I

A size word, not a material.

Plastic is a family, not a substance. Polyethylene, polypropylene, polyethylene terephthalate, polystyrene, polyvinyl chloride and polyamide behave differently, are made differently and are used for different things. The word microplastic says nothing about which of them is in front of you. It says only that the piece is small.

The five millimeter ceiling is close to the width of a pencil eraser. It was proposed partly because it reflects what marine animals can swallow, not because the chemistry of a polymer changes at that point. Researchers have said so plainly for years, and several have argued that if the particles had been called broken plastics instead, the definition would never have become so contested.

Below the ceiling, the ladder continues. Particles under one micrometer are usually called nanoplastics, although some groups reserve that word for anything under one hundred nanometers. A micrometer is a thousandth of a millimeter. A nanometer is a millionth. At that scale the particle is far too small to see, and the instruments needed to find it are different from the ones used for the pieces above.

All of which makes a plain guide harder to write than it should be, and makes the table below the most useful thing on this page.

II

Made small, or made smaller.

The second division in the literature is about origin, and it is the one that explains most of the sources.

Primary microplastics enter the environment already small. Production pellets, the beads once added to cosmetics, and the fibers that leave a synthetic garment in the wash all start at that size and never had a larger life. Nothing had to break for them to exist.

Secondary microplastics are the remains of something bigger. Sun, heat, waves and abrasion work on a bottle, a bag, a rope or a paint layer until it fragments, and the fragments fragment again. There is no natural end point to that process, only smaller pieces, which is why the same object can be counted as a macroplastic one decade and as thousands of microplastics the next.

The distinction matters for policy more than for chemistry. A ban on added microbeads reaches only the first category. Waste collection reaches mainly the second. Neither reaches tires.

III

Laundry, tires, and road dust.

The most cited global accounting of primary microplastics remains the 2017 assessment published by the International Union for Conservation of Nature, which estimated around 1.5 million metric tons released to the oceans each year, somewhere between 15 and 31 percent of all ocean plastics.

Its ranking surprised most readers at the time. The laundering of synthetic textiles accounted for roughly 35 percent of the total. Tire abrasion while driving accounted for about 28 percent. City dust, a mixed category that includes the wear of footwear soles, artificial turf and building coatings, made up about 24 percent. Personal care products, the category that had drawn the legislation, accounted for 2 percent.

Two further findings from that report are worth carrying. The great majority of releases, around 98 percent, begin on land rather than at sea, and reach water by road runoff, wastewater and wind. And the leading source shifts by region: synthetic textiles dominate in Asia, tires dominate across the Americas and Europe.

These are modeled estimates built on assumptions that the authors set out openly, and other groups have published different central figures. The ordering, textiles and tires ahead of everything else, has proved durable.

IV

The instrument sets the number.

A particle has to be found before it can be counted, and it has to be identified as plastic before it counts as one. Those are two separate problems, and each method solves them differently.

Infrared spectroscopy and Raman spectroscopy read the light a particle absorbs or scatters and match the pattern against a library of polymers. Infrared is the workhorse for larger pieces. Raman reaches smaller ones. Pyrolysis gas chromatography with mass spectrometry takes a different route: it heats the sample, reads the decomposition products and reports a mass rather than a count, which is why its results cannot be compared directly with a particle tally.

The 2024 bottled water study that drew so much attention used a newer approach again, stimulated Raman scattering microscopy, which brought the detection limit down to around 100 nanometers. Nothing about the water had changed. The window through which it was examined had.

Two practical constraints sit behind all of this. Plastic is everywhere in a laboratory, so a serious study spends much of its effort on blank controls to keep the analyst's own clothing out of the result. And both the EPA and the National Institute of Standards and Technology have stated that no single technique covers the full range, and that standardized methods for collection, extraction and identification are still being built.

V

Two numbers worth understanding.

The first is 240,000. In January 2024, researchers at Columbia and Rutgers published in the Proceedings of the National Academy of Sciences an average of roughly 240,000 detectable plastic fragments per liter across three bottled water brands sold in the United States, with a range of about 110,000 to 370,000. Around 90 percent were nanoplastics rather than microplastics. A widely quoted 2018 study of bottled water had reported an average of 325 particles per liter, and the gap between the two figures is mostly a gap between instruments.

The second is five grams a week, the credit card. It comes from a 2019 analysis carried out at the University of Newcastle and commissioned by WWF, which combined more than fifty earlier studies and estimated a global average intake of about 2,000 particles, or around five grams, each week.

That figure has since been criticized at length. The source studies used different size windows and different methods, and converting particle counts into a mass requires assumptions about shape and density that the underlying data does not supply. Later reanalyses have produced estimates orders of magnitude lower. The honest position is that the mass a person takes in each week is not currently known with any precision, and that the number which travels best is not the one best supported.

Read every figure in this field with its method attached. A count without a size window and an identification technique beside it is not really a measurement.

VI

Settled, and unsettled.

Occurrence is settled. Microplastics have been reported in fresh water, sea water, soil, air, food and, since a 2022 paper in Environment International that examined blood from 22 anonymous donors and detected polymer particles in 17 of them, in human samples as well. Polyethylene terephthalate, the polymer of drinks bottles, was the most frequently identified in that study.

What those detections mean is unsettled. The World Health Organization reviewed the drinking water evidence in 2019 and concluded that it was limited and methodologically inconsistent, that particles above 150 micrometers were unlikely to be absorbed, and that routine monitoring was not warranted on the evidence then available. It placed the development of standard methods at the top of its list of research needs. European and United Kingdom advisory bodies have reached similar conclusions about the state of the evidence, and about the analytical work still to be done.

So the field sits in an unusual place. The exposure question has moved quickly and the effect question has not, and the responsible way to read a headline is to check which of the two it is describing. Studies referenced here were conducted independently and did not involve any specific Codeage product.

On what an individual can do, the literature is thinner than the commentary around it. The measures most often described are mundane: less single use plastic in contact with hot or acidic food, ventilation and cleaning that lowers household dust, natural fibers over synthetic where the choice exists.

VII

Where this fits.

Codeage reads modern surroundings as one of the conditions a daily routine is designed around, which is why a subject like this one belongs in the library at all. It sits nearest Systemic Balance, the fourth pillar of The Longevity Code. A pillar is a location within a framework. It describes a category, not an outcome for any reader.

One thing should be said directly, because this subject attracts claims that outrun the evidence. No dietary supplement is described in the research as acting on microplastics, and nothing on this page should be read that way. Codeage does not make that claim and will not.

What a house can do is be specific about what it knows, name the limits of the evidence, and formulate around ingredients researched in their own right.