The original post on this thread was from England (as I recall), where I presume there are national curation standards, including bag thickness, and where the U.S. federal standards would be irrelevant. What is the national standard in the UK?

(I suggested the U.S.'s National Park Service standards because they are one of many sets of standards, but I'm sure Parks Canada and other similar agencies around the world have weighed in on the bag-thickness thing.)

Still, 2-mil bags seem a little thin for such potentially curatorially nasty contents.