Doctors 'knowledge of radiation exposure: questionnaire study

10kBq Jaro · Senior Member

Doctors 'knowledge of radiation exposure: questionnaire study

stungun · Veteran Member

Geez Jaro,

Thanks for posting this important study about the dangers of unneeded radiation exposure. I know you were trying to put me down, but perhaps you should have read the conclusion and point of the study you tout. It agrees with my perspective.

Unlike the doctors in the survey, I do know the dose and risk of unnecesary x-rays. I am very conservative in my use of x-rays and bone scans.

Your source lectures correctly about dimwit doctors and overuse and overexposure of their patients to radiation, stating...

"This lack of awareness of the degree of exposure to ionising radiation becomes particularly pertinent when we consider the number of patients who receive inappropriate or repeat examinations."

Dusty · Veteran Member

Stugun,

What is your opinion on Radiation Hormosis?

Dusty

iprimap · Veteran Member

The following may refresh Dr. Stungun's memory concerning radiation hormesis; after working so hard as a physician in saving lives, he may be too tired to recall all the relevant details right now.

Radiation Hormesis Overview: http://www.radpro.com/641luckey.pdf

Radiation Hormesis: Demonstrated, Deconstructed, Denied, Dismissed and Some Implications for Public Policy: www.scientificexploration.org/jse/articles/pdf/17.3_kauffman.pdf

Radiation Hormesis: The Demise of a Legitimate Hypothesis: http://www-unix.oit.umass.edu/~nrephc/Calabrese%203.pdf

There are many more articles about this phenomenon. Some support the hypothesis of hormesis; some do not. Nevertheless, the generally accepted hypothesis of Linear No Threshold (LNT) no longer seems to be valid.

iprimap · Veteran Member

Former NRC Commissioner Ed McGaffigan pointed out the problem of the medical industry's incompetence with regard to the use of radiation in his speech at the RIC in Washington, DC on March 11, 2004 (the entirety of which the interested reader may review at: http://www.nrc.gov/reading-rm/doc-collections/commission/speeches/2004/s-04-003.html). Again, 10kBq Jaro is correct, but that does NOT dismiss the validity of radiation hormesis referenced by Dusty.

One of the issues Greta Dicus used to talk about in the materials area, and one of the most interesting things I came across in the last few weeks, in the last year really, relates to the exposures real people have to ionizing radiation. I’d like to call your attention to an article in the March 6th British Medical Journal -- which you can get online at www.bmj.com -- by Eugenio Picano, who’s an Italian senior medical researcher who writes about medical radiation exposure. This is almost entirely outside of my regulatory responsibility, because most of this exposure comes from machines or accelerator produced material outside NRC purview. You know that your own industry works on keeping occupational doses as low as reasonably achievable, and we all want to know the origin of last year’s increase in occupational doses at the plants. It’s probably the head inspections and the steam dryer repairs that’s causing that, but Dr. Picano makes the point that, according to UNSCEAR data (U.N. Scientific Committee on the Effects of Atomic Radiation), by 1997 in the most affluent countries, medical doses of radiation were equal to doses from natural sources of radiation. You’ve all seen these now outdated tables, you may have them on your own web sites, that the average American gets 360 millirems/year, 300 of it from natural radiation and 60 from medical. Well it isn’t 60 from medical any more, and we’re the most advanced of these nations in terms of making use of diagnostic tools in ways that this doctor feels may be inappropriate. This doctor feels that the medical community is over-doing it in its use of diagnostic scans. It’s not my responsibility, but if I were a member of the public interest groups who are represented here who challenge NRC about millirems, I would be challenging the medical community or asking the medical community to police itself about whether there are people getting doses, very significant doses, who should not be getting doses. Dr. Picano points out in this article that when children get a CT scan, the scanning machines are not adjusted to the mass of the child’s body, so they get needless doses. And we’re not talking millirems, which oftentimes we are in nuclear reactor space. We are talking rems. So I call this article to your attention.

