Isn’t there a different kind of satisfaction to a face scrub?
The grit, the friction, the scrubbed-off dead skin, and a fresh skin afterwards. Thirty seconds of it, then you rinse, and the whole thing disappears down a drain.
But no, it does not vanish. In 2015, a team at Plymouth University bought ordinary exfoliating scrubs off the shelf, extracted the plastic, and measured what one wash sends down the drain. The answer, depending on the product was somewhere between 4,594 and 94,500 polyethylene beads, each with a mean diameter between 164 and 327 micrometers (Napper et al., 2015).
To be clear, that was per wash, not per bottle.
Once those figures hit the public, they created momentum. Parliament hearings cited them, environmental campaigns plastered them everywhere, and they were eventually written into law. India added plastic microbeads to its list of cosmetic raw materials generally not recognised as safe in 2017 (Bureau of Indian Standards, 2017). South Korea, Taiwan, mainland China and the UK all moved within the same window.
Tip of the Iceberg
When you look closely at personal care formulas, those visible scrubbers and beads are just the tip of the problem. Polyethylene is simply the most famous member of a massive family of synthetic polymers lurking in liquid formulas. Polypropylene, PET, polyamide and PMMA all appear routinely, and they are not there to scrub anything. Instead, they form films, control viscosity, gives a cream its opacity, velvety glide and glitter. A comprehensive review found an average of roughly 2,162 synthetic polymer particles in every single gram of surveyed cosmetics (Bikiaris et al., 2024). Polyethylene may lead the pack, but it is far from the only culprit washing out of our sinks.
Leave-on products are bought in greater volumes than rinse-off ones and they often carry two or more microplastic ingredients each, yet research attention and legislation are both concentrated almost entirely on the rinse-off side. Alex et al. (2024) estimated that 13.7 quintillion (1.37 x 1019) microbead particles were released into Indian waterways in 2021. That figure is projected to climb to 16.1 quintillion (1.61 x 1019) by 2030. That is an increase, forecast for a market seven years after microbeads entered the prohibited list. A narrow ban shrinks one category while consumption expands everything around it.
Taking a different path, Europe looked at the same structural failure and drafted a policy that is refreshingly realistic about the scale of the challenge. Under Commission Regulation (EU) 2023/2055, the EU restricted all synthetic polymer microparticles intentionally added to products at concentrations of 0.01% or higher by weight.
Key Details of the Regulation:
- Core Rule: Prohibits the sale of synthetic polymer microparticles (SPMs) on their own or intentionally added to mixtures in concentrations greater than 0.01% by weight.
- Definition: Covers solid polymer particles under 5 mm (or fibers under 15 mm) that are insoluble and non-biodegradable.
- Immediate Ban: Microbeads across all applications faced immediate restriction when the rule went into force on October 17, 2023
Solution and What Still Can’t Be Solved
Walnut shell, apricot kernel, jojoba wax, silica, rice bran, etc solved the scrub problem years ago.
They could not solve the rest of the problem. Ground shell could not form a continuous film on skin. It does not hold structure in an emulsion, survive shear of a homogenizer, or sit stably in a formulation for two years. Beauty brands didn’t turn to synthetic polymers because it lacked imagination on conscience; they used them because plastics deliver precise performance characteristics that raw plant fragments simply can’t match.
This leaves scientists with a remarkably tricky assignment of designing an alternative that acts like a tough, stable plastic inside the jar, but completely dissolves the second it hits the drain.
Solution via Bacteria
Polyhydroxyalkanoate (PHA), are the closest material for a true solution to this problem. Certain bacteria, when fed with enough carbon but starved of nitrogen, produces and store PHA as a form of an energy reservoir. It is similar to the way humans store fat. Harvest the cells, extract the granules, and you have a thermoplastic.
The biological origin changes everything about the same old story. Because enzymes built the polymer, enzymes can break it down as well. When a PHA particle ends up in the ocean, it doesn’t sit around for decades waiting for UV light, a particular set of condition or waves to slowly fragment it like polyethylene does. To marine microbes, it’s just food.
Hyodo et al. (2024) tested PHA by producing PHA microbeads and putting them through a biochemical oxygen demand assay in Tokyo Bay seawater and a five-month submersion at 757 meters depth. Poly(3-hydroxybutyrate) beads reached 85% biodegradation in 25 days, ahead of the cellulose reference at 77%. In the deep sea, where cold and pressure slows everything down, every grade showed clear surface degradation, with weight recovery for P(3HB) at 45% after five months.
