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starcanuck64
2012-Aug-10, 05:51 PM
The basis of so much concern and cost around nuclear power devolves from the belief in the linear no-threshold theory of the risk from low level radiation, but is it accurate?

We have a good idea of the effects of high levels of radiation exposure from nuclear bomb survivors in Japan, but determining if low level exposure creates a heightened cancer risk can be difficult. Human biology has evolved to constantly repair damage done to DNA by natural radiation and cell metabolism.

http://www.world-nuclear.org/sym/1998/cohen.htm

It also appears that the number of hits on cells is not the determining factor in cancer occurance.


There is plenty of very direct and obvious evidence on this. For example, the number of initiating events is roughly proportional to the mass of the animal; more DNA targets means more hits. Thus, the simple theory predicts the cancer risk to be proportional to the mass of the animal. But experience indicates that the cancer risk in a given radiation field is roughly the same for a 30 gram mouse as for a 70 000 gram man, and there is no evidence that elephants are more susceptible than either.

If only the number of hits (which is proportional to the number of initiating events) were relevant (regardless of the mass of the target), then our very definition of dose in terms of radiation hits per unit mass of the target would be misleading. Another obvious example of the failure of the simple basis for the LNT is in the spectacular increase in cancer incidence with age. Young people experience cancer initiating hits as frequently as old people, but the probability for a cancer to develop is much higher in old people.

So are we operating on a false premise when it comes to the main risk seen around large scale nuclear power production?

Most exposure is only going to be at low levels except in the most extreme events, as we can see from Fukushima it took a historical level tsunami to initiate a large release of radioactive material.

danscope
2012-Aug-10, 06:01 PM
The Fukishima disaster , as far as the plants were concerned was a result of the lack of an absolute powersupply to continue cooling the plants. In this, there can be no compromise. "Good enough" doesn't feed the bulldog. It costs money to design and build to the proper standards required of such technology.
That is the problem with compromised designs where profit dominates the design. That is the essential problem with nuclear power.

starcanuck64
2012-Aug-10, 06:22 PM
The Fukishima disaster , as far as the plants were concerned was a result of the lack of an absolute powersupply to continue cooling the plants. In this, there can be no compromise. "Good enough" doesn't feed the bulldog. It costs money to design and build to the proper standards required of such technology.
That is the problem with compromised designs where profit dominates the design. That is the essential problem with nuclear power.

Looking at the record, it doesn't seem much of a problem.

Some of the biggest accidents have been with reactor designs that wouldn't even be comtemplated today, Windscale was a dangerous design optimized for Plutonium production for the UK nulcear weapons program and the Chernobyl accident was a combination of poor design and even poorer standards. Even Three Mile Island wouldn't have occured if there had been adequate instrumentation in the reactor core which would have prevented the control room crew from interfering with the automatic safety measures.

But that's not the point of this thread, the point is, is the underlying assumption that LLR is dangerous due to increased cancer risk even accurate. And if so then do we need to put so many safety requirements around the containment and release of low levels of radiation?

quotation
2012-Aug-10, 07:55 PM
This recent paper from the NIH (National Institutes of Health) provides a summary of the science involved in the LNT debate under the section A SCIENCE (RISK ASSESSMENT) PERSPECTIVE. A quick scan suggests that in this case science may be of limited value in policy decisions:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3375486/
The LNT Debate in Radiation Protection: Science vs. Policy
Kenneth L. Mossman

Antice
2012-Aug-10, 10:21 PM
LNT is what one could call an absolute upper limit method for risk. it's easy to use, and the estimates are always going to be on the high side. that way one can not be accused of understating the risks. (makes it a useful political tool to cover ones back with).

the model itself wouldn't be such an issue if the people using it used it rationally, but in far to many cases we see it used to enforce an ALARA (As low as reasonably achievable) policy, where any amount of radiation release is seen as dangerous. even when said amounts are hardly noticeable against the natural background in said area. If the standards enforced against nuclear power were to be used in any other industry, then that industry would probably have to shut down. especially the airline industry witch exposes not only it's crew, but a huge number of paying passengers to more radiation than what is permissible to expose nuclear plant workers to under normal operations.
actually. If nuclear power industry standards for exposures where enforced in all aspects of life, then large areas of the planet would be judged uninhabitable due to the natural background in said areas. areas where we have data that strongly indicate that cancer incidence once age adjusted is no different than any other place on the planet.

Tbh. the LNT should be replaced by an equally simple to use method with a lower limit instead. The limit could be conservatively set to be not much higher than the areas on the planet with the highest amount of background radiation is to be found, and where people are still not getting any more cancers than average. (age adjusted that is. poverty tends to skew things around a lot and has to be taken into account when trying to compare rates).
A well known fact about cancer incidence is that age is not only the biggest risk factor, but that when coupled with genetic factors are bigger than any other risk factor by several orders of magnitude. wealth also seem to have a rather big effect too. people who don't have access to clean water and safe food don't live long enough to get cancer at any rate.

