Microplastics have moved in a decade from an oceanographic curiosity to a human-exposure question. They have been measured in bottled water, blood, placenta, arterial plaque and brain tissue. The supplement industry mostly packages its products in plastic because plastic is light, cheap and unbreakable. For a dry tablet that choice may matter little. For an oil-based liquid that sits in contact with its container for two years, it deserves a closer look — because oils are exactly the medium into which plastic additives and particles migrate most readily.
The 93% figure and what came after
The number most people have heard comes from a 2018 study of 259 bottles of water from 11 brands across nine countries: 93% contained microplastic particles, at an average of 10.4 particles per litre above 100 µm and roughly 325 per litre when smaller particles were included; polypropylene — the cap material — was the most common polymer identified, pointing to the packaging itself as a source (Mason et al. 2018). The World Health Organization’s 2019 review concluded that the evidence did not yet show a health risk from microplastics in drinking water at the levels measured but called the data “limited” and the research base inadequate. Measurement has since improved dramatically. In 2024 a study using stimulated Raman scattering microscopy, which can resolve particles below one micrometre, counted an average of 240,000 plastic particles per litre of bottled water — 90% of them nanoplastics, small enough to cross biological membranes (Qian et al. 2024). The 2018 figure was not wrong; it was an undercount by two to three orders of magnitude because the instruments could not see the small particles.
They are inside us — and now they are being measured where it matters
Plastic particles have been quantified in human blood in 77% of donors tested (Leslie et al. 2022). In 2024, a prospective study of 257 patients undergoing carotid endarterectomy found microplastics and nanoplastics in the atheromatous plaque of 58%; over 34 months of follow-up those patients had a 4.5-fold higher risk of heart attack, stroke or death from any cause than those without detectable plastic (Marfella et al. 2024). The authors were careful: association, not proof of causation; confounding is possible. But it was the first human outcome study, and it was published in the New England Journal of Medicine. In 2025, post-mortem analysis found plastic concentrations in brain tissue that had increased by about 50% between 2016 and 2024 samples, with brain accumulating more than liver or kidney (Nihart et al. 2025). The honest scientific position today is that the health consequences are unproven and the exposure is confirmed, rising, and avoidable at the margin.
Why oil-based products are the bigger concern
Two separate mechanisms are involved, and oil worsens both. Particle shedding happens at the cap thread, at the dropper pipette, and wherever plastic rubs against plastic; it is mechanical and it happens to water and oil alike. Chemical migration is different. Plastics are not pure polymers — they contain plasticizers, antioxidants, UV stabilizers, slip agents and residual monomers. Migration of these additives into the contents follows partition chemistry: lipophilic additives move into lipophilic media. Regulators know this, which is why EU food-contact testing (Regulation 10/2011) uses vegetable oil or a fatty-food simulant as the worst-case test medium, not water. Bisphenol A is the best-documented example: in 2023 the European Food Safety Authority lowered its tolerable daily intake by a factor of about 20,000, to 0.2 ng/kg body weight per day, after re-evaluating immune effects (EFSA 2023) — a figure so low that modest migration from packaging becomes relevant to it. A fish-oil, vitamin D3 or vitamin E liquid is an almost ideal extraction solvent for whatever the bottle, cap liner and dropper contain, and it has two years to do the extracting.
What glass changes
Borosilicate and Type III soda-lime glass are inert to oils, contain no plasticizers, shed no polymer particles and do not absorb the product. Amber glass additionally blocks most light below ~450 nm, which is why pharmacopoeias specify it for light-sensitive liquids (why B12 needs amber glass). Glass does not make a supplement plastic-free in an absolute sense: the dropper bulb is usually elastomer, the pipette may be glass or plastic, and the cap liner matters. The relevant comparison is exposure: a glass bottle with a glass pipette and a certified food-contact liner reduces the oil’s contact with plastic to a few square millimetres at the closure, versus the entire internal surface of a plastic bottle. For a product taken daily for years (why liquid oil drops as a format), that is the difference between a controlled variable and an unmeasured one.
Proportion and honesty
Nobody should believe that a plastic supplement bottle is a major source of their total plastic exposure; bottled water, food packaging, synthetic textiles and household dust are larger. The point is narrower. The health effects of chronic nanoplastic and additive exposure are an open question with early, concerning human signals; regulators are tightening limits; and for an oil-based product, glass removes the question at trivial cost. Choosing glass is not a health claim. It is the removal of an avoidable uncertainty.
The clinical bottom line
Microplastics are in 93% of bottled waters by older methods and in every sample by newer ones; they are in human blood, plaque and brain; and the first outcome study links plaque plastic to a 4.5-fold rise in cardiovascular events. Oils extract plastic additives far more efficiently than water does, which is why food-contact testing uses oil as the worst case. Packaging an oil-based supplement in amber glass with a glass pipette does not prove a health benefit — it simply takes a two-year extraction experiment off the table.
Primary sources
- Mason SA, Welch VG, Neratko J. Synthetic polymer contamination in bottled water. Front Chem. 2018;6:407. doi:10.3389/fchem.2018.00407
- Qian N, Gao X, Lang X, et al. Rapid single-particle chemical imaging of nanoplastics by SRS microscopy. Proc Natl Acad Sci USA. 2024;121(3):e2300582121. doi:10.1073/pnas.2300582121
- Marfella R, Prattichizzo F, Sardu C, et al. Microplastics and nanoplastics in atheromas and cardiovascular events. N Engl J Med. 2024;390(10):900–910. doi:10.1056/NEJMoa2309822
- Leslie HA, van Velzen MJM, Brandsma SH, et al. Discovery and quantification of plastic particle pollution in human blood. Environ Int. 2022;163:107199. doi:10.1016/j.envint.2022.107199
- Nihart AJ, Garcia MA, El Hayek E, et al. Bioaccumulation of microplastics in decedent human brains. Nat Med. 2025;31:1114–1119. doi:10.1038/s41591-024-03453-1
- EFSA Panel on Food Contact Materials. Re-evaluation of the risks to public health related to the presence of bisphenol A (BPA) in foodstuffs. EFSA J. 2023;21(4):e06857. doi:10.2903/j.efsa.2023.6857
- World Health Organization. Microplastics in drinking-water. Geneva: WHO; 2019. who.int
- Commission Regulation (EU) No 10/2011 on plastic materials and articles intended to come into contact with food. eur-lex.europa.eu
Educational information on supplement quality and consumer protection, not medical advice.
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