Microplastics and nanoplastics are small plastic particles resulting from the degradation of larger plastic materials or manufactured at microscopic sizes for industrial use. Microplastics are generally defined as plastic particles smaller than 5 millimeters, while nanoplastics are measured at the nanometer scale and are often invisible to conventional optical microscopy.
These particles originate from sources such as plastic packaging, synthetic textiles, tire wear, food processing equipment, and consumer products. Once released into the environment, they persist due to their resistance to natural degradation and have been detected in air, water, soil, and food systems.
In recent years, scientific studies have identified micro- and nanoplastics in human blood, lung tissue, placental tissue, and other biological samples. While research into long-term health effects is ongoing, their widespread presence has prompted increased interest in understanding exposure pathways and potential strategies for reducing contact with these materials.
Plastic does not disappear; it transforms. A bottle abandoned on the beach does not rot like driftwood or peel like bark. Unlike organic material, it will not be metabolized by microbes into soil or dissolved back into a cycle of renewal. Instead, the sun weakens its bonds until it cracks, salt and wind grind it into brittle pieces, and waves hammer it against rock. Over weeks, months and years, it splinters into smaller and smaller microplastics, smaller than five millimeters, then fragments under a millimeter, and finally nanoplastics, one hundred thousand times smaller than the width of a human hair. Once created and absorbed, these particles still persist. They are not food for bacteria or fungi; they are synthetic intruders that resist digestion in the environment just as they resist breakdown inside the human body. They simply do not disappear.
At these scales, size determines fate. It is believed that particles larger than 150 microns – the size of a grain of sand – often pass through human digestive tracts unabsorbed, but anything smaller than 20 microns can cross into tissue. When they are the size of viruses – often below 100-nanometers – they can slip through membranes, entering cells, circulating in blood, even breaching the blood–brain barrier. To appreciate scale, a 100-nanometer plastic particle is about a thousand times smaller than the width of a single human hair — small enough to slip between cells or be internalized by them. The shapes of micro- and nanoplastics are as varied as their sizes. Some are smooth spheres, others jagged shards; some long fibers, others thin films. Each shape interacts differently with ecosystems and tissues — fibers catching in lungs, films spreading across soil, jagged fragments piercing cells and blood vessels. Plastics are not one substance but a swarm of shapes and dimensions, each with its own pathways of persistence and invasion.
Each step down in size exposes more surface area, turning plastics into chemical ferries. They soak up pesticides and heavy metals, and they shed their own additives: phthalates that soften plastics into pliable toys, bisphenols like BPA that harden water bottles and receipts, flame retardants in electronics and upholstery, UV stabilizers that keep packaging clear in sunlight. These molecules were engineered to serve industry, but when released from plastics, they travel into water, soil, and human tissues. Unlike organic compounds that may degrade or metabolize, these molecules cling and accumulate everywhere including in our bodies.
In lettuce fields that stretch across the Central Coast of California, fertilizers there sold as “controlled release,” have tiny polymer-coated beads that glisten. Under the California sun and irrigation canals, those coatings flake away into soil. Even “organic” compost carries hidden burdens: fibers from laundry waste, packaging fragments from kitchens. Just like England’s Broadbalk fields, soil cores have shown microplastics accumulating like a second geologic record, year after year, so too are the farms in California, though less studied, almost certainly tend to the same legacy.
Plastics slip across geographical boundaries, and the smaller they are, the more likely they are to slip into every known crevasse, including our bodies. They climb from plankton to anchovy, from lettuce to livestock, from soil and sea to our bloodstream. Unlike organic matter, they do not decay into nutrients, and once inside bodies, they are not metabolized or excreted like food. They stay there and persist as foreign materials in our bodies, synthetic reminders of the modern age. They haunt our oceans, fields, skies, kitchens and bodies alike.