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From John Ray's shorter notes
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May 25, 2024
Cancer-causing microplastics are found in 100% of men's testicles in new study
The appropriate response to this finding is "so what"? The presence of the microparticles seems beyond argument. It is the added term "cancer causing" which is the problem. It is little more than journalistic licence. Evidence for the claim is very thin on the ground.
The main ill effect of the particles pointed to below is its alleged link to lowered sperm counts. Problem: It is doubtful that there has been any lowering of sperm counts
The sperm count furore was a beat-up. One of several problems with the claim is that sperm counts decline with aqe so you need to control for age in your samples and that was often not done. As a population ages, its average sperm counts will decline too. There is no known decline in young men.
I could go on in detail but a basic point is that plastics by the nature of their usage have to be very inert. They very rarely react with anything else. So if they are indeed found in human bodies they can be expected just to sit there, causing no effects of any kind. And that seems very clearly to be the case -- othwerwise we we would have many reports of them causing illess. But it is only when scientists go looking for illness that anything is found -- and even then any effects are very weak. And weak effects are notoriously not replicable so cannot be relied on for any policy response
Microplastics have been found at the top of Mount Everest, deep in the Pacific Ocean's Mariana Trench and now in men's testicles.
Researchers from the University of New Mexico found 12 types of microplastics in all 23 human testes studied.
Data has shown that sperm counts have decreased by 59 percent in the past few decades, with other culprits ranging from cell phones in pants pockets to vape pens.
'We don't want to scare people,' the study's lead author said. 'We want to scientifically provide the data and make people aware.'
The team found that the most prevalent of the 12 microplastics was a polymer material, polyethylene, used in plastic bags and bottles.
The average human concentration was 329.44 micrograms per gram of tissue — vastly more than recent studies of human blood, which came to only tens of micrograms per gram.
Microplastics, smaller than five millimeters in length, enter our bodies through plastic packaging, certain food, tap water and even the air we breathe - and have been linked to cancer and fertility issues.
'There are a lot of microplastics,' the study's lead author Dr. Xiaozhong John Yu, noted. 'We can make our own choices to better avoid exposures, change our lifestyle and change our behavior.'
Dr. Yu was inspired to spearhead the project after a colleague, a professor in the university's pharmacy college named Matthew Campen, found alarming concentrations of microplastics in human placentas.
The presence of this invisible pollution in placentas, so close to unborn children during pregnancy, Dr. Yu noted, led them both to wonder how else microplastics might be impacting reproduction.
Campen, according to Dr. Yu, asked him, 'Have you considered why there is this decline in reproductive potential more recently? There must be something new.'
Dr. Yu and his team found that the concentration of microplastics in the human male testicular tissue was significantly higher than the average Campen found in placental tissue.
For ethical reasons, anonymized human male testicular tissue had been obtained from the New Mexico Office of the Medical Investigator for the new study.
The state's coroners collect these tissue materials during autopsies and then store the material frozen for up to seven years for potential forensic purposes, before being permitted to legally dispose of it.
Preservation methods used to store the human tissue prevented the team from calculating the men's sperm counts.
To fill this gap, the study also looked at tissue from dogs, which showed that the volume of microplastics scaled directly to lower sperm counts in dogs.
'At the beginning, I doubted whether microplastics could penetrate the reproductive system,' Dr. Yu said of his research, published in the journal Toxicological Sciences,
'When I first received the results for dogs I was surprised. I was even more surprised when I received the results for humans.'
Health professionals have been worrying about declining sperm counts in men for years, although the causes appear to be related to multiple environmental factors.
One November 2022 study in the journal Human Reproduction Update, a review that tabulated data from men in 53 countries, found that mean sperm count had plummeted by 51.6 percent between 1973 and 2018 globally.
To analyze their samples, Dr. Yu and his team first chemically dissolved both the human and canine tissue of organic material, fats and proteins, leaving them only with contaminants, like the microplastics, to study.
Spinning the samples in an ultracentrifuge, yielded separated pellets of plastic that could then be identified using traditional lab methods, like mass spectrometry.
Dr. Yu explained that the presence of PVC plastic in particular was quite alarming: 'PVC can release a lot of chemicals that interfere with spermatogenesis [the creation of sperm in the testes] and it contains chemicals that cause endocrine disruption.'
Disruptions to the endocrine system have been known to cause issues with sex and reproductive hormones in humans, fish, and other species.
The health consequence of microplastics in people have gained more attention in recent years, as studies have shown the particles appearing to contribute to inflammatory bowel disease, pancreatic cancer, and Alzheimer's disease.
Amid the growing concerns about microplastics in our bodies and in the environment, 175 UN member countries have agreed to come up with a plan this year to end plastic pollution - a global plastics treaty.
Nevertheless, Dr. Yu expressed caution about jumping to worst case scenario conclusions and said he hopes more scientists will study the connections between microplastics and reproductive health.
'We have a lot of unknowns,' he said.
'We need to really look at what the potential long-term effect [could be]. Are microplastics one of the factors contributing to this decline?'
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