LNT: if it is wrong what would you replace it with?
Discussion
The recent thread on fusion developments raised this again and I'm curious to understand the grumbles better:
For a wider audience than those already 'inside' the madness of radiation dose response:
LNT = Linear non-threshold. A dose response model for risk vs radiation exposure.
Essentially that risk of health effects such as cancer are proportional to exposure to radiation, so even the background radiation we all get by being on the planet means there is an underlying radiation induced risk of cancer.
At background and occupational levels the risk is very low, fractions of a percent vs 1 in 2, 1 in 3 or so risk of cancer in lifetime; depending on which advert/campaign/guidance you agree with.
The perceived flaw as I think I understand it, is that this is used to project potential exposures/health effects/deaths around nuclear facilities and that becomes a stick to beat the operators with and perhaps prevent facilities being built or at least make them more complex and heavily regulated.
If I have misrepresented that and any of those that have recently expressed dis-satisfaction with LNT want to explain it better, crack on.
Fundamental question is; if LNT is wrong - what do you want instead and how will that change things? I'm assuming there in an attraction for a threshold based exposure model so some potential exposures could be zero-d out of the calculation as not being foreseeable?
Part of my reason for asking is I'm not convinced that even if a different model was established and accepted; would it change anything? or enough. The excess of caution in regulation, modelling and forecasting probably has more impact and has probably already gone too far. Public perception of radiation risk is also disproportionate and the fear factor may actually play out more than technical aspects if there was a move to change the framework?
For context: the window I look out of is that I try to advise on compliance with the regulations, so actually I'm most interesting in what the current (or future) laws look like and how to allow operators to work within them. I get the feeling others that post on the matter are involved in 'safety case' type arguments regarding facilities that could have significant off site consequences (or at least according to the current models and methods....). I have tried to keep the language plain, other than LNT in the title, to mitigate in being a rather niche discussion as wider views could be interesting. If it takes off, it could get very technical very quickly!
For a wider audience than those already 'inside' the madness of radiation dose response:
LNT = Linear non-threshold. A dose response model for risk vs radiation exposure.
Essentially that risk of health effects such as cancer are proportional to exposure to radiation, so even the background radiation we all get by being on the planet means there is an underlying radiation induced risk of cancer.
At background and occupational levels the risk is very low, fractions of a percent vs 1 in 2, 1 in 3 or so risk of cancer in lifetime; depending on which advert/campaign/guidance you agree with.
The perceived flaw as I think I understand it, is that this is used to project potential exposures/health effects/deaths around nuclear facilities and that becomes a stick to beat the operators with and perhaps prevent facilities being built or at least make them more complex and heavily regulated.
If I have misrepresented that and any of those that have recently expressed dis-satisfaction with LNT want to explain it better, crack on.
Fundamental question is; if LNT is wrong - what do you want instead and how will that change things? I'm assuming there in an attraction for a threshold based exposure model so some potential exposures could be zero-d out of the calculation as not being foreseeable?
Part of my reason for asking is I'm not convinced that even if a different model was established and accepted; would it change anything? or enough. The excess of caution in regulation, modelling and forecasting probably has more impact and has probably already gone too far. Public perception of radiation risk is also disproportionate and the fear factor may actually play out more than technical aspects if there was a move to change the framework?
For context: the window I look out of is that I try to advise on compliance with the regulations, so actually I'm most interesting in what the current (or future) laws look like and how to allow operators to work within them. I get the feeling others that post on the matter are involved in 'safety case' type arguments regarding facilities that could have significant off site consequences (or at least according to the current models and methods....). I have tried to keep the language plain, other than LNT in the title, to mitigate in being a rather niche discussion as wider views could be interesting. If it takes off, it could get very technical very quickly!
Evidence is what you’d replace it with.
Radiation is an interesting one. I wouldn’t go as far as saying that hormesis is real, but there is some evidence to support it. If LNT was real, we’d see catastrophic increases in illness due to background radiation. They’ve been studied:
https://pubmed.ncbi.nlm.nih.gov/11769138/
The TL:DR version - people in Ramsar, Iran, have been exposed to 10x the radiation that radiation workers are allowed, and they’ve been exposed over generations. You’d expect them to be mutated, riddled with cancer, and having 6 heads. But they’re not. Genetically they’re in better shape than average, and they have lower cancer rates than average. Similar findings have been made, for example the case of Cobalt-60 infused rebar used in Taiwan:
https://www.todayifoundout.com/index.php/2020/12/t...
