New research indicates: glass bottles may release more microplastics than plastic. How this affects health and what to do to avoid the risks - in the Open Oil Market article.
French scientists from the Food Safety Agency ANSES conducted a series of tests on various beverages - water, soda, iced tea, beer, and wine - bottled in different types of packaging. Their results surprised even the researchers themselves: beverages from glass bottles showed significantly higher levels of microplastics than similar drinks in plastic bottles or aluminium cans. In some cases, the level of microplastic particles in glass was found to be five, or even fifty times higher. This brings into question the widely held belief regarding the "purity" of glass packaging.
Unexpected results of the research
The new study conducted by ANSES laboratory in France 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 demonstrated the highest contamination with plastic particles. On average, around 100 microplastic particles were detected per litre of beverage from glass containers. In contrast, the same drink bottled in plastic or metal contained only between 2 to 20 particles per litre. Even the researchers admitted they "expected the opposite result", initially anticipating greater purity from glass.
The paint on the caps - a hidden source of particles
The unexpectedly high contamination of glass bottles is rooted in their caps. Glass bottles for beverages are typically sealed with metal caps that have an inner plastic liner and are painted on the outside. The ANSES study found that the microplastic particles discovered in the contents of glass bottles matched in colour 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 turns out to be the friction of the caps against one another during storage and transport. As the metal caps come into contact before bottling, they subtly scratch each other's painted surface. The tiniest pieces of coating, invisible to the naked eye, then flake off into the bottle when sealed. Thus, each glass container with a painted cap contributes invisible contamination to the drink. By contrast, plastic bottles have solid plastic caps without a layer of paint, which explains why the microplastic levels are significantly lower in them. Additionally, glass bottles with cork or other non-painted caps (such as wine bottles) exhibit virtually no such effect.
Why some beverages are more contaminated
The differences in microplastic levels between types of beverages prompted scientists to consider additional factors. Why, for example, do carbonated drinks and beer in glass contain dozens of particles while water contains only a few? Experts suggest that the properties of the beverage itself and storage conditions may play a role:
- Carbonation and pressure: carbonated beverages (cola, lemonade, beer) create increased pressure inside the bottle. This may enhance the friction of the cap against the neck and promote the flaking of paint particles.
- Acidity of the medium: some carbonated sodas and soft drinks have an acidic pH. The acid can soften the polymer coatings, facilitating the release of microplastic particles.
- Temperature and transportation: fluctuations in temperature, shaking, and prolonged transport amplify the wear on the caps. The movement of bottles in crates or containers leads to constant friction of the caps against each other, increasing the flaking of paint.
Thus, the highest levels of microplastics were found in instances where vulnerable packaging elements (painted caps) coincided with aggressive conditions - pressure from carbonation, chemical composition, and mechanical impact during transport. Water and non-carbonated beverages, on the other hand, were found to be less susceptible to this issue.
Potential health risks
It remains undetermined whether the detected levels of microplastics pose an immediate health threat - researchers do not have a clear "toxicity threshold" for such particles. Nevertheless, the mere presence of microplastics in food and beverages raises concerns among medical professionals and ecologists. Microscopic plastics can accumulate in the body and affect it in numerous ways:
- Accumulation in organs: entering through food and drink, microplastics can deposit in various tissues. Their particles have been found in human lungs, livers, intestines, and even in blood and breast milk. Long-term accumulation of foreign particles risks damaging cells and organs.
- Chronic inflammation: the immune system recognises plastic as a foreign object and attempts to combat it. The constant presence of microplastics can induce chronic inflammatory processes that gradually damage healthy tissues.
- Disruption of gut microbiota: plastic particles in the digestive system may disturb the balance of gut bacteria. Studies show that microplastics alter the composition of microbiota, leading to digestive disorders, weakened immunity, and metabolic disruptions.
- Transport of toxic substances: microplastics attract and adsorb various toxic compounds on their surfaces - from pesticides and heavy metals to dioxins. Entering the body alongside these particles, these chemicals may cause additional harmful effects, including hormonal disruptions.
Although direct harm from small doses of microplastics has not yet been definitively proven, medical professionals agree that excessive "plastic dust" in our diets certainly does not contribute to health. Particularly alarming is its ability to provoke chronic inflammation and transport harmful chemicals into the body - 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 also propose solutions to mitigate it. Beverage manufacturers can relatively easily reduce plastic introduction from caps by improving their processing methods. ANSES experts tested several cap treatment methods prior to sealing and achieved 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, reduced microplastic content by approximately 60%.
- Careful storage of caps. It is crucial to minimise friction between caps before bottling. Manufacturers can adjust storage and transport conditions for caps - for instance, using liners or separators to prevent mass contact between caps. Reducing mechanical impact on the coating will lessen scratching and paint waste.
- Improvement of materials and coatings. Another approach is to develop more abrasion-resistant cap materials. Using paints that are less prone to flaking, or alternative protective coatings, can help minimise particle migration.
Implementing these measures can significantly improve the situation. For manufacturers, adapting processes (cleaning or new storage conditions) is relatively inexpensive, while consumers stand to benefit from a cleaner product without unwanted impurities.
Implications for the beverage industry
The findings from French specialists serve as a wake-up call 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 release harmful substances into their contents. However, the new microplastic factor indicates that glass also carries hidden risks. This does not mean that glass bottles should be abandoned - rather, their design and manufacturing processes require refinement.
For beverage manufacturers, the conclusion is clear: quality control should take into account not only the liquid itself but also all elements of packaging. Additional checks for microplastics and preventative measures (such as the cleaning of caps described) may become the new industry standard. Regulators and consumers are increasingly focusing on the safety and purity of products. Companies investing in "microplastic-free" solutions will gain a reputational advantage.
What this means for consumers
Awareness of this issue enables consumers to make more informed choices. While it is challenging to completely avoid microplastics in contemporary conditions, people are entitled to expect transparency and technological advancement from brands. Simple actions - such as rinsing the neck and cap of a bottle before resealing it - may also slightly reduce plastic contamination in the drink. Ultimately, an increased focus on microplastics from all market participants will encourage the creation of cleaner and safer products for consumers.
