Researchers detected microplastics in human testicles. Volodymyr Zakharov/Getty Images Hide caption
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Researchers detected microplastics in human testicles.
Volodymyr Zakharov/Getty Images
Whether it's the bloodstream, the brain, or the lungs, it seems like every time scientists investigate a new corner of the human body, they discover microscopic pieces of plastic.
Male reproductive organs are no exception.
A new study published this month found that microplastics can accumulate in the testicles of humans and dogs, raising further questions about the potential health effects of these particles.
Animal studies have shown that exposure to microplastics can affect sperm quality and male fertility, but scientists are in the early stages of translating this research to human health. there is.
“Microplastics are everywhere,” said John Yoo, PhD, a toxicologist at the University of New Mexico College of Nursing and lead author of the study. “Quantifying microplastics in humans is the first step toward understanding their potential harmful effects.”
When he began his research, Yu did not expect microplastics to invade male reproductive organs so extensively, given the tight blood-tissue barrier around them. . Surprisingly, the researchers found widespread and high concentrations of microplastics in the testicles of about 24 men and nearly 50 dogs.
The findings may also be linked to the well-documented global decline in sperm counts and other issues related to male fertility, a trend that has been linked to a number of environmental and lifestyle factors, including certain endocrine-disrupting chemicals found in plastics.
This growing body of research is “compelling and should serve as a wake-up call to policymakers,” said Tracy Woodruff, director of the Center for Environmental Research and Health at the University of California, San Francisco.
What amount of plastic was in his testicles?
This is the largest study to measure the extent to which microplastics in water, food, and even the air reach the deepest parts of men's reproductive physiology.
This follows a small-scale analysis published last year by a Chinese research team that detected microplastics in about six human testicles and semen.
For the study, researchers at the University of New Mexico performed autopsies on people between the ages of 16 and 88 and collected testes from about 50 dogs that had been spayed and neutered at a local veterinary clinic.
Because dogs are deeply embedded in the human environment, they can serve as “watchdog” animals for disease and exposure to harmful chemicals. Yu also says that spermatogenesis in dogs is more similar to that in humans than in lab rats.
Rather than counting each individual microplastic particle, the researchers were able to quantify the total amount of plastic by dissolving all the biological tissue and separating the solids.
About 75% of what remained was plastic.
Polyethylene (PE) accounted for the majority. It is the most widely used plastic in the world and is used in packaging, bags, and all sorts of other products.
Matthew Kampen, who observed these tiny particles up close, describes them as “shard-like, pierced fragments” because they are “old, brittle, and fragmented.”
“We don't know what their function is in the body,” said Campen, a professor in the UNM College of Pharmacy and one of the study's authors. “Clearly, tiny, tiny particles can disrupt cell behavior.”
Polyvinyl chloride (found in PVC plumbing) has emerged as another prominent culprit, being the second most common microplastic in dog testicles. Vinyl chloride is classified as a carcinogen and long-term exposure, such as in drinking water, may increase the risk of cancer.
Additionally, Yu and his team found a correlation between reduced sperm counts and the presence of PVC in the dog's testicles (human samples could not be analyzed due to storage methods). .
There was also an association between increased PVC levels and decreased testicular weight. Something similar is seen with polyethylene terephthalate (PET), another common source of plastic, which recent research suggests may be harmful.
Woodruff said body weight, which is frequently used by regulatory agencies to assess the effects of chemicals, is a somewhat “rough” indicator of its impact on testicular health.
Influence?
Although the study comes with many caveats and doesn't prove that microplastics cause direct problems with male fertility, Yu said the results are “worrisome” and lay the groundwork for more targeted research into “the relationship between microplastic exposure and its potential effects on sperm.”
Emerging evidence suggests that microplastics may have toxic effects on reproductive health.
A 2022 California evidence review concluded that there was “suspicion” that microplastics negatively impact sperm quality and testicular health, but that soon changed from “suspicious” to “likely.” She says it may change. High quality research has been published.
“In the history of studying health problems caused by chemicals and the environment, there has been a tendency for indicators of health damage to be more prominent at first, followed by indicators that have some evidence behind them,” Woodruff says. The health hazards caused by these microplastics will continue to increase. ”
In a University of New Mexico study, the concentration of microplastics in human testes was on average three times higher than that of dogs.
Kampen said there are still many unknowns, including whether specific concentrations pose a threat to health and how this varies depending on the type of microplastic and where it accumulates in the body.
“We're just at the tip of the iceberg,” says Kampen, who has used the same technique to quantify microplastic levels in other tissues and organs.
The amount in the testicles is significantly higher than that found in the placenta, Yu said, and second only to the amount observed in the brain.
Further research is needed into how microplastics enter the testes. Kampen suspects that they “hitchhike” through the gut via tiny fat particles that are metabolized and spread throughout the body.
It is believed that the accumulation of microplastics in the testicles can affect reproductive health in a number of ways. Yu says microplastics can physically interfere with spermatogenesis, disrupt the barrier between the testicles, and act as vectors for harmful chemicals.
Dr. Sarah Krzastek, a urologist at Virginia Commonwealth University, says they can cause inflammation and cause oxidative stress, which can affect fertility down the line.
“As these environmental exposures continue to accumulate, this is probably another piece of the puzzle of what has contributed to male fertility decline over the years. What impact does that have clinically? “We don't know yet,” she says.
Richard Lee, a reproductive biologist at the University of Nottingham, said the findings were “alarming”.
“Having something unnatural like that in your testicles is not particularly good for your reproductive health,” Lee says.
In his lab, Lee found that exposure to phthalates, chemicals that leach from plastics, can reduce sperm's swimming ability and increase DNA fragmentation in the sperm heads, likely contributing to a decline in sperm quality in household dogs over the past few decades, a trend that mirrors what's been seen in humans.
Of course, testicles are just part of the male reproductive system.
Professor Lee said research is currently being conducted to show that these chemical pollutants can affect the hormonal control of reproduction at various levels in the body, including in the brain.
How to study ubiquitous substances
Dr. Shana Swan, a reproductive epidemiologist who has documented declining sperm counts worldwide, says she is concerned about the buildup of microplastics. However, it is not yet clear that finding them in the testicles rather than in other parts of the body is more concerning from a reproductive health perspective.
For example, in her research she has shown how fetal exposure to endocrine-disrupting chemicals such as phthalates affects male reproductive function and “leads to lifelong reproductive damage.” I researched what was going on.
Swan said a limitation that runs through much of the recent research on microplastics is that samples can be accidentally exposed to microplastics in the environment, and that they may not actually be present in the person's body. This means that it may lead to a distorted impression of things.
She points out that similar quality control issues existed nearly a quarter of a century ago, when scientists first began measuring phthalates in human tissue.
“I think a lot of care needs to be taken to show that this is really a beginning. This is indicative, it's important, it's preliminary,” she says.
Researchers at the University of New Mexico have developed a quality control process to ensure that samples are inadvertently exposed to as little microplastics as possible. Kampen says there is so much plastic in the human body that the amount that could potentially contaminate a sample is “trivial.”
But more broadly, the field faces some major challenges going forward, especially as it seeks to uncover stronger links between these tiny particles and poor reproductive health and disease. He admits that he does.
“A lot of the problem is that they're so ubiquitous. There's no good management anymore, right? Everyone is exposed,” he says.
