“It does strike me as kind of ‘eww,'” Tracey Woodruff, who directs the program on reproductive health and the environment at the University of California San Francisco, and who was not involved in the study, told Business Insider.

Woodruff isn’t exactly surprised that microplastics are showing up in testicles. They’ve already been found in our bloodstream, and in other human organs such as the liver, the heart, and the lungs. In March, a New England Journal of Medicine study even suggested microplastics lodged into blood vessels in our necks might be playing a role in heart attack and stroke risk. And microplastics had already been found in testes in one 2023 Chinese study. In fact, in a rapid, systematic review of 2,000 microplastic research papers that Woodruff did for California legislators last year, she and her team found that microplastics can harm the reproductive health of both men and women, while also upping cancer risk, and hurting lungs.

But Dr. Ranjith Ramasamy, an expert in reproductive urology, says if it’s true that microplastics are invading testicles, that’s of extra concern.

“The only two organs in the human body that are protected spaces are the testes and the brain,” he told BI. “I think we need to first study the question of how microplastics even got there in the first place.”

The testicles, like the brain, have a special blood barrier that stuff isn’t supposed to get through

Jonathan Kitchen/Getty Images

It makes sense that microplastics might flow into organs like the heart or the kidneys. Microplastics come from all kinds of things we consume and breathe in, including dust, food containers, makeup, and water bottles.

Small particles consumed through your mouth flow to your gut, then enter your bloodstream, and invade all corners of the body, from the lungs to the liver. But getting into a woman’s ovaries, which are “soaked in blood” and located inside the body should be easier than invading a man’s testicle, Ramasamy said.

“I am shocked,” he said.

To get into the brain or the testicles requires surmounting an extra tough hurdle, that special blood barrier.

Early studies (in mice) are starting to suggest that microplastics do have the capacity to penetrate the blood-brain barrier, though. And if the results of this new testicle study hold true in other labs, it would be a damning sign that the same is true for mens’ testes.

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Still, Ramasamy cautions that we need to understand much more about what’s really going on with all the microplastics in our bodies, and precisely how they are impacting our health, before we start pointing to plastic ingestion as the most important reason for fertility issues in modern-day society.

“Before we start alarming everybody saying, ‘you’re drinking too much from plastics and that’s why your fertility is going down.’ I think we just need to be a little bit cautious,” he said. “Do microplastics play a role as an environmental toxin? I 100% agree. But does it play a role by entering inside the testes and blocking sperm production? That I don’t know.”

Scientists don’t understand why microplastics are bad — but they are urging regulators to step in

Scientists know that certain chemicals inside plastic disrupt our hormones.

Chemicals like BPA are colloquially known as “hormone-disrupting” chemicals, and plastic makers are developing new ones all the time. In addition to the specific chemicals that are used to make a plastic, there may also be physical issues to worry about with plastic ingestion.

In this study, men had three times the amount of microplastic in their testicles as dogs. Does that matter? We don’t really know.

“I don’t think the amount is as important as the types that are found and the potential damage that it can cause,” Ramasamy said.

Is having plastic floating around in your bloodstream problematic because of the chemicals we’re being exposed to within it, which can include known toxins like PFAS, or does it cause issues because it’s getting stuck in places it shouldn’t be? The answer to these scientific questions is probably pretty complicated, experts say.

“What we’re seeing now is that these microplastics are a vehicle for these chemicals, which we know are toxic, and they also themselves could be toxic,” Woodruff said.

This is why she is in favor of regulating plastics much like we do air pollutants.

“We have a real opportunity here to address microplastics and plastics right now,” she said. “Plastic production is projected to triple by 2060, but we don’t have to do that — we don’t have to have more plastic.”

One thing experts agree on: you should stop microwaving your plastic

Experts BI spoke with all agreed that microwaving less plastic is a good idea.

“Drinking from it is one thing, but heating them and eating from it or drinking from it, I think it’s definitely wrong,” Ramasamy said.

The reason scientists get so bent out of shape about microwaving plastic is because when plastic gets heated up, it becomes much easier for the chemicals in the plastic to leech out and get absorbed by the body.

Certainly, Ramasamy said, environmental pollutants — including microplastics — are one reason for declining fertility.

“I always ask the question, did our parents use the amount of plastics that we do today?” he said. “The answer is absolutely not.”

Interestingly, men over the age of 55 in the new study didn’t have as much microplastic in their system as younger men did.

Even “greener” looking takeout containers these days, like cardboard boxes, are often built with a special plastic coating inside so liquid doesn’t seep out. So, try to put your food on a ceramic or glass plate or in a real bowl when you can.

Woodruff says trying to drink from fewer plastic bottles, washing your hands before you eat, and leaving your shoes at the door are all good practices for minimizing exposure too.