Indoor environment factor · measured in particles/m³

Microplastics

Part of: Particulate matter (PM₂.₅ and PM₁₀)

Also: microplastic particles, synthetic fibres

Plastic particles below 5 mm, and the fibres shed by synthetic textiles, that occur in indoor air and settled dust. Indoor concentrations are typically higher than outdoors because the sources — clothing, furnishings, floor coverings and packaging — are inside with us.

G-0098 · Updated 6 September 2026 · Coridum Research

Why it matters indoors

The indoor environment is where most exposure happens, because most of the sources are indoor objects: synthetic clothing and bedding, upholstery, carpets, curtains, packaging and the wear of plastic surfaces. Characterisation studies of indoor environments find fibres dominating the count, and settled dust holding far more than the air at any moment. The comparison with outdoor air generally favours indoors as the larger exposure, simply because people spend most of the day there.

What is measured, and what that number means

There is no agreed method yet. Studies differ in the smallest size they can detect, in whether they count fibres and fragments together, and in whether they report particles per cubic metre of air or per gram of dust — so two papers can disagree by orders of magnitude without either being wrong. Any single number for indoor microplastics should be read together with its size cut-off and its sampling method. This is also why microplastics appear in no exposure limit anywhere: there is no agreed quantity to set a limit against.

Why the particle is not the whole exposure

Plastic particles carry the additives that were put into the plastic — plasticisers, flame retardants, stabilisers — and adsorb other substances from the surroundings. Reviews describe this as a combined exposure: the particle, the chemicals bound to it, and the surfaces it has been in contact with. Studying the particle alone therefore understates what is being inhaled or swallowed with dust.

What is not established

Health effects at indoor concentrations. The plausible pathways are inflammation from persistent particles and the transfer of the chemicals they carry; both are supported by laboratory work rather than by human evidence at real indoor levels. Anyone stating a threshold for indoor microplastics today is going beyond the literature.

What reduces it

The measures are the ordinary ones and their effect is measured on dust rather than on health: fewer synthetic textiles in the room where people sleep, wet cleaning and vacuuming that removes rather than resuspends, ventilation, and shoes off at the door.

Identifiers

MeSH
D000080545

In the literature

  1. Zhai Characterization and quantification of microplastics in indoor environments… (2023). Heliyon. doi:10.1016/j.heliyon.2023.e15901 CKB 0929
  2. A narrative review of microplastics in the indoor and outdoor environment, human effects, and ecological risks (2024). Journal of Air Pollution and Health. doi:10.18502/japh.v9i1.15082 CKB 0939
  3. Alijagic The triple exposure nexus of microplastic particles, plastic-associated chemicals, and environmental pollutants from a human health perspective (2024). doi:10.1016/j.envint.2024.108736 CKB 0946

Studies in the Coridum Knowledge Base in which this term is used. The definition follows standard usage in WHO, ISO and textbook sources; it is not quoted from these papers.

CKB = document number in the Coridum Knowledge Base, our curated library of peer-reviewed studies. Follow the DOI for the original paper.