I strongly believe that we as humans have a moral duty to worry more about getting everyone who don't have access to basic goods such as energy and clean water rather than tiny amounts of radiation. especially when the alternative is to keep on burning ancient biomass and making a big mess of the planet, thus making it even harder for those in the third world to get a decent chance at life.

HenrikOlsen
2012-Aug-13, 10:26 AM
The basis of so much concern and cost around nuclear power devolves from the belief in the linear no-threshold theory of the risk from low level radiation, but is it accurate?
Short answer, no, but it's the least bad model we have that is consistent with observed data.

Unfortunately it's the result of extrapolation1 because it's basically impossible to separate risk factors when the risk is so a low.

1) that greatest sin of the Ancient Greeks, by far outweighing sodomy for damage caused.

starcanuck64
2012-Aug-13, 05:09 PM
Short answer, no, but it's the least bad model we have that is consistent with observed data.

Unfortunately it's the result of extrapolation1 because it's basically impossible to separate risk factors when the risk is so a low.

1) that greatest sin of the Ancient Greeks, by far outweighing sodomy for damage caused.

So as a result when we're told that for instance 30,000 people will die as a result of the Chernobyl accident, that's based on a model of cellular damage from radiation that is largely speculative?

It seems to me with the well established risk factors around the use of other sources of energy, that nuclear power gets a bad rap based on some questionable forecasts of negative impacts. We could be building a much safer, sustainable energy infrastructure if people weren't constantly being bombarded with how dangerous all radiation is based on the methodology around the LNT.

"We're not sure but we're going to assume the worst", seems a pretty poor approach to take in regards to a fuel source that is about 1,000,000 times more energy dense than the stuff we burn in massive amounts currently.

HenrikOlsen
2012-Aug-13, 10:44 PM
If you're told 30,000 people for Chernobyl, and they claim to have used LNT to get that number, then it's a guesstimate of the upper limit of expected deaths.

The thing is, LNT is rather bad for duch a calculation exactly because it'a a guesstimate and noone knows how wrong it is, only that if it's wrong it is so by predicting too many deaths.

On the other hand, it's a reasonable predictor for setting safety limits as they by definition may only err to the conservative side.

starcanuck64
2012-Aug-13, 11:41 PM
If you're told 30,000 people for Chernobyl, and they claim to have used LNT to get that number, then it's a guesstimate of the upper limit of expected deaths.

The thing is, LNT is rather bad for duch a calculation exactly because it'a a guesstimate and noone knows how wrong it is, only that if it's wrong it is so by predicting too many deaths.

On the other hand, it's a reasonable predictor for setting safety limits as they by definition may only err to the conservative side.

It still doesn't make much sense to me.

We've evolved for millions of years in an environment where there is constant natural radiation from space and isotope decay yet there seems to be this absolute limit on "unnatural" sources of radiation associated with nuclear power.

If we do have the cellular mechanisms to respond to the effects of LLR which seems almost certain, then why bother with treating radiation at low levels as a risk...and more importantly why not make it clear to the public of the uncertainty involved in establishing risk at low levels of radiation exposure.

Just reading here where there tends to be a higher level of informed people, some seem convinced that any exposure to radiation from nuclear power is unacceptable.

Van Rijn
2012-Aug-13, 11:55 PM
It seems to me with the well established risk factors around the use of other sources of energy, that nuclear power gets a bad rap based on some questionable forecasts of negative impacts. We could be building a much safer, sustainable energy infrastructure if people weren't constantly being bombarded with how dangerous all radiation is based on the methodology around the LNT.


But I don't think that really comes up much. Far too often, there isn't any rational discussion of risk at all. Something is either "safe" or it isn't. If any increased radiation at all is detectable, everybody is doomed. If risk is discussed at all in a typical story, you get some maverick that claims radiation risk so high that most of the people living in Denver would be dead if they were right.

I would be thrilled if the typical news story rationally discussed radiation risk based on LNT, rather than the (far too common) story by a writer who has no clue what he's writing about, or "simplifies" the subject so much he gets it flat wrong, or is deliberately sensationalizing the story.

quotation
2012-Aug-14, 02:37 PM
To me this discussion sort of begs the question as to why the nuclear industry isn't doing more to fight back against disinformation. They've obviously got a branding problem, so where's the PR firm to "set the record straight"? I hear about "clean coal" and how great domestic natural gas is going to be every day, but don't think I've ever seen an ad promoting nuclear power. Why is that? Could it be that the fossil fuel interests are trying to maximize existing investment? I mean, if all of a sudden the demand for oil and coal dropped by say 50%, due to the sudden public acceptance of nuclear power, wouldn't that take quite a bite out of the ol' balance sheet? In that scenario, doesn't LNT play a vital role in keeping nuclear power an unacceptable solution by showing that no dose is safe, thus reinforcing the public's negative perceptions?

kzb
2012-Aug-14, 05:14 PM
There is no shortage of campaigning groups claiming the dose/response relationship is supra-linear at low doses. That is, low doses of radiation cause more cancers than predicted by LNT. They have studies which purport to back this up.

