How we score microplastic exposure

Every product in our database carries two numbers rather than one. That is the whole methodology in a sentence, and it is the thing that makes these pages different from a scanner app that shows you a red circle and a warning triangle.

The score is additive and the components are rendered on every product page. Nothing is stored as a total — the page adds the parts each time it builds, so a page cannot drift from the reasoning behind it, and you can always see which component is carrying the number.

The grade sets a hard ceiling on the confidence a page may claim. It is enforced in code rather than by editorial discipline: a grade D page cannot report 90% confidence even if someone types it into the data. Across the 132 products currently in the database, the distribution is 12 grade A, 29 grade B, 70 grade C and 21 grade D.

One of the five components is measured release, and it only scores points where a laboratory actually counted particles. So two identical PET bottles — one in a tested cohort, one not — will not get the same number. The tested one scores higher.

That is deliberate. We will not award exposure points for particles nobody has counted, because doing so would let us assign any number we liked to anything and call it data. The gap is carried by the confidence figure instead: a grade B page saying "60, at 72% confidence" is telling you the number can move, and in which direction. Comparisons across evidence grades should be read with that in mind, which is why every head-to-head page shows both grades side by side.

• No brand pays for a score. There is no product, tier or arrangement that changes a number in this database. Scores are computed from the components above and nothing else touches them.

• No sponsored placements in rankings. Category orderings are sorted by the computed score. There is no promoted slot and no paid inclusion.

• Affiliate links never influence a score. Where we earn a commission we say so on the page and in our affiliate disclosure. A product does not move up for being commissionable, and several of our lowest-scoring recommendations earn us nothing at all.

• Brands can dispute a score, not buy one. We publish the components, so a dispute has something specific to argue with. Send evidence and we will re-score in public, including when that means correcting ourselves.

Full detail: affiliate disclosure · how the brand certification programme is kept separate

A corrections policy is worth nothing without a correction in it, so here is the first one, made while building this database.

If you find something wrong — a misattributed study, a product we have scored on stale packaging information, a claim that outruns its source — tell us via the contact page. Substantive corrections are published with a date and a description of what was wrong, in this section, permanently. We do not quietly edit.

25 sources currently underpin the scores, each with the finding we cite it for and the limitation that finding carries. We list the limitation because a study quoted without its boundaries is how the microplastics conversation got as noisy as it is.

1. agencyposition

   US Food and Drug Administration. Microplastics and nanoplastics in foods.

   Cited for: States that current scientific evidence does not demonstrate that the levels of microplastics detected in foods pose a risk to human health, while listing detection and characterisation as a research priority.

   Does not establish: A statement about the state of evidence, not a finding of safety. "Not demonstrated to be harmful" and "demonstrated to be harmless" are different claims, and the agency is explicit that the research is ongoing.

2. reportreview

   Earth Action with rePurpose Global (2026). Microplastic migration from consumer packaging.

   Cited for: Estimated roughly 1,000 tonnes of microplastics migrate from packaging into food and drink annually — about 130 mg per person per year — with PET bottles responsible for around a third, and found UV exposure can raise release up to 100×.

   Does not establish: An industry-funded modelling exercise, not a laboratory study, and not peer-reviewed. We use it for the relative ranking of formats rather than for any absolute number.

3. peer-reviewedhuman

   Nihart AJ, Garcia MA, El Hayek E, et al. (2025). Bioaccumulation of microplastics in decedent human brains. Nature Medicine.

   Cited for: Measured higher plastic concentrations in brain tissue than in liver or kidney, rising roughly 50% between 2016 and 2024 samples.

   Does not establish: Post-mortem tissue with no exposure history, and the analytical method has been publicly challenged by other researchers. Treat the direction as informative and the absolute numbers as contested.

4. conferencelaboratory

   Mohanty S et al. (2025). Chewing gum as a source of microplastics in saliva. Pilot study presented at ACS Spring 2025.

   Cited for: Chewing gum released around 100 microplastic particles per gram into saliva, with some samples reaching 600 per gram — synthetic and "natural" gum bases behaved similarly.

   Does not establish: A pilot presented at a conference, one participant, ten gum brands, not yet peer-reviewed. We cite it because it is the only direct measurement that exists, and we grade pages that rest on it accordingly.

5. peer-reviewedlaboratory

   Qian N, Gao X, Lang X, et al. (2024). Rapid single-particle chemical imaging of nanoplastics by SRS microscopy. PNAS 121(3).

   Cited for: Counted roughly 240,000 plastic particles per litre in bottled water, about 90% of them nanoplastics that earlier optical methods could not see at all.

   Does not establish: Three unnamed US brands, small sample. It measured particles, not absorption or any health outcome, and the brands were not disclosed — so it cannot be attributed to a specific label.

6. peer-reviewedhuman

   Marfella R, Prattichizzo F, Sardu C, et al. (2024). Microplastics and nanoplastics in atheromas and cardiovascular events. New England Journal of Medicine 390:900–910.

   Cited for: Polyethylene was detected in 58.4% of excised carotid plaques; those patients had a 4.53× higher rate of heart attack, stroke or death over 34 months.

