If Andorians have cobalt blood, are they dangerously radioactive?
No. The cobalt blood detail (first mentioned in the Star Trek: The Next Generation core book) is meant to be a cute joke, not unlike the reference to “Andorian Blues” in an episode of Deep Space Nine. It’s not meant to be serious biology. If you can’t rest easy without a pseudo-scientific response, though, try this: Andorians have Cobalt-59 content comparable to the iron content in humans. Which is to say, you’d need to kill five or six adult male Andorians and distill them down to get a whole ounce of Cobalt-59 out of them. Also, Cobalt-59, in its natural form, is not very radioactive at all. The cobalt used to treat cancer, irradiate foods and so on is cobalt that has spent a year in a nuclear plant, being bombarded until about 10% of the cobalt gains an extra neutron.