On the other hand, we have the Hormesis Brigade. Those who claim that small doses of radiation are beneficial. Some of them sleep with thorium-containing welding rods under their mattresses I believe. Again, they have studies which purport to demonstrate radiation hormesis.

Is LNT without threshold the actual scientific truth at low doses? Probably not, but I think it is an acceptable compromise between the factions. What it does is constrain the nuclear industry to keep to high standards.

Do you want to live in a world with elevated background levels of radiation? If the anti-LNT hormesis people have their way, this is what could happen.

quotation
2012-Aug-14, 06:24 PM
I want to live in a world where electricity costs a fraction of what it does today, while doing as little environmental damage as possible. This thread and several like it have shown me the only way that is possible (in my lifetime) is via nuclear power. Nothing I've read (and they're all seemingly tied to the LSS) indicates that anything below 200 mSv can be correlated to disease, yet science, perhaps due to its very nature, cannot conclusively say that, so the politicos have taken science out of the equation (so to speak) as having nothing relevant to offer in terms of policy decisions, which strikes me as not a good thing. If for some reason we had to produce SMRs (small modular reactors) like liberty ships to ensure our way of life, I think this whole argument would go away rather quickly.

kzb
2012-Aug-15, 11:57 AM
I want to live in a world where electricity costs a fraction of what it does today, while doing as little environmental damage as possible. This thread and several like it have shown me the only way that is possible (in my lifetime) is via nuclear power. Nothing I've read (and they're all seemingly tied to the LSS) indicates that anything below 200 mSv can be correlated to disease, yet science, perhaps due to its very nature, cannot conclusively say that, so the politicos have taken science out of the equation (so to speak) as having nothing relevant to offer in terms of policy decisions, which strikes me as not a good thing. If for some reason we had to produce SMRs (small modular reactors) like liberty ships to ensure our way of life, I think this whole argument would go away rather quickly.

There is no way that doses to the public of 200mSv from power generation would ever become politically acceptable. What you are suggesting is that seafood, the land that we build homes on, the very air we breathe, would be chronically contaminated with fission products the world over. The dose/response relationship does have uncertainties at low doses (although, from memory, I think it is linear to welll below 200mSv/y), but at the moment those uncertainties go both ways.

You've also go to remember. in calculating radiation dose from internal intakes, there are a lot of broad-brush assumptions and generalisations on the way to the answer. It's really not that scientific: it's just a tool to protect the public and workforce. The dose coefficient for tritium was increased by a factor of 2 only a couple of years ago.

quotation
2012-Aug-15, 01:34 PM
There is no way that doses to the public of 200mSv from power generation would ever become politically acceptable. What you are suggesting is that seafood, the land that we build homes on, the very air we breathe, would be chronically contaminated with fission products the world over. The dose/response relationship does have uncertainties at low doses (although, from memory, I think it is linear to welll below 200mSv/y), but at the moment those uncertainties go both ways.

You've also go to remember. in calculating radiation dose from internal intakes, there are a lot of broad-brush assumptions and generalisations on the way to the answer. It's really not that scientific: it's just a tool to protect the public and workforce. The dose coefficient for tritium was increased by a factor of 2 only a couple of years ago.

Protection is well and fine up to a point, but beyond that point seems counter-productive with regard to the overall social costs and benefits. In the NIH report noted in #4 above for example,


The LSS makes a clear statement that at low doses (<200 mSv) radiogenic cancer risk cannot be measured. It is unclear from the data whether the risk is zero or too small to be measured reliably.

There is little argument that US radiation protection has been successful in protecting nuclear workers and the public from radiation exposure. But economic costs of risk management are considerable and raise serious questions about whether limited resources are being allocated optimally to address public health and environmental problems. One issue is LNT theory is used to justify dose reduction to levels at or close to zero above natural background based on the idea that no dose is acceptable. As doses approach natural background levels costs of further reductions become considerable. It is unclear these near-background dose diminutions provide concomitant public health or environmental benefits.

Personally, I think LNT is being used by opponents of nuclear power, (who are likely closely associated with the fossil fuel industry), to stymie further development/deployment of nuclear until existing fossil investments have been maximized, but don't want to stray too far afield in such discussion, lest it become political.

