BELOW ONE MICROMETER

What Is Nanoplastic

A nanoplastic is a plastic particle smaller than 1 µm, although some agencies put the line at 100 nm and the EU microplastics restriction sets no lower size limit. This page explains where the size lines are drawn, how nanoplastics form and why smaller particles behave more like colloids than like litter.

9 min readUpdated 2026-11-03ReviewedBWell supportedCLimitedDDisputedPProvenance

Nanoplastics on a log scale from 1 nm to 10 mm, with this site's 1 µm upper limit, the 100 nm EU/EFSA limit and a protein, virus, bacterium, red blood cell, hair and sand grain for comparison. Data: Hartmann 2019; ISO 24187; EU 2022; EPA.Nanoplastics ObservatorySite original

A nanoplastic is a piece of plastic smaller than 1 µm, one thousandth of a millimeter. This site draws the line there, following two definition papers; some agencies use 100 nm. Nothing switches on at 1 µm¹. As particles shrink, gravity matters less, molecular jostling more, and the molecules they collect steer them. Cut one 1 mm cube of plastic into 100 nm cubes and you get a trillion pieces with 10,000 times the surface (our calculation, below).

1 µm

upper size limit of nanoplastics used on this site

1 nm to <1,000 nm; proposed by Gigault et al. 2018 and Hartmann et al. 2019²^,³

a convention, not a natural boundary; graded P because it is a definition checked against the two papers

PProvenance

100 nm

upper limit in the EU nanomaterial definition (any material) and in EFSA's 2016 nanoplastic range

Commission Recommendation of 10 June 2022: at least 50% of a material's particles by number with one or more external dimensions of 1–100 nm, plus further conditions; EFSA 2016 statement on food⁴^,⁵

legal and agency texts, read in the original; the EU test classifies a material, not a single particle

PProvenance

0.1 µm

temporary enforcement floor of the EU microplastics restriction, which itself has no lower size limit

REACH Annex XVII entry 78 (Regulation (EU) 2023/2055); 0.3 µm for fiber-like particles; applies until methods can quantify smaller particles⁶^,⁷

stated in the Commission's explanatory guide, version 1.1

PProvenance

Estimate

Our calculation: a cube 1 mm on each side has a surface of 6 mm². Cut it into cubes 100 nm on each side and you get 10,000 × 10,000 × 10,000 = one trillion pieces. Each has a surface of 0.00000006 mm², so together they expose 60,000 mm², which is 10,000 times more. Mass and volume do not change. For polystyrene (about 1.05 g/cm³) the cube weighs about 1 mg.

Where the size lines are drawn

The word "microplastics" took hold after 2004, when Richard Thompson and colleagues reported microscopic plastic fragments and fibers in marine sediments and plankton, without defining the term⁸^,³. Twenty years later they call it the first publication to use the term (level P)⁹.

The upper bound came from a NOAA workshop in September 2008, whose participants "defined microplastics as plastic particles smaller than 5mm" and required no lower bound. They kept visible particles in the class on purpose, because research was at an early stage (level P)¹⁰.

No physical law fixes these lines. Hartmann and colleagues call the 5 mm limit only "somewhat biologically informed" and name classes after metric units³. This site combines two conventions: nanoplastics from 1 nm to below 1,000 nm, as in Gigault et al. and Hartmann et al., and microplastics from 1 µm to 5 mm, keeping the NOAA bound (level P)²^,³^,¹⁰.

Definitions also differ on which dimension counts. Hartmann and colleagues propose the largest one and, for fibers, ask each study to state its choice³. The EU nanomaterial test needs one external dimension in range. REACH entry 78 needs all dimensions at 5 mm or less, or a fiber-like length of 15 mm or less (level P)⁴^,⁶. This site reports the dimension a cited study used.

Who	Nanoplastic	Microplastic	Other classes	Note
This site	1 nm to <1 µm	1 µm–5 mm	none	nano limit from Gigault and Hartmann; 5 mm from NOAA
NOAA workshop, 2008¹⁰	not defined	below 5 mm	none	no lower bound required
EFSA, 2016⁵	about 1–100 nm	0.1–5,000 µm	none	food safety statement
Gigault et al., 2018²	1–1,000 nm	not defined	none	unintentionally produced, colloidal behavior
Hartmann et al., 2019³	1 to <1,000 nm	1 to <1,000 µm	mesoplastics 1 to <10 mm; macroplastics ≥ 1 cm	optional split at 100 nm; largest dimension counts
ISO 24187:2023¹¹	no class	1–1,000 µm	large microplastics 1–5 mm	taken from ISO/TR 21960:2020, modified
EU nanomaterial definition, 2022, simplified⁴	1–100 nm in at least one external dimension (any material)	not covered	none	a test of a material's number-based size distribution; see the note below the table
EU REACH entry 78, 2023⁶	no lower size limit	all dimensions ≤ 5 mm; fiber-like ≤ 15 mm long	none	"synthetic polymer microparticles": size alone does not decide scope