LNT depends on an assumption that low doses of something are harmful - but that depends on the thing you are considering, and the system that uses the thing. If I immerse a person in water, they drown. As soon as their head is out of the water, they don’t drown. If I make people stand in an inch of water, I don’t get 0.0001% drownings. LNT Is attractive to people with an axe to grind because any very small number multiplied by a population leads to a lot of people dying, which leads to funding.
If you look at the diesel debate, apparently thousands of people are dying from it (40,000 premature deaths a year!), yet we struggle to find them. Lung health (as measured by rates of COPD per 100K) is better in London than in the Highlands of Scotland. How can this be?
Radiation is an interesting one. I wouldn’t go as far as saying that hormesis is real, but there is some evidence to support it. If LNT was real, we’d see catastrophic increases in illness due to background radiation. They’ve been studied:
https://pubmed.ncbi.nlm.nih.gov/11769138/
The TL:DR version - people in Ramsar, Iran, have been exposed to 10x the radiation that radiation workers are allowed, and they’ve been exposed over generations. You’d expect them to be mutated, riddled with cancer, and having 6 heads. But they’re not. Genetically they’re in better shape than average, and they have lower cancer rates than average. Similar findings have been made, for example the case of Cobalt-60 infused rebar used in Taiwan:
https://www.todayifoundout.com/index.php/2020/12/t...
LNT depends on an assumption that low doses of something are harmful - but that depends on the thing you are considering, and the system that uses the thing. If I immerse a person in water, they drown. As soon as their head is out of the water, they don’t drown. If I make people stand in an inch of water, I don’t get 0.0001% drownings. LNT Is attractive to people with an axe to grind because any very small number multiplied by a population leads to a lot of people dying, which leads to funding.
If you look at the diesel debate, apparently thousands of people are dying from it (40,000 premature deaths a year!), yet we struggle to find them. Lung health (as measured by rates of COPD per 100K) is better in London than in the Highlands of Scotland. How can this be?
Edited by rxe on Saturday 12th February 11:27
rxe, thanks for commenting.
I'm not going to nest quotes as I'll probably mess that up, so will add bold against a couple of points.
Recent ICRP conferences do support looking at other models, but none are yet more convincing for universal use. Roger Coates said at the 2019 ICRP conference (and last years SRP) that there does need to be a sense of proportion at dealing with lower doses/dose rates and that it (LNT) shouldn't be the only factor in decision making; it is a bit daft that you'll have a boundary condition of not exceeding an exposure that is orders of magnitude below natural background radiation. He certainly supports the idea that the dose restraints have gone far enough/too far already. Particularly if you multiply layers of caution in each stage of an assessment.
But what would you change? or like to see changed?
Part of the problem might be an excess in emphasis on the P of ALARP rather than the R, so 'as low as practicable' rather than 'as low as reasonable'. So is the flaw not LNT, but how exposures are perceived?
By the way; I'm not firmly in the camp of 'LNT is right, get on with it', more that I am not convinced that having spent most of the 20th century discovering radiation and how to use it, followed by discovering it not being entirely risk free and increasing tightening of restrictions/dose limits. To move onto 'nah, actually not that bad, as you were....' might be a bit of a pushing water uphill task!
Through force of pandemic, the population is perhaps now more epidemiologically aware (or thinks it is...) so may be the timing is right to push back?
I'm not going to nest quotes as I'll probably mess that up, so will add bold against a couple of points.
rxe said:
Evidence is what you’d replace it with.
Radiation is an interesting one. I wouldn’t go as far as saying that hormesis is real, but there is some evidence to support it. If LNT was real, we’d see catastrophic increases in illness due to background radiation. They’ve been studied:
https://pubmed.ncbi.nlm.nih.gov/11769138/
The TL:DR version - people in Ramsar, Iran, have been exposed to 10x the radiation that radiation workers are allowed, and they’ve been exposed over generations. You’d expect them to be mutated, riddled with cancer, and having 6 heads. But they’re not. Genetically they’re in better shape than average, and they have lower cancer rates than average. Similar findings have been made, for example the case of Cobalt-60 infused rebar used in Taiwan:
https://www.todayifoundout.com/index.php/2020/12/t...
