A new study found that human testicles might contain plastic and that high levels of plastic might be affecting male fertility.

The study, published in Toxicological Sciences on May 15, 2024, looked at microplastic levels in both canine and human testicles.

It found that there was a "pervasive presence" of microplastics in both canine and human testicles and that there were "potential consequences on human fertility".

A lot of microplastics in testicles

A total of 12 types of microplastics were found and analysed in 47 canine and 23 human testicular samples.

The most common plastic found was polyethylene terephthalate (PET), found in plastic bags and bottles, followed by polyvinyl chloride (PVC).

The human testicles had upwards of three times more plastics than the dogs.

Mean total microplastic levels in the testicles, measured as concentrations per gram of tissue, were 122.63 µg/g in dogs and 328.44 µg/g in humans.

No clear causal link

A key caveat provided by the researchers was that there was "significant inter-individual variability" in microplastic levels.

This means that there was a large amount of variation in microplastic levels found in the testicular samples.

Moreover, since the human testicles were preserved, according to The Guardian, they could not yield sperm counts.

The degree to which the findings of this study can be generalised therefore remains circumspect.

Nevertheless, the canine testicles were used to examine potential correlations with sperm count and the weights of the testicles and epididymis, a narrow, tightly coiled tube at the back of the testes that stores sperm.

Lowered sperm counts and testis weight

The study found lowered sperm counts in canine testes that sported higher levels of PVC.

The study also found a negative correlation between specific polymers, such as PVC and PET, and the normalised weight of the testis.

That is, the higher the concentration of certain common plastics, the lighter the testis.

However, these are just correlations that do not establish a clear causal link between high microplastic levels and lowered fertility.

One of the researchers who worked on the paper told The Guardian that PVC particles can release chemicals that interfere with spermatogenesis, the process by which sperm cells are produced.

This is not the first study to postulate links between microplastic levels and fertility.

A paper published in January 2022 examined the effects of microplastic exposure on mice.

It found that exposure to microplastics caused the sperm count of male mice to be "significantly reduced", while female mice were found to have a "decreased ovary size" and "reduced pregnancy rate".

Male sperm counts have been dwindling over the past few decades.

According to another article by The Guardian, human sperm counts in the West have halved over the past 40 years for reasons that remain unclear to researchers.

Microplastics everywhere

According to the World Health Organisation, microplastics are "ubiquitous" in our environment.

Although there is no scientifically agreed-upon definition for microplastics, they generally are small plastic particles less than 5mm in length.

They can be ingested through drinking water, breathed in through the air, or even found in the food we eat.

The effects of microplastics on human health are not clear but that they are likely to do harm in high doses, according to the WHO.

A paper published in April 2022 in the Journal of Hazardous Materials posited that ingested microplastics can induce cell death in humans.

Top photo from Canva.