Research reveals microplastics present in all testicles studied

Microplastics might sound like a ‘80s cartoon series based on a set of action figures — but the reality is significantly less fun. A recent study attracted worldwide headlines when researchers found the presence of microplastics in every testicle they studied. Microplastics might impact male fertility, experts warn, and could be a reason why global sperm counts have declined 50% in the last 40 years.

Key takeaways

Microplastics are tiny particles of plastic less than five millimeters in size. Nanoplastics, an even tinier form of microplastics, can infiltrate cells.
Scientists are increasingly concerned about the effect microplastics may have on human health, including male fertility. A recent study found microplastics in every testicle examined, including endocrine-disrupting plastics PE, PVC, and PET.
Microplastics could affect male fertility by disrupting the endocrine system, which is responsible for producing and regulating hormones like testosterone.

What are microplastics?

Microplastics are tiny particles of plastic less than five millimeters in size. Primary microplastics are designed to be small (think the microbeads in cosmetic products), while secondary microplastics are produced when larger pieces of plastic degrade.

Microplastics smaller than 1 micrometer, also known as nanoplastics, are particularly concerning to scientists because they can infiltrate cells. Microplastics have been detected throughout the human body, including in the saliva, blood liver, kidneys, placenta — and, in recent studies, the testicles.

Because plastic has become so ubiquitous in modern life, microplastics are found just about everywhere — in dust, trash, fabrics, personal care products, water, air, soil, and food. They can take hundreds or thousands of years to decompose.

Chemicals found in microplastics

Plastics are composed of large molecules called polymers. Polymers are chemical compounds that are bound together in long, repeating chains. Polymers can be natural — wool, cotton, and wood are polymers — or synthetic. Plastics came about in the early 20th century when chemists found they could engineer polymers to have certain properties, such as strength and moldability.

Common polymers found in microplastics include polyethylene, PVC, PET, and polycarbonates. These polymers contain endocrine-disrupting chemicals or EDCs, which can interfere with hormones like testosterone. Experts believe EDC exposure is the primary reason behind the worldwide 50% drop in male fertility.

Polyethylene (PE)

The most widely used plastic in the world, PE is commonly used for packaging, plastic bags, children’s toys, and many other consumer products.
PE contains phthalates, chemical compounds designed to make plastics more durable. Phthalates are known to act as endocrine disruptors.

Polyvinyl chloride (PVC)

Most notably used in plumbing and construction (such as PVC pipes or vinyl plank flooring), PVC can also be found in clothing, shower curtains, and inflatable products.
PVC is known to emit phthalates. When burned or landfilled, it has been found to release dioxins, a toxin linked to fertility problems. Long-term exposure to PVC can also increase cancer risk.

Polyethylene terephthalate (PET)

PET is the chemical name for polyester. Nearly ubiquitous in clothing — from underwear to overcoats — PET is also used to make containers that hold beverages, food, and personal care and household items. Your soda or water bottle is probably made from PET.

Research has determined that PET bottles leach endocrine disruptors into their contents. One study found PET-bottled water caused estrogenic activity.¹

Polycarbonate plastics (PC)

PC is commonly used in baby bottles, refillable water bottles, sippy cups, and many other food and drink containers. It is also found in eyeglass lenses, compact discs, dental sealants, and plastic dinnerware.

Polycarbonate plastics typically contain bisphenol A or S (BPA or BPS), both of which are known endocrine disrupting substances.

How humans ingest microplastics

We eat, drink, and inhale microplastics every day. Research suggests we consume more than 100,000 microplastic particles a year. That’s about 5 grams, or the weight of a credit card, each week.²

The most common source of microplastic exposure is through our food:

Drinking water (either bottled or unfiltered tap).
Seafood that has accumulated microplastics from the water.
Food and beverages that have absorbed plastic chemicals from their packaging, such as plastic bags, wrappers, or bottles.
Heating or cutting plastic items during cooking. A 2023 study found that plastic cutting boards release significant quantities of microplastics into food.³ In another study, researchers found microwaving just one square centimeter of plastic for three minutes released 4.22 million microplastic and 2.11 billion nanoplastic particles.⁴

We may also be exposed to microplastics elsewhere in the home, such as:

By opening plastic packaging.⁵
When synthetic fibers in clothes, textiles or furniture degrade, releasing microplastics into the air and settling into dust. “Microfibers which shed from textiles are the main contributor to micropollution,” one study found.⁶
From personal care products like cosmetics.
From vehicle tires.

