Researchers at the University of New Mexico have found significant concentrations of microplastics in the testicular tissue of humans and dogs.
Numerous studies have found that microplastics are obliquus in the environment and can even infiltrate every organ including the brain. Nonetheless, there is limited data on microplastics within the human reproductive system and their potential consequences on sperm quality.
The scientists designed their study to quantify and characterise the prevalence and composition of microplastics within both canine and human testes and investigate potential associations with the sperm count, and weights of testis and epididymis.
The team focused on dogs as well as humans because dogs often share human’s environment, as well as some biological characteristics, the corresponding author of the study Xiaozhong Yu explained in a statement. Dogs are thus closer to humans than rats and mice usually used in microplastics testing, which may facility results comparison.
The study found 12 types of microplastics in all canine (47) and human (23) testes tested. The researchers found the most prevalent polymer in both human and canine tissue was polyethylene (PE), followed by PVC in dogs only.
The academics obtained anonymised human tissue from the New Mexico Office of the Medical Investigator, which collects tissue during autopsies and stores it for seven years before disposing of it. The canine tissue came from City of Albuquerque animal shelters and private veterinary clinics that perform spay-neutering operations.
In dogs, the average concentration of microplastics in testicular tissue was 122.63 micrograms per gram of tissue. In human tissue the average concentration was 329.44 micrograms per gram.
The team was able to count the sperm in the canine samples, but not in the human samples, which had been chemically preserved. They found that higher levels of PVC in the dog tissue correlated with a lower sperm count. There was no correlation with tissue concentration of PE, however. The scientists also observed a negative correlation between PVC and PET and the normalised weight of the testis.
“The plastic makes a difference – what type of plastic might be correlated with potential function,” Yu said. “[Plasticised] PVC can release a lot of chemicals that interfere with spermatogenesis and it contains chemicals that cause endocrine disruption.”
Going forward, the scientists said further research in needed to understand how microplastics might affect sperm production in the testes.
“We have a lot of unknowns,” said Yu. “We need to really look at what the potential long-term effect. Are microplastics one of the factors contributing to [the global] decline [in sperm count and quality]?”
The team shared its findings in ‘Microplastic presence in dog and human testis and its potential association with sperm count and weights of testis and epididymis’, recently published in Toxicological Sciences.
As scientists and the public become more informed about the potential impacts of microplastics pollution, political bodies have started to propose measures to tackle the issue. The European Union, for example, has published a set of measures aimed at reducing microplastic pollution from pellets. California has become the first US state to adopt a microplastics reduction strategy.