Every human testicle examined in new study contained microplastics

Harmful microplastics aren’t only detectable in lungs, bloodstreams, and placenta—they can be found in human testicles, as well, according to a study published in the journal Toxicological Sciences.

After obtaining 23 postmortem human testes and 47 pet dog testes from veterinary neuterings, researchers used a process called pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), heating samples to the point of decomposition. What remained was then separated and examined for the presence of microplastics using highly sensitive equipment.

The results were extremely troubling. All of the surveyed testes—canine and human—contained measurable amounts of microplastic material. Although researchers noted “significant inter-individual variability” across their sources, the human testicles averaged almost three times higher plastic concentration levels than the dogs—330 micrograms-per-gram versus 123 micrograms-per-gram. They also identified 12 separate varieties of microplastics in the testicles, with polyethylene (used to make plastic bottles and bags) being the most common.

[Related: Microplastics have officially been found in our bodies.]

“At the beginning, I doubted whether microplastics could penetrate the reproductive system,” study co-author Xiaozhong Yu said during a recent interview with The Guardian. “When I first received the results for dogs I was surprised. I was even more surprised when I received the results for humans.”

Researchers say these new findings may further support a current theory that microplastics are contributing to the global decline in overall sperm counts. PVC, for example, was also detected in the testes, and has been linked to spermatogenesis interference and endocrine issues. While the full extent of microplastics’ health effects aren’t known yet, evidence strongly indicates the particles can raise the risk of heart attacks and strokes, among other complications like tissue inflammation.

The age range for human samples came from males between the ages of 16 and 88, but the team voiced specific concerns about the younger generations, given the decades’ long rise in the amount of plastic pollution generated around the world. It’s unsettling news, but given microplastics are now found bottom of the ocean and atop Mount Everest, it probably shouldn’t be surprising that they also reside in far more personal places.