When we picture plastic pollution, most of us imagine bottles floating in the sea or a turtle caught in a fishing net. These images are disturbing, but they show only the part of the problem that we can see. Scientists are increasingly worried about something far smaller: microplastics, pieces of plastic less than five millimeters long, many of them too tiny to be seen without a microscope.
Microplastics come from two main sources. Some are manufactured small on purpose, like the tiny beads that were once added to face washes and toothpastes to scrub the skin. After research showed that these beads were washing straight into rivers and seas, several countries, including the United States and Britain, banned them. Most microplastics, however, are created when larger plastic items break apart. Sunlight, waves and friction slowly crack bottles, bags and packaging into smaller and smaller fragments. Car tires shed tiny particles as they wear down on roads, and clothes made from synthetic materials such as polyester release thousands of tiny fibers every time they are washed.
Because they are so light, microplastics travel remarkably far. They have been found inside tiny creatures living in the Mariana Trench, the deepest part of the ocean, as well as in Arctic ice and in snow near the top of Mount Everest. They are in tap water, bottled water, salt and seafood. In 2022, Dutch researchers reported finding plastic particles in the blood of most of the volunteers they tested, and other studies have detected them in human lungs.
What does this mean for our health? The honest answer is that nobody knows yet. Laboratory studies have shown that microplastics can damage cells and that some plastics contain chemicals that interfere with the body's hormones. But it is difficult to measure exactly how many particles a person takes in, and long-term studies on humans are only beginning. Scientists warn against both panic and complacency: the risk is uncertain, but the exposure is real and growing.
Since microplastics are almost impossible to remove once they are in the environment, most experts argue that the solution must start earlier. Some washing machines are now sold with filters that catch fibers before they enter the drains, and France has passed a law meant to make such filters standard in new machines. Researchers are developing tires that shed less material. Above all, reducing the amount of plastic we produce and throw away would slow the flow of new fragments into the world.
Microplastics are a reminder that plastic does not really disappear. It simply becomes smaller, until it is part of the water we drink, the food we eat and, it seems, our own bodies.