The EU nanomaterial row is a summary. The full definition counts particles on their own and as identifiable parts of aggregates or agglomerates. It also covers elongated particles (two dimensions below 1 nm, one above 100 nm) and plate-like ones (one below 1 nm, two above 100 nm). A material with a volume-specific surface area below 6 m²/cm³ is excluded (level P)⁴.

REACH entry 78 is narrower in substance and wider in size. Its "synthetic polymer microparticles" are solid polymers that make up at least 1% of a particle's weight or coat it; natural unmodified, degradable, soluble and carbon-free polymers are excluded. The sales ban has derogations and transition periods and does not cover particles formed unintentionally, such as packaging fragments (level P)⁶. Details are on Policy & regulation.

Entry 78 sets no lower size limit, so it can reach particles a few nanometers across. Its 0.1 µm floor (0.3 µm for fiber-like particles) is temporary and for enforcement only, until methods can quantify smaller particles (level P)⁶. And a 500 nm particle is a nanoplastic here, a microplastic for EFSA, and below every named class in ISO 24187 (level P)¹¹^,⁵.

Where nanoplastics sit on the size scale

A logarithmic scale from 1 nm to 10 mm. Nanoplastics sit below 1 µm, beside proteins, viruses and bacteria; a dashed line at 100 nm marks the EU and EFSA alternative; microplastics run from 1 µm to 5 mm, past red blood cells, sand grains and a human hair. Source:³^,²^,¹¹^,⁵^,¹⁰^,⁴^,⁶^,¹²^,¹³^,¹⁴Nanoplastics ObservatorySite original

Data table

label	value	unit	value_max	kind	source
typical soluble protein	3	nm	6	reference	S-222
bacteriophage virus	70	nm		reference	S-222
EU nanomaterial upper limit; EFSA nanoplastic upper limit	100	nm		threshold-alternative	S-213, S-009
REACH temporary enforcement floor (fiber-like 300 nm)	100	nm		threshold-regulatory	S-214
this site: nano below, micro above	1000	nm		threshold-site	S-005, S-004
E. coli bacterium (width to length)	1000	nm	2000	reference	S-222
red blood cell diameter	7000	nm	8000	reference	S-222
smallest sand grain	62500	nm		reference	S-223
human hair, average diameter	70000	nm		reference	S-231
plankton net mesh used for floating microplastics	333000	nm		reference	S-212
ISO 24187: microplastic ends, large microplastic begins	1000000	nm		threshold-iso	S-003
largest sand grain	2000000	nm		reference	S-223
upper limit of microplastics (NOAA 2008, this site, REACH)	5000000	nm		threshold-site	S-212, S-214
Hartmann et al.: mesoplastics end, macroplastics begin	10000000	nm		threshold-alternative	S-005

Shapes and polymers

Shape labels vary. Hartmann and colleagues list spheres, beads, pellets, foams, fibers, fragments, films and flakes, noting that the first three are often synonyms. They prefer "irregular particles" to "fragments", because some cosmetic abrasives are made irregular (level P)³. On this site "fragment" means only an irregular piece broken off a larger item.

Common polymers include polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET) and polyurethane (PU)¹⁵; polyamide (PA, nylon) appears in the teabag example below¹⁶. Density decides first whether a particle floats: PP and PE are lighter than water, solid PS, PVC and PET heavier (level B)¹⁷.

Tire wear particles are a borderline case. Tires usually contain 40–60% synthetic polymers, and some polymer chemists do not count rubber as plastic; Hartmann and colleagues propose including them³. Kole and colleagues compile emission estimates averaging 0.81 kg per person per year worldwide (estimate, level C)¹⁸. This site states whether a cited study counts them.