The mechanical data in the same study matters equally. Their P(3HB) beads recorded compressive strength of 13.3 MPa, above polyethylene at 11.8 MPa and polypropylene at 11.2 MPa. A bead that collapses during manufacturing is not a product, however well it degrades.
Looking at the broader picture, a meta-analysis by Dilkes-Hoffman et al. (2019) calculated an average marine biodegradation rate for PHAs between 0.04 and 0.09 mg per day per cm². That rate seems small until you account for particle shape or geometry. A 200-micrometre bead is almost entirely surface area, which is why a microscopic sphere vanishes in weeks, while a thick-walled PHA bottle would take years.
There is one caution that replacement materials must face the rigorous testing that original plastics escaped. Marine biodegradability is measured, not assumed, and it varies by grade, by particle size, and by receiving environment.
Frequently Asked Questions
Does a “biodegradable” label mean a material breaks down in the sea?
Not on its own. Biodegradation is specific to the environment it is measured in, and industrial composting conditions look nothing like cold seawater. Commission Regulation (EU) 2023/2055 handles this by exempting polymers only where degradability is demonstrated against specified test criteria, rather than accepting the claim at face value (European Commission. 2023). The useful question about any alternative is which environment it was tested in and for how long.
Aren’t walnut shell and other natural exfoliants already the answer?
For scrubs, yes. But the problem is not ending with just scrubs and exfoliants. Walnut shells, apricot kernel, etc cannot form a film on skin, stabilize an emulsion or survive processing sheer. Replacing those functions needs a material with polymer behaviour which is a different problem scenario than just replacing an abrasive.
References
Alex, R. K., Maes, T., & Devipriya, S. P. (2024). Clean, but not green: Emission assessment, forecast modelling and policy solutions for plastic microbeads from personal care products in India. Emerging Contaminants, 10(3), 100326. https://doi.org/10.1016/j.emcon.2024.100326
Bikiaris, N. D., Nikolaidis, N. F., & Barmpalexis, P. (2024). Microplastics (MPs) in cosmetics: A review on their presence in personal-care, cosmetic, and cleaning products (PCCPs) and sustainable alternatives from biobased and biodegradable polymers. Cosmetics, 11(5), 145. https://doi.org/10.3390/cosmetics11050145
Bureau of Indian Standards. (2017). IS 4707 (Part 2): 2017 — Classification for cosmetic raw materials and adjuncts: Part 2, List of raw materials generally not recognized as safe for use in cosmetics (4th rev.). Bureau of Indian Standards.
Dilkes-Hoffman, L. S., Lant, P. A., Laycock, B., & Pratt, S. (2019). The rate of biodegradation of PHA bioplastics in the marine environment: A meta-study. Marine Pollution Bulletin, 142, 15–24. https://doi.org/10.1016/j.marpolbul.2019.03.020
European Commission. (2023). Commission Regulation (EU) 2023/2055 of 25 September 2023 amending Annex XVII to Regulation (EC) No 1907/2006 of the European Parliament and of the Council as regards synthetic polymer microparticles. Official Journal of the European Union. https://eur-lex.europa.eu/eli/reg/2023/2055/oj/eng
Hyodo, N., Gan, H., Ilangovan, M., Kimura, S., Kasuya, K., Isobe, N., & Iwata, T. (2024). Coastal and deep-sea biodegradation of polyhydroxyalkanoate microbeads. Scientific Reports, 14, 10302. https://doi.org/10.1038/s41598-024-60949-z
Kukkola, A., Chetwynd, A. J., Krause, S., & Lynch, I. (2024). Beyond microbeads: Examining the role of cosmetics in microplastic pollution and spotlighting unanswered questions. Journal of Hazardous Materials, 476, 135053. https://doi.org/10.1016/j.jhazmat.2024.135053
Napper, I. E., Bakir, A., Rowland, S. J., & Thompson, R. C. (2015). Characterisation, quantity and sorptive properties of microplastics extracted from cosmetics. Marine Pollution Bulletin, 99(1–2), 178–185. https://doi.org/10.1016/j.marpolbul.2015.07.029
