Microplastics and Tea Bags: How Everyday Infusions Pose Hidden Health Risks

Microplastics and nanoplastics are emerging contaminants that pose a growing threat to environmental and human health. Defined as plastic particles less than 5 mm in size, microplastics originate from a variety of sources, including industrial waste, cosmetic products and the degradation of larger plastic items. Nanoplastics, even smaller, measure less than 1,000 nanometers and are capable of penetrating biological barriers. While much of the concern surrounding these pollutants has focused on marine ecosystems, their presence in food and beverage packaging – particularly in items perceived as healthy – raises additional alarms. One such example is microplastics and tea bags.

A study conducted by the Mutagenesis Group at the Autonomous University of Barcelona (UAB) has provided compelling evidence that commercial tea bags release vast quantities of micro- and nanoplastics (MNPLs) when infused in hot water. More importantly, this study is the first to demonstrate that these particles can be absorbed by human intestinal cells, potentially entering the bloodstream and dispersing throughout the body.

Microplastics and tea bags: Scope of the problem

What are tea bags made of?

Commercial tea bags are no longer made exclusively from paper. Modern variants often contain synthetic polymers such as:

• Nylon-6: Known for its durability and heat resistance
• Polypropylene: A widely used thermoplastic in food-grade packaging
• Cellulose: A semi-synthetic material derived from plant fibers, sometimes chemically treated for added strength

These materials, while effective in maintaining the structural integrity of the bag during brewing, contribute to the release of plastic particles under high temperatures and help explain the link between microplastics and tea bags.

Particle release by polymer type

Using hot water to prepare an infusion causes these materials to shed particles at an alarming rate. The UAB study investigated the link between microplastics and tea bags, quantifying the particle release per milliliter (mL) of brewed tea as shown in Table 1.

Table 1. The quantity and average particle size of particles released by each polymer type when brewing tea with tea bags composed of polypropylene, cellulose and nylon-6.

These figures reflect a significant and previously underappreciated source of microplastic exposure for regular tea drinkers, demonstrating a link between microplastics and tea bags.

Credit: iStock.

Analytical techniques for characterizing microplastics

Accurate characterization of MNPLs in complex biological and environmental matrices requires advanced analytical tools. The UAB team employed a suite of complementary techniques to identify a link between microplastics and tea bags and assess the physical and chemical properties of particles released from the tea bags:

Imaging and spectroscopy methods

• Scanning electron microscopy: Provided high-resolution surface images of the particles.
• Transmission electron microscopy: Offered detailed internal structure visualization at the nanoscale.
• Attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR): Enabled identification of polymer types based on molecular vibrations.

Particle size and charge analysis

• Dynamic light scattering: Measured the hydrodynamic size distribution of particles.
• Laser Doppler velocimetry: Assessed zeta potential to understand particle surface charge.
• Nanoparticle tracking analysis: Tracked individual particles in liquid samples to determine size and concentration.

According to lead researcher Dr. Alba Garcia, "We have managed to innovatively characterise these pollutants with a set of cutting-edge techniques, which is a very important tool to advance research on their possible impacts on human health."

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Biological interaction with human cells

To evaluate potential health effects from microplastics and tea bags, the team exposed stained MNPLs to various types of cultured human intestinal cells. This experimental approach allowed them to assess cellular uptake and localization of plastic particles.

Key findings

• Highest uptake in mucus-producing cells: Among the cell types tested, mucus-secreting intestinal cells internalized the highest volume of MNPLs.
• Intracellular localization: Particles were found not only within the cytoplasm but also in the nuclei of cells, raising concerns about possible genetic-level effects.

These results suggest a mechanism through which MNPLs could cross intestinal barriers and gain access to systemic circulation, potentially affecting distant organs over time.

Implications for food safety and human health

The ability of microplastics to interact with and be absorbed by human cells underscores the need for rigorous food safety assessments and regulatory oversight.

While long-term effects are still under investigation, potential health risks could include:

• Inflammation and immune response: Chronic exposure may trigger immune dysregulation.
• Genotoxicity: The presence of plastics in cell nuclei suggests a theoretical risk of DNA damage.
• Bioaccumulation: Repeated exposure could lead to the accumulation of particles in tissues.

Regulatory gaps

Currently, there are no universally standardized test methods for assessing MNPL contamination in food-contact materials, including microplastics and tea bags. Researchers emphasize the need for:

• Standardized testing protocols: To evaluate contamination levels across products
• Regulatory frameworks: To establish safe limits and guide manufacturing practices
• Public awareness campaigns: To inform consumers about potential risks

"As the use of plastic in food packaging continues to increase, it is vital to address MNPLs contamination to ensure food safety and protect public health," the study authors state.

Toward a safer future

The study was carried out under the European PlasticHeal project, which aims to understand how MNPLs affect human health and develop tools to mitigate exposure.

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To reduce contamination from microplastics and tea bags, manufacturers could consider:

• Alternative materials: Using fully biodegradable and heat-stable natural fibers
• Improved manufacturing standards: Limiting the use of thermoplastics in food-contact components
• Consumer guidance: Encouraging the use of loose-leaf tea or paper-based bags without plastic reinforcement

The link between microplastics and tea bags presents a tangible route of human exposure to plastic pollution. With the demonstrated ability of these particles to interact with and be absorbed by intestinal cells, concerns over long-term health effects are warranted. By leveraging advanced analytical techniques and promoting regulatory reform, the scientific community can play a pivotal role in safeguarding public health.

Continued research and interdisciplinary collaboration are essential to fully understand the risks posed by MNPLs and to develop effective strategies for minimizing their presence in everyday consumer products.

This article is a rework of a press release issued by the Autonomous University of Barcelona. Material has been edited for length and the content has been updated to provide additional context and details of related developments since the original press release was published on our website. This article includes text that has been generated with the assistance of AI. Technology Networks' AI policy can be found here.