Mr. Lacoste at yesterday’s breakout session said that the French public divides radiation into three sorts, and their attitude towards the three sorts of radiation is as follows. Natural radiation doesn’t exist. In large parts of France obviously that’s not true. There’s lots of nice granite around. Artificial radiation that this industry is involved in is bad. Medical radiation is good. I suspect Americans would hold similar views. If you think about a typical nuclear power plant, I suspect that the workers there, given the age of the workers, probably get at least an average medical dose. If you have 1,000 workers at the plant, and they’re getting 300-400 millirems on average from medical exposure, they are getting far more dose from the medical exposures than they get from working in the power plant -- 300-400 person-rem from medical scans compared to 126 person-rem according to Jim Dyer’s chart from yesterday’s session. And the medical dose has been increasing rapidly for years. This is extraordinary.

I personally have had far more than an average dose in recent years because I had melanoma four and a half years ago and I get PET scans and CT scans routinely. I am a very sophisticated consumer of such tests -- probably more sophisticated than my oncologist. I’m sure I’m rare in having discussions with him about whether we can tone this dose down a little bit, and do we really need both a CT scan with contrast and a PET scan every four months. And we’ve worked it through. But most consumers aren’t where I am. My son was not there. Three years ago my son was in the Senate Page program and while horsing around with a South Carolina football player in his dorm he managed to get tossed into a door. His sternum didn’t get fractured but he fainted from the pain in his sternum. When he got to DC General Hospital in the middle of the night, in addition to a chest x-ray to look at the sternum, they did a CT scan of his brain. There was no call for such a scan, but they probably needed to amortize that piece of equipment. If I had been consulted, I would never have agreed to that CT scan.

I am bothered by the “images are us” culture in parts of the medical community, as discussed by Dr. Picano. If you listen to WTOP news radio here in Washington, every morning you will hear advertisements for heart scans, full-body scans, any scan you can think of for asymptomatic patients. Of course, they do not advertise you’re getting rems as you get these scans. They do not advertise radiation at all. There is concern in the U.S. medical community and among State regulators and the FDA about overuse of CT scans with children. And perhaps some actions have been taken, but Dr. Picano sees the need for far more action. I suspect he is right. As I say, this part of my talk is aimed at some of my friends in the public interest groups for them to think about.

-----

Given information like this, I for one trust not a single doctor when it comes to administration of x-rays, use of irradiations, or implementation of body scans using radioactive sources. Unlike professionals in the commercial or US Naval nuclear community, there is little if any formal initial or continuing training on radiation and radioactive materials for doctors who have the authority to use such. That in itself should give an outcry of protest from both public and insurance agencies. Sadly, it increases the amount of regulatory action that US NRC has to take against incompetent physicians and other medical staff. Now here is indeed an area in which Dr. Stungun can be of some use (but being a messianic whistleblower against DOE is so much more flattering to the ego than saving the lives of little children).

stungun · Veteran Member

Hi Dusty and all,

RE: What's my opinion of hormesis?

Well, the Nat'l Acad of Science recently addressed radiation hormesis in BEIR 7. The NAS panel seemed loaded with pro-hormesis people, but ended up cutting hormesis to pieces! Slammed hormesis and reiterated to linear no threshold THEORY that the medical professionals are SUPPOSED to follow.

Note, most podiatrists I know use their x-ray machine as a cash generator, x-raying everything they can, needed or not. ( I do speak up against it)

I spoke with one published hormesis advocate. He agreed with me that hormesis did NOT apply to alpha emitters like plutonium, but only to gamma radiation. He also agreed that it did NOT apply to pregnant women and children, just adults.

Despite the BEIR 7 slamming of hormesis, I actually think that it is often true for gamma exposure on the ADULT immune system. I also think this skews nuclear worker studies, by boosting or delaying the detrimental internal alpha exposure. The "healthy worker effect" is well known for employed adults in ANY occupation, but I think external gamma radiation hormesis adds a booster to nuclear workers.

But the bottom line remains, ZERO extra man made radiation recommended for pregnant women and children...

10kBq Jaro · Senior Member

SG wrote:

Your source lectures correctly about dimwit doctors.....

I'm not sure I would call the doctors "dimwit," and find the description particularly odd, coming from someone whose most intelligent response to-date has been "yada, yada, yada...."

