The Misleading Claim that “Glass Bottles Have More Microplastics Than Plastic Bottles”

You may have seen the headlines or posts claiming that glass beverage bottles contain more microplastics than plastic bottles. These claims state that glass bottles have 5 – 50 times more microplastics than plastic bottles. This sounds unbelievable and can be depressing or demoralizing for those who are actively trying to avoid microplastics. 

The claim that glass bottles have more microplastics than plastic bottles is slightly misleading. Although there are studies that show that glass bottles contain more microplastics than glass bottles, the situation is far more nuanced. 

I’m going to walk you through what the latest research actually shows, what’s missing, and the best ways to actually avoid microplastics from bottled beverages.

A summary of the studies that show that glass bottles have more microplastics than plastic bottles

There are three peer-reviewed papers that form the core of the “glass bottles have more microplastics” narrative. We’re going to examine these individuality to help us piece together the real story. 

Firstly, the Wang and Wang study that was published in Heliyon in 2024[1]. This study looked at aluminum, glass, and plastic soda bottles in four US cities: Atlanta, Chicago, Los Angeles, and Washington DC. The scientists used laser direct infrared spectroscopy to detect microplastics between 20 and 500 micrometers in length (the size is important as we’ll discuss later). They found glass bottles had an average of 228 +/- 84 microplastics per 100mL (2280 microplastics in a glass liter bottle). This is in contrast to plastic bottles, which had on average 104 +/- 30 microplastic particles per 100mL (1040 microplastics in a plastic liter bottle). Therefore, the authors concluded that glass bottles had roughly twice as many microplastics as plastic bottles. 

Another study, the Chaïb et al. study published in the Journal of Food Composition and Analysis in 2025, conducted by France’s national food safety agency ANSES, analyzed water, soft drinks, beer, and wine across multiple container types[2]. The team used Micro-Fourier Transform Infrared (uFT-IR) spectroscopy to detect microplastics in the range of 30 to 500 micrometers, similar to the Wang and Wang study. 

They found that glass soda bottles contained 103.4 microplastics per liter versus plastic soda bottles at 2.1 particles per liter. This finding was consistent in other beverages too. Glass iced tea had 86.3 microplastics per liter versus 2.2 microplastics per liter in plastic. Glass lemonade beverages had 111.6 microplastics per liter versus plastic bottles at 1.5 microplastics per liter. Therefore, it appears that glass bottles have 50x more microplastics than plastic bottles. 

Lastly, a Oßmann et al. study published in Water Research in 2018 used micro-Rama spectroscopy to push microplastics detection down to 1 micrometer, a fraction of the range of the two previous studies[3]. With this expanded range, they reported glass water bottles had 6,292 +/- 10,521 microplastics per liter, compared to plastic water bottles at 2,649 +/- 2,857 microplastic particles per liter. 

All three of these studies, performed by independent labs across three different countries using three different detection methods, had similar directional conclusions: glass bottles have more microplastics than plastic bottles.

A critical analysis of the studies that show that glass bottles have more microplastics than plastic bottles

Of these three studies, only the Chaïb team ran a controlled experiment to identify the source of microplastic contamination. They took empty bottles, cleaned them, filled them with filtered water, and sealed them with new metal caps. When the caps weren’t cleaned, the resulting “beverage” contained 287 microplastics per liter. In contrast, when they pre-cleaned the caps by blowing them out with air, the microplastic count dropped to 106 particles per liter. Furthermore, when they both cleaned the caps with air and rinsed them with ethanol, the microplastic count dropped to 87 microplastic particles per liter.

At this point, it was clear that the bottle caps were playing a role in microplastic counts. You may be saying, “Deplasto, what do you mean that “new metal caps” contribute to microplastic counts?” – we’ll get to it in a second. 

With this finding, the team looked at the uFT-IR data to understand what was happening. It turns out that the particles being detected in the bottles matched the color and polymer composition of the paint on the outside of the metal caps. Most of these paints were polyester-based (PET and alkyd lacquers). Polyester is commonly used as a fabric in sweat-resistant workout clothing, bedding, and other kinds of materials. 

The scientists uncovered that the mechanism was simply: metal caps are stored in bulk before being applied to the bottles, they rub against each other, microscopic scratches form on the painted cap, paint flakes off, the flakes end up inside the surface of the cap when it’s put on the bottle, and then these paint flakes fall into the bottle the first time it’s opened. uFT-IR, which analyzes the chemical composition of molecular compounds, was detecting polymers (of which plastics are made of), but these polymers were made of paint and not from microscopic plastic particles as we traditionally think of. 

This finding was similar to that of the Oßmann team from 2018. They discovered that these “microplastics” in the bottles were actually pigment particles from the printed paper labels on the glass bottles. These pigments (Pigment Blue 15, Pigment Violet 23, Pigment Yellow 83, and Pigment White 6) were exactly the same pigments used to print the paper label on the bottles. They proposed that during the industrial washing of the reusable glass bottles, the printed paper labels shed ink into the washing liquid, and then made their way back into the bottles during the wash cycle. 

