Homo gamma

Best to keep in mind that the LET, "linear energy transfer", of such gammas is very insignificant from a biological standpoint. The chance of such a gamma producing the necessary multi-hit effect in a single cell is remote if not impossibly small. Multiple hits on a single cell are necessary to transform a cell into a fully dys-functioning progeny for the eventuality of lethal tumor development. It is a ironic that the highest LET is seen with alphas, which are otherwise thought to be quite harmless from external exposure. But not so, in an intra-cellular context. The alpha emitter can indeed produce multiple radical species within a single cell. Perhaps not "much" of a problem as a "one off" but definitely a risk from a statistical standpoint when taken over trillions of cells repeatedly exposed. The lesson: do not ingest or otherwise allow alpha emitters to reside in one's cells. Gammas, relatively OK, and K40 is the ready example that has been with us from the "beginning". It's a numbers game that can be confusing.

K40 is a convenient peak to calibrate a spectrum to and ensure that the detector is seeing something real. Maybe every reactor needs a referee jar of KCl salt on top.

Radon can turn to Pb inside your lungs while firing a harsh gamma or more through (hopefully, not into) a lung or two.

Quote from Paradigmnoia

Radon can turn to Pb inside your lungs while firing a harsh gamma or more through (hopefully, not into) a lung or two.

Yes, but more important biologically, carcinogenically, is the daughter alpha production. Radon has a multiple path decay route. Rarely is radon itself the culprit with its beta decay path (low LET), it is the various daughter products that are all radioactive, and several are alpha emitters (high LET). These have an array of half lives that are of course typically charged products. They are metallic solids in bulk. I suspect as individual ions they may have far lower fugacity than radon. As charged "subnano"-particles, they attach themselves to surfaces and to dust motes in the ambient or in tissues. They can be deposited deep within the lung, especially if they are in a critical size range that is likely to land beyond the ciliary / mucosal expulsion machinery of a healthy lung. It is widely thought that the decays that produce alphas are by far the main risk in radon exposure, these are seen in Pb-214 and Bi-214 which are themselves products of the initial radon decay.

See this brief radon outline that does not include all the decay paths, but the ones considered big health risks:

http://www.radonguide.com/radon-decay-chain.html

It may be beneficial to recall that the energetic product of some LENR reactions can also be alphas at MeV energies. Please make certain those are not somehow produced in one's lungs instead of in whatever "reactor" one is experimenting with.