   Does not establish: Observational, in patients already undergoing surgery for carotid disease. It shows an association, not that microplastics caused the events, and it cannot be traced back to any particular product.

7. peer-reviewedlaboratory

   Hussain KA, Romanova S, Okur I, et al. (2023). Assessing the release of microplastics and nanoplastics from plastic containers and reusable food pouches. Environmental Science & Technology 57(26):9782–9792.

   Cited for: Three minutes of microwaving released up to 4.22 million microplastic and 2.11 billion nanoplastic particles per square centimetre of container surface.

   Does not establish: Polypropylene and polyethylene containers with water and acetic acid, not real food. The headline figure is the worst case in the study, per cm², not per meal.

8. peer-reviewedlaboratory

   Yadav H, Khan MRH, Quadir M, et al. (2023). Cutting boards: an overlooked source of microplastics in human food? Environmental Science & Technology 57(22):8225–8235.

   Cited for: Chopping on a plastic board generated an estimated 14.5–71.9 million polypropylene microplastics per person per year, and around 79.4 million from a polyethylene board.

   Does not establish: Controlled chopping by a set protocol, extrapolated to annual figures. Real kitchens vary enormously in board use, knife type and replacement frequency.

9. peer-reviewedlaboratory

   Zangmeister CD, Radney JG, Benkstein KD, Kalanyan B (2022). Common single-use consumer plastic products release trillions of sub-100 nm nanoparticles per litre into water during normal use. Environmental Science & Technology 56(9):5448–5455.

   Cited for: Nylon bags, LDPE food-storage bags and similar single-use plastics shed trillions of sub-100 nm particles per litre in ordinary contact with water.

   Does not establish: Deionised water at controlled temperature. Nanoparticle counts are inherently large numbers; the study is about their existence and quantity, not their fate in the body.

10. peer-reviewedlaboratory

    Luo Y, Gibson CT, Chuah C, et al. (2022). Raman imaging for the identification of Teflon microplastics and nanoplastics released from non-stick cookware. Science of the Total Environment 851:158293.

    Cited for: A single crack in a non-stick coating released around 9,100 fluoropolymer particles, and a surface with broken coating released up to 2.3 million during a few minutes of simulated cooking.

    Does not establish: A deliberately damaged coating under a controlled scraping protocol, not normal use of an intact pan. It establishes that damaged non-stick is a particle source; it does not tell you the release from a pan you have not scratched.

11. peer-reviewedlaboratory

    Ranjan VP, Joseph A, Goel S (2021). Microplastics and other harmful substances released from disposable paper cups into hot water. Journal of Hazardous Materials 404:124118.

    Cited for: A disposable paper cup released roughly 25,000 micron-sized particles into 100 mL of hot water within 15 minutes — about the life of a takeaway coffee.

    Does not establish: Hot deionised water rather than coffee or tea, and a single cup type. It shows the polyethylene lining degrades at drinking temperature; it does not quantify a dose from a real latte.

12. peer-reviewedreview

    Rolsky C, Kelkar V (2021). Degradation of polyvinyl alcohol in US wastewater treatment plants and subsequent nationwide emission estimate. International Journal of Environmental Research and Public Health 18(11):6027.

    Cited for: Estimated that roughly 75% of the polyvinyl alcohol from dissolvable detergent pods and sheets passes through US wastewater treatment without fully degrading.

    Does not establish: A modelling estimate built on literature degradation rates rather than direct plant sampling, and it has been publicly disputed by industry bodies who cite conditions under which PVA does biodegrade. The disagreement is genuine and unresolved.

13. peer-reviewedlaboratory

    Li D, Shi Y, Yang L, et al. (2020). Microplastic release from the degradation of polypropylene feeding bottles during infant formula preparation. Nature Food 1:746–754.

    Cited for: Polypropylene infant bottles prepared to WHO sterilisation guidance released 1.3–16.2 million microplastic particles per litre of formula.

    Does not establish: Release scaled with water temperature — the highest numbers came from the 70°C step WHO recommends for killing bacteria. The study explicitly did not recommend abandoning that step, and no health outcome was measured.

14. peer-reviewedlaboratory

    Du F, Cai H, Zhang Q, Chen Q, Shi H (2020). Microplastics in take-out food containers. Journal of Hazardous Materials 399:122969.

    Cited for: Take-out containers released 3–29 microplastic particles each, with polypropylene containers the most common source.

    Does not establish: Counts particles above the detection limit of the method used, so it says nothing about the nanoplastic fraction, which other work suggests dominates by number.

15. peer-reviewedmaterial

    Sobhani Z, Lei Y, Tang Y, et al. (2020). Microplastics generated when opening plastic packaging. Scientific Reports 10:4841.

    Cited for: Simply tearing, cutting or twisting open plastic packaging generates microplastics at the opening — 10–30 nanograms per 300 cm of tear.

    Does not establish: Mass, not particle count, and it does not follow whether those particles land in the food. It is the reason cap and seal design belongs in an exposure score at all.