Six shape classes used on this site to sort plastic particles: fragment, fiber, film, bead, foam and pellet. Diagram; shapes are schematic and not to scale.Nanoplastics ObservatorySite original

Common plastics by density, compared with water

A dot plot of polymer densities. Polypropylene and polyethylene fall below the pure-water and seawater lines and float; polystyrene, PVC and PET lie above them and sink. Source:¹⁷^,¹⁹Nanoplastics ObservatorySite original

How this was calculated

Polymer ranges from the review table of Wu et al. 2020. Water densities are our calculation with the TEOS-10 equation of state (GSW toolbox): pure water 0.998 g/cm³ at 20 °C; seawater of absolute salinity 35 g/kg at the sea surface 1.025 g/cm³ at 20 °C, 1.023 at 25 °C and 1.028 at 0 °C.

Data table

label	value	unit	value_max	source	kind	value_min
polypropylene (PP)	0.9	g/cm³	0.91	S-221
polyethylene (PE)	0.92	g/cm³	0.97	S-221
pure water at 20 °C (reference line)	0.998	g/cm³		S-225	reference
seawater at the surface, salinity 35 g/kg: 20 °C (reference line), range from 25 °C to 0 °C	1.025	g/cm³	1.028	S-225	reference	1.023
polystyrene (PS), solid	1.04	g/cm³	1.1	S-221
polyvinyl chloride (PVC)	1.16	g/cm³	1.58	S-221
polyethylene terephthalate (PET)	1.37	g/cm³	1.45	S-221

How nanoplastics form

Primary particles are made at their final size, such as pre-production pellets and microbeads; secondary particles form from larger items by fragmentation or wear and tear³. Primary nanoplastics exist too, such as the 0.2 µm polystyrene beads used as model particles²⁰. Gigault and colleagues reserve the word for unintentionally produced particles, which by our reading excludes such beads².

Sunlight drives much of the breakdown. Lambert and Wagner kept pieces of a polystyrene coffee-cup lid in water under visible and UV light at 30 °C. After 56 days the water held about 126 million particles per milliliter, average size 224 nm, against 41 million in controls (level C)²¹. Their counting method does not identify the polymer.

Not all the mass lost stays particulate. Pfohl and colleagues aged cryo-milled polyamide and polyurethane powders under UV light. Dissolved organic compounds, which are molecules rather than particles, made up a major share of the mass lost, alongside fragments down to 10 nm (level C)²².

Heat can also shed particles, but the best-known example is disputed (level D). Hernandez and colleagues steeped plastic teabags at 95 °C and reported about 11.6 billion "microplastics" and 3.1 billion "nanoplastics" per cup. They matched the dried residue to nylon and PET by spectroscopy¹⁶. Their nano line was 100 nm, and only about 2.3 million particles exceeded 1 µm; by this site's convention nearly all would be nanoplastics, if they are plastic²³.

Busse and colleagues, including a scientist of Germany's Federal Institute for Risk Assessment (BfR), argue that drying the extract let dissolved oligomers precipitate and be counted as particles²⁴^,²³. Identifying single particles by Raman spectroscopy, they found 5,800–20,400 plastic particles above 1 µm per bag, apparently washed off its surface rather than shed by brewing²³.

Hernandez and colleagues reply that their submicrometer counts come from nanoparticle tracking analysis of the liquid, without drying, and that the two studies used methods that cannot be compared²⁵. BfR's 2025 assessment holds that the reply does not answer the main criticism²³. What this means for everyday choices is on What you can do.

Four grey electron micrographs of rough polystyrene particles, white arrows on surface cracks, 10 µm scale bars — Polystyrene particles unheated (top left) and after laboratory heating at 70 °C for 6 or 12 hours, scanning electron micrographs; arrows mark cracks; scale bars 10 µm. Simulated aging, not field weathering; no nanoscale release is shown. Figure 4B, Sarkar et al. (2021)²⁶.Figure 4B from Sarkar A.K., Rubin A.E., Zucker I. (2021), Environmental Science & Technology 55(15):10491–10501, https://doi.org/10.1021/acs.est.1c02196 · CC BY 4.0 · croppedCC BY 4.0Source ↗

Clear, glassy round polyethylene pellets, each a few millimeters wide, lying above a red centimeter ruler — Clear polyethylene pellets beside a centimeter ruler, each a few millimeters across. Pellets are primary microplastics, made at this size. The photographer gives no date or place."Polyethylene balls5" by Lluis tgn, via Wikimedia Commons, CC BY-SA 3.0CC BY-SA 3.0Source ↗

Why smaller particles behave more like colloids

Small particles have more surface for their mass. For a sphere or a cube, surface divided by volume equals six divided by the diameter or edge, so it rises tenfold for each tenfold drop in size. Mitrano and colleagues expect no stepwise change at the nanoscale. Surface processes such as pollutant adsorption may still matter more as a given mass is cut smaller¹.

