It appears that when microplastics come into contact with blood, they facilitate the creation of potentially dangerous molecules—a process thought to be driven by the large surface area of the particles, which lowers the energy barrier for such reactions. If this occurs within the human body, it could explain the link between microplastics, cellular damage, and various other health issues. The findings of this new study have been published in the journal Nature.
Recent research has identified a connection between microplastics—which form as plastic products break down in the environment—and health problems such as cognitive decline and cardiovascular disease. According to Wei Min of Columbia University in New York, this is likely due to the production of destructive molecules known as reactive oxygen species (ROS). By reacting with other molecules inside cells, these species can trigger inflammatory processes and other forms of cellular dysfunction.
Until now, however, it remained unclear to what extent common types of plastic could cause such issues. Since these materials do not always contain oxygen, they are not typically considered chemically reactive. “From a purely chemical standpoint, they should be inert,” Min notes.
To investigate this, Min and his colleagues examined microparticles of several widely used plastics—including polystyrene, polyethylene, and polypropylene—and discovered that water plays a key role in the process.
Using techniques such as fluorescence microscopy and electron paramagnetic resonance (EPR) spectroscopy, the researchers demonstrated that reactive oxygen species—specifically hydroxyl radicals—form spontaneously at the interface between the plastic and the water. As a result, the water ceases to be “ordinary water,” the scientist explains.
The team also determined that this effect is linked to the emergence of electrical charges at the interface between the plastic and the water. These charges can facilitate the stripping of electrons from hydroxide ions (OH⁻) in the water, leading to the formation of highly reactive hydroxyl radicals, says Min.
Experiments revealed that the resulting electrical charge attracts biological molecules—such as DNA—to the surface of microplastic particles suspended in the water; this appears to cause damage to proteins and red blood cells.
The researchers also tested whether hydroxyl radicals are generated when microparticles are placed in blood serum. The effect was weaker, but “still detectable,” Min notes. It is worth noting that while microplastics have previously been reported in human blood, such findings could potentially be the result of sample contamination or false positives. If microplastics do indeed enter our bloodstream, laboratory studies suggest they could trigger cellular inflammation, as well as DNA damage and cell death—processes often driven by reactive oxygen species.
According to Min, these findings may help explain the mechanism behind the formation of these molecules, though he points out that the scale of this effect remains unclear and other mechanisms may also be involved. Much also depends on whether the body is capable of eliminating microplastics. “How much plastic is actually in the average person’s body?” the scientist asks. “At the moment, we have no idea.” Hao Chen of the New Jersey Institute of Technology calls these findings “very important”: while they do not provide a direct answer to the question of how dangerous microplastics are, they “serve as a starting point” for understanding how microplastics interact with cells.
Matthew Campen of the University of New Mexico describes these results as a “crucial piece” of that understanding. The surface area of microplastics likely plays a key role in their impact; the scientist notes that a plastic sphere half a centimeter in diameter can break down into a quadrillion microparticles, each 50 nanometers in size, which increases the total surface area by a factor of 100,000.
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When researchers added surface A surfactant (surface-active agent)—a chemical substance that weakens the cohesive forces between water molecules—slows down the process of radical formation. In the human body, certain lipids can act as surfactants. “Once microplastic particles enter the lungs, they immediately become surrounded by surfactants,” explains Kampen. “In most scenarios within a biological system, they would be surrounded specifically by these lipids. The key question is whether the situation worsens over time; we need to gain a precise understanding of how microplastics affect—or could potentially affect—our health, so that we can take steps to avoid such exposure.”
The findings may also assist scientists in developing safer materials, notes Min. The researchers discovered that the most hydrophobic (water-repellent) types of plastic they tested—such as polyethylene and polypropylene—exhibit a higher capacity for generating radicals compared to more hydrophilic materials, like PET (polyethylene terephthalate).
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