Yes, of course the limits are below "dangerous" levels. That, in itself, says nothing about what we should call "safe" levels.
Radiation has two types of dangers, chronic and acute. Our understanding of what levels of radiation cause acute damage is pretty limited and not very precise since we simply don't have that much data. However, I highly doubt that anything close to those levels of radiation were measured anywhere outside the reactor complex.
In terms of chronic danger, the official stance is that there is no safe amount of radiation exposure and the general principle in managing exposure is ALARA (As Low As Reasonably Achievable). Lifetime cancer risk is cumulative so higher levels just add to that cumulative risk faster.
Thus there isn't really a clear "level of acceptable impact" but rather, we set arbitrary levels to to to limit that cumulative addition of cancer risk. Like with many things, that risk is a price you pay for other things that are important to you, like flying, living in denver, or getting xrays.
that is quite logical, scientific and consistent with approaches taken in relation to other biological hazards.