In a 2022 Dutch study of 22 volunteers, researchers detected plastic in 17 blood samples and reported an average concentration of 1.6 micrograms per millilitre across the cohort. The small study demonstrated that detection in blood was possible; it did not establish a population-wide average or show that particles reach every organ.
That baseline observation comes from the first study to quantify plastic in human blood, a 2022 Dutch analysis that has since been replicated, argued over, and expanded. Follow-up work has now reported detectable microplastics in the majority of participants tested across multiple countries. The particles are also being pulled out of placentas, breast milk, semen, cerebrospinal fluid, and carotid plaque.
What these concentrations actually look like
The fragments detected in blood are vanishingly small in mass but persistent in presence. An adult carries roughly five liters of blood, and the polymer fragments detected cycle through the heart every minute, traveling continuously through the circulatory system.
Laboratory and animal research proposes several routes by which sufficiently small particles might cross epithelial barriers, including transcytosis and uptake through specialised immune-sampling tissue. Those mechanisms should not be treated as proof that particles routinely cross the human gut unnoticed.
The polymers that keep showing up
The Dutch team identified five plastics in the blood samples. Polyethylene terephthalate, the PET used in almost every clear beverage bottle sold worldwide, was the most abundant by mass. Polystyrene, the base of foam cups and rigid takeaway lids, was the most frequently detected. Polyethylene, the workhorse of plastic bags and squeeze bottles, showed up in about half the donors. Poly(methyl methacrylate) and polypropylene made up the rest.
The correspondence with everyday packaging is not a coincidence. A review of human biomonitoring studies compiled by Earth Times notes that polyethylene, polypropylene, polystyrene and PET dominate detections in blood, organs and tissues because they dominate the global plastic supply.
Bottles shed PET faster when they are warm, and faster still when they are left in the sun in a hot car. Takeaway containers release polypropylene and polystyrene the moment hot food touches them. Tea bags sealed with polypropylene mesh can release substantial quantities of nanoplastic particles into boiling water.
How something that size gets into the bloodstream
The gut lining is engineered to be selective. Nutrients cross, most of the traffic does not. A nanoplastic fragment should not fit through the tight junctions between epithelial cells. But the particles do not always take that route.
Some cross by transcytosis, the process by which the gut normally samples large molecules for immune surveillance. Others hitch a ride through M cells overlying Peyer’s patches, gut-associated lymphoid tissue whose job is to sample the intestinal contents. Once past the epithelium, the fragments enter capillaries and, from there, the systemic circulation. Inhalation offers a second highway: microplastics deposited in the alveoli of the lungs can pass into pulmonary capillaries directly.
The Italian carotid study, and why it changed the tone
For most of the past decade the honest scientific answer to whether this is harmful was: we do not know yet. That answer shifted when researchers analyzed carotid artery plaque removed from patients undergoing surgery to clear dangerously narrowed neck arteries.
The researchers found plastic particles in some excised carotid plaques. During follow-up, the group with detected particles had a higher rate of heart attack, stroke or death, but the observational association does not prove that the particles caused those outcomes or quantify risk for the general population.
Correlation is not causation, and the study could not prove the plastic drove the events rather than simply marking sicker patients. But it was the first prospective clinical result to tie the presence of microplastics inside a human tissue to a measurable outcome. According to the Chicago Tribune, University of New Mexico toxicologist Matthew Campen has noted the growing body of research linking higher plastic levels to worse health outcomes.
What the particles do once they arrive
Inside cells, the fragments behave less like inert grit and more like slow-release irritants. Analysis catalogs the biological effects seen in animal and cell studies: reactive oxygen species production, mitochondrial dysfunction, pro-inflammatory signaling, disruption of the epithelial barrier, shifts in the gut microbiome, and low-grade systemic inflammation.
Some of the harm may come from the polymer itself. Some almost certainly comes from what is dissolved in it. Thousands of chemicals are added to plastics during manufacturing — plasticizers, flame retardants, UV stabilizers, colorants. Phthalates, used to make PVC flexible, are known endocrine disruptors. Bisphenols mimic estrogen. PFAS, added for grease resistance, persist in the body for years. A microplastic fragment is a delivery vehicle for a chemical cocktail that would otherwise be diluted in the environment.