that is an awful webpage! fortunately I found one that actually had numbers and analysis of the event that was more structured and I could mostly follow
LNT depends on an assumption that low doses of something are harmful - but that depends on the thing you are considering, and the system that uses the thing. If I immerse a person in water, they drown. As soon as their head is out of the water, they don’t drown. If I make people stand in an inch of water, I don’t get 0.0001% drownings. LNT Is attractive to people with an axe to grind because any very small number multiplied by a population leads to a lot of people dying, which leads to funding. wouldn't disagree that collective dose extrapolations are crude and open to misinterpretation and perhaps selective use to make points, but to be fair to the standard setters, that is acknowledged and cautioned against
If you look at the diesel debate, apparently thousands of people are dying from it (40,000 premature deaths a year!), yet we struggle to find them. Lung health (as measured by rates of COPD per 100K) is better in London than in the Highlands of Scotland. How can this be? I don't know, but as with some of the examples of high exposure/low cancer rates - multi-variables, COPD and cancer have multiple causes. I googled '40,000 premature deaths a year' and first hit was a BBC fact check, which linked the stat to several conditions, not just COPD.
The problem with saying 'look at the evidence, see here...' is that selecting specific cases to support a perspective is perhaps cherry picking. I don't have the time or intellect to dig through to find the good stuff or to doubt the bad, so am minded to trust those that can, for instance NCRP. Who fairly recently (2018) said The NCRP Committee recognises that the risks from LD/LDR exposures are small and uncertain. The Committee judged that the available epidemiologic data were broadly supportive of the LNT model and that at this time no alternative dose-response relationship appears more pragmatic or prudent for radiation protection purposes.Radiation is an interesting one. I wouldn’t go as far as saying that hormesis is real, but there is some evidence to support it. If LNT was real, we’d see catastrophic increases in illness due to background radiation. They’ve been studied:
https://pubmed.ncbi.nlm.nih.gov/11769138/
The TL:DR version - people in Ramsar, Iran, have been exposed to 10x the radiation that radiation workers are allowed, and they’ve been exposed over generations. You’d expect them to be mutated, riddled with cancer, and having 6 heads. But they’re not. Genetically they’re in better shape than average, and they have lower cancer rates than average. Similar findings have been made, for example the case of Cobalt-60 infused rebar used in Taiwan:
https://www.todayifoundout.com/index.php/2020/12/t...
that is an awful webpage! fortunately I found one that actually had numbers and analysis of the event that was more structured and I could mostly follow
LNT depends on an assumption that low doses of something are harmful - but that depends on the thing you are considering, and the system that uses the thing. If I immerse a person in water, they drown. As soon as their head is out of the water, they don’t drown. If I make people stand in an inch of water, I don’t get 0.0001% drownings. LNT Is attractive to people with an axe to grind because any very small number multiplied by a population leads to a lot of people dying, which leads to funding. wouldn't disagree that collective dose extrapolations are crude and open to misinterpretation and perhaps selective use to make points, but to be fair to the standard setters, that is acknowledged and cautioned against
If you look at the diesel debate, apparently thousands of people are dying from it (40,000 premature deaths a year!), yet we struggle to find them. Lung health (as measured by rates of COPD per 100K) is better in London than in the Highlands of Scotland. How can this be? I don't know, but as with some of the examples of high exposure/low cancer rates - multi-variables, COPD and cancer have multiple causes. I googled '40,000 premature deaths a year' and first hit was a BBC fact check, which linked the stat to several conditions, not just COPD.
Edited by rxe on Saturday 12th February 11:27
Recent ICRP conferences do support looking at other models, but none are yet more convincing for universal use. Roger Coates said at the 2019 ICRP conference (and last years SRP) that there does need to be a sense of proportion at dealing with lower doses/dose rates and that it (LNT) shouldn't be the only factor in decision making; it is a bit daft that you'll have a boundary condition of not exceeding an exposure that is orders of magnitude below natural background radiation. He certainly supports the idea that the dose restraints have gone far enough/too far already. Particularly if you multiply layers of caution in each stage of an assessment.
But what would you change? or like to see changed?
Part of the problem might be an excess in emphasis on the P of ALARP rather than the R, so 'as low as practicable' rather than 'as low as reasonable'. So is the flaw not LNT, but how exposures are perceived?
By the way; I'm not firmly in the camp of 'LNT is right, get on with it', more that I am not convinced that having spent most of the 20th century discovering radiation and how to use it, followed by discovering it not being entirely risk free and increasing tightening of restrictions/dose limits. To move onto 'nah, actually not that bad, as you were....' might be a bit of a pushing water uphill task!
