New Research Shows: Glass Bottles May Release More Microplastics Than Plastic. How This Affects Health and What to Do to Mitigate Risks — in the 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 findings surprised even the researchers themselves: beverages from glass bottles showed a significantly higher presence of microplastics than similar drinks in plastic bottles or aluminum cans. In some instances, the level of microplastic particles in glass was found to be five to fifty times higher. This raises questions about the established belief in the "purity" of glass containers.
Unexpected Research Findings
The new study conducted by ANSES compared the level of microplastics in popular beverages based on their packaging. In every tested category — whether carbonated soft drinks, iced tea, beer, or mineral water — glass bottles exhibited the highest levels of plastic particle contamination. On average, approximately 100 microplastic particles were found per liter of beverage in glass containers. In contrast, the same beverage packaged 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 glass would offer greater purity.
Paint on Caps – A Hidden Source of Particles
The explanation for the unexpectedly high contamination levels in glass bottles lies in their caps. Beverage glass bottles are usually sealed with metal caps that feature an inner plastic liner and are painted on the outside. The ANSES study found that the microplastic particles identified in the contents of glass bottles matched in color and composition with the paint covering these metal caps. In other words, the painted metal cap becomes a source of microplastics in the beverage.
The cause of plastic entering the drink was friction between the caps during storage and transportation. When metal caps touch each other before bottling, they discreetly scratch each other's painted surfaces. Tiny bits of paint, invisible to the eye, then flake off into the bottle during sealing. Therefore, each glass container with a painted cap contributes invisible contamination to the drink. In contrast, plastic bottles are fitted with solid plastic caps without a paint layer, explaining the significantly lower levels of microplastics. Additionally, glass bottles with corks or other unpainted caps (such as wine bottles) exhibit minimal effects.
Why Some Beverages Are More Contaminated
Differences in microplastic levels among beverage types led scientists to consider additional factors. For instance, why did carbonated drinks and beer in glass show dozens of particles, while water had only a few? Experts speculate that the properties of the beverages themselves and storage conditions may play a role:
- Carbonation and Pressure: Carbonated beverages (cola, lemonade, beer) create elevated pressure inside the bottle. This could increase friction between the cap and the neck, contributing to paint particle flaking.
- Acidity of the Environment: Some carbonated soft drinks and sodas have acidic pH levels. Acids can soften polymer coatings, making it easier for microplastic particles to be released.
- Temperature and Transportation: Temperature fluctuations, shaking, and prolonged transportation increase wear on the caps. The movement of bottles in crates or containers results in constant friction, increasing paint flaking.
Thus, the highest levels of microplastics were found in cases where vulnerable packaging elements (painted caps) were combined with aggressive conditions — the pressure of carbonation, chemical composition, and mechanical impact during transport. Water and non-carbonated beverages, on the other hand, proved less susceptible to this issue.
Potential Health Risks
While it has not been established whether the detected level of microplastics poses an immediate health threat — scientists lack a clear "toxicity threshold" for such particles — the mere presence of microplastics in food and beverages raises concerns among medical professionals and ecologists. Microscopic plastics can accumulate in the body and impact it in various ways:
- Accumulation in Organs: When ingested 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. Long-term accumulation of foreign particles poses risks of 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 may induce chronic inflammatory processes that gradually damage healthy tissues.
- Disruption of Gut Microbiota: Plastic particles in the digestive system can disturb the balance of intestinal bacteria. Research indicates that microplastics alter the microbiota's composition, which can lead to digestive disorders, weakened immunity, and metabolic disruptions.
- Transport of Toxic Substances: Microplastics attract and adsorb various toxic compounds — from pesticides and heavy metals to dioxins — on their surface. When these chemicals enter the body alongside microplastic particles, they can cause additional harmful effects, including hormonal disruptions.
Although direct harm from small doses of microplastics has yet to be conclusively proven, medical experts agree that extra "plastic dust" in our diet cannot be conducive to health. Particularly concerning is its ability to provoke chronic inflammation and transport harmful chemicals into the body — factors that could contribute to the development of serious diseases over time.
Ways to Reduce Microplastics in Packaging
Fortunately, having identified the source of contamination, researchers propose solutions to mitigate it. Beverage manufacturers can relatively easily reduce plastic contamination from caps by improving technological processes. ANSES experts tested several cap treatment methods before sealing and achieved significant reductions 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%.
- Careful Storage of Caps. It is essential to minimize cap-to-cap friction before bottling. To achieve this, manufacturers can alter storage and transportation conditions — for example, using gaskets or dividers to prevent mass contact between caps. Reducing mechanical impacts on the coating will decrease the formation of scratches and paint waste.
- Improving Materials and Coatings. Another approach is to develop cap materials that are more resistant to wear. Utilizing paints less prone to flaking or alternative protective coatings can minimize particle migration.
Implementing these measures could significantly improve the situation. Adapting processes (cleaning or new storage conditions) would be relatively inexpensive for manufacturers, resulting in a cleaner product for consumers without unnecessary impurities.
Implications for the Beverage Industry
The discovery by French specialists serves as a signal for the entire beverage and packaging industry. Glass containers have long been promoted as an eco-friendly alternative to plastic: they do not create plastic waste, are recyclable, and do not leach harmful substances into the contents. However, this new microplastic factor indicates that hidden risks also accompany glass. This does not mean that glass bottles should be abandoned — rather, there is a need to enhance their design and production cycle.
For beverage manufacturers, the message is clear: quality control should consider not only the liquid itself but also all packaging components. Additional checks for microplastics and preventive measures (such as the described cap cleaning) may become the new industry standard. Regulators and consumers are increasingly focused on the safety and purity of products. Companies investing in "microplastic-free" solutions will gain reputational advantages.
What This Means for Consumers
Awareness of this issue helps consumers make more informed choices. While it is challenging to completely avoid microplastics in modern circumstances, individuals have the right to expect transparency and improvements in technology from brands. Simple actions — such as rinsing the neck and cap before resealing a bottle — may also slightly decrease plastic contamination in beverages. Ultimately, increased attention to microplastics from all market participants will stimulate the creation of cleaner and safer products for consumers.
