American scientists who detected microplastics in human testicles have said the discovery might be linked to declining sperm counts in men.
The researchers tested 23 human testes, as well as 47 testes from pet dogs. They found microplastic pollution in every sample, with polyethylene, used in plastic bags and bottles, being the most common, followed by PVC.
The human testicles had been preserved and 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, reports The Guardian.
The findings demonstrate a correlation but further research is needed to prove microplastics cause sperm counts to fall, wrote the study authors in the journal Toxicological Sciences.
Sperm counts in men have been falling for decades, with chemical pollution like pesticides implicated by many studies. Microplastics have also 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.
Vast amounts of plastic waste are dumped in the environment and microplastics have polluted the entire planet, from the summit of Mount Everest to the deepest oceans. People are known to consume the tiny particles via food and water as well as by breathing them in.
The particles could lodge in tissue and cause inflammation, as air pollution particles do, or chemicals in the plastics could cause harm.
Recently, doctors warned of potentially life-threatening effects after finding a substantially raised risk of stroke, heart attack and earlier death in people whose blood vessels were contaminated with microscopic plastics.
“At the beginning, I doubted whether microplastics could penetrate the reproductive system,” said Professor Xiaozhong Yu, at the University of New Mexico in the US. “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 post-mortems in 2016, with the men ranging in age from 16 to 88 when they died. “The impact on the younger generation might be more concerning now that there is more plastic than ever in the environment,” Yu said.
The study involved dissolving the tissue samples and then analysing the plastic that remained. The dogs’ testes were obtained from veterinary practices that conducted neutering operations.
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.
“PVC can release a lot of chemicals that interfere with spermatogenesis and it contains chemicals that cause endocrine disruption,” Yu said.
The human testes had been routinely collected by the New Mexico Office of the Medical Investigator and were available after a seven-year storage requirement after which the samples are usually discarded.
A smaller study last year 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.
Study details
Microplastic presence in dog and human testis and its potential association with sperm count and weights of testis and epididymis
Chelin Jamie Hu, Marcus A Garcia, Alexander Nihart, Rui Liu, Lei Yin, Natalie Adolphi, Daniel Gallego, Huining Kang, Matthew Campen, Xiaozhong Yu.
Published in Toxicological Sciences on 15 May 2024
Abstract
The ubiquitous existence of microplastics and nanoplastics raises concerns about their potential impact on the human reproductive system. Limited data exists on microplastics within the human reproductive system and their potential consequences on sperm quality. Our objectives were to quantify and characterise the prevalence and composition of microplastics within both canine and human testes and investigate potential associations with the sperm count, and weights of testis and epididymis. Using advanced sensitive Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS), we quantified 12 types of microplastics within 47 canine and 23 human testes. Data on reproductive organ weights, and sperm count in dogs were collected. Statistical analyses, including descriptive analysis, correlational analysis, and multivariate linear regression analyses were applied to investigate the association of microplastics with reproductive functions. Our study revealed the presence of microplastics in all canine and human testes, with significant inter-individual variability. Mean total microplastic levels were 122.63 µg/g in dogs and 328.44 µg/g in humans. Both humans and canines exhibit relatively similar proportions of the major polymer types, with PE being dominant. Furthermore, a negative correlation between specific polymers such as PVC and PET and the normalized weight of the testis was observed. These findings highlight the pervasive presence of microplastics in the male reproductive system in both canine and human testes, with potential consequences on male fertility.
The Guardian article – Microplastics found in every human testicle in study (Open access)
See more from MedicalBrief archives:
Microplastics in arteries increase risk of heart attack/stroke
Plastics found in placentas as US bans ‘forever chemicals’ in food wrappings
Premature birth rate may be linked to plastics – US study
Microplastics found in human blood for first time – Dutch study