NEW MEXICO (KRQE) – A new study by University of New Mexico (UNM) researchers found microplastics in the testicular tissue of both humans and dogs, a discovery they say adds to growing concern about how microplastics may impact human reproductive health.

According to the paper published in the journal “Toxicological Sciences,” the research team found 12 types of microplastics in 47 canine and 23 human testes. The team was led by  Xiaozhong “John” Yu, MD, PhD, MPH, a professor at the UNM College of Nursing.

“At the beginning, I doubted whether microplastics could penetrate the reproductive system,” Yu said in an interview with UNM. “When I first received the results for dogs, I was surprised. I was even more surprised when I received the results for humans.”

Researchers decided to study human and canine tissue for a couple of reasons, one of which is that dogs live alongside people and share their environment. They also share some biological characteristics.

Researchers found that the most common plastic in both human and canine tissue was polyethylene (PE), which is used to make plastic bags and bottles. In dogs, that was followed by polyvinyl chloride (PVC), which is used in industrial, municipal, and household plumbing and many other applications.

In dogs, the average concentration of microplastics in testicular tissue was 122.63 micrograms per gram of tissue (a microgram is a millionth of a gram). In human tissue, the average concentration was 329.44 micrograms per gram – nearly three times higher than in dogs.

Matthew Campen, a regents professor at the University of New Mexico College of Pharmacy, said he was not surprised to see that Yu’s team discovered plastic in the tissue samples. Campen led a separate study that found microplastics in placenta samples.

“I think what was surprising was that the plastics that we found between the humans and the dog samples was that the dog samples were much lower than the humans,” Campen told Nexstar’s KRQE. “The level is three times as much as we saw in the placentas. So already we’re looking at a tissue that either seems to accumulate them more for whatever reason, or maybe it’s simply that the testes are older than placentas.”

Yu’s team also discovered correlations between certain types of plastic and reduced sperm count in the canine samples. Campen said more research is needed to examine how microplastics may impact sperm count.

“I think the main takeaway is that change needs to happen, and it’s not something that we can necessarily do at an individual level. We really need to change waste management, period. We need to. We absolutely need to reduce plastics use and improve recycling, but there’s bigger things that need to happen related to the generation of waste-to-energy treatment plants and taking this much more seriously than the entire planet has done to this point,” said Campen.