SG wrote:

Well, the Nat'l Acad of Science recently addressed radiation hormesis in BEIR 7. The NAS panel seemed loaded with pro-hormesis people, but ended up cutting hormesis to pieces! Slammed hormesis and reiterated to linear no threshold THEORY that the medical professionals are SUPPOSED to follow.

BEIR 7 is a dud, as explained in the report below, particularly in the section "Comparison between the Joint Report and the BEIR 7 Report". Furthermore, the NAS panel was NOT "loaded with pro-hormesis people" and ignored a great deal of scientific data that clashed with its unfounded LNT preconceptions. Medical professional are NOT supposed to follow LNT for estimating risk -- it is supposed to be nothing more than a regulatory tool, which greatly overestimates health effects at low doses (i.e. its highly conservative, relative to actual risks).

05/10/2005

Dose-effect relationship and estimation of the carcinogenic effects of low doses of ionizing radiation

The Joint Report of the Académie des Sciences (Paris) and of the Académie Nationale de Médecine

Maurice Tubiana, André Aurengo*

* On behalf of the working group which has prepared the Joint Report, correspondence : Maurice Tubiana, MD – Centre Antoine Béclère – Faculté de Médecine – 45 rue des Saints-Pères, 75006 Paris, France

** Académie des Sciences – Académie Nationale de Médecine (Paris).

Dose-effect relationships and estimation of the carcinogenic effect of low doses of ionizing radiation – M. Tubiana, A. Aurengo, D. Averbeck, A. Bonnin, B. Le Guen, R. Masse, R. Monier, A.J. Valleron, F. de Vathaire. - Paris 2005, 94 pages, 306 references (English text – March 2005) www.academie-medecine.fr/actualites/rapports.asp

<SNIP>

Because of these epidemiological limitations, the only method for estimating the possible risks of low doses (< 100 mSv) is extrapolation from carcinogenic effects observed between 0.2 and 3 Sv.

A linear no-threshold relationship (LNT) is often used for that purpose. The LNT model, used in 1956 by Russell to evaluate the radio-induced mutations in the germ cell line in the mouse, was introduced between 1960 and 1980 for the purposes of regulation in radioprotection with regard to all mutagenic and carcinogenic effects in humans. At that time, LNT was considered a convenient pragmatic relationship but not a model based on scientific data.

<SNIP>

8 – Comparison between the Joint Report and the BEIR 7 Report

The joint report was released in March 2005. Four months later, in July 2005, the BEIR 7 report was published. Contrarily to the French Academies report, it concludes that the linear no-threshold relationship (LNT) should be used for assessing the carcinogenic risks of low or very low doses. Since both reports rely to a large extent on the same data, the causes of this disagreement needs to be investigated. We shall consider below the various sources of this controversy.

8.1 Epidemiology

Both reports reach the same conclusion: There are no convincing data demonstrating a carcinogenic effect of doses below 100 mSv delivered to infants, children or adults. This is an important conclusion. Not long ago some proponents of the LNT claimed that the analysis of the data of A-bomb survivors (Brenner et al 2003) showed an excess of solid tumors after low doses. However, this conclusion was open to question because the statistical methodology used in these papers mixed individuals who had received up to 125 mSv. It was therefore felt their conclusions for doses below 100 mSv were not convincing. The same remarks can be made regarding the data on radiation workers (Cardis 2005).

However, there are two major differences between the Joint Report and the BEIR report.

The first concerns in utero irradiation. BEIR 7 acknowledges the existence of a controversy regarding these data but concludes that doses of 10-20 mSv delivered to the fetus were responsible for an excess in the incidence of leukemia and solid tumor. As discussed above, the conclusions of the Joint Report are different. The association may have been linked with various biases, such as an underlying maternal disease leading to both the X-ray examination and the excess of cancer incidence. Furthermore, the doses delivered at that time to fetuses may have been, in some cases, much larger than those calculated. Risks of leukemia were not increased among the offspring of Japanese atomic bomb survivors who were pregnant at the time of the bombing; and no increase was observed in twin studies and in several cohort studies or recent surveys (Naumburg, Shu).

