Plastic and silicone

Cheap, light and unbreakable, and the subject of the loudest health claim in tea. That claim is worth going through carefully, because the widely quoted figure has been assessed by a national food safety regulator and found to be wrong by a very large factor.

What it is

Two different chemistries with a shared reputation. Carbon-based plastics, nylon, polyethylene, PET and plant-derived polylactide, are hydrophobic polymers built on a carbon and hydrogen skeleton. Silicone is not one of them: it is built on a silicon and oxygen framework, is stable across a wider temperature range, stays cool to the touch because it conducts heat poorly, and does not shed microplastic particles.

What it does to your tea

Chemically very little in the cup, though plasticisers have been detected in infusions. Plastics do not dissolve in hot tea; particles come off through mechanical wear during packing, transport and handling. The extraction behaviour is unremarkable: woven nylon teabags are more porous than cellulose paper, with pores around four times the diameter, and infuse only slightly faster.

What it suits

Travel, children, and anywhere breakage matters. Silicone is the better of the two for anything reusable, since it tolerates heat, stays cool to hold and sheds nothing.

Care and cleaning

Dishwasher-safe as a rule. Silicone holds odours from strongly flavoured teas and is worth keeping to one kind. Replace any plastic item that has gone chalky or crazed, since surface degradation is what generates particles.

What people get wrong

Repeating the 11.6 billion figure. A 2019 study reported that one plastic teabag at 95 degrees Celsius releases about 11.6 billion microplastic and 3.1 billion nanoplastic particles, and it travelled everywhere. The German Federal Institute for Risk Assessment assessed it and found the counts for particles above one micrometre probably two to three orders of magnitude too high, caused by drying the extract before electron microscopy so that dissolved substances precipitated and were counted as plastic. Most of what was counted appears to be oligomers, which dissolve in hot water and are not microplastics. Against the study's 2.3 million, independent work found 5,800 to 20,400. The BfR's position on health is that there is no evidence of harmful effects of microplastic particles on human health. Plastic teabags do shed particles. The number in circulation is not the size of it, and this page states what was measured and what a regulator concluded rather than making a health claim in either direction.

Made of this

teabert, the tealytics teapot, keeper of the kettle

The scary number was checked by a regulator and came back a hundred to a thousand times smaller. Worth knowing before you throw out your kit.

Sources

one plastic teabag at 95 °C was reported to release about 11.6 billion microplastic and 3.1 billion nanoplastic particles Hernandez, L. M. et al. (2019). Environmental Science & Technology
the German Federal Institute for Risk Assessment found those counts probably two to three orders of magnitude too high and states there is no evidence of harmful effects of microplastic particles on human health Bundesinstitut für Risikobewertung (BfR)