Study finds microplastic presence in all human and canine testicular tissue

In the aforementioned study that went viral in spring 2024, university researchers in New Mexico looked at testicular samples from 47 humans and 28 dogs.⁷ (Dogs are considered “sentinel animals” — animals that can be studied to understand risks to human health — because they’re exposed to many of the same environmental factors as humans.)

The scientists measured the amount of microplastics in testicular samples by dissolving the biological tissue and observing the solids that were left. About 75% of what remained was plastic. Ultimately, microplastics were found in every sample studied — 12 types of microplastics in all, including PE, PVC, PET, and PC.

This is not the first study to find something similar. In 2023, a small study in China found evidence of microplastics in semen as well as the testicles.⁸ In that research, polystyrene (the chemical in Styrofoam), PE, and PVC were the most common polymers found in the samples studied.

How do microplastics get to the testicles?

Experts know microplastics — and especially nanoplastics — can move around the body through the bloodstream. But exactly how they get into specific organs is unclear, researchers say.

In terms of the testicles, microplastics might “hitchhike” through the gut via tiny fat particles that are metabolized and spread throughout the body, suggests Dr. Matthew Campen, a professor focusing on pollutants and toxicants at the UNM College of Pharmacy.⁹

How microplastics may impact male fertility

In general, microplastics’ impact on male fertility is an under-studied area. A 2023 paper called evidence of reproductive health damage from microplastics “lacking.”⁸

But it’s not a wild extrapolation to suggest microplastics could cause reproductive harm. Several studies have found that exposure to other endocrine disruptors in plastic, such as phthalates, can negatively affect sperm quality.¹⁰

In a 2024 mini-review of studies, researchers found that exposure to BPA, found in microplastics, can cause damage to the blood-testis barrier, testis dysfunction, defects in sperm and semen quality, altered gene expression, and immunological responses that may negatively affect the male reproductive system.¹¹

In another 2024 review, scientists found that “exposure to bisphenols can lead to adverse effects on male fertility, including declined semen quality, altered reproductive hormone levels, and adverse reproductive outcomes.”¹²

In the New Mexico study, researchers noted a correlation between the presence of microplastics and lower testicular weight.⁷ Testicular weight may decrease due to a loss of germ cells used to make sperm, among other reasons — none of which are positive for fertility.

The research team also found that the presence of PVC in the canine testicles was correlated with lower sperm count. They didn’t analyze sperm count in the human samples.⁷ This suggests that the chemicals in microplastics could have a wide-ranging impact on sperm production and male fertility.

Learn more about endocrine-disrupting chemicals and male fertility.

Can you test your testes or semen for microplastics?

Unfortunately, no test is available for you to test your own semen for microplastics — it’s still relatively advanced lab work. There are urinalysis tests that can detect common chemical compounds found in plastic, such as bisphenols and phthalates, but those tests can’t tell you where the microplastics live in your body.

The best way to understand if your sperm production is at risk is with a semen analysis. In this simple test, a lab scientist examines a sample of your semen to assess your sperm count and the overall health of your sperm. While a semen analysis can’t detect specific microplastics, it can give you a holistic picture of your fertility health.

For now, if you’re wondering if you’re microplastic-free, the odds are: almost certainly not. The founder of the plastic urinalysis told Time that BPA is found in over 90% of individuals tested.¹³“These chemicals are everywhere,” concluded pediatrician and plastics researcher Dr. Christos Symeonides.¹³