The alternative is not "we don't know, so we'll assume the effect is zero"; it's "we don't know, so we'll assume the effect is the largest not ruled out by evidence." And that would make estimates of the effects of radiation in nuclear accidents far worse.
The alternative is not "we don't know, so we'll assume the effect is zero"; it's "we don't know, so we'll assume the effect is the largest not ruled out by evidence." And that would make estimates of the effects of radiation in nuclear accidents far worse.