Tea bags are paper--cheap, simple, harmless paper--except when they're not. Today many packaged tea sellers have moved to plastic bags, which are often marketed as "silky" bags because, well, it sounds better. But they're made of plastic or nylon, materials that bring with them certain health concerns. We've read about particles from plastic water bottles being toxic. When she heard about plastic being used in tea bags, The Atlantic writer Taylor Orci decided to see if those tea bags are be dangerous, too. The results of her research aren't encouraging.
Orci learned that plastic tea bags are most commonly made from polyethylene terephthalate or food grade nylon. Phthalates are materials widely used in the plastic industry--they're also the materials in plastic bottles linked to health issues like infertility and hormone disruption. She discovered that, unsurprisingly, these plastics and nylons have melting points far above boiling water's 212 degrees. Tea drinkers don't have to worry about plastic bags melting and poisoning them. But that's not the only issue.
"There is another temperature point for plastics, though, that we may need to worry about, called the "glass transition" temperature (Tg) ," writes Orci. At glass transition temperature, the plastic material becomes more porous. Bonds aren't breaking, and the solid isn't changing states into a liquid, but that doesn't really matter--what matters is that, at the glass transition temperature, a plastic tea bag will start leaching more chemicals.
Orci continues: "In the case of PET and food grade nylon (either nylon 6 or nylon 6-6), all have a Tg lower than the temperature of boiling water. For example, while the melting point of PET is 482 degrees Fahrenheit, the Tg is about 169 degrees. Both nylons have a lower glass transition temperature than PET. (Remember that water boils at 212 degrees.)"
The question is, are there unhealthy phthalates in these plastic tea bags that we should worry about? As long as the plastics aren't leaching anything bad, there's little cause for concern. Orci found that Lipton's platic tea bags claim to use "the same food grade material clear water and juice bottles are made of." But, as mentioned earlier, those bottles aren't exactly safe. Studies have shown notable concerning effects on human and animal health.
While plastic tea bags aren't going to make you sick overnight--and probably never will do much to you, unless you drink a ton of tea--it makes sense to limit exposure to them, just like other similar plastics. More health studies and explicit regulations on what's safe for use in foods would help, too. Read Orci's full article for more information from experts and the argument for plastic tea bags, which notes the pollution of paper manufacturing.