"Just responding to his most recent post. I have said pretty much the same thing in several posts hoping rephrasing it or the use of a little nuance in the angle would move the discussion forward. Regulations are not the summit of our knowledge they are stew of politics. This is a change whose time has come, radiation hormesis and the decline of the linear non-threshhold dose effect relationship have been ascending in the radiation protection community for some time the regulations just have not kept up (there I go again from a new angle)."
BIER 7 was clear on hormesis. Relevant ICRP publications are clear on this topic. My intention was to contribute, not to antagonize.
I apologize.
No need to apologize I just saw no movement from what seemed to be 'reduced limits were a step backwards'. Finally something new to rebut. The third citation is on Hormesis is from a Rio Grande Chapter HPS Spring Meeting in a slide presentation ( I like emoticons and lots of pictures
) the first two are a little drier but clearly state that dose projections under 100 mSv are not valid due to questions on the linear non-threshhod model.
RADIATION RISK IN PERSPECTIVE
POSITION STATEMENT OF THE
HEALTH PHYSICS SOCIETY*In part because of the insurmountable intrinsic and methodological difficulties in determining if the health
effects that are demonstrated at high radiation doses are also present at low doses, current radiation protection
standards and practices are based on the premise that any radiation dose, no matter how small, may result in
detrimental health effects, such as cancer and hereditary genetic damage. Further, it is assumed that these
effects are produced in direct proportion to the dose received, that is, doubling the radiation dose results in a
doubling of the effect. These two assumptions lead to a dose-response relationship, often referred to as the
linear, no-threshold model, for estimating health effects at radiation dose levels of interest. There is, however,
substantial scientific evidence that this model is an oversimplification. It can be rejected for a number of
specific cancers, such as bone cancer and chronic lymphocytic leukemia, and heritable genetic damage has not been observed in human studies. However, the effect of biological mechanisms such as DNA repair, bystander
effect, and adaptive response on the induction of cancers and genetic mutations are not well understood and
are not accounted for by the linear, no-threshold model.
https://hps.org/documents/risk_ps010-2.pdfRISK ASSESSMENT
POSITION STATEMENT OF THE
HEALTH PHYSICS SOCIETY*Risk assessment should include consideration of uncertainties
The establishment and use of risk coefficients to estimate public health determinants from individual or
population exposures must be considered in the context of uncertainties in the estimates. It is essential that all
uncertainties, assumptions, and inferences used in this assessment process be explicitly stated and that any
biases incorporated into the assessments for the purpose of ensuring prudent public health protection (such as
“margin of safety”) be clearly noted, including consideration of dose and species extrapolations and statistical
uncertainties. In addition to “best guess” or central estimates of risk, ranges of risk should be provided. Any
conservative assumptions, safety margins, and uncertainty factors should be clearly delineated.
Limitations of extrapolation of risk to low dose
Health risks of radiation exposure can only be estimated with a reasonable degree of scientific certainty at
radiation levels that are orders of magnitude greater than levels established by regulators for protection of the
public.
Radiological risk assessment, particularly for radiogenic cancer, currently is only able to demonstrate a
consistently elevated risk in those groups of the study populations that have been exposed to radiation at high
doses (>1 Sv). In order to estimate radiation risk in the low-dose region, typical of most occupational and
environmental exposures, health effects in the high-dose region are extrapolated to the low-dose region using
a variety of mathematical models, including the linear, no-threshold model. Cancer and other health effects
have not been observed consistently at low doses (<100 mSv) because the existence of a risk is so low as to not
be detectable by current epidemiological data and methods.
In the absence of direct observations, estimation of radiogenic health risks at low doses must be viewed
with caution. In most instances, to estimate risks (e.g., cancer) of small doses of radiation, a linear
extrapolation from large doses to zero is used. Extrapolation assumes that the pathway of radiogenic
effects is identical at any dose, which may not be valid. At high doses (>1 Sv), cell killing and cell
replacement occurs, creating an environment favorable for tumor growth. At low doses (<100 mSv), cell
killing and proliferation of surviving cells (which may be mutated or otherwise damaged) is much less
probable. In discussing the question of the limitations of extrapolation to estimate radiogenic risk in the 10
microsievert range, the National Academy of Sciences, in its 1990 BEIR V report noted, “ . . . the possibility
that there may be no risks from exposures comparable to external natural background radiation cannot be
ruled out. At such low doses and dose rates, it must be acknowledged that the lower limit of the range of
uncertainty in the risk estimates extends to zero” (NRC 1990).
The Health Physics Society recommends that assessments of radiogenic health risks be limited to dose estimates near and above 100 mSv. Below
this level, only dose is credible and statements of associated risks are more speculative than credible.
Thus, compliance with regulations to achieve very low levels of exposure result in enormous expenditures
of money with no demonstrable public health benefits.https://hps.org/documents/riskassessment_ps008-1.pdfThe LNT Hypothesis vs. Radiation
Hormesis: Different Implications for
Managing the Fukushima and other
Radiological Emergencies
http://www.rgchps.org/wp-content/uploads/2011/04/LNT-Hypothesis-vs-Radiation-Hormesis.pdf