Noclevername
2012-Aug-15, 01:39 PM
Personally, I think LNT is being used by opponents of nuclear power, (who are likely closely associated with the fossil fuel industry), to stymie further development/deployment of nuclear until existing fossil investments have been maximized, but don't want to stray too far afield in such discussion, lest it become political.

In my experience, just the opposite. Most anti-nukes that I've met or heard speak are also anti-fossil fuel, anti-corporate and often anti-technology in general. They usually favor solar and wind.

quotation
2012-Aug-15, 02:06 PM
Yeah, I know who you're talking about. I actually studied those groups for a number of years and while I came to respect many tenets of "pragmatic" Green philosophies such as those espoused by the Citizen's Clearinghouse for Hazardous Waste, ultimately came to the conclusion that in many cases they were but un-witting pawns in a greater game fostered by status quo interests. Take Al Gore for example: the Occidental Petroleum heir. It's simply a question of who has the most to lose from a thriving nuclear power industry.

kzb
2012-Aug-15, 05:11 PM
I think the problem is not LNT per se, but its application in the following manner:

100,000 people getting 1 microsievert is held to be the same population detriment as 1 person getting 100,000 microsieverts (or 100mSv). I think this is where it is going wrong.

starcanuck64
2012-Aug-15, 05:39 PM
There's also debate on whether or not some of the original researchers of the effects of low dose radiation suppressed evidence that there in fact was a threshold below which the risk factor was not linear, not just with radiation but with chemical toxins.

http://news.sciencemag.org/scienceinsider/2011/10/attack-on-radiation-geneticists.html


The allegations come from Edward Calabrese, a toxicologist at the University of Massachusetts, Amherst. In two recent papers, Calabrese concludes that Muller and Stern downplayed evidence that very low levels of radiation might be harmless, and he contends that Muller knowingly misrepresented the scientific state of the art in his Nobel acceptance speech in Stockholm. Those distortions, Calabrese says, are still affecting risk calculations today.

Whatever the outcome of the debate on modifying the risk factor around LLR, we still have to deal with the fact that the current use of fossil fuels poses a systemic danger through the scattering of another form of radiation, long wavelength electromagnetic, which is having the effect of forcing the climate into a more unstable state which also poses significant risk.

Nuclear power handled responsibly most likely isn't going to broadcast large amounts of radiation into the environment where people are going to receive damaging doses. With modern technology the risk factor is even lower than it has been in the past, with some processes the fuel burn up is almost complete and there are much less TRUs to worry about for long term storage. We would in fact be removing one of the most hazardous elements in the nuclear power industry as existing stockpiles of high level waste are consumed in modern reactors.

If, as it seems likely, there is a threshold below which radiation exposure becomes much less damaging than has been assumed in the past and we have the means to control that risk to acceptable levels then the main objection to nuclear power becomes much less credible.

headrush
2012-Aug-18, 07:55 AM
I have problems accepting the LNT model. It is described as being conservative and therefore the "safe" option but there seem to be issues relating to its interpretation. For instance, the model plots risk against dosage, but people appear to conflate "risk" with "certainty". There are also issues with assuming that contracting cancer equates to death in all cases. This is not true.

At the level of radiation where the data is insufficient, the model is at or below the 1% increased risk level. These terms are significant IMHO, increased because there is still a risk of contracting cancer even if a person is never exposed to radiation, and risk level because there is no hard evidence that any number of people will be affected at all.

I agree, one cannot say definitively that there is no risk, but that is not the same as saying there is some risk. I think the model should assume a threshold and say that below this point the risk is immeasurable and therefore can be treated as non-existant, given that (a) we don't know what causes cancers in all cases, and (b) if there were significant problems then we would have data and the LNT could be proved correct or otherwise.

HenrikOlsen
2012-Aug-18, 09:05 AM
Your suggestion might work if the sample which failed to determine the risk was larger than the number of people exposed as a result of policy based of the model.
But since the number of people exposed is going to be larger than the number of people used to determine the limit, and there is no evidence in the numbers that can be determined for a threshold, the only safe solution is to assume there is no threshold.

I think the main issue in all of this is that many people argue policy based on risk, rather than on acceptable risk.
People are perfectly willing to accept risks that are thousands of times higher provided they don't involve radiation and provided they actively expose themselves to the risks.

For example, each and every year tens of millions of people voluntarily pay large amounts of money in order to subject themselves to radiation burns, with resulting increase in cancer rate, and nobody batters an eye about it.

swampyankee
2012-Aug-18, 02:23 PM
The repair mechanisms at the cellular level are probably quite old, possibly predating evolution of eukaryotes. It's likely that a more robust repair mechanism would result in slower cell division than one that's barely good enough, so the organisms with a more robust mechanism would be at a reproductive disadvantage, and soon be outnumbered by those with less robust mechanisms: Deinococcus radiodurans does not seem to be out-competing organisms with less robust repair mechanisms. Even if it a more robust repair mechanism does not result in a reproductive disadvantage, it would probably result in a more homogeneous population, which would result in a genetic lineage less able to tolerate environmental changes. Again, excessive robustness would be disadvantageous.

