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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 16, 2014 11:47 am 
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Thanks to everyone for comments.

I didn't include references to Brazil beaches and Ramsar, Iran, because the average exposures to people there are much lower than the frequently quoted maximums. Also, in reviewing the studies of health effects, the numbers of people with cancers are so small that I couldn't justify any conclusions.

I wrote "a dose over 5000 mSv is usually fatal", meaning that it is fatal more often than not, not that it is simply fatal.

The dose/response graphs atomic bomb survivors, as shown in the RERF study that Jaro quoted, aggregate the "interesting" low dose exposures (< 100 mSv) together. More detailed data is available and it seems to show cancer incidence decreasing with increasing exposures under 50 mSv; I'm studying this more. It also suggests rationale for an acute exposure limit of 50 mSv. That's the limit for radiation workers, I believe. However the detailed data seems to suggest no health effects at that exposure, although LNT would predict a 1/2% cancer risk.

I thought it was important to footnote the statements that might be controversial to some readers.

Sorry about the font size and page width, but it looks good on an iPhone. Click on it to get to a 6-pages scrollable pdf, http://home.comcast.net/~robert.hargrav ... ixPage.pdf .

The reference to the Taiwan apartment buildings is to the revised article that was published after the critique.


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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 16, 2014 12:00 pm 
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Hello Dr. Hargraves.

Regarding the 5000 mSv dose, this is often fatal if prompt, but almost never fatal when taken over a year. That's well under 0.6 mSv/hour.

The bomb survivor study is hardly relevant to nuclear power risks at all, since nuclear power risks to the public are all chronic, with doses spread over days (for the short lived stuff) to decades (cesium and such).

It's important to make this distinction, and use some sort of example that we are familiar with. the one glass of wine for a year making a deadly dose of 365 glasses of year being a good example (most people drink alcohol on a regular/semiregular basis).


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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 16, 2014 1:33 pm 
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Cyril,
How prompt is prompt?
If we want to shift the conversion to dose rate rather than total dose we should have some terms to talk about. I presume that the real situation is more complex than either dose rate or total dose. You have been giving examples of aspirin or alcohol to show that total dose is completely inadequate.

If you were to receive a dose rate 5Sv/hr for one hour I presume this would be a fatal dose.
But given that same dose rate for 1 second and it would not be.
So dose rate doesn't seem right either.

Perhaps something like total dose w/in a cellular repair half-life (a day?).


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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 16, 2014 2:36 pm 
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Lars wrote:
Cyril,
How prompt is prompt?
If we want to shift the conversion to dose rate rather than total dose we should have some terms to talk about. I presume that the real situation is more complex than either dose rate or total dose. You have been giving examples of aspirin or alcohol to show that total dose is completely inadequate.

If you were to receive a dose rate 5Sv/hr for one hour I presume this would be a fatal dose.
But given that same dose rate for 1 second and it would not be.
So dose rate doesn't seem right either.

Perhaps something like total dose w/in a cellular repair half-life (a day?).


A practical and reasonably realistic approach is probably to ignore the first X millisieverts per hour, and then treat the excess over that as either LNT or QNT. So like a threshold model. Quadratic models are likely more realistic.

Where X would be in the ballpark of 0.1 mSv/h for adults and a lot lower for children (maybe 0.01 mSv/h for children).


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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 16, 2014 2:41 pm 
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It would be even more scientifically pleasing to have an even higher resolution, like dose rate per second. Not sure if that's practical.


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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 16, 2014 6:10 pm 
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robert.hargraves wrote:
I thought it was important to footnote the statements that might be controversial to some readers.


Yes, footnotes are good for your more diligent and educated readers, but for the general public you should also include
links to other material that is also intended for the general public. In other words, don't expect your average reader to read a specialized scientific journal paper to verify a claim or figure. Ideally, what you want is a link to a widely recognized governmental or scientific organization such as WHO or Scientific American. Even more ideally, you want to use direct quotes that can be easily verified from official reports and statements from such organizations.


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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 17, 2014 1:01 am 
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Cthorm wrote:

No, 150 microsievert readings from Half Moon Bay…
I thought the readings were in counts per minute. 150µSv/hr is actually quite high.

Went to look. Yup, all the pictures on Google showed CPM.

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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 17, 2014 1:21 am 
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Clearly neither the irradiation dose rate nor total dose received is an entirely satisfactory metric on its own. What is important is the rate at which cellular damage occurs relative to the rate at which it can be repaired. Total dose is the best measure for exposures that are short relative to the cellular repair timescale (seconds or minutes), while dose rate is the best measure for ongoing exposures over time periods that are long relative to the cellular repair timescale (months or years). Things get more difficult at intermediate timescales - biological systems are complicated and cellular repair occurs on multiple timescales that cannot be adequately described by a single kinetic parameter like a half-life.

