New Study Shows: Glass Bottles May Release More Microplastics Than Plastic. What This Means for Health and How to Mitigate the Risk — in Open Oil Market Article.
French scientists from the food safety agency ANSES conducted a series of tests on various beverages—including water, soda, iced tea, beer, and wine—packaged in different types of containers. Their results astonished even the researchers themselves: drinks from glass bottles showed significantly higher levels of microplastics than comparable drinks in plastic bottles or aluminum cans. In some instances, the concentration of microplastic particles in glass was found to be five, even fifty times higher. This challenges the long-held belief in the "purity" of glass packaging.
Unexpected Findings of the Research
The new study conducted by ANSES laboratory in France compared the microplastic levels in popular beverages based on their packaging. In every tested category—whether it was carbonated soft drinks, iced tea, beer, or mineral water—glass bottles exhibited the highest contamination levels with plastic particles. On average, one liter of beverage from glass containers contained around 100 microplastic particles. In contrast, the same beverage packed in plastic bottles or metal cans contained only 2 to 20 particles per liter. Even the researchers admitted that they "expected the opposite result," initially assuming greater purity for glass.
Paint on Caps — A Hidden Source of Particles
The unexpectedly high levels of contamination in glass bottles can be traced back to their caps. Glass drink bottles are typically sealed with metal caps that have an internal plastic liner and are painted externally. The ANSES study found that the microplastic particles detected in the contents of glass bottles matched in color and composition with the paint that covers these metal caps. In other words, the painted metal cap acts as a source of microplastic in the beverage.
The entry of plastic into the drink occurs due to friction between caps during storage and transport. The metal caps, rubbing against each other prior to bottling, subtly scratch the painted surface of one another. Minute pieces of paint, invisible to the naked eye, then shed into the bottle during capping. Thus, every glass container with a painted cap introduces invisible contamination into the beverage. In contrast, plastic bottles are equipped with all-plastic caps devoid of a paint layer, which explains the significantly lower levels of microplastics found in them. Additionally, glass bottles with cork or other unpainted caps (such as wine bottles) showed virtually no similar effect.
Why Some Beverages Are More Contaminated
Differences in microplastic levels between types of beverages have made scientists consider additional factors. For instance, why did carbonated drinks and beer in glass contain dozens of particles, while water had only a few? Experts suggest that the nature of the beverage and storage conditions may play a role:
- Carbonation and Pressure: Carbonated beverages (cola, lemonade, beer) create elevated pressure inside the bottle. This may increase cap friction against the neck of the bottle and contribute to paint flaking.
- Acidity of the Medium: Some carbonated sodas and lemonades have an acidic pH. Acids can soften the polymer coatings, facilitating the release of microplastic particles.
- Temperature and Transport: Fluctuations in temperature, shaking, and prolonged transportation enhance cap wear. The movement of bottles in crates or containers causes constant friction between caps, promoting the wear of paint.
Consequently, the highest levels of microplastics were found in scenarios where vulnerable packaging elements (painted caps) interacted with aggressive conditions—carbonation pressure, chemical composition, and mechanical stress during transport. Water and non-carbonated beverages, conversely, were less susceptible to this issue.
Potential Health Risks
So far, it has not been established whether the detected levels of microplastics pose an immediate health threat—scientists do not have a clear "toxicity threshold" for such particles. Nevertheless, the very fact that microplastics are present in food and beverages raises concerns among medical professionals and environmentalists. Microscopic plastic can accumulate in the body and impact it in various ways:
- Accumulation in Organs: When entering the body through food and drinks, microplastics can settle in various tissues. Their particles have already been found in human lungs, liver, intestines, and even in blood and breast milk. Prolonged accumulation of foreign particles threatens cell and organ damage.
- Chronic Inflammation: The immune system recognizes plastic as a foreign object and attempts to combat it. The constant presence of microplastics can induce chronic inflammatory processes that over time damage healthy tissues.
- Disruption of Gut Microbiota: Plastic particles in the digestive system can disturb the balance of gut bacteria. Studies indicate that microplastics alter the composition of gut microbiota, which can lead to digestive disorders, reduced immunity, and metabolic disruptions.
- Transport of Toxic Substances: Microplastics attract and adsorb various toxic compounds on their surface—from pesticides and heavy metals to dioxins. When these particles enter the body, the chemicals can cause additional harmful effects, including hormonal disruptions.
Although direct harm from small doses of microplastics has not yet been conclusively proven, medical professionals agree that excess "plastic dust" in our diet is not conducive to health. The alarming capability to provoke chronic inflammation and carry harmful chemicals into the body are factors that may over time contribute to the development of serious diseases.
Ways to Reduce Microplastics in Packaging
Fortunately, having identified the source of contamination, researchers propose solutions for its reduction. Beverage manufacturers can relatively easily mitigate the entry of plastic from caps by improving processing methods. ANSES experts tested several cap treatment methods prior to capping and achieved a significant reduction in microplastics. Here are the key measures:
- Pre-Cleaning Caps. Blowing new caps with compressed air followed by rinsing with filtered water and alcohol before bottling reduced microplastic content by approximately 60%.
- Gentle Storage of Caps. It is important to minimize friction between caps prior to bottling. To achieve this, manufacturers can modify storage and transportation conditions for caps—such as using pads or dividers to prevent mass contact of caps. Reducing mechanical impact on the coating minimizes scratches and paint waste.
- Improving Materials and Coatings. Another direction is the development of more abrasion-resistant caps. Using paints less prone to flaking or alternative protective coatings can minimize particle migration.
Implementing these measures can significantly improve the situation. For manufacturers, adapting processes (cleaning or new storage conditions) can be relatively inexpensive, while the benefit for consumers will be a cleaner product without excess impurities.
Implications for the Beverage Industry
The findings of French specialists serve as a signal for the entire beverage and packaging industry. Glass packaging has long been promoted as an eco-friendly alternative to plastic: it does not create plastic waste, is recyclable, and does not release harmful substances into its contents. However, the new factor of microplastics indicates that glass also harbors hidden risks. This does not mean that glass bottles should be abandoned—instead, there is a need to improve their design and manufacturing processes.
The takeaway for beverage producers is clear: quality control must not only assess the liquid itself but also all packaging elements. Additional checks for microplastics and preventive measures (such as the mentioned cap cleaning) could become a new industry standard. Regulators and consumers are increasingly focusing on the safety and purity of products. Companies investing in "microplastic-free" solutions will benefit in terms of reputation.
What This Means for Consumers
Awareness of this issue helps consumers make more informed choices. While completely avoiding microplastics in today's environment is challenging, consumers have a right to expect transparency and enhanced technologies from brands. Simple actions—such as rinsing the bottle neck and cap before resealing—may slightly reduce plastic contamination in beverages. Ultimately, increasing awareness of microplastics among all market participants drives the creation of cleaner and safer products for consumers.
