[bcoates]

Why does it make very little sense? If the exposure was below the threshold dose at which radiation has been established to be carcinogenic it sounds like the most defensible position. The alternative is to say that anything can have an effect on cancer risks, which even if true in some pedantic sense isn't a useful way of looking at risk.

It's not like large-scale low-dose ionizing radiation is an unknown phenomenon: radiation exposure from the ground and sunlight vary widely, and we have very large data from chernobyl and 1950s above-ground nuclear testing.

[mpyne]

The very idea that there is a threshold below which cancer risk is not appreciably affected is itself controversial.

In fact, even saying controversial would not be enough, most major health physics societies assume there is no such threshold and that any exposure increases risk. Only France's national society and (IIRC) one U.S. health physics society seem to be confident enough in the current research to stake out a claim that there is a threshold.

With all that said I personally lean towards the idea of a threshold-based response, though the no-threshold models are certainly easier to use for planning purposes (for which they've been used to assess risk for decades). Even if there is a threshold, that threshold may depend on length of previous exposure (acclimation) and may only be good for exposure within a certain time limit, both of which again make use within models more difficult (though not impossible).

[ars]

See: http://en.wikipedia.org/wiki/Radiation_hormesis

It's controversial politically, not scientifically.

People have a knee jerk reaction to the idea of any radiation - except if it's natural of course, despite that making no sense.

[mpyne]

Hormesis is actually conversial, but is not what I'm referring to.

Besides hormesis the other popular models seem to be LNT (linear response, no threshold) and LT (linear response, above a threshold).

LNT is used by most right now, mostly because it's the most conservative-possible model that fits the very-high-exposure data that we do have from atomic bomb survivors. It is the model which gives us ALARA and 'Man-REM' planning.

LT is more what I would lean towards given available studies of very-low-exposure, but that still leaves open the question of what that would actually mean for public health advice, radiation worksite planning, etc.

[lostlogin]

Can people comment if they down vote please? I see no errors above and this seems a little harsh.

[ekianjo]

You'll have to explain me why it's OK to live in Colorado then where the natural levels of radioactivity are about 6 times higher than in other places in the country.

There's very clearly a threshold effect, just like in many natural phenomenons. Political nonsense is what is causing confusion, not the scientific basis. And most of the "science" trying to prove otherwise is based on too few numbers to be statistically significant. (the cases of reported leukemias, for example, is very often misleading when you look at the ACTUAL numbers and not just the percentages.)

If you use "no-threshold" for planning purpose then you can't technically live on Earth anywhere, since there's natural radioactivity all around us and cosmic rays as well through the atmosphere.

The regulatory limits for radiations are based on No Science whatsoever. Currently, at least. We know radiations kill with certainty at very high levels, there is no debate about that, but at low levels it's just a political issue more than anything else.

[w1ntermute]

In that case, we should also avoid living in cities with naturally high levels of background radiation, such as Rome.

[mpyne]

Or Denver, or even Ramsar (IIRC), Iran.

The fact that people can survive in those areas without noticeable increase in risk of cancer seems to lend credence to the idea that there is a threshold that one can become acclimated to. But it's still a politically sensitive topic, enough so that the experts still don't want to push away from the harbor of the current ALARA recommendations.

[ekianjo]

> But it's still a politically sensitive topic

Yeah, and God Forbid we talk about the positive aspects of radiations - some level of radiation is actually beneficial to kill some bacteria in your bodies and reduce some types of ailments and cancers. This has been observed (but certainly NOT widely reported in the media for which Nuclear Energy is the Devil Incarnate) in several studies.

[lostlogin]

I agree. However parts of the nuclear industry would do the whole industry a great service if they cleaned themselves up. Up front honesty about mistakes and accidents might make a bad headline or 2, but it they look far worse when the retrospectascope is peering in after a big problem. A critical media and general population would (IMHO) be more accepting of accidents if major events (Fukishima being a big, unusual example) weren't followed by months of backtracking, half truths and lies.

[ekianjo]

I totally agree with you, but at the same time many countries force "top secret" level on all nuclear information to the public. It is certainly the case in France and probably elsewhere too, and there is as much responsibility on the government side that there is in the industry.

We need both total transparency and proper education on the risks/benefits of nuclear technology.