- Multiple factors contribute to infertility, including environmental factors.
- Researchers are seeking to understand how various components of the environment impact male fertility.
- A recent study confirmed the presence of microplastics in dog and human testes. Further analysis of dog tissue suggests microplastics may impact sperm count and testis weight.
Male infertility continues to be a worldwide problem, but it is not always clear what factors contribute to it.
Due to increasing evidence that microplastics have found their way into different biological systems, from blood to lungs, researchers have become interested in identifying and understanding the potential impact of microplastics on reproductive systems, as well.
A study recently published in Toxicological Sciences has examined microplastics and their presence in male reproductive organs.
Researchers identified 12 different microplastic types in dog and human testis samples. In dogs, researchers found that higher amounts of certain microplastics were associated with reduced sperm counts and testis weight.
As research moves forward, experts hope to better understand how the presence of microplastics may contribute to declines in male fertility.
There are many potential causes of male infertility, including endocrine disorders, genetics, and even certain medications. Exposure to environmental toxins can also cause male infertility.
Male infertility can be a significant struggle and can take a particularly heavy psychological toll.
James A. Kashanian, MD, director of Male Sexual Health in the Department of Urology at Weill Cornell Medicine, not involved in the current research, noted the following to Medical News Today:
“Male factor infertility is thought to contribute to 50% of all infertility cases and be the sole cause of a couple’s infertility in 20-30% of cases. Unlike women who are rendered infertile during menopause there is no cutoff age range for a man to be rendered infertile or unable to conceive naturally. With that said, there are age related changes in men that occur as men age. Similarly, various medical problems, illicit drugs, medications, and environmental exposures can affect male reproductive hormones, sperm counts and sperm quality. Some of these risk factors can be reversed but others can have long lasting effects, like certain gonadotoxic chemotherapy.”
There are times when doctors have no idea what is causing male infertility, making it even more challenging to decide the best course of action. In recent decades, there has also been a noted decline in sperm counts worldwide.
Experts are interested in addressing how the environment impacts male fertility and what changes can potentially lead to better fertility rates.
The researchers behind the current study wanted to understand more about the relationship between microplastics and male reproductive systems.
They looked at testis tissues from dogs and men. They obtained canine testis tissues from routine dog neuter surgeries and anonymized samples from men via the New Mexico Office of the Medical Investigator. Altogether, the research included samples from 47 dogs and 23 men.
Researchers identified 12 different microplastic types in the dog and human testis samples. They found that the amount of microplastics in men was about three times higher than in dog reproductive tissue.
Among humans and dogs, the most common type of polymer was polyethylene (PE), and the second most common was polyvinyl chloride (PVC).
PE is commonly used in packaging, water supply systems, and agricultural films. PVC is also very common, used in construction, medical equipment, packaging, and insulation for electronics.
Tracey Woodruff, PhD, professor and director of Environmental Research and Translation for Health (EaRTH) Center at the University of California, San Francisco, also not involved in the study, explained to MNT that:
“This study evaluates the types of plastics found in the testis, and it is not surprising that PE is the most common – because PE is the most commonly produced plastic – it is used in plastic bags, bottles, food containers, carpet films, etc. Bottom line – if it is being produced then there is a good chance some of it is ending up in us and our pets. As for health effects – this adds further evidence to our work showing that MPs [microplastics] are suspected to adversely affect the male reproductive system.”
Researchers were able to examine the dog tissue samples further to determine more about how the presence of microplastics influenced fertility.
The results suggested that certain microplastic types were associated with decreases in sperm count and declines in testis weight.
These results reached a level of statistical significance in the analysis.
One microplastic type was associated with an increase in sperm count, and two were associated with an increase in testis weight. However, these results were not statistically significant.
Interestingly, researchers did not find an association between PE and the observed properties, though PVC was associated with decreases in testis weight. Thus, it is possible that microplastics negatively affect male fertility, but more research is required.
In Kashanain’s opinion:
“The current study highlights how environmental factors, ubiquitous in western civilization, can penetrate the testicle and semen. Higher levels of these microplastics can potentially cause deleterious effects on testicular function, ie testosterone production and sperm production. Unfortunately, many environmental factors, like those studied in this article, accumulate over decades and are not easily reversed.”
Overall, this study adds to what we know about the presence of microplastics in the human body. However, more research is required to understand the full impact of microplastics on reproduction.
Since the research that focused on fertility used data from dogs, more research is needed to see how this corresponds to people.
The study also has a number of other limitations. First, it looked at a relatively small number of tissue samples obtained from one area of the United States. Further research examining even more samples from a more comprehensive data pool may be helpful.
Second, the human tissue samples were from 2016, which could have impacted the results. Researchers also acknowledge that the humans from which samples came typically did not experience natural deaths, so experts cannot broaden the results to an entire population.
Their approach to analyzing tissue samples also requires further refinement, and researchers presumed that some smaller nanoparticles could have been lost in ultracentrifugation. Furthermore, the study could not account for certain factors that could have impacted the amount and types of microplastics they observed.
Finally, the results cannot establish causality.
Ultimately, the study authors noted that their research “highlights the need to determine the dose-response effects of these microplastics and to conduct mechanistic studies on the reproductive system.”
