Microplastics — small things persist

Tires, textiles, paints, packaging, wastewater and food chains. Theory, formulas, worked examples and applications.

Not all of them come from a broken bottle

A microplastic is not one single type of object

The term "microplastic" groups together polymer particles of very different sizes, shapes and chemical compositions, not a single, uniform substance. Some were deliberately manufactured small from the start, such as the exfoliating microbeads that some cosmetics used to contain, now banned in many jurisdictions. But most of the microplastics circulating in the environment today were not manufactured that way: they arise from the wear and progressive fragmentation of much larger objects during normal use — tires wearing down against asphalt, paint flaking off, artificial turf fraying, textile fibers shedding when clothes are washed, industrial pellets spilled during transport — or from the later fragmentation of larger plastic waste already abandoned in the natural environment. Rain, wind, urban sewers and rivers then act as transport routes, carrying these particles from their point of origin to much more distant places, including the ocean floor and remote regions with no nearby industrial activity.

A treatment plant retains a lot, but not everything

A well-operated wastewater treatment plant does in fact retain a very high fraction of the microplastic particles that reach it dissolved in the water, through the same sedimentation and filtering processes originally designed to remove other suspended solids. But that retention is neither perfect nor final: the captured particles concentrate in the treatment's residual sludge, which then needs its own management, and a fraction of the smallest particles escapes even the best-operated treatment, especially during heavy rain events that cause the sewer system to overflow. Moreover, a household filter installed in a specific home's washing machine, however useful at that individual scale, does nothing at all to resolve the tire-particle emissions produced directly on any road's asphalt, nor the accidental loss of industrial pellets during bulk transport. Cleaning up these particles once they are already dispersed in the open ocean is, in practice, far more difficult and costly than preventing their release at the source.

What science knows today, and what it still doesn't

Microplastic particles have been detected in drinking-water samples, in a wide variety of foods, and in air samples both indoors and outdoors, confirming that human exposure to these particles is now widespread. The World Health Organization openly acknowledges that widespread exposure, but it also acknowledges major data gaps about its real consequences for human health at the concentrations and particle sizes typically found. This means it is not rigorously correct to claim it has been scientifically proven that microplastics cause any specific everyday illness, but neither is it correct to conclude, without further qualification, that their widespread presence carries no importance whatsoever. The particle's exact size, the specific type of polymer, the chemical additives incorporated during manufacturing, and the real exposure dose all decisively shape the potential risk, and the smallest particles, known as nanoplastics, are additionally especially difficult to detect and measure with the analytical techniques available today.

Acting at the source, without exaggerating or being indifferent

Reducing the use of dispersible single-use plastic, driving and braking smoothly to reduce tire wear, keeping tires at the correct pressure, keeping clothing in good condition for longer instead of replacing it frequently, washing it only when truly necessary, responsibly containing industrial pellets during their transport and handling, and improving urban stormwater management are all decisions that directly attack the problem at its source, rather than trying to solve it only at the end of the chain. While scientific research keeps advancing to better understand the real risk to human health, the health priority established for drinking water remains, based on the evidence available today, controlling well-known microbiological pathogens and chemical contaminants, not microplastics, whose relative risk is still being characterized.

Act without exaggerating

  • Reduce the use of dispersible single-use plastic; it's the easiest source to avoid at origin.
  • Drive and brake smoothly, and keep tires at the correct pressure: it directly reduces the wear that releases particles.
  • Keep clothing in good condition and wash it only when necessary, especially synthetic fabrics.
  • If you handle industrial pellets, contain them and avoid spillage during transport and handling.
  • Support improved urban stormwater management: it reduces the overflows that bypass treatment.

Don't confuse widespread exposure with proven harm

The WHO acknowledges widespread human exposure to microplastics and, at the same time, major data gaps about their real health effects. It is not rigorous to claim they cause a specific everyday illness, nor to conclude they don't matter at all. A household washing-machine filter does not solve tire emissions on the road: acting at the source matters more than any end-of-chain solution.

The numbers, with their source

Tyres and synthetic textiles, the largest source of primary microplastics

According to a landmark IUCN report, so-called "primary" microplastics — those released already small, without needing to fragment from a larger object — can account for up to 30% of all the plastic polluting the world's oceans, and in many developed countries constitute an even larger source of marine plastic pollution than larger waste that later fragments. Within those primary microplastics, vehicle tire wear alone accounts, according to the same IUCN report, for around 28% of the total, making it the second-largest individual source after synthetic textile fibers shed when washing clothes; the two sources combined explain nearly two-thirds of all primary microplastics reaching the ocean.

Source: IUCN — Invisible plastic particles from textiles and tires a major source of ocean pollution.

Detected in drinking water, food and air, but with major gaps on the real risk

The World Health Organization confirms that microplastics have been detected in drinking-water samples, food and air worldwide, but explicitly acknowledges that the scientific evidence available today still does not allow precisely quantifying the real risk to human health at typical exposure concentrations, and calls for more research before setting specific regulatory limits based on health risk.

Source: WHO — Microplastics in drinking-water.

What this table is missing

No aggregated percentage of microplastic sources replaces the specific local question: the dominant source of microplastics in a coastal city with heavy road traffic can be radically different from that of an agricultural region with intensive greenhouse plastic use, and effective solutions depend on correctly identifying the dominant source in each specific place.

Sources