In other words, both studies found that the “microplastics” being detected in the glass bottles were mainly paint, lacquer, and printing ink. Rather than degraded container material or weathered plastics, the particles being detected were actually industrial coating residue from caps and labels. 

Why, then, are these studies claiming that they’re finding microplastics in glass bottles? 

Simply put, it’s because of how microplastics are defined. 

The most widely cited definition of microplastics, established at a National Oceanic and Atmospheric Administration (NOAA) workshop in 2009, is “any solid synthetic polymer particle smaller than 5 millimeters”. All plastics are polymers, but not all polymers are plastic. Polymers include coatings, paints, lacquers, adhesives, and printing inks. Under spectroscopic analysis, these particles may be considered a synthetic polymer, and consequently counted as a microplastic. The alkyd lacquer from the bottle caps and the polyester binder from the paper label both qualify as synthetic polymers and, therefore, “microplastics”. 

To illustrate this point further, the Wang and Wang study cited that the most abundant detected microplastic was polyurethane acrylate varnish, compromising 24% of all particles found. They concluded that this most likely came from the coatings and sealing materials used in manufacturing equipment. Nevertheless, it still counted as a microplastic in the headline number. 

Technically speaking, none of these studies are flawed in their findings (I’m sure that there may be flaws in methodology, but that’s beside the point). The authors are following the field’s standard definition of microplastics and the standard methodology for detecting them. Unfortunately for us, when we read that their soda contains hundreds of microplastic particles per liter, this may include physical plastic particles and other synthetic polymers, like paint flakes and other industrial coatings. 

And, of greater concern, both microplastics and industrial coatings are toxic. Studies have found that alkyd lacquers and printing inks may contain heavy metals, which are arguably just as harmful if not more so than microplastics. You don’t want either of them in your body. So, although these studies may not have actually found thousands of “microplastic” particles per drink, they’re still finding harmful particles. 

In conclusion, the findings of “more microplastics in glass bottles than plastic bottles” is more complex as it accounts for:

1. Polymer-binder paint flakes from the bottle caps that contain pigment embedded in resin matrices. While these are technically microplastics per the NOAA definition, they’re not standard plastic particles. 
2. Discrete pigment particles from label inks that are introduced during industrial washing. These are not microplastics in any meaningful sense, but were reported as such in the Oßmann study as part of the “overall particle burden”.
3. Actual degraded plastic particles from the cap material, the cap lining, or the bottle interactions with internal seals. These are microplastics as we traditionally think of them. 

Studies using stronger analytical methods show that plastic bottles release significant nanoplastics

We’ve focused on three key studies which show that glass bottles have more polymer contaminants than plastic bottles. However, all these studies are limited by their detection methods. This is significant because studies show that smaller plastic particles can more easily cross biological barriers, penetrate tissues, and cause oxidative stress and inflammation. 

A well-known study from Qian et al., published in PNAS in 2024, used stimulated Raman scattering microscopy to detect microplastics down to 100 nanometers – technically, nanoplastics[4]. These particles are 10 times smaller than the lower limit of the Oßmann study and 300 times smaller than the lower limit of the Chaïb study. Think of this as a pair of binoculars that can see 10 to 300 times further, meaning significantly more particles can be detected. 

At the resolution used in the Qian study, they found approximately 240,000 microplastic particles per liter in plastic bottled water, with 90% of them being nanoplastics rather than microplastics. The most common types of plastic were polyamide, which likely came from the filtration step in the manufacturing process, and Polyethylene terephthalate (PET), which is what the bottle was made of. Of note, there is a critique of this study by Materic in PNAS in 2024, stating that the blanks weren’t properly set up[5].

Two other studies support the idea that plastic bottles still release substantial numbers of microplastics and nanoplastics. Winkler et al. (2019), published in Water Research, tested whether mechanical stress causes microplastic release from PET water bottles. They found that the opening and closing of the bottles increased microplastic counts, but the release came from the bottleneck-cap system and not the bottle walls. Surprisingly, the walls of the plastic bottles resisted mechanical stress. This suggests that the microplastics in PET water bottles come from the opening of the cap and not the bottle walls. 

Another study from Chen et al. (2023), also published in Water Research, tested the effects of carbonation on particle release from plastic bottles. They showed that microplastics were released from three separate types of plastic bottles. But, they also found that microplastic and nanoplastic release increased with carbonation. Therefore, plastic carbonated beverages are likely to release microplastics and release more than non-carbonated beverages. 

Ultimately, though, no study has directly compared nanoplastic release between glass and plastic bottles. The evidence to date shows the following:

1. Plastic bottles still release significant quantities of microplastics and nanoplastics, and at levels that standard detection methods don’t capture
2. The plastic caps are a primary source of microplastic contamination
3. Carbonated beverages in plastic bottles release more microplastics than non-carbonated beverages

In conclusion, the claim that “glass bottles release more microplastics than plastic bottles” does have credibility, but the picture is incomplete. The studies that make these claims don’t account for smaller microplastics (nanoplastics), and no study has directly compared these materials head-to-head in this size range. 