The second difference regards workers contaminated with radium and patients contaminated with thorium. In both series the follow-up is longer than for the A-bomb survivors, the number of individuals contaminated is large, cancers (osteosarcoma or liver cancers) are observed following high doses but not following low doses and the existence of a threshold is obvious and not disputed (at about 10 Gy for radium [Carnes] and 2 Gy for hepatomas). As discussed above, several hypotheses, which are not mutually exclusive, can be made to explain the absence of cancer (Tubiana 2003). Whatever the mechanism involved, these data are not consistent with a linear relationship. These data are of great importance because, at equal doses, the alpha-particles are at least as carcinogenic as electrons. The omission of these data in the BEIR 7 report is surprising. Is it because these data correspond to heavy particles? The BEIR 7 report is devoted to low doses (below 100 mSv) and yet over ninety percent of the report discusses effects resulting from much higher doses, which is understandable because data should be put in perspective. Therefore data concerning alpha-particles should not be omitted. Unfortunately, the carcinogenic effect of low doses of radon is difficult to appreciate in humans because of the possible bias associated with tobacco; nevertheless the existence of a dose rate effect with radon suggests a non-linearity (Monchaux).

8.2 Animal Data

The BEIR 7 acknowledges, as does the Joint Report, that most animal dose-effect relationships are not linear but are either linear-quadratic, quadratic or with a practical threshold or even an hormetic effect. However, the BEIR 7 report does not discuss two important review papers, those of Tanooka (2001) and Duport (2003) which showed the high proportion of animal data with practical threshold or an hormetic effect. These two papers are not quoted in the BEIR report. If this is because the writers of the report disagree with their conclusions, it is regrettable that they do not explain why.

The BEIR report is entirely based on a technical NRPB memorandum by A.A. Edwards (1992), which unfortunately is not available in the libraries that we consulted. Therefore we were unable to check whether it is consistent with the more recent data. At any rate, there is a clear disagreement between the interpretation of the animal data in the BEIR 7 and the Joint Report.

8.3 Biological Data

8.3.1 Both reports conclude that there are two safeguard mechanisms of the cell genome: DNA repair and programmed cell death. Both also conclude that the temporal abundance of radiation-induced damage is a major factor in the efficiency/fidelity of DNA repair and hence the frequency of induced mutation (p. 432 of the BEIR report). The Joint Report argues that in these conditions the incidence of mutations should not increase linearly with doses since the mutagenic effect should be greater at high doses or high dose rate.

However, surprisingly, the BEIR report does not discuss this point.

8.3.2 The BEIR report feels that the probability of error-free or error-prone repair does not vary with dose and dose rate. During the discussion of the Vilenchik and Knudson data (2000), it rejects a possible variation in efficacy/fidelity of DNA repair and states: "There is evidence that argues against the inducibility of repair genes" in mammalian cells. The Joint Report has a different point of view. It underlines the data which show variations in the efficacy/fidelity of DNA repair. These variations can be due to several mechanisms such as activation of some biochemical phenomena (Sancar, Shiloh), cell cycle arrest which allows additional time for repair, variations in the efficacy of repair associated with the temporal abundance of damages within a cell (Dikomey and Brammer 2000), or the existence of a threshold in doses or dose rate below which the radiation damage sensor ATM is not activated (Collis et al 2004, Rothkamm and Lobrich 2003). Moreover, the Joint Report feels that Vilenchik and Knudson have convincingly shown that the mutagenic effect, per unit dose, is greater at high dose rate, whereas the BEIR 7 report remains skeptical regarding these data.

The BEIR report also expresses skepticism regarding phenomena which appear to be related to modulation of DNA repair efficacy, such as low dose hypersensitivity, adaptive response, hyperfast early cell response (Fernet et al 2000, Ponette et al 2000). This skepticism is mainly based on the absence of a mechanistic basis. The Joint Report does not share the skepticism of the BEIR report about the significance of these data for two reasons: i) these phenomena are now not disputed and mechanisms are being uncovered (see above); ii) the absence of a mechanistic basis has never in science justified overlooking data.

8.3.3 DNA repair is only one of the guardians of the damaged genome. The other one is the elimination of damaged cells by death, due either to apoptosis (which is inducible and which varies with dose and dose rate) or to the lack of activation of cell defense mechanisms.

