microplastics were found in 69% of the follicular fluid samples — the fluid where oocytes, future eggs, develop. In the case of semen, the percentage drops to 55%. Seminal plasma, aside from being the transport medium for sperm, also keeps them alive. The difference could be due to the small sample size. However, Dr. Gómez, lab director at Next Fertility Murcia, notes another possible explanation: “Women undergoing in vitro fertilization receive hormonal treatment that increases ovarian vascularization, which means greater blood flow.” The three entry routes of these plastic particles into the body — inhaled, ingested, or through the skin — all end up in the same place: the bloodstream.

The microplastics were characterized by the team led by Professor Pilar Viñas, head of the Analytical Chemistry Department at the University of Murcia. Using direct laser infrared microscopy, they detected nine types of plastic materials, though their distribution varied between the seminal plasma and follicular fluid samples. “In both groups, various commonly used microplastic polymers were identified, such as polytetrafluoroethylene (PTFE), polystyrene (PS), polyethylene terephthalate (PET), polyamide (PA), and polyurethane (PU),” Viñas explained.

The concentration was very low — sometimes just two or three particles per sample. “It’s not known how microplastics got into biological fluids, although their concentration is much smaller than that of non-plastic particles like carbonate,” says Viñas. Even so, one sample contained up to 38 particles of Teflon (PTFE). The smallest particle size detected was 20 microns (0.02 millimeters). Nanoplastics — which are even smaller — are only now starting to be studied in humans. It remains to be seen whether they are also present in biological fluids.

In the book Espermageddon, author Niels Christian Geelmuyden compiles several studies on the impact of microplastics on the reproductive system. One such study shows how oysters exposed to polystyrene “produce fewer eggs and less mobile sperm.” But no studies yet exist on how they affect the human reproductive system. Dr. Gómez also points out that in laboratory animal studies, “they are given plastic to drink or eat in very high concentrations.” While these are suspicions and not confirmed facts, Gómez notes, microplastics could potentially have inflammatory and oxidative effects, possibly affecting “sperm count or oocyte development.” That’s why he believes it’s essential to expand research in this area.

The few studies that have linked the presence of microplastics in the human body with health have found worrying results. For instance, patients with microscopic plastics in their arteries have a 4.5 times higher risk of heart attack, stroke, and death. Microplastics have been observed to concentrate in the bloodstream and brain — but also in breast milk, the liver, and intestines. Some studies suggest they could damage DNA, though their long-term effects remain unknown. Gómez emphasizes that they did not detect alterations in sperm motility or oocyte viability in this study, but the sample was small and preliminary, and he believes it is urgent to broaden the scope of such research.

Professor Fay Couceiro, an Environmental Pollution expert and head of the Microplastics Research Group at the University of Portsmouth in the U.K., says that “considering the global decline in fertility rates, analyzing the possible causes is highly relevant and timely.” Speaking to the specialist site SMC, she added: “Finding microplastics is not that surprising, since we have found them in many other parts of our bodies.”

Couceiro concluded by echoing the study authors: “Presence is not the same as impact, and the authors are clear in stating that, while they have found microplastics in the reproductive fluids of men and women, we still do not know how they affect us.”

Dr. Stephanie Wright, associate professor of environmental toxicology at Imperial College London, also speaking to SMC, points out that microplastics are everywhere, “including in the laboratory” — suggesting potential sample contamination as a possible explanation. In her view, “the data provided do not support their presence as a result of human exposure rather than a methodological artifact, so they should be interpreted with caution at this early stage.” However, to rule out and control this risk, the researchers also analyzed the containers for all 51 samples — and found no microplastics in them.