This type of behavior is not unique to ionizing radiation. For the wine example, the extreme cases of a glass a day for a year and 365 glasses in a day are clear, but what about 7 glasses every friday night? It won't kill you, but it isn't exactly healthy either. Safety standards for exposure to hazardous chemicals include both time weighted averages that establish safe average levels that people can be exposed to on a daily basis without excessive long term risk, as well as short term exposure limits aimed at avoiding acute illness. Safety standards for ionizing radiation should be established the same way.


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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 17, 2014 4:01 am 
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Titanium48 wrote:
Clearly neither the irradiation dose rate nor total dose received is an entirely satisfactory metric on its own. What is important is the rate at which cellular damage occurs relative to the rate at which it can be repaired. Total dose is the best measure for exposures that are short relative to the cellular repair timescale (seconds or minutes), while dose rate is the best measure for ongoing exposures over time periods that are long relative to the cellular repair timescale (months or years). Things get more difficult at intermediate timescales - biological systems are complicated and cellular repair occurs on multiple timescales that cannot be adequately described by a single kinetic parameter like a half-life.

This type of behavior is not unique to ionizing radiation. For the wine example, the extreme cases of a glass a day for a year and 365 glasses in a day are clear, but what about 7 glasses every friday night? It won't kill you, but it isn't exactly healthy either. Safety standards for exposure to hazardous chemicals include both time weighted averages that establish safe average levels that people can be exposed to on a daily basis without excessive long term risk, as well as short term exposure limits aimed at avoiding acute illness. Safety standards for ionizing radiation should be established the same way.


Good points. A practical approach is to simply ignore the first 0.1 millisieverts per hour (maybe 0.01 mSv/h for children) then treat the rest as linear or even quadratic damage.

This solves both problems that dose rate and dose have.

As an example, with this approach you are granted no damage from living in a high background radiation area, but a medical scan of (say) 10 mSv is still counted as 9.9 mSv of damage, reflecting the danger of prompt exposure.

The approach works better with smaller timescales to deal with resolution problems. A dose rate per second would be most scientifically pleasing. But 0.03 microsievert per second doesn't mean much to people...


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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 20, 2014 8:54 pm 
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I think that page is effective, but I'd put the relationship to DNA damage done by ionizing radiation as opposed to other sources higher up. If more people realized just how dynamic the DNA molecule really is and how minor the effect of radiation is in almost all cases then they may be able to get over some of this fear they have.


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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 21, 2014 1:29 pm 
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There are about 1000 paper versions in distribution, and a similar number of emails. You can help by emailing a pdf version to your contacts, asking them to read, consider, and forward the brochure.
http://home.comcast.net/~robert.hargrav ... ixPage.pdf


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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 22, 2014 4:18 am 
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Cyril R wrote:
Better than a yearly limit is an hourly limit. 0.1 mSv/h looks a safe dose rate for adults, even if permanently present as a chronic dose rate.
This looks much higher than any other limit I've seen. About the most extreme has been about 20µSv/hr for adult males and adult females, not of child bearing years.

I've recently seen a presentation where the exact same Greys results in a higher Sieverts for children because of a "tissue multiplier" like the particle multiplier for alphas...

Does anyone know anything about this?

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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 22, 2014 4:23 am 
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Robert,
Excellent brochure. There is at least one error. Muller did not get the Nobel Prize for the LNT. He got it for demonstrating that X-Rays are mutagenic at high doses. He then used the Bully Pulpit to start the great lie, anti-nuclear lie #1, "there is no safe dose".

HE actually told the literal truth, but only half the truth, so it became the basis of the lie. He said that there was no question that DAMAGE was linearly proportional to dose. And he was correct. What he left out was all the other stuff that made HARM non-linear.

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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 22, 2014 7:21 am 
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I'll see if I can reword the Muller statement in the next edition. Here's what he said at the Nobel Prize lecture.

"These facts have since been established with great exactitude and detail, more especially by Timoféeff and his co-workers. In our more recent work with Raychaudhuri (1939, 1940) these principles have been extended to total doses as low as 400 r, and rates as low as 0.01 r per minute, with gamma rays. They leave, we believe, no escape from the conclusion that there is no threshold dose, and that the individual mutations result from individual "hits", producing genetic effects in their immediate neighborhood."

http://www.nobelprize.org/nobel_prizes/ ... cture.html

The "as low as 400 r" dose of 4 Sv would be a near-death experience for humans.

Note that the lowest rate he mentioned is 0.01 r per minute, or ~ 0.876 Gray/year (~876 mSv/y).


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 Post subject: Re: Radiation: The Facts
PostPosted: Jan 22, 2014 8:05 am 
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0.01 rad/minute is 0.6 rad/hour, 5256 rad/year. 52 gray/year.

This is an extremely dangerous dose rate! Not relevant to nuclear power risks to the public at all.

I guess a Nobel Prize doesn't really mean anything.


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