Re: During the meanwhile ...
@Tim Parker
"..from the Cornwall Council August this year - The HPA have recently introduced a new target level for radon of 100 Bq m-3..."
Umm.
Quoting a council ruling derived from HPA advice doesn't really cut it for me. I see a lot of HSE-type advice produced from bodies responsible for safety of various kinds which, on deeper investigation, prove to be founded on statistical misrepresentation. This seems to be a trend - possibly influenced by the Climate Change fiasco.
In this case I went looking for the HPA research which would justify your comments about Cornwall's elevated risk, and couldn't find it. They just say:
"The Target Level has been introduced because research published since 1990 has given scientists a greater understanding of the risks to health of exposure to radon below 200 Bq m-3 and because HPA now has considerably more experience of the effectiveness of remediation measures."
So perhaps they seem to be tightening the targets because they can, as much as because it is advisable? I went looking for radon research since 1990, and found the Wiki quoting the BEIR VI report, entitled 'Health Effects of Exposure to Radon'.
"According to the UNSCEAR modeling, based on these miner's studies, the excess relative risk from long-term residential exposure to radon at 100 Bq/m3 is considered to be about 0.16 (after correction for uncertainties in exposure assessment), with about a threefold factor of uncertainty higher or lower than that value. In other words, the absence of ill effects (or even positive hormesis effects) at 100 Bq/m3 are compatible with the known data."
So my (limited) research (purely checking abstracts) suggests that, at low levels, the statistical noise overwhelms any signal. This means that a positive figure indicating a small risk can easily be picked while staying within the error bands. Which is politically expedient...
Doesn't mean there isn't a problem with radiation at low levels. Does mean, as you say, that the issue is not black and white. And, in my view, it does mean that much current research in any activist-influenced area of science should be looked at very carefully....