So is the LNT damage model correct? Maybe or maybe not, but if there is a threshold below which damage doesn't occur, it's probably well below the natural background radiation level.

starcanuck64
2012-Aug-18, 04:37 PM
There has to be some threshold, all life has evolved in the presense of natural background radiation, sometimes with increased levels as during a magnetic field flip where the magnetosphere is gone for a period. There doesn't seem to be evidence of higher levels of extinction at these times although it's hard to say about increased cancer rates.

Also as the article in the OP states, if the effect was linear, wouldn't there be increased rates of cancer in larger organisms due to increased exposure.

The LNT may be a "safe" way to avoid any exposure that mught be harmful but as HenrikOlsen states it doesn't capture the relative risk involved. Most people probably don't even know it exists, all they are aware of is the impression that all radiation exposure is dangerous(unless you're getting your skin nice and toasty brown). By having a more flexible although complex model it could help remove this misconception of risk. People could stop feeling that having a nuclear power plant in their region could fry them at any moment.

headrush
2012-Aug-18, 09:35 PM
... and therein lies the point. People are prepared to burn their skins to a crisp and pay for the privilege. But mention radiation and they are dead set against it. Maybe sunburn should be be measured in rads or mSv.
Just for kicks, what is the average level of radiation from the sun as an equivalent to measure against ?

ETA: I now realise that uvb is not the same as nuclear radiation, but in the course of my googlin' I happened onto some interesting data. (http://www.world-nuclear.org/info/inf05.html)

HenrikOlsen
2012-Aug-19, 06:41 AM
Quite interesting reading:

Reports two decades after the accident make it clear that the main health effects from the accident are due to the evacuation of many people coupled with fear engendered, and thousands have died from suicide, depression and alcoholism. The 2006 Chernobyl Forum report said that people in the area suffered a paralysing fatalism due to myths and misperceptions about the threat of radiation, which contributed to a culture of chronic dependency. Some "took on the role of invalids." Mental health coupled with smoking and alcohol abuse is a very much greater problem than radiation, but worst of all at the time was the underlying level of health and nutrition. Psycho-social effects among those affected by the accident are similar to those arising from other major disasters such as earthquakes, floods and fires.

starcanuck64
2012-Aug-21, 12:46 AM
Not to downplay the danger of inhaling or ingesting radioactive material, but the main risk factor in nuclear power production seems to be the fear of contamination, not the actual contamination.

If you factor in modern technology now being developed where the radioactive material is contained in solution in a salt which is stable at high temperatures and is not damaged by high levels of radiation at near normal pressures, then the risk of large scale release of radioactive material in aerosol form(where it's most dangerous) becomes very low. Modern PWR reactors also feature many passive safety features which make them much more resistant to failure.

swampyankee
2012-Aug-21, 01:42 PM
There has to be some threshold, all life has evolved in the presense of natural background radiation, sometimes with increased levels as during a magnetic field flip where the magnetosphere is gone for a period. There doesn't seem to be evidence of higher levels of extinction at these times although it's hard to say about increased cancer rates.

Also as the article in the OP states, if the effect was linear, wouldn't there be increased rates of cancer in larger organisms due to increased exposure.

The LNT may be a "safe" way to avoid any exposure that mught be harmful but as HenrikOlsen states it doesn't capture the relative risk involved. Most people probably don't even know it exists, all they are aware of is the impression that all radiation exposure is dangerous(unless you're getting your skin nice and toasty brown). By having a more flexible although complex model it could help remove this misconception of risk. People could stop feeling that having a nuclear power plant in their region could fry them at any moment.

"There has to be some threshold...." while this may be logical, I don't think it necessarily follows that the cellular repair mechanisms need be capable of even dealing with background radiation: all that's required is that the damage due to radiation accumulate slowly enough to permit the organism to reproduce with reasonable fidelity.

"Also as the article in the OP states, if the effect was linear, wouldn't there be increased rates of cancer in larger organisms due to increased exposure." How much research is there comparing rates of cancer in larger vs smaller organisms, and are they corrected to allow for the fact that larger organisms tend to live longer, have different metabolic rates, etc?

"....(unless you're getting your skin nice and toasty brown)..." many people know that there is a danger associated with tanning, and accept the consequences. In any case, tanning is a voluntary exposure, and I think this is a critical difference. An exposure from a malfunctioning or damaged nuclear plant is involuntary. Given that many people have long experience with companies lying, deliberately distributing shoddy or defective goods, blowing up the financial sector, etc, why should they be considered trustworthy. So, logically, who can blame anybody for not wanting a potential danger in their backyard: you can't trust the operator, because you know they'll lie to protect executive bonuses and profits, regardless of anything else, and you can't trust the regulator because, you know, it's the government?

quotation
2012-Aug-21, 01:43 PM
Not to downplay the danger of inhaling or ingesting radioactive material, but the main risk factor in nuclear power production seems to be the fear of contamination, not the actual contamination.

