Microplastics in Men's Underwear: Why Your Boxers Might Be Shedding Into Your Body

By Andrew Havill, Co-Founder & CEO of QUOR

In 2024, a team of researchers at the University of New Mexico analyzed 23 human testicular tissue samples. They found microplastics in every single one.

Not "in most of them." In every one.

The researchers didn't speculate about health implications. That wasn't the scope of the study. They were documenting that these particles had made it into an organ protected by one of the tightest biological barriers in the male body. How they got there, and what they're doing, is what the next decade of research will try to answer.

This article is about one plausible route of exposure almost nobody is discussing. The fabric you're wearing against that exact tissue for sixteen hours a day.

What Microplastics Actually Are

Microplastics are plastic particles smaller than 5 millimeters. The smaller ones, below 1 micrometer, are called nanoplastics. They come from two sources. Primary microplastics are manufactured at small size, like the microbeads once used in exfoliating scrubs. Secondary microplastics are what you get when larger plastic objects break down through friction, UV exposure, or washing.

Synthetic textiles are one of the largest sources of secondary microplastics in the environment. A single load of laundry can release hundreds of thousands of fibers. Those fibers end up in wastewater, in the ocean, in the air, and increasingly, in us.

Microplastics have now been documented in human blood, placental tissue, breast milk, the brain, the heart, the lungs, and as of the 2024 study, the testes. The research is not fringe. It's being published in mainstream peer-reviewed journals, and it's happening fast.

Where Your Underwear Fits In

Most men's underwear is some combination of polyester, nylon, and conventional elastane. All petroleum-based plastics. Polyester is PET, the same material as a plastic water bottle, spun into fiber. Nylon is a polyamide. Elastane is a polyurethane-polyurea copolymer.

When these fabrics rub against skin, they shed. When they get warm and humid, they shed. When they get washed, they shed a lot. The shedding happens at microscopic scale, so you don't see it, but it's well-documented in textile research.

Consider the environment inside a pair of briefs or boxer briefs. Warm, humid, in constant contact with tissue, worn for most of the waking day. Then washed, worn, washed again, hundreds of times over the life of the garment. Every cycle is an opportunity for fiber release.

The fabric also sits in direct contact with the scrotum, which is thin-skinned, highly vascularized tissue that sits outside the body for thermoregulatory reasons. Sperm production requires a temperature roughly 4°F below core body temperature, which is why the scrotum hangs away from the torso. That same thin, exposed skin is also more permeable than most tissue on your body.

Whether microplastics shed from synthetic underwear contribute measurably to the microplastic load now being found in testicular tissue is a study that hasn't been published yet. But given what we know about fiber shedding, tissue permeability, and where microplastics have been found, it's not a wild question. It's the obvious next one.

Why This Isn't Fearmongering

There's a version of this conversation that gets hysterical fast, and it's worth separating the signal from the noise.

The hysterical version says microplastics are poisoning you and every synthetic thing you own is a threat. That's not what the research says, and it's not useful.

The sober version says this. Microplastics are accumulating in human tissue at rates we didn't anticipate. The health implications are still being studied. Exposure is coming from many sources at once, and no single change eliminates it. But if you think about total exposure as a budget, the fabric you wear next to your skin for two-thirds of every day is a reasonable place to look.

You can't control the microplastics in your drinking water, your air, or your food packaging. You can control the ones potentially shedding from your underwear.

The Answer Is Already on the Shelf. It's Just Not in Your Drawer.

TENCEL Lyocell is the fabric that solves this cleanly, and it's the fabric QUOR is built around.

TENCEL is a branded lyocell fiber produced by Lenzing, an Austrian fiber company that has spent decades engineering this material. The raw input is eucalyptus wood from sustainably managed forests. The pulp is dissolved in a non-toxic organic solvent, spun into fiber, and 99% of that solvent is recovered and reused in a closed-loop system. The result is a cellulose fiber with almost none of the environmental or chemical baggage that plagues both synthetic production and conventional viscose processing.

A few properties matter, in order of importance.

It doesn't shed microplastics. TENCEL is cellulose. When the fiber eventually breaks down, it returns to organic matter. No persistent plastic particle left behind. For a fabric spending sixteen hours a day against reproductive tissue, this is the property that matters most.

It manages moisture better than cotton, absorbing roughly 50% more and actively wicking it away from the skin rather than holding it. It's naturally antibacterial because of how the fiber structure regulates moisture, not because of added antimicrobial chemistry. And because it moves moisture and breathes, it doesn't create the micro-insulation layer that polyester and nylon build between fabric and skin, which matters for a tissue designed to run cooler than the rest of your body.

Quality TENCEL Lyocell carries OEKO-TEX Standard 100 certification, which tests the finished fabric for regulated harmful substances. GOTS doesn't apply to TENCEL. Any brand claiming both is confused about their own supply chain.

Cotton is a plant fiber that doesn't shed microplastics, but it saturates and stays wet, degrades quickly, and comes with conventional farming's chemistry problem unless it's GOTS-certified organic. Bamboo viscose is marketed as natural but is produced through a chemically intensive process that makes the finished fabric closer to rayon than to the original plant. The FTC has penalized brands for marketing bamboo viscose as "natural bamboo."

TENCEL Lyocell is the fabric that actually does what the other two claim to do. It's more expensive to source, it requires a specific supply chain, and it requires a brand willing to build the product around the fiber rather than the other way around. That's why almost no men's underwear brand in the US leads with it.

How QUOR Built the Answer

The QUOR Performance Boxer is 95% TENCEL Lyocell and 5% BPA-free elastane through the body of the garment, which gives it the fit and recovery that pure cellulose can't provide on its own.

The inner pouch, the part of the garment that sits against the most sensitive tissue, is 100% TENCEL Lyocell with no stretch fiber at all.

The decision was deliberate. The stretch blend handles the engineering problem of fit and wear across a full day of movement. The pure TENCEL pouch handles the biological problem of what's touching reproductive tissue for sixteen hours a day. One fabric can't solve both problems well. So we used two, positioned exactly where each one makes sense.

The garment is OEKO-TEX Standard 100 certified for the fabric, BPA free, and built to the standard we'd want for ourselves.

What to Actually Do

If you take one thing from this article, make it this. The fabric pressed against your reproductive tissue for sixteen hours a day is worth a moment of deliberate choice.

Look at what you're wearing now. Check the fiber content on the label. If it's 90% polyester or nylon with some elastane, you're wearing a petroleum product against an organ that's particularly sensitive to what touches it. That doesn't make it catastrophic. It makes it worth considering.

The standards you already apply to the food you buy, the water you drink, the supplements you take, should extend here too. What you wear is an input. Treat it like one.