These mechanisms and their variation with dose or dose rate are not discussed in the BEIR 7 report or by the ICRP preliminary report (2004).

The BEIR report expresses some doubt about the validity of the technology used in the important paper from Rothkamm and Lobrich (2003). It seems to be skeptical about the direct equation between the induction of DSB and the phosphorylation of the histome H2AX. The Joint Report recognizes that some verifications are needed but nevertheless concludes that the data must be taken into account for two reasons. First, the convergence between the data of Vilenchik (2000, 2003), Rothkamm and Lobrich (2003) and Collis (2004) cannot be overlooked. Second, the data published recently by Lobrich et al (2005) confirm the validity of this technique. With regard to this article, it has been argued that since a DNA repair is observed following CT-scan (doses of 10 to 20 mGy) this article contradicts the 2003 one.

However, the lack of DNA repair was reported after a much lower dose (1.2 mGy). Hence there is no contradiction between the two sets of data, but the threshold above which the cells do not disappear and repair is triggered is unknown (between 5 and 15 mGy).

The so-called dosimetric argument (Rossi and Kellerer, 1972) is often invoked in favor of the use of LNT even for the smallest dose. But Rossi himself (Rossi and Zaider 1997, Rossi 1997) has vigorously protested against this misuse of his theory.

The BEIR 7 draft report overlooks the complexity of the defense mechanisms and their high efficacy at low doses (Feinendegen and Neumann 2005).

8.4 Carcinogenesis.

The BEIR report refers to the traditional model in which carcinogenesis results from the accumulation in a single cell of several specific alterations (8 to 10). In fact statistical computations have shown that this accumulation has a low probability (Brash). Moreover, a large number of recent data have shown the role in carcinogenesis of interaction between the initiated cell, the surrounding normal cells, the stoma, and the immunocompetent cells which infiltrate tissues and tumors. The experimental data concerning contamination by radionuclides (beta or alpha emitters) suggest that a single isolated mutated cell has a very low probability of originating a detectable tumor. This conclusion is consistent with the epidemiological data, discussed above, made on individuals contaminated with alpha-emitters such as radium or thorium. The BEIR report and the tentative ICRP report do not discuss these data.

8.5 Although the BEIR 7 report advocates the use of LNT, it gives a great importance to the DDREF and advises a dose-effect relationship which embodies a DDREF factor and which is therefore not linear but curvilinear. However, surprisingly, the BEIR report does not discuss the mechanisms which are involved in the DDREF. It is likely that the lower mutagenic effect of a low dose rate is related to a better DNA repair and is not observed in cells with an impaired DNA repair.

8.6 In summary, the divergences between the Joint Report and the BEIR are not as great as they may appear. The BEIR 7 report conclusion (p. 443) is: "The committee judges that the balance of evidence from epidemiologic, animal and mechanistic studies tends to favor a simple proportionate relationship at low doses between radiation dose and cancer risk." But, this sentence is followed by a word of caution: "Uncertainties on this judgment are recognized and noted." Nevertheless, the report recommends the use of the linear no threshold relationship (LNT) for assessing the risks of small or very small doses. Conversely, the Joint Report states that the use of LNT for assessing the risks of doses below 20 mSv is unjustified and should be discouraged. The Joint Report feels that the most recent data clearly show the efficacy of the two guardians of the genome, DNA repair and programmed cell death, varies with doses and dose rates, whereas the BEIR 7 report is skeptical and does not take these data into account. With regard to carcinogenesis, the BEIR 7 report assumes that lesions accumulated in a single cell suffice to initiate a carcinogenic process. However, the Joint Report points out that the analysis of animal data and the lack of a carcinogenic effect in subjects contaminated with alpha-emitter nuclides is not consistent with this assumption.

Moreover, several recent data show that cancer is not simply a cellular disease but also involves dysfunction of the tissue control and immunosurveillance, such as those which are observed after the death of a large proportion of cells. Therefore the basic radiobiological assumptions of the LNT are not in accordance with recent data.

