Every number on this page ships with a dated rationale document and an effective date — see §2b of the architecture spec. Rows marked Proposed are an interim baseline MPFREE has posted for discussion — not a Scientific Advisory Board determination. No row on this page has ever had a number invented with no derivation behind it; a row is either silent, marked proposed with its reasoning linked, or marked ratified once a constituted SAB reviews it.
Liquid, food contents, active crop tissue, and primary product formulation. Must test below the current SAB-published threshold for the applicable matrix, using µFTIR, Raman microspectroscopy, and/or Py-GC-MS as specified per method below.
Farm mulches, processing effluent, primary/secondary packaging. No persistent synthetic polymer content, verified by material composition audit; degradability claims require independent third-party test data.
A microplastic is currently defined, under the cross-matrix framework this Standard follows, as a solid, water-insoluble plastic particle with at least one dimension between 1 µm and 1,000 µm [1]. No single method covers that whole range with one output type, which is why three methods are required rather than one.
Particle count and polymer identity via infrared spectral matching. Conventional practical size floor ≈ 20 µm [2]; specialized large-area ATR variants have reached ≈1.3 µm in research settings, though not yet at routine accredited-lab scale [3].
Particle count and polymer identity via inelastic light scattering. Practical size floor ≈1 µm — an order of magnitude finer than conventional µFTIR [4].
Total polymer mass via pyrolysis and mass spectrometry — reported down to nanogram levels across common polymers [5]. Destroys the sample, so it produces no particle size, shape, or count data [6] — but has no size floor at all, which is what makes it the only method here that captures the sub-1-µm nanoplastic fraction neither optical method can resolve.
The proposed baseline above — non-detect at each method's own validated quantification limit — is deliberately not an invented count or mass figure; see the full rationale for why that's the one number derivable from real cited method characteristics without fabricating a cutoff. This also lines up with the WHO's 2019 call for standardized measurement methods as a precondition for a more confident risk assessment [7]. Read the full rationale →