University of New Mexico researchers found high levels of microplastics in the testicular tissue of humans and dogs, sparking concerns about the potential impact on human reproductive health. The findings were published in the journal Toxicological Sciences and were led by Xiaozhong “John” Yu, MD, PhD, MPH, a professor at UNM College.The Journal of Nursing discovered 12 different kinds of microplastics in the testes of 47 dogs and 23 humans. Yu, a researcher involved in the study, stated that microplastics were found in all of the testes. The team also developed a new way to measure the amount of microplastics in the tissue samples. This method revealed a connection between certain types of plastic and a decrease in sperm count in the dogs. Yu, who focuses on studying the effects of environmental factors on the human reproductive system, mentioned that heavy metals, pesticides, and chemicals that disrupt the endocrine system have all been linked to a worldwide decrease in sperm count and quality.In recent years, Dr. Yu had a discussion with his colleague, Dr. Matthew Campen, about the presence of microplastics in human placentas. Dr. Campen, a professor in the UNM College of Pharmacy, pointed out the decline in reproductive potential and suggested that there might be something new causing this. Inspired by this conversation, Dr. Yu designed a study using the same experimental method as Dr. Campen’s lab in the placenta research. The team obtained anonymized human tissue from the New Mexico Office of the Medical Investigator, which collects tissue during autopsies.The researchers collected and stored canine tissue for seven years before disposing of it. The tissue was obtained from animal shelters and veterinary clinics that perform spay-neuter operations in the City of Albuquerque. The team then chemically treated the samples to remove fat and proteins, and used an ultracentrifuge to spin each sample, leaving a plastic pellet at the bottom of a tube. The plastic pellet was heated to 600 degrees Celsius in a metal cup, and gas emissions were analyzed using a mass spectrometer to determine the presence of microplastics in dogs.The concentration of testicular tissue was 122.63 micrograms per gram of tissue, with the average concentration in human tissue being 329.44 micrograms per gram, which is nearly three times higher than in dogs and significantly higher than in placental tissue, as found by Campen.
Yu expressed initial doubt about whether microplastics could penetrate the reproductive system, but was surprised by the results for dogs and even more so by the results for humans. The most prevalent polymer found in both human and canine tissue was polyethylene (PE).
The study focused on the effects of polyethylene (PE) and polyvinyl chloride (PVC) on sperm count in both dogs and humans. PE is commonly used in making plastic bags and bottles, while PVC is used in various industrial, municipal, and household plumbing applications.
Researchers were able to determine the sperm count in the canine samples, but not in the human ones due to chemical preservation. They found that higher levels of PVC in the tissue were associated with a lower sperm count, while there was no correlation with tissue concentration of PE.
Lead researcher, Yu, noted that the type of plastic used can have an impact on potential function. PVC, in particular, can release chemicals that interfere with sperm production.The study compared human and canine tissue for a couple of reasons, one being that dogs live alongside people and share their environment. They also share some biological characteristics. “Compared to rats and other animals, dogs are closer to humans,” he said. “Physically, their spermatogenesis is closer to humans and the concentration has more similarity to humans.” Canine sperm counts also seem to be dropping, he added. “We believe dogs and humans share common environmental factors that contribute to their decline.” The study also found that dog sperm has a similar concentration of chemicals that cause endocrine disruption as human sperm.
Microplastics are created when plastic is exposed to sunlight and breaks down in landfills. They can be carried by the wind or into nearby waterways, and some are so tiny that they are measured in nanometers (a billionth of a meter). Microplastics are now found everywhere in the environment, despite the fact that plastic use worldwide continues to increase. Yu pointed out that the average age of the men in the OMI autopsy samples was 35, which means they were exposed to plastics decades ago, when there was less plastic in use. “The impact on the younger generation might be more concerning,” Yu said, now that there is more plastic in the environment than ever before.”
According to Yu, the presence of microplastics in the testes has raised concerns about potential impacts on sperm production.
This discovery opens the door for further investigation into the effects of microplastics on sperm production, according to Yu. He emphasized the need for additional research, stating that there are still many uncertainties surrounding this issue. Yu also highlighted the importance of examining the potential long-term consequences and whether microplastics are a contributing factor to the decline in sperm quality.
Yu stressed the importance of not causing unnecessary alarm when sharing his findings. He clarified that the goal is to present the data in a scientific manner and raise awareness about the prevalence of microplastics. Yu encouraged individuals to make informed choices to minimize their exposure to microplastics by changing their lifestyle and behavior.