<SNIP>

Another meta-analysis (Duport 2003) has shown that among the experimental studies in which the incidence of cancer was sufficiently high in control animals, a reduction of this incidence was observed following low dose irradiation in 40% of them. This observation is consistent with the concept of hormesis. This finding does not justify generalization of this concept; however, it does confirm its existence.

In summary, animal experiments show the existence of a dose below which no excess in tumor incidence is detectable, which suggests the existence of a practical threshold.

Furthermore, most of the dose-effect relationships are not linear but rather linear-quadratic or quadratic and a hormesis is observed in about 40% of the experiments. The existence of a threshold is particularly obvious following contamination by N-emitter radionuclides. It is of interest that the same observation is made in humans because it shows that animal data can provide useful information for humans.

7 - Epidemiology

7.1 Carcinogenesis by long half-life alpha-emitting radionuclides

When an alpha-particle crosses a nucleus, the dose received by the cell is approx. 370 mGy and from 1 to 20 events can occur in the DNA molecules, causing important damage. Most cells are killed, but not all because cancers do occur. However, in this study the relatively small number of cells which are affected are surrounded by normal cells.

Painters of luminous dials contaminated with radium-226 and 228 have been subjected to several investigations covering over fifty years of monitoring. Other investigations have studied patients who had received thorotrast, a thorium-based contrast product used in the past in vascular radiology. They have also been monitored for more than 50 years.

Painters of luminous dials have presented a high frequency of osteosarcomas, but no excess cancers have been observed for absorbed doses of less than 10 Gy, contrasting with a marked increase for doses of more than 20 Gy (Carnes et al 1997).

Patients who have received thorotrast have presented hepatomas. In this case also, a threshold is observed: at about 2 Gy for hepatomas. Several non mutually-exclusive hypotheses have been put forward to explain the lack of effect with lower doses, which contrasts with the very high incidence with larger doses (Tubiana 2003):

1. It might be necessary for several alpha-particles to cross the cell to trigger carcinogenesis (Miller et al 1999).

2. The process triggered in a cell can lead to cancer only if the adjacent cells are nonfunctional (which, in the case of -particles would necessitate high doses) and so no longer exercise normal tissue control on the proliferation of the initiated cell.

3. If there are few cells damaged, these are eliminated by apoptosis, this elimination would not take place when there are large numbers of damaged cells.

4. Cells that cause cancers may not be induced directly but by a bystander effect. This mechanism is effective only at high doses.

On the basis of present knowledge, it is difficult to choose between these hypotheses but these data show that, with this type of irradiation, the bystander effect and radiation-induced genomic instability do not cause cancer when the number of damaged cells is small.

Moreover, none of these hypotheses is compatible with the postulates on which the LNT relationship is based.

<SNIP>

d) The current uncertainties regarding the carcinogenic effect of low dose irradiation underlines the interest of comparing the incidence of cancer and congenital malformations in geographic regions with high or low dose natural irradiation background and similar lifestyle.

Currently the data of studies carried out in India and China have not detected any differences, although chromosomal aberrations in the circulating lymphocytes confirm the high level of irradiation. These data are consistent with the hypothesis of a threshold but the data are not yet conclusive and the studies must continue.

While LNT may be useful for the administrative organization of radioprotection, its use for assessing carcinogenic risks induced by low doses, such as those delivered by diagnostic radiology or the nuclear industry, is not based on valid scientific data. For example, the results of the Berrington and Darby article (2004) estimating the number of lethal cancers induced by X-ray examinations should be considered with great caution. This type of data triggers unjustified anxiety among patients who have had radiological or nuclear medicine examinations. The concept of collective dose cannot be used for evaluating the cancer risk in a population.

======================================

Note: the original pdf copy of the article included the Greek symbol for "alpha," which was automatically converted to "N". This has now been corrected and the "N" changed to the text word "alpha."

-- Edited by 10kBq Jaro at 22:40, 2005-10-07

stungun · Veteran Member

I understand there was dissent to BEIR 7. But the bottom line to doctors remains the same- A fetus can survive a pre-natal x-ray with NO problem, but there is an inherent, proven risk, so unless it means life or death to the mother, the x-ray is avoided.

