“If there’s no safe dose,”
The government and most rad health outfits use a linear, no threshold model for risk. That means that any amount of radiation carries some risk.
It scales linearly. BIER VI calculated one excess cancer death in a population of 100 exposed to 10 REM whole body, out of a background of 42 (statistically 42 out of 100 will die of cancer, expose the 100 to 10 REM and the cancer deaths become 43, everyone else dies from other causes). So in a linear model 10 REM has roughly a 1% risk, and 1 REM a .1% risk, and so forth on down to zero. But every exposure including background carries SOME risk, so they say “no safe dose” and push the concept of ALARA, keep all doses as low as reasonably attainable.
The model also assumes that, since there is no threshold, it is possible that a tiny dose could start a fatal cancer in a susceptible person, and this includes background radiation.
Some papers suggest a benefit to health from small radiation doses. This is pretty controversial. it’s called Radiation Hormesis. The “official” rad health policies do not recognize that, though.
Suppose instead of discussing "official" government regulations and bureaucracy, how about we discuss reality and common sense, considering that they're mutually exclusive most of the time?
A tiny dose stimulates the immune system to repair any damage caused. The idea that it can cause a fatal cancer flies in the face of common sense, and should be discarded as the nonsensical superstition that it is.
Cancer Control Related to Stimulation of Immunity by Low-Dose Radiation
LDR increases cellular antioxidant activity; facilitates DNA damage repair; reduces malignant transformation and mutagenesis, and stimulates immune surveillance.(6–10) All these may contribute to the effect of LDR on the reduction of cancer incidence. There have been experimental studies illustrating: a) the suppressive effect of LDR on tumor growth, metastasis and carcinogenesis, b) the increased anti-cancer immunity, including enhanced NK and CTL activity, and c) the increased IFNγ and IL-2 secretion. All these data point to the significance of enhanced immune responses in cancer control.(11–23)