Through force of pandemic, the population is perhaps now more epidemiologically aware (or thinks it is...) so may be the timing is right to push back?
That was an awful site but I was running out of time and forgot the incident was in Taiwan .... was trying to find it in Korea for far too long.
Overall, I think we need to be honest enough to say "we have no evidence for harm" at low doses. Your example of "lower than background" is a good one - we don't have health concerns going to Newquay (~3x "normal" background) or Edinburgh (~2x "normal" background), indeed we would view both of those locations as nice places to live. But all you have to do is live there for a year, and you've taken ~half the dose that would exceed the limit for a radiation worker.
If LNT was gospel. you'd expect clear differences in cancer rates and longevity that would be visible between Cornwall and the rest of the country. I was quite surprised to have a look at the studies of Radon exposure, which seem to struggle to find a significant link.
We've had enough experience of nuclear releases to have a reasonable body of evidence on this. Greenpeace's view of Chernobyl was based on LNT and predicted that nearly a million people would die. No axe to grind there. Later studies have found increases in solid tumours post-Chernobyl, but these were greater in regions of Ukraine where fallout didn't land. Possibly a case of if you go looking for cancer, you'll find it. They have found material increases in Thyroid cancer, but these are high dose events, downwind of a burning reactor.
As I said, my general concern with this approach is that it allows people to calculate some number based on almost nothing that then when multiplied by a population, gives a huge number of deaths. As a result, we have policy dictated by an approach that we know is pretty bogus.
Overall, I think we need to be honest enough to say "we have no evidence for harm" at low doses. Your example of "lower than background" is a good one - we don't have health concerns going to Newquay (~3x "normal" background) or Edinburgh (~2x "normal" background), indeed we would view both of those locations as nice places to live. But all you have to do is live there for a year, and you've taken ~half the dose that would exceed the limit for a radiation worker.
If LNT was gospel. you'd expect clear differences in cancer rates and longevity that would be visible between Cornwall and the rest of the country. I was quite surprised to have a look at the studies of Radon exposure, which seem to struggle to find a significant link.
We've had enough experience of nuclear releases to have a reasonable body of evidence on this. Greenpeace's view of Chernobyl was based on LNT and predicted that nearly a million people would die. No axe to grind there. Later studies have found increases in solid tumours post-Chernobyl, but these were greater in regions of Ukraine where fallout didn't land. Possibly a case of if you go looking for cancer, you'll find it. They have found material increases in Thyroid cancer, but these are high dose events, downwind of a burning reactor.
As I said, my general concern with this approach is that it allows people to calculate some number based on almost nothing that then when multiplied by a population, gives a huge number of deaths. As a result, we have policy dictated by an approach that we know is pretty bogus.
rxe said:
Possibly a case of if you go looking for cancer, you'll find it. They have found material increases in Thyroid cancer, but these are high dose events, downwind of a burning reactor.
As I said, my general concern with this approach is that it allows people to calculate some number based on almost nothing that then when multiplied by a population, gives a huge number of deaths. As a result, we have policy dictated by an approach that we know is pretty bogus.
Certainly true that if you go looking you'll find things, or perhaps a factor in Taiwan, you closely watch a population and discover that because they are being monitored they are healthier than average; UK radiation workers fall into 'healthy worker effect' and generally have better stats than the population as a whole.As I said, my general concern with this approach is that it allows people to calculate some number based on almost nothing that then when multiplied by a population, gives a huge number of deaths. As a result, we have policy dictated by an approach that we know is pretty bogus.
The thyroid aspect reminds me; even over 25 years after the accident they were insisting that we had thyroid ultrasounds as part of the medical surveillance to work on site. Obviously no cancers to found, but thyroids are obviously a part of the body that has plenty of issues so quite a few nodules and other odd things were found!
The policy isn't going to change very quickly, as with Covid any science in the argument quickly gets overtaken by politics/caution and a lack of common sense.
Dogwatch said:
There are stories of wildlife living and flourishing in contaminated areas long before any human will go there. Perhaps we should take a cue from that?
The wildlife flourishes because they're filling the vacuum left by people fleeing. Which is all well and good, but how many of them get cancer or have birth defects?Gassing Station | Science! | Top of Page | What's New | My Stuff