16. peer-reviewedlaboratory

    Hernandez LM, Xu EG, Larsson HCE, et al. (2019). Plastic teabags release billions of microparticles and nanoparticles into tea. Environmental Science & Technology 53(21):12300–12310.

    Cited for: A single nylon or PET pyramid tea bag steeped at 95°C released about 11.6 billion microplastic and 3.1 billion nanoplastic particles into one cup.

    Does not establish: Four commercial bags, brewed empty of tea leaves to avoid interference. The particle count is enormous but the total mass is small, and the study measured release into water, not what happens after you drink it.

17. peer-reviewedmaterial

    Winkler A, Santo N, Ortenzi MA, et al. (2019). Does mechanical stress cause microplastic release from plastic water bottles? Water Research 166:115082.

    Cited for: Refilling and mechanically stressing PET bottles measurably increased particle release compared with first use.

    Does not establish: A laboratory stress protocol rather than observed household reuse. It establishes direction — reuse of single-use PET makes things worse — more firmly than magnitude.

18. peer-reviewedlaboratory

    De Falco F, Cocca M, Avella M, Thompson RC (2019). Microfibre release to water, via laundering, and to air, via everyday use. Environmental Science & Technology 54(6):3288–3296.

    Cited for: Found that simply wearing polyester garments released microfibres to air at a rate comparable to, and in some cases exceeding, what the same garments released to water during laundering.

    Does not establish: A small number of garment types under controlled movement. It is the study that opened the air pathway rather than one that quantifies a household dose.

19. agencyposition

    World Health Organization (2019). Microplastics in drinking-water.

    Cited for: Concluded that microplastics in drinking water do not appear to pose a health risk at current levels, while calling the underlying evidence limited and urging more research.

    Does not establish: Predates the nanoplastic detection methods that changed the particle counts by three orders of magnitude. Its conclusion is about what was measurable in 2019.

20. peer-reviewedlaboratory

    Mason SA, Welch VG, Neratko J (2018). Synthetic polymer contamination in bottled water. Frontiers in Chemistry 6:407.

    Cited for: 93% of 259 bottles across 11 international brands contained microplastic; an average of 325 particles per litre across all size classes.

    Does not establish: Nile-red staining and optical microscopy only reliably resolve particles above ~100 μm, so its counts are a floor, not a total. Lower numbers here do not mean less plastic than the 2024 study — they mean a less sensitive method.

21. peer-reviewedmaterial

    Schymanski D, Goldbeck C, Humpf HU, Fürst P (2018). Release of plastic particles from different packaging into mineral water. Water Research 129:154–162.

    Cited for: Compared formats head to head: single-use PET averaged 14 particles/L, returnable PET 118/L, glass bottles 50/L and beverage cartons 11/L.

    Does not establish: The glass result is the one people skip. Glass was not zero — particles came from the cap and the filling line, not the bottle wall. Small sample per format.

22. peer-reviewedlaboratory

    Kim JS, Lee HJ, Kim SK, Kim HJ (2018). Global pattern of microplastics in commercial food-grade salts: sea salt as an indicator of seawater microplastic pollution. Environmental Science & Technology 52(21):12819–12828.

    Cited for: Found microplastics in 36 of 39 commercial salt brands from 21 countries, with sea salt carrying far more than rock or lake salt — the contamination tracked regional seawater pollution.

    Does not establish: Salt is eaten in grams, not litres. Even the worst brands worked out to a small annual particle intake next to bottled water, and the study is better read as a measurement of the ocean than as a warning about your salt cellar.

23. peer-reviewedlaboratory

    Kosuth M, Mason SA, Wattenberg EV (2018). Anthropogenic contamination of tap water, beer, and sea salt. PLoS ONE 13(4):e0194970.

    Cited for: Detected synthetic particles in 81% of tap water samples worldwide, in all 12 brands of beer tested, and in all 12 brands of sea salt.

    Does not establish: Overwhelmingly fibres, which are as likely to come from airborne contamination during sampling as from the product — the authors say so. It establishes ubiquity rather than any particular source.

24. peer-reviewedlaboratory

    Napper IE, Thompson RC (2016). Release of synthetic microplastic plastic fibres from domestic washing machines. Marine Pollution Bulletin 112(1–2):39–45.

    Cited for: A single 6 kg wash released between roughly 138,000 and 728,000 synthetic microfibres depending on fabric type, with acrylic the worst and polyester-cotton blends the best of those tested.

    Does not establish: Measures release into wash water, which is an environmental pathway. It says nothing about what you inhale from the same garment while wearing it, which is the human-exposure question and is much less studied.

25. peer-reviewedlaboratory

    Liebezeit G, Liebezeit E (2013). Non-pollen particulates in honey and sugar. Food Additives & Contaminants: Part A 30(12):2136–2140.

    Cited for: Reported fibres and fragments in honey and sugar samples, one of the first claims that microplastics were present in everyday sweeteners.

    Does not establish: Substantially disputed. A 2017 replication by Mühlschlegel and colleagues, using stricter airborne-contamination controls, found far lower levels and attributed much of the original signal to laboratory contamination. We cite it with that dispute attached, because citing it without would be misleading.