Microplastics have been found in human testicles, and researchers say the discovery might be linked to declining sperm counts in men, reported The Guardian.
Scientists tested 23 human testes, as well as 47 testes from pet dogs. Microplastic pollution was found in every sample.
The human testicles had been preserved so their sperm count could not be measured.
However, the sperm count in the dogs’ testes could be assessed and was lower in samples with higher contamination with PVC (polyvinyl chloride).
According to the report, sperm counts in men have been falling for decades, with chemical pollution such as pesticides implicated by many studies.
Prof Xiaozhong Yu, at the University of New Mexico in the United States, said:
In the beginning, I doubted whether microplastics could penetrate the reproductive system.
When I first received the results for dogs I was surprised. I was even more surprised when I received the results for humans.
The testes analysed were obtained from postmortems in 2016, with the men ranging in age from 16 to 88 when they died.
The dogs’ testes were obtained from veterinary practices that conducted neutering operations.
Yu said “The impact on the younger generation might be more concerning” now that there is more plastic than ever in the environment.
The study, published in the journal Toxicological Sciences, involved dissolving the tissue samples and then analysing the plastic that remained.
The human testicles had a plastic concentration almost three times higher than that found in the dog testes: 330 micrograms per gram of tissue compared with 123 micrograms.
Polyethylene, used in plastic bags and bottles, was the most common microplastic found, followed by PVC. Said Yu:
PVC can release a lot of chemicals that interfere with spermatogenesis and it contains chemicals that cause endocrine disruption.
A smaller study in China in 2023 also found microplastics in six human testes and 30 semen samples.
Recent studies in mice have reported that microplastics reduced sperm count and caused abnormalities and hormone disruptions.
Microplastics have also recently been discovered in human blood, placentas and breast milk, indicating widespread contamination of people’s bodies.
The impact on health is as yet unknown but microplastics have been shown to cause damage to human cells in the laboratory.
Microplastics are plastic pieces that measure less than five millimetres across.
Sperm count refers to the number of sperm cells in a semen sample and a low sperm count negatively affects male fertility.