The concentration in tissue is not evenly distributed. Microplastics have reached the human brain at concentrations higher than in the liver or kidney.
The measurement problem
Not every scientist agrees on the numbers. Some researchers have raised serious doubts about several high-profile detections, arguing that some of the signals attributed to plastics could be contamination from lab equipment or misidentified organic material. Plastic is so ubiquitous — in dust, in filters, in the tubing used to draw blood — that ruling out contamination is genuinely difficult.
Different laboratories use different tools. Fourier-transform infrared spectroscopy can identify polymers but struggles below about 20 microns. Raman spectroscopy sees smaller particles but is confused by fluorescence. Pyrolysis gas chromatography–mass spectrometry measures polymer mass by burning the sample and identifying the breakdown products — accurate for mass, blind to particle count.
A 2025 Medscape analysis of the field found that methodological heterogeneity prevents direct comparison between studies. Two labs sampling the same blood can report different values depending on which polymers they scan for and how they filter out background.
Where the fragments come from
The sources are mundane. Synthetic textiles shed fibers with every wash. Car tires abrade against asphalt and release rubber dust that drifts into waterways. Plastic cutting boards release tens of millions of microparticles into food during a year of chopping. Non-stick cookware sheds fluoropolymer flakes when scratched. Indoor dust in a typical home contains measurable polyethylene and polyester fibers from carpets and upholstery.
Bottled water is one of the most concentrated sources. A 2024 Columbia University study using stimulated Raman scattering microscopy found roughly 240,000 detectable plastic fragments per liter of bottled water, most of them nanoplastics small enough to enter cells directly. Heating food in plastic containers accelerates leaching. Microwaving a polypropylene container for three minutes can release over four million microparticles per square centimeter of surface area.
Plastic production doubled between 2000 and 2020 and is on track to triple by 2060. The San Francisco Estuary Institute has documented that even relatively clean bodies of water carry microplastic concentrations in the hundreds of particles per liter, which is the same water that feeds regional treatment plants supplying millions of people.
What the body does with it
Some fragments leave. Feces contain measurable microplastics in nearly every adult sampled, suggesting most of what is swallowed passes through. The particles that cross into circulation face a different fate. Nanoplastics have been recovered from the liver, spleen, and kidneys — the organs that filter blood — and from lymph nodes, where phagocytic cells sequester foreign material they cannot break down.
Human enzymes do not readily digest polymers such as polyethylene and polystyrene, but current evidence does not establish that every detected fragment accumulates rather than clears. Comparisons with asbestos or silica are hypotheses about persistence and inflammation, not evidence that the materials carry the same risk.
How the microplastics in the body affect long-term health, the BBC noted in a 2025 explainer, remains genuinely uncertain. The strongest human evidence is still the Italian cardiovascular study. Everything else — links to Alzheimer’s, Parkinson’s, impaired fertility, developmental problems in children — sits at the animal-model or epidemiological-correlation stage.
What comes next
The U.S. Department of Health and Human Services announced $144 million in April 2025 to standardize testing methods and study whether microplastics can be removed from the body. The European Food Safety Authority is drafting exposure thresholds. Researchers at the University of Helsinki reported in early 2026 that microplastics can even be detected deep inside human bones, extending the tissue list further.
Meanwhile the fragments keep arriving. Every bottle cracked open on a hot day, every takeaway lid pressed onto soup, every load of polyester laundry, every set of tires on the morning commute contributes to a background rain of polymer that finds its way into the water, the air, the food, and eventually the blood.
The first human blood sample confirmed to contain plastic was drawn in 2021. The child born today will spend an entire lifetime with a bloodstream that has never been polymer-free, and the polymers riding along will be the same ones molded, four decades earlier, into the shapes of bottles and clamshells and lids that were used once and thrown away.
Correction, September 20, 2026: The headline and body were revised to attribute the blood concentration to the small 2022 study and to distinguish detection and association from proven accumulation or harm.