On quick search, I provide the ER protocol from United Medical Center at http://www.umcwy.org/Services/ER.htm

"Females need to know when their last menstrual period was. This is important especially if you need an x-ray. Please be aware that any female of childbearing age will need to have a pregnancy test done before they have an x-ray. This is to be absolutely sure that there is not possibility that the x-ray may do harm to an unborn child."

So, Jaro, I already said I believe hormesis is true in adults for background gamma radiation. How do you respond to ...

1) Does hormesis apply to fetuses? What proof or study shows that?

2) Your studies compare areas of increased gamma background. Do you believe that applies to internal alpha irradiation? Besides the tiny 26 LANL workers, one of whom got the rare osteosarcoma, do you have any internal alpha hormesis studies?

10kBq Jaro · Senior Member

SG wrote:

I understand there was dissent to BEIR 7.

You see this is where we differ, right off the bat : I understand that BEIR 7 was prepared by a select group of dissenters from the rest of the radiation science/ heath physics community, as explained in the Joint Report - BEIR 7 comparison paper above.

As regards alpha-emitters, here is a reiteration of text from the above paper:

Painters of luminous dials have presented a high frequency of osteosarcomas, but no excess cancers have been observed for absorbed doses of less than 10 Gy.

....to which I would only add that a nation-wide US survey has found a very statistically signifficant correlation between reduced levels of cancer, and counties with higher levels of radon -- an alpha-emitting, naturally ocurring radioactive gas which decays to other alpha emitters such as polonium-210, all with biological effects similar to plutonium, also an alpha emitter.

stungun · Veteran Member

Jaro,

You presented evidence of potentially no effect at low doses, but the question was on hormesis, which requires an improvement of health from alpha inhalation.

And you did not answer the fetal hormesis question...

You can call the BEIR 7 "dissenters" if you want to, but the present accepted THEORY is LNT, NOT hormesis. Hormesis is a minority opinion, not the established accepted opinion. While I have already said I believe there is a hormesis effect on adults from low increased background gamma, your claim of main stream hormesis belief is like the "intelligent design" religious advocates who want equal footing in school science with evolution...

-- Edited by stungun at 23:18, 2005-10-07

10kBq Jaro · Senior Member

Forgive me if I don't jump into your "fetal hormesis" trap (...no, fetal irradiation will not prevent abortion or car accidents, or what have you...)

The fact remains that a nation-wide US survey has found a very statistically signifficant correlation between reduced levels of cancer, and counties with higher levels of radon. Such correlations do NOT prove hormesis (fetal or otherwise) -- but then neither was I trying to prove hormesis. That part is only your imagination.

The so-called Linear No-Threshold or LNT hypothesis is in fact NOT a "theory."
A theory is a big step above hypothesis in scientific status.

And contrary to your misconceptions about "the established accepted opinion," applying LNT by extrapolating from high radiation doses to low doses, is discouraged:
As stated in the POSITION STATEMENT OF THE HEALTH PHYSICS SOCIETY, "RADIATION RISK IN PERSPECTIVE," (posted at http://hps.org/documents/radiationrisk.pdf ), "in accordance with current knowledge of radiation health risks, the Health Physics Society recommends against quantitative estimation of health risks below an individual dose of 5 rem in one year or a lifetime dose of 10 rem in addition to background radiation. Risk estimation in this dose range should be strictly qualitative accentuating a range of hypothetical health outcomes with an emphasis on the likely possibility of zero adverse health effects.
There is substantial and convincing scientific evidence for health risks following high-dose exposures. However, below 5-10 rem (which includes occupational and environmental exposures), risks of health effects are either too small to be observed or are nonexistent. [....] Collective dose (the sum of individual doses in a defined exposed population expressed as person-rem) has been a useful index for quantifying dose in large populations and in comparing the magnitude of exposures from different radiation sources. However, collective dose may aggregate information excessively, for example, a large dose to a small number of people is not equivalent to a small dose to many people, even if the collective doses are the same. Thus, for populations in which almost all individuals are estimated to receive a lifetime dose of less than 10 rem above background, collective dose is a highly speculative and uncertain measure of risk and should not be used for the purpose of estimating population health risks."

stungun · Veteran Member

Hi Jaro,

The thread had turned to hormesis, but I understand now that you are not claiming hormesis for the fetus nor alpha emitters. It was not a trap. I am just stating the bottom line for wind power vs nuclear power. We need to protect the fetus.

