Researchers have found another anatomical organ where microplastics – in all forms and components – are found: human testicles.
And while they can’t say for sure, they suspect that the presence of these jagged bits and strands of polymers like polyethylene, polyvinyl chloride and polystyrene could be – in part – behind a global trend in the declining quality and quantity of sperm.
In 2022, a team of researchers published a paper showing that worldwide sperm counts fell by about 1.2% per year between 1973 and 2018. From the year 2000, that rate accelerated to more than 2.6% per year.
“What I think will get people’s attention with this study is the fact that plastic is in the testicles and could potentially contribute to disorder in the function of the testicles,” said Leonardo Trasande, a pediatrician and expert in the field public policy at New York University’s Grossman School of Science. Medicine and Wagner School of Public Service.
“What should have gotten people excited all along is the fact that we knew that the invisible chemicals — the phthalates, the bisphenols and the PFAS used in plastic materials — are already known to be problems,” he said. “And if this is what it takes to get people’s attention, I’m a little sad. Because we already had enough evidence that plastics are bad for testicular function.”
Others, including Philip Landrigan, director of the Program for Global Public Health and the Common Good at Boston College, said the study was “consistent with a slew of papers that have appeared in recent years” showing these particles in a variety of organs , including the heart, liver, lungs and brain.
“It’s no surprise that microplastics are in the testicles. The plastic is ubiquitous in today’s world, the stuff breaks down and the smaller the particle, the easier it can move in and through the human body,” he said.
Xiaozhong Yu, a professor of environmental health at the University of New Mexico – and author of this latest study – said he had been researching the effects of various chemicals on sperm production for years, and only recently did a colleague suggest that he look for microplastics in the testicles .
“I said, ‘Are you kidding?’” he said, recalling the conversation, explaining that he was pretty sure he wouldn’t find microplastics in tests because these sperm-producing factories – just like the brain – be insulated by a protective barrier.
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Still, they took the plunge.
They started trying it in the testicles of dogs. They were able to purchase 47 from sterilization clinics. (The pet owners have all given permission.)
They found microplastics in small dogs, large dogs, young dogs and old dogs. The plastic pieces were in every dog testis they examined. The amount ranged from 2.36 micrograms per gram to 485.77 micrograms per gram. The average was 122.63 micrograms per gram and 12 polymers were identified. The most common were polyethylene – the material found in plastic packaging, films and bottles – and polyvinyl chloride – a material found in most household water pipes.
He said he immediately went back to investigate their quality control. Perhaps the testicles became infected at some point during the procedure or testing?
He and his team were able to rule that out, though Landrigan noted that contamination was still possible — unless everything from purchasing to analysis was done in a “clean” space without plastic.
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Yu and his team then decided to look at human samples. Ultimately, they were able to examine 23 testicles from men aged 16 to 88. The tissue was obtained from men who had died in an accident and whose testicles had been preserved after autopsy. He said all the samples came from men who had died in 2016 and were made available after a seven-year retention period, after which such samples are usually discarded.
Once again they found microplastics in every sample they examined, and as with dog testicles, there was a wide variation – from 161.22 micrograms per gram to 695.94 micrograms per gram, with an average of 328.44 micrograms per gram – almost three times larger than what they found in dogs.
The microplastics in human testicles also consisted of a variety of polymers, with polyethylene being the most common, followed by ABS (acrylonitrile, butadiene and styrene monomers – which is used to make a variety of products including toys, automotive parts, medical equipment and consumer electronics), N66 (a type of nylon), polyvinyl chloride and others.
The researchers also noted a relationship between the concentrations of PVC and polyethylene and the weight of the testicles: the higher the concentration, the lower the weight.
“In general, reduced testicular weight is indicative of reduced spermatogenesis,” the authors wrote in the article.
Yu said the difference between polymer types in humans and dogs – with dogs showing higher concentrations of PVC than men – likely has to do with differences in lifestyle. He said consumer trends show a general aversion to eating or drinking from bottles and food items made from PVC, which contains bisphenol A – an additive linked to health and developmental harm.
However, he started looking at dog toys and noticed that many of them were made of this type of plastic.
“People choose to avoid it,” he said. But the market hasn’t changed in the same way for dogs.
When asked what the main route of exposure was for dogs and humans, he said: “Microplastics are everywhere – in the air, in the drinking water, in the food, in our clothes. We don’t know exactly what the most likely route is. But they are everywhere.”
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He also noticed variation within the groups. Testes from dogs obtained from public veterinary clinics showed higher levels of microplastics than those from private clinics, “possibly reflecting the influence of socio-economic differences on dogs’ living environment and lifestyle.”
The researchers also could not find a link between age and microplastic concentration – a finding that surprised them. (Although men over 55 had the least amount).
“The absence of a clear age-dependent accumulation of microplastics in human testes may be due to unique physiological and biological processes of spermatogenesis,” they wrote, noting the continuous renewal and release of sperm, which “increases the build-up of microplastics over the course of of time could help alleviate’. time.”
That hypothesis, they noted, was supported by the presence of microplastics in human seminal fluid.
“The reality is that the petrochemical industry has been given a pass all these years,” said Trasande, the NYU professor. “We know that plastics come from the petrochemical industry… and it is no secret that as a society we have paid by letting the petrochemical industry pollute us. Now we are paying for the consequences. And if we don’t change course quite quickly, we will have even bigger problems ahead as plastic consumption is growing and not slowing down.”
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Landrigan agreed, noting that countries were currently negotiating to sign a treaty that would restrict the use of plastic and the production of bottle caps.
“Plastic production is increasing exponentially,” he said, noting that it has increased more than 200-fold since the 1950s. He said plastic production is on track to double by 2040 and triple by 2060. A total of about 8 billion tons of plastic have been produced since 1950, he said, and about 6 billion tons “are floating around us, most of it.” in the form of microplastics.”
He said the anatomical location of this latest microplastic discovery could hit close to home for lawmakers, who so far haven’t been too concerned.
He said he had to testify in the Senate several years ago about endocrine disruptors, and said sperm count was reduced in men who had been exposed.
“Two senators sat back and unconsciously crossed their legs,” he said. “The body language was great.”
This story originally appeared in the Los Angeles Times.