And a chemistry set that contains brittle lead ores/alloys that "tend to flake and crumble" is not something I'd want a 12 year old using unsupervised. Nor would I trust the vast majority of adults for that matter...

It's more useful for things like "living within 50 miles of a nuclear power plant for a year (0.3 µSv) is the equivalent of eating 3 bananas (0.1 µSv each)."

Relevant xkcd - https://xkcd.com/radiation/

Note also the "Yearly dose from natural potassium in the body 390 µSv"