According to the latest issue of _Which?_, some of the main brands of
tea use polypropylene in the bags. The article says to "look out for
stitched bags with a tag (remove any staples before chucking them on
your compost heap)".


This explains why I sometimes find thinned down bags in the worm bin
output. Well, now I know to stop throwing them back in the top, which
is what I normally do with anything that isn't "fully digested" yet.

I don't see any reason to start removing staples, though --- I think
they rust away in the worm bin.