Plastic Tea Bags: What the Research Found

Those elegant pyramid-shaped tea bags in premium blends? Many of them are plastic — woven nylon or PET mesh. In 2019, a research team at McGill University asked a simple question nobody had checked: what does steeping a plastic bag in near-boiling water release into the cup? The answer made headlines worldwide.

The McGill study

The researchers bought four commercial teas packaged in plastic mesh bags, cut the bags open, emptied and rinsed them (so they were measuring the bag, not the tea), then steeped the empty bags in 95 °C water for five minutes — a normal tea-brewing scenario.

Using electron microscopy and spectroscopy, they reported that a single bag released approximately 11.6 billion microplastic particles and 3.1 billion nanoplastic particles into a single cup (Hernandez et al., 2019, Environmental Science & Technology). The particles' composition matched the bags themselves — nylon and PET.

Those numbers dwarf earlier estimates of microplastic content in other foods and beverages, which typically counted particles per liter in the hundreds or thousands. The difference is partly real (steeping plastic at 95 °C is a worst-case scenario for particle release) and partly methodological — the McGill team counted nanoparticles, which most food studies at the time couldn't detect at all.

What the study did and didn't show

It did show that plastic tea bags shed enormous numbers of particles under normal brewing conditions, and that heat matters — steeping at brewing temperature released far more than room-temperature water.

It didn't show harm. The study measured release, not health effects. A companion experiment exposed water fleas (Daphnia magna) to the released particles and observed behavioral and developmental changes at high doses — but water fleas are not humans, and the doses were experimental. As covered in our health effects guide, presence and dose are not the same as demonstrated human harm.

It also didn't test paper bags. That matters, because the story there is more nuanced than "paper = safe."

What about ordinary paper tea bags?

Most conventional paper tea bags are not pure paper. Many are heat-sealed with a thin layer of polypropylene, and some "paper" bags use plastic fibers for wet strength. Follow-up research has found particle release from paper-style bags too — a 2024 study measured particles in the hundreds of millions per milliliter from cellulose bags, though composition and methods differ enough between studies that direct comparisons are tricky (Banaei et al., 2024, Chemosphere).

Some brands have switched to plant-based PLA ("bioplastic") mesh or sealant. PLA is marketed as compostable, but it is still a polymer, and studies suggest PLA bags also shed particles — roughly a million PLA nanoplastics per teabag in one analysis (Banaei et al., 2023, Journal of Hazardous Materials). "Bioplastic" solves a composting problem, not necessarily a particles-in-your-cup problem.

How to tell if your tea bags are plastic

No labeling law requires disclosing bag material, but rough heuristics help:

• Silky, shiny pyramid bags — almost certainly nylon or PET mesh (some newer ones are PLA)
• Bags that feel like paper — mostly paper, possibly with polypropylene heat-sealing at the crimped edges
• A crimped/folded bag closed with a staple and string — usually the least-plastic conventional design
• The burn test is unreliable and not recommended — check the brand's packaging or website instead; many now state their material

Switching is easy and arguably makes better tea

This is one of the cheapest microplastic swaps there is, because the alternative is just… tea:

1. Loose-leaf tea + a stainless steel infuser. One-time purchase of a few dollars, zero plastic contact, and loose leaf is often better quality than bagged for the price.
2. A teapot with a built-in stainless or ceramic strainer if you brew for more than one.
3. If you stay with bags, prefer brands that explicitly state plastic-free, staple-closed paper bags, and avoid the shiny pyramid mesh for daily drinking.

One perspective worth keeping: tea itself remains a healthy beverage by all available evidence, and nobody should quit tea over this study. The finding is about the packaging, and the packaging is trivially replaceable — which makes it a rare microplastics story with a fully satisfying ending.

This article describes research findings and general information, not personalized health advice.