Six actions to avoid microplastics in glass and plastic bottles

• Replace bottled water with filtered tap water
  • Bottled water generally contains more microplastics than tap water, and home filtration appears to remove a significant portion of what remains. A 2022 review of 21 studies found that microplastic concentrations were consistently higher in bottled water than in tap water[8]. Filtering your water using glass or stainless steel filtration products and drinking the water from bottles of the same material helps you to avoid microplastics from the plastic bottles, caps, and manufacturing process itself.

• Don’t reuse single-use plastic bottles, and minimize repeated opening and closing.
  • One study found that repeatedly opening and closing plastic bottles increased microplastic release, with most particles coming from the bottleneck and cap rather than the bottle walls[6]. A separate study found that older, more frequently reused bottles carried higher microplastic counts than newer ones, so only use single-use bottles once if required[3]. 

• Consider using dry, powdered drinks or drink flavoring rather than bottled drinks
  • Although there’s no study showing a direct head-to-head comparison of microplastic quantities in powdered drinks versus bottled drinks, generally speaking, it appears that dry powders have far lower microplastic quantities than bottled drinks. Studies of milk and protein powders found that the raw powdered product contains relatively low amounts of microplastics, with most coming from the manufacturing and packaging process[9,10]. 

• If you need to drink from bottles, choose non-carbonated beverages
  • Carbonation puts the bottles under pressure, and that pressure drives more polymer particles into the drink. A 2023 experiment found that more microplastics and nanoplastics were released from plastic bottles as the concentration of carbon dioxide increased[7]. Therefore, if you have the choice, choose non-carbonated beverages[7]. 

• Let your favorite brands know that you want them to test their products for microplastics
  • Most major beverage companies don’t test for microplastics in their products, and there are still no regulatory limits for microplastics in food or beverages. Vote with your money. Let your favorite companies know that you want them to test their products for microplastics and nanoplastics. 

• Use Deplasto’s Microplastic Defense and Microplastic App 
  • We also know that microplastics and nanoplastics cause oxidative stress, cause inflammation, and disrupt normal hormones. We also know that, unfortunately, you can’t avoid microplastics entirely. Consequently, if you’re concerned about the impact of microplastics on your body, you should be supplementing your body’s needs and tracking your microplastic intake. Deplasto has a nutritional supplement with six, science-backed ingredients studied alongside microplastics in cell and animal studies. Additionally, Deplasto has a microplastic intake tracking app with over 100 different foods, drinks, and activities to help you understand your biggest daily contributors. 

Thanks for learning more about microplastics found in glass bottles and let us know if you’re interested in other topics. 

Sources cited

1. Wang, Y., & Wang, Y. (2024). Assessing microplastic contamination in soda beverages: A multi-city, multi-container laser direct infrared spectroscopy study. Heliyon, 10(12), e32805.
2. Chaïb, I., Doyen, P., Merveillie, P., Dehaut, A., & Duflos, G. (2025). Microplastic contaminations in a set of beverages sold in France. Journal of Food Composition and Analysis, 144, 107719.
3. Oßmann, B. E., Sarau, G., Holtmannspötter, H., Pischetsrieder, M., Christiansen, S. H., & Dicke, W. (2018). Small-sized microplastics and pigmented particles in bottled mineral water. Water Research, 141, 307-316.
4. Qian, N., Gao, X., Lang, X., Deng, H., Bratu, T. M., Chen, Q., Stapleton, P., Yan, B., & Min, W. (2024). Rapid single-particle chemical imaging of nanoplastics by SRS microscopy. Proceedings of the National Academy of Sciences, 121(3), e2300582121.
5. Materić, D. (2024). Nanoplastics measurements must have appropriate blanks. Proceedings of the National Academy of Sciences, 121(48), e2411099121.
6. Winkler, A., Santo, N., Ortenzi, M. A., Bolzoni, E., Bacchetta, R., & Tremolada, P. (2019). Does mechanical stress cause microplastic release from plastic water bottles? Water Research, 166, 115082.
7. Chen, Y., Xu, H., Luo, Y., Ding, Y., Huang, J., Wu, H., Han, J., Du, L., Kang, A., Jia, M., Xiong, W., & Yang, Z. (2023). Plastic bottles for chilled carbonated beverages as a source of microplastics and nanoplastics. Water Research, 242, 120243.
8. Gambino, I., Bagordo, F., Grassi, T., Panico, A., & De Donno, A. (2022). Occurrence of microplastics in tap and bottled water: Current knowledge. International Journal of Environmental Research and Public Health, 19(9), 5283.
9. Zhang, Q., Liu, L., Jiang, Y., Zhang, Y., Fan, Y., Rao, W., & Qian, X. (2023). Microplastics in infant milk powder. Environmental Pollution, 323, 121225.
10. Chen M, Dong R, Lai W. Heavy metal and Microplastic exposure from sports protein Supplements: Integrated health risk modeling and scenario analysis. Environ Res. 2026 Mar 15;295:123988. doi: 10.1016/j.envres.2026.123988. Epub 2026 Feb 6. PMID: 41655677.