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Omnipresent in the environment, microplastics have just been discovered in testicles. This pollution could contribute to the global decline in fertility. Explanations.
They had already been found in the placenta, in babies’ stools, in breast milk, in the heart, in the bloodstream… It is now in human testicles that microplastics have been discovered. Results which are worrying regarding their possible effects on human reproductive health.
(Micro)plastic is not fantastic…
Microplastics form when plastic is exposed to ultraviolet rays from the sun and degrades in landfills. They can be blown by the wind or carried into nearby waterways, and some pieces are so small they are measured in nanometers (a billionth of a meter). They are now ubiquitous in the environment as the global use of plastics continues to grow.
Prof. Xiaozhong Yu from the University of New Mexico studies the impact of various environmental factors on the human reproductive system. He says heavy metals, pesticides and endocrine-disrupting chemicals have all been implicated in a global decline in sperm numbers and quality in recent years. But a conversation with his colleague Professor Matthew Campen, who revealed the presence of microplastics in the human placenta, led him to wonder if something else might be at work.
Levels of microplastics 3 times higher in human testicles
His team obtained de-identified human tissue from the New Mexico Office of the Medical Investigator, which collects tissue during autopsies and stores it for seven years before disposing of it. The canine tissues came from animal shelters in the city of Albuquerque and private veterinary clinics that perform sterilization operations.
Using a method combining centrifugation and mass spectrometry, the researchers found that the average concentration of microplastics in the dogs’ testicular tissue was 122.63 micrograms per gram of tissue (one microgram is one millionth of a gram). In human tissue, the average concentration was 329.44 micrograms per gram, almost three times higher than in dogs and significantly higher than the average concentration found in placental tissue.
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A possible impact on fertility
The team discovered 12 types of microplastics in 47 canine and 23 human testicles. Researchers found that the most common polymer in human and canine tissues was polyethylene (PE), which is used to make plastic bags and bottles. In dogs, next comes PVC, used in industrial, municipal and domestic plumbing, as well as many other applications.
The team was able to count sperm in the canine samples (but not in the human ones, which had been chemically preserved) and found that higher levels of PVC in the tissues correlated with lower sperm counts. However, there was no correlation with tissue PE concentration.
“PVC can release many chemicals that interfere with spermatogenesis and contains chemicals that cause endocrine disruption” said Professor Yu.
He also notes that the average age of the men in the autopsy samples used was 35, meaning their exposure to plastic began decades ago, when there was less plastic in circulation. “The impact on the younger generation may be more concerning now that there is more plastic in the environment than ever“, did he declare.
Researchers will continue their work to better understand how microplastics could affect sperm production in the testicles.
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