An article in the Wall St Journal this past weekend agrees: http://online.wsj.com/article/SB10000872396390444772404577589270444059332.html
I found it linked from a William Tucker editorial: http://www.nucleartownhall.com/blog/william-tucker-at-last-some-common-sense-on-fukushima/

starcanuck64
2012-Aug-21, 06:07 PM
"There has to be some threshold...." while this may be logical, I don't think it necessarily follows that the cellular repair mechanisms need be capable of even dealing with background radiation: all that's required is that the damage due to radiation accumulate slowly enough to permit the organism to reproduce with reasonable fidelity.

There are cellular mechanisms which do repair the breaks in DNA caused by ionizing radiation, this would indicate there is some threshold below which the repair mechanism do make radiation damage less of a risk factor...a threshold. And in the OP article it talks about studies showing that High level exposure preceeded by LLR exposure shows less cellular damage than if there had been no prior exposure, indicating that LLR stimulates those repair mechanisms.


"Also as the article in the OP states, if the effect was linear, wouldn't there be increased rates of cancer in larger organisms due to increased exposure." How much research is there comparing rates of cancer in larger vs smaller organisms, and are they corrected to allow for the fact that larger organisms tend to live longer, have different metabolic rates, etc?

The fact that they are so long lived would tend to argue that there are other more important risk factors for cancer other than exposure to radiation which is a constant.


"....(unless you're getting your skin nice and toasty brown)..." many people know that there is a danger associated with tanning, and accept the consequences. In any case, tanning is a voluntary exposure, and I think this is a critical difference. An exposure from a malfunctioning or damaged nuclear plant is involuntary. Given that many people have long experience with companies lying, deliberately distributing shoddy or defective goods, blowing up the financial sector, etc, why should they be considered trustworthy. So, logically, who can blame anybody for not wanting a potential danger in their backyard: you can't trust the operator, because you know they'll lie to protect executive bonuses and profits, regardless of anything else, and you can't trust the regulator because, you know, it's the government?

They're getting it anyway, it's a question of relative risks. A system wide forcing of the climate into a hotter state with the current large scale emission of greenhouse gases plus all the other health risks associated with mining, piping, refining and burning fossil fuels many which contain toxic compounds and elements, including radioactive material, or a move to an energy system that does have risks but localizes them much more, with MSRs to a much greater degree. You'd need to plant explosives inside the hot loop of the reactor to just get the material out of the main containment vessel. Otherwise it's just going to drain into cooled holding vessels underneath the primary containment vessel if it gets ruptured.

In a perfect system we wouldn't have to put up with corporate wrongdoing, but has that ever been a reality? It's a question of choosing which energy model offers the lowest amount of risk with the greatest benefit. Regulation is a neccessity in both models, but how regulated is the system we have now. The Gulf of Mexico is full of trillions of particles of dispersed oil from the Deepwater Horizon blowout, not far from where I live they're strip mining hundreds of square miles of boreal forest and using huge amounts of water, natural gas, and coal to produce synthetic crude, in the US East entire mountaintops are removed for coal with all the waste left behind from processing and burning that fuel. There's a mine in Montana that ships 35 miles of trains full of coal to power plants a day.

We can keep doing all that or switch to a fuel source that is six orders of magnitude more energy dense and much more containable given the proper regulations in conjunction with burning the least carbon intensive fossil fuels like natural gas while developing the renewables. We already live with a highly dysfuntional energy model that more than few professionals have been warning us for decades is having serious global consequences.

People to a large degree are already being forced to accept conditions that negatively impact them.

HenrikOlsen
2012-Aug-22, 01:08 PM
There are cellular mechanisms which do repair the breaks in DNA caused by ionizing radiation, this would indicate there is some threshold below which the repair mechanism do make radiation damage less of a risk factor...a threshold.
The question is to a large extent moot as the threshold would be below the naturally occurring level of radiation from radioactive potassium in the body, which fits quite comfortably on the linear part of the model.

There may be a level below which all damage might theoretically be repaired, but the body's natural radioactivity is already above that level, so it's really quite pointless to consider it for risk assessment.

As for the question about large vs small animals and cancer for exposure, note that the unit for exposure is energy absorbed per body mass.
And that there are no known animals that are free of cancer (yes, sharks can get cancer too).

starcanuck64
2012-Aug-22, 04:58 PM
The question is to a large extent moot as the threshold would be below the naturally occurring level of radiation from radioactive potassium in the body, which fits quite comfortably on the linear part of the model.

