Researchers from the University of New Mexico have discovered significant concentrations of microplastics in the testicular tissue of both humans and dogs, raising concerns about potential impacts on reproductive health. The findings were published in a recent paper in the journal Toxicological Sciences by a team led by Xiaozhong “John” Yu, MD, PhD, MPH, a professor at the UNM College of Nursing.
The study reported the detection of 12 types of microplastics in 47 canine and 23 human testes. "Our study revealed the presence of microplastics in all human and canine testes,” said Yu. The team also quantified the amount of microplastics present in these samples using an innovative analytical method that demonstrated correlations between certain types of plastic and reduced sperm count in dogs.
Yu, who specializes in studying environmental impacts on human reproduction, has previously identified heavy metals, pesticides, and endocrine-disrupting chemicals as factors contributing to global declines in sperm count and quality. However, a conversation with colleague Matthew Campen, PhD—a professor at UNM's College of Pharmacy who documented microplastics in human placentas—prompted Yu to consider other potential influences.
Yu designed his study using similar experimental methods to those employed by Campen's lab for placenta research. The team obtained anonymized human tissue from the New Mexico Office of the Medical Investigator and canine tissue from Albuquerque animal shelters and private veterinary clinics.
After chemically treating samples to dissolve fats and proteins, they used an ultracentrifuge to isolate plastic residues. These were then heated to 600 degrees Celsius for analysis via mass spectrometry. The average concentration of microplastics found was significantly higher in human tissue (329.44 micrograms per gram) than in canine tissue (122.63 micrograms per gram).
Yu expressed surprise at these results: “At the beginning, I doubted whether microplastics could penetrate the reproductive system. When I first received the results for dogs I was surprised. I was even more surprised when I received the results for humans.”
The most prevalent polymer found in both human and canine tissue was polyethylene (PE), commonly used in plastic bags and bottles, followed by PVC, a widely-used material in plumbing and other applications. The team found that higher levels of PVC correlated with lower sperm counts in dogs, but there was no correlation with PE concentrations.
Yu emphasized that the type of plastic could be linked to potential effects on reproduction: “PVC can release a lot of chemicals that interfere with spermatogenesis and it contains chemicals that cause endocrine disruption.”
The study compared human and canine tissues due to shared environmental exposure and biological similarities. Yu noted that dogs' spermatogenesis is closer to humans', and like humans, canine sperm counts appear to be declining.
Microplastics result from the degradation of larger plastic items due to exposure to ultraviolet radiation or landfill conditions. They are now ubiquitous in the environment as global plastic use continues to increase. Yu expressed concern about potential impacts on younger generations who have been exposed to higher levels of plastics from an early age.
While these findings indicate a need for further research into how microplastics might affect sperm production, Yu urged caution rather than panic: “We don’t want to scare people. We want to scientifically provide the data and make people aware there are a lot of microplastics. We can make our own choices to better avoid exposures, change our lifestyle and change our behavior.”
