The research specifically deals with cellulose bags which are often sealed with glues containing synthetic polymers.
The picture from the study of the cellulose bags show a round “pillow” style bag which is likely sealed with a glue, unlike some cellulose bags which are folded and stapled:
> The tea bags used for the research were made from the polymers nylon-6, polypropylene and cellulose. The study shows that, when brewing tea, polypropylene releases approximately 1.2 billion particles per milliliter, with an average size of 136.7 nanometers; cellulose releases about 135 million particles per milliliter, with an average size of 244 nanometers; while nylon-6 releases 8.18 million particles per milliliter, with an average size of 138.4 nanometers.
So while polypropylene is the worst of the three by an order of magnitude, the cellulose pillow-style bag still leaches a large number of particles.
Notably, the authors tested OEM empty teabags for polypropylene and nylon, but chose a supermarket brand of cellulose pillow-style bags with tea still inside.
The picture from the study of the cellulose bags show a round “pillow” style bag which is likely sealed with a glue, unlike some cellulose bags which are folded and stapled:
https://ars.els-cdn.com/content/image/1-s2.0-S00456535240263...
From the article that summarized the study:
> The tea bags used for the research were made from the polymers nylon-6, polypropylene and cellulose. The study shows that, when brewing tea, polypropylene releases approximately 1.2 billion particles per milliliter, with an average size of 136.7 nanometers; cellulose releases about 135 million particles per milliliter, with an average size of 244 nanometers; while nylon-6 releases 8.18 million particles per milliliter, with an average size of 138.4 nanometers.
So while polypropylene is the worst of the three by an order of magnitude, the cellulose pillow-style bag still leaches a large number of particles.
Here’s the study: https://www.sciencedirect.com/science/article/pii/S004565352...
Notably, the authors tested OEM empty teabags for polypropylene and nylon, but chose a supermarket brand of cellulose pillow-style bags with tea still inside.