Gravity loses its grip gradually. In still water at 20 °C, an isolated polystyrene sphere 10 µm across sinks about 10 mm per hour and one of 1 µm about 0.1 mm per hour. One of 100 nm needs about 110 years per meter. Across solid polystyrene densities that is 57 to 139 years (our calculation, see the method note, level P).

Collisions with water molecules, called Brownian motion, also move particles. Their spread grows with the square root of time, settling in proportion to it. In one hour the 1 µm sphere sinks about 100 µm and wanders about 56 µm along one axis. The 100 nm sphere sinks about 1 µm and wanders about 180 µm (our calculation, level P). Gigault and colleagues make colloidal behavior part of their definition².

Real particles rarely stay single, so even particles far below 1 µm can leave suspension. Nanoplastics clump with each other (homoaggregation) or with natural particles (heteroaggregation), and the clumps can settle or stick to soil and sediment grains (level B)²⁷. Inside a heteroaggregate, a nanoplastic goes where the larger clump goes¹.

In water, natural organic matter and microbial secretions coat nanoplastics in an "eco-corona" that changes their surface and fate (level B)²⁸. In biological fluids proteins form a similar corona; Monopoli and colleagues argue, from engineered nanoparticles, that this coat is what cells meet (level B)²⁹.

Size also affects which barriers a particle passes in laboratory systems. Li and colleagues grew wheat and lettuce in hydroponic and sand culture with fluorescent polystyrene beads. Beads of 0.2 µm entered roots through cracks where lateral roots emerge and reached the shoots; 2 µm beads took that route more slowly (level C)²⁰.

Nanoplastic particles have not yet been extensively measured in the environment, so Mitrano and colleagues compare them with engineered nanomaterials and natural colloids to anticipate their fate¹. The human body is covered on Human body.

Same mass, smaller pieces: number and total surface of one 1 mm cube

Our calculation with ideal cubes: two log-scale lines against piece size from 1 mm down to 10 nm. The number of pieces rises a thousandfold and the total surface tenfold for every tenfold cut in size, reaching one trillion pieces and 60,000 mm² at 100 nm. Source:¹Nanoplastics ObservatorySite original

How this was calculated

Our calculation: number = (1 mm / edge)³; total surface = number × 6 × edge². Ideal cubes, no mass lost to dissolution. The cited source supports why surface area matters (adsorption); the numbers are arithmetic, not data.

Data table

label	value	unit	surface_mm2
1 mm	1	pieces	6
100 µm	1000	pieces	60
10 µm	1000000	pieces	600
1 µm	1000000000	pieces	6000
100 nm	1000000000000	pieces	60000
10 nm	1000000000000000	pieces	600000

Method

How we computed the settling and Brownian numbers: Stokes' law for one smooth polystyrene sphere (1.05 g/cm³; 1.04–1.10 g/cm³ for the range) in still pure water at 20 °C, density 0.998 g/cm³ (TEOS-10) and viscosity 1.002 mPa·s (IAPWS formulation)¹⁹^,³⁰. Settling speed is about 2.8 µm/s at 10 µm, 28 nm/s at 1 µm and 0.28 nm/s at 100 nm. Brownian spread is the one-dimensional root-mean-square displacement from the Stokes–Einstein equation, √(2Dt): at 100 nm about 2.9 µm after 1 second and 180 µm after 1 hour. Real particles aggregate, gain coatings and meet currents, so these are idealized estimates, not measurements.

What particles carry

A particle carries chemicals as well as polymer: plasticizers, flame retardants, antioxidants, stabilizers, pigments and fillers¹⁵. Plasticizers typically make up 10–70% of a plastic's weight where used, about 80% go into PVC, and phthalates are among the most common (level B)¹⁵. EFSA states that microplastics "can contain on average 4%" additives (level C)⁵. The PlastChem report lists 16,325 known plastic chemicals and flags more than 4,200 as of concern (level P)³¹.

Particles also sorb pollutants. One study summarized by Hahladakis and colleagues found polychlorinated biphenyls (PCBs) on polypropylene pieces from the sea at 100,000 to 1 million times the surrounding water's concentration (level C)¹⁵. Whether a particle harms an organism and whether its chemicals do are separate questions; Human body keeps them apart.

