A 2019 study commissioned by the World Wildlife Fund estimated that the average person consumes about 5 grams of microplastics every week — roughly the weight of a credit card. While some researchers have questioned whether that number is too high, no one disputes the basic reality: plastic particles are making their way into your body, and they're showing up in places that matter.
Microplastics have been found in human blood, placental tissue, lung cells, and even in the first stool of newborns. A 2024 study found them in every single placenta tested, with concentrations ranging from 6.5 to 790 micrograms per gram of tissue. Even more concerning: placentas from preterm births contained higher concentrations than those from full-term births.
Whether you're consuming a credit card's worth of plastic every week or significantly less than that, the point is this: microplastics are everywhere, they're in you, and scientists are just beginning to understand what that means for human health — especially for the most vulnerable among us.
What Microplastics Actually Are
Microplastics are exactly what they sound like: tiny fragments of plastic, defined as anything smaller than 5 millimeters (about the size of a sesame seed). An even smaller subset, called nanoplastics, measures less than one micrometer — far narrower than a human hair. These aren't exotic substances from industrial facilities. They're breaking off from things you touch every day.
Microplastics enter the environment in two ways. Primary microplastics are manufactured small — think microbeads in face scrubs or the pre-production plastic pellets used in manufacturing. Secondary microplastics form when larger plastic items break down through exposure to sunlight, heat, and mechanical wear. Your yoga pants shed microfibers in the wash. Car tires release particles as they wear down on asphalt. That plastic cutting board in your kitchen sheds up to 50 grams of microplastic per year as you slice vegetables.
Once in the environment, these particles don't disappear. Plastic can take hundreds of years to fully degrade, and in the meantime it just keeps breaking into smaller and smaller pieces. The microplastics researchers are finding in placentas today likely originated from plastic products made 40 or 50 years ago.
The Three Pathways Into Your Body
Microplastics reach you — and your baby — through three main routes: ingestion, inhalation, and skin absorption.
Ingestion is the biggest pathway. Microplastics have been found in seafood (especially shellfish and fish), table salt, honey, sugar, chicken, bottled water, and tap water. Bottled water contains an average of 240,000 plastic particles per liter — most of them nanoplastics too small to see. Drinking water — both bottled and tap — is the single largest source of plastic ingestion.
Inhalation matters more than most people realize. Indoor air contains 1.5 times more microplastic particles than outdoor air. These come from synthetic carpets, upholstered furniture, clothing fibers, and other plastic-containing household items. Urban dwellers may inhale between 39,000 and 52,000 microplastic particles annually just from breathing indoor air.
Skin absorption is the least-studied pathway, but early research suggests that damaged or inflamed skin may allow nanoplastics to penetrate more deeply than healthy skin would.
Once ingested or inhaled, most microplastics pass through your system and are excreted. But not all of them. Particles smaller than 20 micrometers can cross biological membranes. The smallest ones — the nanoplastics — can enter cells, move into the bloodstream, and potentially reach organs throughout the body including the brain, liver, and reproductive tissues.
What Microplastics Might Be Doing
We know microplastics are in our bodies. What we don't fully know yet is what they're doing once they're there.
Animal studies and research on human cells have linked microplastic exposure to inflammation, oxidative stress, disrupted gut bacteria, immune system changes, and hormonal interference. In mice, polystyrene microplastics accumulate in the liver and promote inflammation and insulin resistance. In human intestinal cells, nanoplastics can enter cell nuclei and cause DNA damage.
Human studies are more limited, but the patterns are concerning. A study of 1,750 mother-infant pairs found associations between higher placental microplastic concentrations and reduced birth weight, shorter birth length, and smaller head circumference — with boys appearing more vulnerable than girls.
People with inflammatory bowel disease had significantly higher concentrations of microplastics in their stool than healthy individuals. Microplastics were detected in cirrhotic liver tissue at higher concentrations than in healthy liver samples. Patients with arterial plaque containing microplastics were at higher risk of heart attack, stroke, and death.
The challenge is that microplastics aren't one thing. They're a mix of different polymers (polyethylene, polypropylene, PVC, nylon), different sizes, different shapes, and different chemical additives. A particle of polyethylene from a water bottle may behave very differently in the body than a fragment of nylon from a carpet fiber.
Why Babies and Pregnant Women Are More Vulnerable
Babies face microplastic exposure from multiple directions. Microplastics cross the placenta during pregnancy, exposing the developing fetus. They've been found in breast milk, meaning nursing infants ingest them. And infants who are formula-fed from plastic bottles face additional exposure — bottle-fed babies may consume over a million microplastic particles in their first year.
The concern isn't just the volume of exposure. It's the timing. Pregnancy and early childhood are critical windows for development. The fetus and infant are building organ systems, establishing metabolic pathways, and programming long-term health. Environmental exposures during these periods can have outsized effects.
Researchers are exploring whether prenatal microplastic exposure might help explain some puzzling health trends — rising rates of preterm birth, declining sperm counts in young men, and increases in inflammatory bowel disease and early-onset colon cancer in people under 50. These are correlations, not proven causes, but they're worth investigating.
The Research Is Young, But the Direction Is Clear
Scientists don't yet have standardized methods for detecting and measuring all types of microplastics, especially the smallest nanoplastics. They don't know exactly how long microplastics stay in the body or whether some people are more genetically vulnerable than others. They can't yet say with certainty which exposure levels are safe and which aren't.
But here's what they can say: microplastic exposure is universal, it's increasing, and early evidence suggests it's not harmless. The direction of the research is consistent — microplastics have biological effects, and vulnerable populations like pregnant women and infants deserve particular attention.
The good news is that this isn't a problem you're powerless against. You can't eliminate microplastic exposure entirely — they're too ubiquitous for that — but you can significantly reduce it, especially in the places where it matters most: the products that touch your food, your water, and your baby's body every single day.