A New Study Reveals: Glass Bottles May Release More Microplastics than Plastic Ones. What It Means for Health and How to Mitigate the Risk — in Open Oil Market.
French researchers 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 in glass bottles exhibited significantly higher levels of microplastics compared to their counterparts in plastic bottles or aluminum cans. In some cases, the level of microplastic particles in glass was found to be five, and even fifty times, higher. This revelation calls into question the established perception of the "purity" of glass containers.
Unexpected Research Findings
The new study conducted by the ANSES laboratory in France compared levels of microplastics in popular drinks based on packaging types. In every tested category—whether it was carbonated soft drinks, iced teas, beer, or mineral water—glass bottles showed the highest contamination levels with plastic particles. On average, a liter of beverage from glass containers contained roughly 100 microplastic particles. In comparison, the same beverage packaged in plastic bottles or metal cans contained only between 2 to 20 particles per liter. Even the researchers confessed that they “expected the opposite result”, initially assuming greater purity in glass.
Paint on Caps – A Hidden Source of Particles
The reason behind the unexpectedly high contamination levels in glass bottles lies in their caps. Glass beverage bottles are typically sealed with metal caps featuring a plastic liner and are painted on the exterior. The ANSES study discovered that the microplastic particles found in the contents of glass bottles matched in color and composition the paint covering these metal caps. In other words, the painted metal cap becomes a source of microplastics in the beverage.
The introduction of plastic into the drink is due to friction between the caps during storage and transport. The metal caps, coming into contact with one another before bottling, subtly scratch each other's painted surfaces. The tiny bits of coating, which are invisible to the eye, then flake off into the bottle during sealing. Therefore, each glass container with a painted cap contributes to invisible contamination of the drink. In contrast, plastic bottles feature single-piece plastic caps without a layer of paint, which explains why the level of microplastics in them is significantly lower. Additionally, glass bottles with cork or other unpainted caps (such as wine bottles) show negligible effect.
Why Some Beverages Are More Contaminated
The discrepancies in microplastic levels among different types of beverages prompted scientists to consider additional factors. Why, for instance, did carbonated drinks and beer in glass contain dozens of particles, while water had only a few? Experts speculate that the properties of the beverage itself and storage conditions may play a role:
- Carbonation and Pressure: Carbonated beverages (cola, lemonade, beer) generate increased pressure inside the bottle. This may enhance the friction of the cap against the bottle neck and contribute to the delamination of paint particles.
- Acidic Environment: Some carbonated sodas and beverages possess an acidic pH. The acidity can soften polymer coatings, facilitating the release of microplastic particles.
- Temperature and Transportation: Temperature fluctuations, shaking, and prolonged transport heighten wear on bottle caps. Movement of bottles within crates or containers results in constant friction between caps, increasing paint delamination.
Thus, the highest levels of microplastics were found in scenarios where vulnerable packaging elements (painted caps) were combined with aggressive conditions — pressure from carbonation, chemical composition, and mechanical stress during transport. Water and non-carbonated beverages, on the other hand, turned out to be less susceptible to this problem.
Potential Health Risks
It remains unclear whether the detected level of microplastics poses a direct health threat—scientists do not have a definitive "toxicity threshold" for such particles. Nonetheless, the mere presence of microplastics in food and beverages raises concerns among health professionals and ecologists. Microscopic plastics can accumulate in the body and impact health in various ways:
- Accumulation in Organs: Ingested through food and drink, microplastics may settle in various tissues. Their particles have been found in human lungs, liver, intestines, and even in blood and breast milk. Prolonged accumulation of foreign particles can jeopardize cellular and organ health.
- Chronic Inflammation: The immune system recognizes plastic as a foreign object and attempts to combat it. The constant presence of microplastics may cause low-grade inflammatory processes over time, which can damage healthy tissues.
- Disruption of Gut Microbiota: Plastic particles in the digestive system can disrupt the balance of gut bacteria. Studies show that microplastics alter microbiota composition, which may lead to gastrointestinal disorders, reduced immunity, and metabolic disruptions.
- Transport of Toxic Substances: Microplastics attract and adsorb various toxic compounds — from pesticides and heavy metals to dioxins. When these particles enter the body, such chemicals can exert additional harmful effects, including hormonal disruptions.
Although direct harm from small doses of microplastics is yet to be conclusively proven, medical professionals agree that excess "plastic dust" in our diet is certainly not conducive to health. Particularly concerning is its ability to provoke chronic inflammation and transport harmful chemicals into the body—factors that may contribute to serious diseases over time.
Ways to Reduce Microplastics in Packaging
Fortunately, having identified the source of contamination, researchers are suggesting solutions to mitigate it. Beverage manufacturers can relatively easily reduce plastic leaching from caps by improving technological processes. Experts at ANSES have tested several cleaning methods for caps prior to sealing, achieving substantial reductions in microplastics. Here are the key measures:
- Pre-Cleaning of Caps. Blowing new caps with compressed air, followed by rinsing with filtered water and alcohol before bottling, can reduce microplastic content by approximately 60%.
- Gentle Storage of Caps. It's essential to minimize friction between caps before bottling. Manufacturers may alter storage and transport conditions for caps—such as using pads or dividers to prevent mass contact between caps. Reducing mechanical impact on the coating will decrease scratching and paint waste.
- Improving Materials and Coatings. Another direction involves developing more wear-resistant materials for caps. Using paints less prone to flaking or alternative protective coatings will minimize particle migration.
Implementing these measures can significantly enhance the situation. Adaptation of processes (cleaning or new storage conditions) would be relatively cost-effective for manufacturers, while the effect for consumers would be a purer product free from unnecessary impurities.
Implications for the Beverage Industry
The revelations from French specialists serve as a wake-up call for the entire beverage and packaging industry. For years, glass containers have been promoted as an environmentally friendly alternative to plastic: they do not create plastic waste, are recyclable, and do not leach harmful substances into their contents. However, the new factor of microplastics indicates that glass also has hidden risks. This does not mean that we need to abandon glass bottles — rather, improvements in their design and manufacturing processes are required.
The takeaway for beverage manufacturers is clear: quality control must consider not only the liquid itself but also all packaging components. Additional testing for microplastics and preventive measures (such as the described cleaning of caps) might become the new standard in the industry. Regulators and consumers are increasingly attentive to product safety and cleanliness. Companies investing in "microplastic-free" solutions will benefit their reputation.
What This Means for Consumers
Awareness of this issue allows consumers to make more informed choices. While it is challenging to completely avoid microplastics in today’s landscape, individuals have the right to expect transparency and improvements from brands. Simple actions—such as rinsing the neck and cap before resealing a bottle—can also slightly reduce plastic contamination in beverages. Ultimately, increasing focus on microplastics from all market participants stimulates the creation of cleaner and safer products for consumers.