Yes, the Health Physics folks for sure push the wording you quoted. They are sorta right, I agree exact numbers would not be appropriate.

I was refering to the medical community and the NAS, as opposed to the 3 year head nodding HP people, but, I guess you are free to consider HP "the experts".

RE: Is LNT a theory or hypothesis

I am easy. I'll go along with hypothesis. They both sorta mean, "NOT A FACT" to me, but the semantics are debate-able.

Here is that exact debate from Physician's Weekly, and the nuclear medicine MD takes your "hypothesis" side. I sorta like the other guy's view, but it is not too important either way to me...

http://www.physweekly.com/archive/96/06_17_96/pc.html

Is The Linear, No-Threshold Theory Of Radiation Obsolete?

Stanley Goldsmith, M.D.
Editor-in-Chief, Journal of Nuclear Medicine YES The linear, no-threshold theory of radiation was never more than a working hypothesis, originated in the 1950s as a prudent operational guideline. But it has acquired the aura of fact even though no one has ever generated any evidence for it.

Recently, the BEIR 5 report-drawn up by a group of authorities in epidemiology, radiation, and cancer-concluded that there is a possibility that the risk at the level of 10 rad a year, which is twice the former guideline for workers, might be zero.

Johns Hopkins researchers have followed 750,000 workers at nuclear shipyards for over four decades. Among 90,000 workers exposed to nuclear areas on ships, only 26 cases of leukemia have been found, exactly the rate expected in the general population. Among workers exposed to less than 0.5 rad, fewer cases were seen than the LNT would suggest.

In parts of the world, Denver among them, where high altitude and uranium in the soil increase natural background radiation, there's no increase in the incidence of malignancies, fetal deformities, or sterility.

Some studies can be interpreted to say that low levels of radiation are good for you, a concept known as hormesis. Dr. Bernard Cohen of the University of Pittsburgh compared radon levels in homes with lung-cancer rates for 1,600 U.S. counties. He found higher levels of radon linked to lower rates of lung cancer. In the Hopkins study, nuclear workers exposed to less than 0.5 rad had far fewer cancers than nonnuclear workers.

One can't extrapolate from in vitro studies, which suggest a mechanism for these observations, to a multicellular organism, and I don't think hormesis is real. But what's real is that there is no injury from low or even moderate radiation levels.

Daniel Strom, Ph.D., C.H.P.
Staff Scientist, Health Protection Department, Pacific Northwest National Laboratory NO The notion that the linear, no-threshold theory is obsolete ignores heritable predispositions to cancer and other genetic defects. But reviews by the National Academy of Sciences and international bodies find plenty of fruit fly and in vitro evidence that LNT holds when it comes to germ-cell damage.

Two reports were issued in the fall of 1995 by the U.S. National Council on Radiation Protection and Measurements and the British National Radiological Protection Board. They asserted that the body of evidence from both laboratory animals and human studies allows presumption of a linear, no-threshold response at low doses and low-dose rates. Those who hold the public trust have no choice but to use the LNT for radiation protection for the foreseeable future.

Most epidemiologists put little credence in Dr. Cohen's "ecologic" design, because such analyses do not associate individual exposures with individual outcomes. The association was home-radon levels averaged by county with lung-cancer rates averaged by county.

Some conclude that data on atom-bomb survi-vors show that radiation protects at low doses. But there are huge error bars at low doses that include LNT in those analyses.

Even if all cancer could be prevented or cured, the world would still need stringent radiation-dose limits. The current occupational whole-body dose limit of 5 rems annually, based on cancer risk, would climb only to 15 rems, in order to prevent cataracts.

EPA's home action level for radon-4 picocuries/L-would rise to just 21 picocuries/L. That would be low enough to achieve the current limit of 50 rems to the bronchial epithelium, a worldwide standard designed to prevent acute radiation injury.

-- Edited by stungun at 06:41, 2005-10-08