You are beating up a staw man. I never said there is no acceptable risk or even that low doses of radiation are not acceptable in some situations.
Truly sorry about that. I do skitter about and fly off with my agenda hanging out sometimes.
I do appreciate the quandary faced by diagnosticians and those trying to establish occupational exposure guidelines, these measurements do matter. There was a time when even shoe stores had fluoroscope X-ray machines children would play with after school, emitters were much stronger and few doctors used lead aprons. Some hypothesis -- preferably a provable one -- is necessary. The "As Low As Reasonably Achievable" is a good effective dose of common sense intended to become a policy and legal framework, but what numbers and equations will we plug into it?
It may be that for every hundred workers exposed to some small level of radiation -- aside from the horde that is happy with playing it really safe, there may be some dozen who are actively hoping that allowable 'safe' limits can be raised, with sound supporting reasons, so they do not have to live with the regulatory Sword of Damocles hanging so close above their heads. I would be one of those. Nuclear energy sounds a lot safer than some of the potentially lethal hazards I face daily.
You are right to pose there might be a non-linear risk curve hidden in the noise (of low dose risks). There are proposals to reconcile low-dose adjustments to LNT in such a way that it does not present such a hard 'barrier' when conflating dose with mortality, and (perhaps, me guessing) from a consensus that in a field of exponential or even quadratic relationships, drawing a straight line through anything more complicated than cow-counting is uncomfortable.
A Dose Rate Effectiveness Factor (DREF) attempts to half risk per unit dose at low doses or low dose rates (or both) from its point on the linear scale. Arbitrary but probably closer to reality. NASA takes it down to the organ level and calculates a career limit. Add to that cancers that may lie dormant, held in check by the body's own immune responses and you have a lot of 'noise' and extra screening to sift through.
Maurice Tubiana, MD has compiled an excellent 'fact check' on LNT The Linear No-Threshold Relationship Is Inconsistent with Radiation Biologic and Experimental Data which summarizes many sources (167 ref citations!) to conclude that there is no (small) elephant in the living room. He even covers nine studies that suggest that low does may exhibit Hormesis (a beneficial effect).
As you might guess, finding evidence of hormesis was astounding and is a hot research potato. But an ecological study done by an outspoken Bernard_Cohen is mentioned on the DREF page, emphasis mine:
"Efforts to confirm directly the effects of indoor radon have led to mixed and highly controversial conclusions. One class of studies, termed ecological studies, looks for correlations between the average radon level in a region and the lung cancer fatality rate. In the largest and best known of these studies, covering 1,729 counties in the United States, Bernard Cohen finds the county-by-county lung cancer rates to be inversely correlated with average radon levels. Although many readers have interpreted this study as suggesting hormesis, Cohen limits his conclusions to saying that the results refute the linearity hypothesis. This study covered most of the US population, and therefore the statistical uncertainties are small.
However, these conclusions are hotly disputed by those who contend that ecological studies are inherently flawed. They call instead for reliance on epidemiological studies in which comparisons are made between groups of individuals, where the radon exposure and health history is determined for each person."
Cohen's study has its detractors who argue he did not properly control for smoking.
Which reminds me of a theory I came up with many years ago when all the hype about second-hand smoke began in the early 80s. The cornerstone of the argument was that a growing number of non-smokers in the US were being diagnosed with lung cancer. A smoker was always somewhere nearby... so who else could be blamed? But some years prior... the 1973 Oil Crisis had started a revolution of remodeling and revised design criteria to hermetically seal homes from attic to basement, in order to provide (for the first time) efficient use of heating. Also thermal imaging was used to spot warm air escaping from foundations, windows, and cracks for a complete seal. Which resulted in less air flow, allowing odorless and invisible heavier-than-air radon to seep through porous basement walls and accumulate in these newly-sealed houses. Radon sump pumps are relatively new additions. Even if my theory was correct and smokers do not have so much blood on their hands, someone has noticed. Second hand smoke now the SECOND leading cause of lung cancer among non-smokers.
I do not find low-dose radiation hormesis to be a farfetched idea. In modern medical practice where doctors intentionally provoke immune responses to make treatment more effective or 'jumpstart' a patients own defenses, it is not too difficult to imagine natural background radiation also doing so -- even to the point where in healthy populations some epidemiological dependence on it may arise. Like the Carter-era energy-efficient Americans trapped inside their radon bubbles, many life forms are distantly evolved from burrowing creatures with their snuffle-noses on and under ground.