Tea Bags and Invisible Pollution: Microplastics, Nanoplastics, and Health Risks in 2025
One of my very first articles, written in 2020, explored the release of microplastics from tea bags steeped in hot water. The long-term health risks remain poorly understood. For example, it is known that the development of simpler organisms such as plankton is disrupted under exposure conditions similar to everyday tea consumption: one tea bag in a mug. So, what have researchers discovered in 2025?
What is a tea bag?
Defining the exact composition of a tea bag is not easy, as manufacturers are not required to disclose its components. Today, many materials are used, whether derived from petrochemicals or plants. These include petroleum-based plastics such as nylon fibers, popular biodegradable plant-based plastics like PLA, and raw plant materials such as cellulose. There may be blends of plastics, combinations of plastics and plant materials, or strictly plant-based materials.
A seemingly "paper" tea bag may contain cellulose mixed with plastics. A pyramid-shaped bag might be made of nylon (often called "crystal bags") or biodegradable PLA. A "cotton" bag could contain nylon and cellulose, or be fully woven from abaca or hemp.
Tea bag design
From a practical standpoint, a tea bag with a fine mesh pattern is often used for broken tea leaves, while a wider mesh is used for whole leaves. Fibers may be joined with plastics to reinforce the bag's durability in hot water. Beyond the costs of materials—which are rarely detailed in scientific publications—the design can impact the infusion process: the fiber arrangement and the physical-chemical properties of the materials (hydrophobicity, porosity, etc.).
For instance, a woven nylon bag (regular grid pattern) allows approximately 20% more efficient infusion during the first minute compared to non-woven or irregularly patterned bags. The material type (e.g., woven nylon vs. nylon-cellulose hybrid vs. 100% cellulose) affects the tea bag's porosity. It appears that the more plant-based materials are used, the more hydrophobic and less porous the bag becomes, potentially limiting the diffusion of tea compounds into water.
However, tea bag design may come with a health cost. Microfractures can form when the bag is placed in hot water, releasing fiber fragments. This happens across all material types, although woven nylon fibers seem less prone to this issue. Unfortunately, this is another source of microplastic contamination in water. Even biodegradable plant-based plastics are not harmless; they may release 1,000 times fewer plastics than petroleum-based ones, but they still contribute to aqueous contaminants. Small amounts of microplastics have also been detected with purely plant-based bags. This could be due to industrial treatment of fibers or contamination from plastic packaging. Indeed, plastic packaging also releases microplastics over time, which may cling to its contents.
Environmental concerns
Environmental concerns surrounding the breakdown of plastic tea bags are troubling. Even biodegradable PLA bags showed no degradation after 12 weeks in soil and negatively affected soil biodiversity, including worm mortality.
Not just microplastics
Microplastics are not the only elements found in modern materials. Many everyday products contain nanomaterials—particles 1,000 times smaller than micro-materials. These are closely monitored for their impact on human health. In France, titanium dioxide (E171), a nanoparticle used as a food additive, has been banned since 2020 due to its confirmed toxicity and potential carcinogenicity. Predicting the toxicity of nanomaterials is difficult, making it essential to identify nanoplastics released from tea bags to enable long-term health evaluations.
Unfortunately for tea drinkers, recent studies have confirmed that standard commercial tea bags release nanoplastics. The type and amount of nanoplastics vary depending on the material, with lower release rates seen in nylon. In a 2024 study, researchers cultured human intestinal cells responsible for mucus and barrier formation in the presence of different nanoparticles released from tea bags. Depending on the cell type and nanoparticle, changes were observed in cell morphology, mucus production, and barrier function. Nanoparticles were also found inside the cell nuclei.
This is concerning because the nucleus contains the cell's DNA. Nanoparticle-induced changes could lead to cell death or abnormal proliferation. While media attention has focused on early studies about microplastics, emerging research on nanoplastics reveals their ability to access cellular compartments inaccessible to larger particles. Like titanium dioxide, further toxicity and carcinogenicity studies are needed to identify the safest materials for long-term health.
Bibliography
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