There may be a level below which all damage might theoretically be repaired, but the body's natural radioactivity is already above that level, so it's really quite pointless to consider it for risk assessment.

As for the question about large vs small animals and cancer for exposure, note that the unit for exposure is energy absorbed per body mass.
And that there are no known animals that are free of cancer (yes, sharks can get cancer too).

Cancer itself takes place as part of a complex chain of events, the initial break in DNA just being one, and there are different degrees of damage that can lead to cancer. From what I understand a double break in DNA is much more likely to produce the kind of mutation that can lead to a cancerous cell than a single strand break. And cancer is also age dependent to a large degree which would indicate a systemic decline that contributes to the growth of tumor cells.

If cancer itself isn't a simple linear process and radiation exposure is a constant that all life has evolved with over several billion years then why does increased radiation levels get so much play in the public forum. Especially since we really don't know at a fine detail what the real effect is of LLR?

The amount of toxic exposure from the "artificial" radiation introduced into our lives is a tiny fraction of the toxic effect of producing and consuming billions of tons of fossil fuels a year. We probably know with a lot more certainty the negative effects of mercury, arsenic, lead, some hydrocarbons and yet they're widely broadcast into the environment with little thought.

It just seems truly bizarre to me people spend so much time pulling their hair out over a risk factor that in real world terms is insignificant while actively embracing an energy and economic model that often puts them in intimate contact with all sorts of serious toxins.

The LNT is meant to capture the risk involved in introducing a potentially harmful condition(radiation) into our lives, countries like Germany and Japan are moving back to using coal for baseload power because of the political resistance to nuclear power, and yet any sensible examination of the physical risk involved(before you even get to climate change) would indicate that fossil fuels are much more of a health risk.

starcanuck64
2012-Aug-22, 09:53 PM
I need to read up on this subject, the more this discussion goes on the less I understand it.

Does anyone have any good articles or books to recommend?

edit- Already I have serious questions about how representative the LNT can be, it was created before the DNA molecule was even identified. Just a small amount of reading shows how complex and resilient cellular function and repair has to be.

http://en.wikipedia.org/wiki/DNA_repair


DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its genome. In human cells, both normal metabolic activities and environmental factors such as UV light and radiation can cause DNA damage, resulting in as many as 1 million individual molecular lesions per cell per day.[1] Many of these lesions cause structural damage to the DNA molecule and can alter or eliminate the cell's ability to transcribe the gene that the affected DNA encodes.

Another article is dealing with how some areas with high levels of natural background radiation can have lower rates of cancer than neighbouring areas such as Ramsar Iran.

http://en.wikipedia.org/wiki/Linear_no-threshold_model


A 2005 study[13] of Ramsar, Iran (a region with very high levels of natural background radiation) showed that lung cancer incidence was lower in the high-radiation area than in seven surrounding regions with lower levels of natural background radiation. A fuller epidemiological study[14] of the same region showed no difference in mortality for males, and a statistically insignificant increase for females.

I really need to sit down with a good book on the subject to get a grasp of it.

Van Rijn
2012-Aug-22, 11:26 PM
I don't have time right now to discuss this, but I'm adding a couple of links before I lose them:

http://www.physics.harvard.edu/~wilson/publications/ppaper644.html

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2647823/

They're discussing assumptions about the linear model which is also used to evaluate chemical carcinogens. There's some interesting background on how the linear model argument got started, and some possible alternatives, at least on the chemical side.

starcanuck64
2012-Aug-22, 11:37 PM
Since that time, physicists have tended to accept Crowther's suggestion that cancer incidence is linear with exposure to radiation, but biologists and physicians have often continued to believe in thresholds.

An interesting division.

Thanks for the articles, they should really help.

starcanuck64
2012-Aug-23, 04:42 PM
I'm starting to realize that this is a political issue more than a technical one.

starcanuck64
2012-Aug-23, 05:43 PM
http://www.pnas.org/content/109/2/443.full


Single time or single dose measurements are snapshots and might not capture the complexity of the IR response of DNA damage-sensing proteins. Here, we present a methodology and a mathematical kinetic model that can characterize the DNA damage response simultaneously across both time and dose levels. Our results provide a more accurate model of RIF dose response, and underscore fundamental concerns about static image data analysis in the dynamic environment of the living cell. We observe that as the number of DSB increases in a cell, the number of RIF does not increase proportionally and the kinetics of RIF formation/disappearance is altered; RIF appear faster but remain longer in the cells as dose levels increase. These nonlinear processes cast considerable doubts on the general assumption that risk to IR is proportional to dose and could be interpreted as the consequence of DNA repair centers in human cells.


