What Are Microplastics and Why Do They Matter?

By Lowtoxgear Editorial · Updated

The term microplastics entered mainstream coverage in the mid-2010s, but the scientific concern is older. What began as research into ocean pollution has evolved into a broader investigation into how plastic particles move through ecosystems and into living organisms — including people. Understanding what microplastics are and where they come from is the starting point for making sense of that research.

For practical reduction strategies across food, water, air, and textiles, see the cornerstone How to Reduce Microplastics in Your Body: A Practical 2026 Guide. For the broader indoor-exposure context, see the Low-Tox Home: Complete Guide.

The short answer

Microplastics are plastic particles smaller than 5 millimetres in any dimension — from visible fragments down to particles invisible to the naked eye. The smallest are called nanoplastics (under 1 micrometre) and can pass through cell membranes. They come from the breakdown of larger plastic items, from manufactured microbeads, and from the shedding of synthetic textile fibres during washing. They are now found everywhere: deep ocean sediment, Arctic snow, mountain air, human bloodstream, and placental tissue. Regulatory agencies are actively studying health effects; the precautionary scientific consensus is that reducing exposure is reasonable while definitive harm thresholds are established.

Two types: primary and secondary

Microplastics are classified by their origin:

Primary microplastics are manufactured at a small size intentionally:

Synthetic textile fibres — the largest primary source by volume. Polyester, nylon, and acrylic fabrics shed microfibres during washing. These fibres are typically 1–100 micrometres in diameter and several hundred micrometres long.
Microbeads — tiny plastic spheres once used as exfoliants in cosmetics and personal care products. Most countries have now banned them from rinse-off products, but they persist in the environment from historical use.
Plastic pellets (nurdles) — the raw material used in plastic manufacturing. Spills during transport and handling release billions of pellets into waterways annually.

Secondary microplastics form when larger plastic items fragment through UV exposure, mechanical abrasion, wave action, and biological processes. A plastic bottle on a beach, a plastic bag tumbling in a river, or a car tyre on a road — all gradually break apart into smaller and smaller particles that never fully disappear.

Where they end up

Microplastics have been detected in virtually every environment studied: deep ocean sediment at 11,000 metres, Arctic sea ice, remote mountain streams, agricultural soil, tap water, bottled water, beer, table salt, honey, seafood, and air. The persistence and mobility of plastic means that once particles are released into any environment, they cycle through ecosystems indefinitely.

In humans, microplastics have been found in blood (in 77% of samples in a 2022 Dutch study), lung tissue, placental tissue, and — in a 2024 study — testicular tissue. Detection in tissue does not automatically establish harm, but it does confirm that particles are crossing biological barriers previously assumed to be more protective.

Why clothing is particularly significant

Synthetic textile fibres are estimated to account for 35% of marine microplastics by mass (IUCN, 2017 estimate — more recent estimates vary but textiles consistently rank as a top source). The mechanism is direct: washing releases fibres from fabric into the wash water. Wastewater treatment removes the majority, but not all — and the captured fibres in sewage sludge are typically spread on agricultural land, creating a separate pathway into soil and food.

Unlike other plastic sources that require years of fragmentation to produce microplastics, synthetic clothing produces them immediately, with every wash, throughout the garment's life. A single garment that lasts ten years and is washed weekly releases fibres 520 times.

For a detailed breakdown of which fabrics shed the most and why, see Do Synthetic Fabrics Shed Microplastics? and Natural Fibres vs Synthetics: Which Clothing Actually Sheds Microplastics.

What about the health effects?

The honest answer is that the health effects of microplastic exposure in humans are not yet fully established. Laboratory research shows that microplastics can trigger inflammatory responses in human cells and that they carry adsorbed chemical pollutants (pesticides, flame retardants, endocrine disruptors that bind to plastic surfaces in the environment). Studies in marine animals show tissue damage, reproductive effects, and behavioural changes at high concentrations.

What has been established for humans is tissue presence. The WHO's 2019 report on microplastics in drinking water stated that current evidence was insufficient to characterise risk at typical exposure levels, while calling for more research and improved waste management. Research published since 2019 — including the tissue-level findings — has increased the urgency of that call.

For a full review of current evidence, see Microplastics in the Human Body: What Current Research Shows. For fertility-specific research, see Microplastics and Fertility and Microplastics and Male Fertility.

What to do

Prioritise natural fibres for high-wash clothing. Wool, cotton, linen, and hemp shed particles that biodegrade rather than persist. See the natural fibre clothing collection.
Use a laundry filter or wash bag for synthetics. Guppyfriend bags and external drain filters capture 50–90% of shed fibres before they reach the sewer. See How to Reduce Microplastics from Laundry for a ranked guide and Microplastics and Washing Machines for the mechanism.
Reduce the total volume of synthetic clothing purchased. Less synthetic clothing in your wardrobe means fewer wash cycles releasing fibres.
Address indoor air and dust sources. Synthetic carpets, curtains, and bedding shed continuously into the air you breathe. See Microplastics in Indoor Air.
Apply the broader playbook. See How to Reduce Microplastics in Your Body for diet, water, air, and textile strategies combined.

What Are Microplastics and Why Do They Matter?

The short answer

Two types: primary and secondary

Where they end up

Why clothing is particularly significant

What about the health effects?

What to do

Related guides

Foundational

Clothing & laundry

Health & specific concerns

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