Glossary

Microplastics: Plastic particles from 1 µm to 5 mm on this site; ISO 24187 uses 1–1,000 µm.
Nanoplastics: Plastic particles from 1 nm to below 1 µm on this site; some authors use 1–100 nm.
Submicron plastics: Hartmann et al.'s optional label for 100 nm to below 1,000 nm, used when "nano" stops at 100 nm³.
Primary plastic particles: Particles made at their final size, such as pellets, microbeads and laboratory model beads.
Secondary plastic particles: Particles formed from larger items by fragmentation or wear and tear.
Fragment: An irregular piece broken from a larger item.
Fiber: A thread-like particle much longer than it is wide; REACH counts a length-to-diameter ratio above 3 as fiber-like.
Film, bead: A thin, flat, flexible particle; a spherical particle, also called a sphere.
Foam: A light, porous particle; Hartmann et al. suggest "expanded cellular plastics" as a neutral term.
Pellets (nurdles): Pre-production plastic pellets a few millimeters across, from which products are molded.
Tire wear particles: Particles from tire abrasion, mixing synthetic rubber, filler and road material; studies differ on whether they count.
Oligomer: A short chain of a few linked monomer units; unlike the polymer, some dissolve in hot water.
Colloid: A dispersion of particles small enough that random molecular motion slows their settling; aggregation can still remove them.
Eco-corona: A coat of natural organic matter and microbial substances on a particle in the environment; in body fluids, a protein corona.
Nanomaterial (EU): A material in which at least half the particles by number have an external dimension of 1–100 nm, with further conditions⁴.

Questions

Is a nanoplastic the same as a nanoparticle?

No. "Nanoparticle" covers any particle in the nanometer range, including soot, metal oxides and engineered silver particles. A nanoplastic is made of plastic polymer. The EU nanomaterial definition applies to any material and classifies a sample by its particle size distribution, so a nanoplastic sample may or may not meet it. (level P,⁴,¹)

Do nanoplastics stay suspended forever?

No. An isolated 100 nm polystyrene sphere settles extremely slowly in still water (our calculation), but real nanoplastics aggregate with each other and with natural particles, and the clumps can settle or attach to sediment and soil grains. Water chemistry and surface coatings affect how quickly this happens. (level B,²⁷,²⁸,¹)

Do nanoplastics eventually disappear?

How fast nanoplastics break down outside the laboratory has not been measured in the sources reviewed here. Under UV light in one lab study, polyamide and polyurethane powders lost a major share of their mass as dissolved organic compounds, besides fragments down to 10 nm. Rates in soil or deep water remain open. (level C,²²)

Where to go next

How scientists find and count particles this small, and why their size limits shape every number, is on How we measure it. The From planet to cell sequence shows the same scale ladder as an animation, and Four microworlds shows particles in air, water, soil and tissue. Laws that use these definitions are on Policy & regulation.

Sources

Mitrano DM, Wick P, Nowack B (2021). Placing nanoplastics in the context of global plastic pollution. Nature Nanotechnology. doi:10.1038/s41565-021-00888-2 review
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Hartmann NB, Hüffer T, Thompson RC, Hassellöv M, Verschoor A, Daugaard AE et al. (2019). Are We Speaking the Same Language? Recommendations for a Definition and Categorization Framework for Plastic Debris. Environmental Science & Technology. doi:10.1021/acs.est.8b05297 journal article
European Commission (2022). Commission Recommendation of 10 June 2022 on the definition of nanomaterial (2022/C 229/01). Official Journal of the European Union C 229, 14.6.2022, p. 1–5. eur-lex.europa.eu/legal-content/EN/TXT/?uri=CELEX:32022H0614(01) web open access
EFSA Panel on Contaminants in the Food Chain (CONTAM) (2016). Presence of microplastics and nanoplastics in food, with particular focus on seafood. EFSA Journal. doi:10.2903/j.efsa.2016.4501 report open access
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Evidence levels and provenance

AConsensus: Multiple independent studies or a systematic review plus a statement by a scientific body.
BWell supportedUsed on this page: Several independent studies with concordant findings.
CLimitedUsed on this page: Few studies, narrow conditions, or methodological caveats.
DDisputedUsed on this page: Conflicting results; both sides are shown.
EUnknown: No reliable evidence found; the search scope is stated.

PProvenanceUsed on this page: Provenance: checked against the primary record. A separate category, not an evidence grade: used for bibliographic facts, legal texts, official metadata, definitions quoted from a standard, the site's own arithmetic and statements about the site's process.

Editorial categories of this site. A–E grade scientific findings, per claim, with a one-line rationale; D and E are not lower rungs of the A–C scale. P is not a grade: it marks facts checked against their primary record.