Impact of Results for Regulating Risk of IR on Human Populations. The current literature has assumed the linear-no-threshold hypothesis (LNT), which implies that any amounts of IR are harmful. LNT is used to set dose limits for radiation occupational workers or the general public. The LNT is based mainly on data from the Japanese atomic bomb survivors and secondarily on arguments involving the dose-response of surrogate endpoints. Gene mutations are thought to be the initiating events of cancer and they can occur via misrejoining of two DNA DSBs or via point mutation. Physical laws lead us to believe DSB frequencies are proportional to dose. Therefore, it is well accepted that point mutations are linear with dose because it requires only one DSB, whereas DSB misrejoinings are dependent to the dose squared (39). In the dose range of radiation cancer epidemiology, the quadratic term is almost always negligible, especially at low dose rates, as the first lesion is probably repaired before the second mutation occurs (40). However, the amount of DSB clustering at 1 Gy suggests a much higher quadratic term for DSB misrejoining than expected. Therefore, extrapolating risk linearly from high dose as done with the LNT could lead to overestimation of cancer risk at low doses.

http://junksciencecom.files.wordpress.com/2011/09/calabrese-muller-1.pdf


Abstract In his Nobel Prize Lecture of December 12,
1946, Hermann J. Muller argued that the dose–response for
radiation-induced germ cell mutations was linear and that
there was ‘‘no escape from the conclusion that there is no
threshold’’. However, assessment of correspondence
between Muller and Curt Stern 1 month prior to his Nobel
Prize Lecture reveals that Muller knew the results and
implications of a recently completed study at the University of Rochester under the direction of Stern, which
directly contradicted his Nobel Prize Lecture. This finding
is of historical importance since Muller’s Nobel Lecture
gained considerable international attention and is a turning
point in the acceptance of the linearity model in risk
assessment for germ cell mutations and carcinogens.

I need to go over this in more detail, but the evidence does point to the model much of the policies regarding radiation exposure are based on is inaccurate.

starcanuck64
2012-Aug-23, 11:03 PM
Some interesting preliminary findings on the effect of very low levels of radiation(below background levels) on cells.

http://www.wipp.energy.gov/pr/2011/Low%20Background%20Radiation%20Experiment%20News%2 0Release.pdf


Results so far, as reported in the Health Physics article, indicate that the cell growth of the
bacteria in the WIPP underground, exposed to less background radiation than the control group,
is hampered.

“Initial results from June 2010 show … the growth of ‘radiation starved’ cells are (sic) inhibited
compared to cells grown in the presence of background radiation levels,” the researchers
reported.

“The noise in the data is still fairly high,” Smith clarified. “It’s preliminary, and we still need more
data to show it as statistically different.”

HenrikOlsen
2012-Aug-24, 10:21 AM
It's interesting to note here that some chemical reactions are catalyzed by radiation (just look at UV-hardening of dental polymer fillings), I wonder if that is part of the effect,

quotation
2012-Aug-24, 12:58 PM
I'm starting to realize that this is a political issue more than a technical one.
ya think?
http://www.nucleartownhall.com/blog/william-tucker-on-hormesis-my-apologies-to-ted-rockwell/
From Ted Rockwell:

I’m really frustrated! I’ve been involved with radiation protection since I edited The Shielding Manual in 1956. And with radiation, since I wrote “Frontier Life Among the Atom Splitters” for the SatEvePost (Dec 1, 1945). Continuously since then, I’ve been told that we should never mention hormesis, never try to tell people that radiation behaves like everything else in the world: a little is beneficial, too much is harmful. Like sunshine, like exercise, like all those nasty poisons in our daily vitamins. I’ve been writing, and lecturing, and talking to the person next to me on the airplane. And I’ve never met anyone who had trouble understanding or believing that simple concept. Yet “the experts” keep proclaiming that, although we all understand and believe it ourselves (how can you deny the data?), we shouldn’t try to tell it to the public or the Congress or the media. It’s time to knock off that destructive behavior. Its only function is to protect persons who believe their job depends on scaring people. Radiation protection is an honorable function, and done right, it can help us find ways to operate more profitably, not less. But we in the nuclear community have continually bad-mouthed ourselves and our profession. It’s time to stop it. There is a vast body of good scientific evidence that in the dose range of interest, more radiation is beneficial. But a great deal of effort has gone into hiding that fact. The relevant policy-setting reports like NCRP-136 and -121 concede that the data demonstrate hormesis, but they recommend it would be “prudent” to assume the opposite. It’s not science, but a strange sense of prudence, that leads people to want to hide hormesis.

starcanuck64
2012-Aug-24, 05:23 PM
It's interesting to note here that some chemical reactions are catalyzed by radiation (just look at UV-hardening of dental polymer fillings), I wonder if that is part of the effect,

I was wondering if it could be the lack of ionizing radiation stimulus on the DNA "repair center" that would result in more genetic damage and less expression of dysfunctional genes.