The modern tea bag, often recognizable by its “silky” texture and pyramid shape, is frequently made from Polylactic Acid, or PLA. This bio-based material has replaced traditional paper bags in many premium tea brands due to its superior mesh structure, which allows for better water flow and tea leaf expansion. The concern for consumers arises because this material is still a form of plastic, and steeping it in near-boiling water introduces the potential for chemical migration and particle release into the beverage. This article examines the scientific findings regarding the safety of PLA tea bags, focusing on the evidence concerning chemical leaching and microplastic contamination.
Understanding Polylactic Acid (PLA)
Polylactic Acid is a bioplastic derived from fermented plant starches, commonly sourced from corn, sugarcane, or cassava. Unlike traditional plastics manufactured from petroleum, PLA is considered a renewable and bio-based alternative. The process involves fermenting plant sugars into lactic acid, which is then polymerized into a resin that can be spun into fine fibers.
This resulting mesh fiber is used in tea bags because it provides a strong, transparent, and heat-resistant structure. While it is marketed as a more environmentally responsible choice, PLA is still classified as a polymer. The material is compostable, but only under the specific high-heat and microbial conditions found in industrial composting facilities, not typically in a home compost pile.
Chemical Leaching When Steeped
The primary chemical safety question revolves around whether the polymer chain breaks down and releases its constituent molecules into the hot water. This process is known as leaching or migration, where small molecular components transfer from the plastic material into the food or beverage. PLA is an aliphatic polyester, and its thermal stability is a factor when exposed to typical steeping temperatures, which can range from 170°F to 212°F (77°C to 100°C).
Regulatory bodies in the United States and the European Union have approved PLA for food contact applications, meaning it meets strict standards for minimal chemical migration under normal use conditions. This approval is based on the material’s general stability and the low toxicity of its breakdown products. Lactic acid, the monomer unit of PLA, is a naturally occurring organic compound already present in the human body and many foods.
However, the temperature of near-boiling water (around 95°C or 203°F) creates a dynamic environment that can accelerate the migration process. The overall scientific consensus has historically been that the release of chemical compounds from PLA into beverages is minimal and falls within safe regulatory limits.
The Issue of Microplastic Release
Distinct from chemical leaching is the mechanical concern regarding the physical shedding of small plastic particles, known as microplastics and nanoplastics. Microplastics are generally defined as particles smaller than 5 millimeters, while nanoplastics are smaller than 100 nanometers. When plastic tea bags, including those made from PLA, are exposed to high heat, the physical mesh structure can degrade, causing tiny fragments to break off.
One widely cited study from 2019 demonstrated the significant scale of particle release from plastic tea bags, finding that steeping a single bag at 95°C released billions of microplastic and nanoplastic particles. More recent research has specifically confirmed that PLA tea bags also release nanoplastics into the water.
A 2023 study found that PLA nanoplastics were released from commercial tea bags, quantifying about one million nanoplastics per tea bag. While this quantity is significantly lower than the billions reported in the earlier study, it confirms that PLA is not entirely exempt from particle shedding. The health implications of ingesting these particles are still a subject of ongoing research, though initial studies on model organisms have shown some dose-dependent behavioral and developmental effects.
Safe Steeping Practices and Material Alternatives
Consumers who wish to reduce potential plastic exposure can adopt several practical steeping adjustments. Since high temperatures accelerate the release of particles, allowing boiling water to cool for a minute or two before pouring it over the tea bag can help mitigate the risk. Avoiding prolonged steeping times may also limit the duration of the plastic-water interaction, minimizing the amount of material that can leach or shed.
For a nearly plastic-free tea experience, the most straightforward alternative is to switch to loose-leaf tea. Loose leaves can be steeped using various methods:
- Stainless steel mesh infusers.
- Ceramic steeping cups with built-in filters.
- Unbleached paper pulp tea bags.
Traditional paper tea bags, which are often sealed with a small amount of plastic, can still be a source of microplastics, making a transition to loose leaf the most secure option.