Microplastics: The Invisible Pollutant

Toss a plastic bottle into a river and it never really leaves. It simply breaks apart, again and again, until the pieces shrink below five millimetres across, roughly the width of a grain of rice. At that point scientists give them a name: microplastics. The unsettling part is where they keep turning up. Researchers have pulled them from the deepest ocean trenches, prised them out of Arctic sea ice, traced them in the air of busy cities, and found them circulating in human blood.

They reach us by two routes. Some are made small on purpose. The tiny beads that once roughened our face scrubs and toothpaste were manufactured at that size, and these are known as primary microplastics. The rest, called secondary microplastics, are the wreckage of bigger things, the bottles, carrier bags, and clothing fibres that sunlight, wind, and water slowly grind down. Our wardrobes turn out to be a surprising offender: a single spin of a fleece jacket in the washing machine can shed hundreds of thousands of plastic fibres straight into the wastewater.

More than anywhere else, this debris ends up at sea. Ocean currents sweep the particles together into enormous garbage patches that drift far from any coastline. Sea creatures of every size, from specks of zooplankton to vast whales, swallow the fragments, often mistaking them for a meal. From there the plastic climbs the food chain, growing more concentrated at each step in a process called biomagnification, until it reaches the fish and shellfish that land on our own plates.

What all of this does to the human body is still an open question, and the early answers are not reassuring. Microplastics have already been found in lung tissue, in the liver, and even in the placentas of unborn babies. In the laboratory, at heavy doses, some of these particles and the chemical additives baked into them can throw hormones off balance and stir up inflammation. Researchers are quick to add a caveat, though: the amounts showing up in human tissue so far sit well below the levels used in those experiments.

Governments have responded in fits and starts. A number of countries, the United Kingdom and the United States among them, have outlawed microbeads in cosmetics. Yet those beads were only ever a sliver of the total problem. Tougher measures, such as forcing washing machines to carry built-in filters or setting new standards for synthetic fabric, have crawled along far more slowly.

A growing number of researchers say the real fix lies further upstream, in how we make and dispose of plastic in the first place. Until far less of it escapes into the world to begin with, scrubbing the planet clean of what is already out there will stay a task close to impossible.