Thank you for the opportunity to comment on the Committee 1 Task Group Report C1 Foundation Document Biological and Epidemiological Information on Health Risks Attributable to Ionizing Radiation: A summary of judgements for the purposes of radiological protection of humans
Many aspects of the report are thoughtful and well-considered including its recognition of the shortcomings of both the science and the models. It is refreshing that the committee erases some of the previously held assumptions in favor of ones that better fit the science. However, we take issue with many of the shortcomings (even the recognized ones) as we contend that what the public finds acceptable is certainly not what industry or government would accept.
We are pleased that after much unnecessary squabbling over a threshold dose for radiation, ICRP and other related committees such as BEIR VII are concluding that every dose of radiation, no matter how small, carries the potential of disease induction.
Similarly, we welcome that the ICRP are accounting for cancer incidence, and not merely cancer deaths, in their radiological protection models.
Finally, we are pleased to see that ICRP recognize that different types of ionizing radiation impart different kinds of damage, and that radiosensitivity varies among exposed tissues in the human body.
In short, there are many scientific assumptions in this report which are to be commended.
However, we feel that several of your basic premises are flawed.
You state that the purpose of this report is to establish guidelines for protecting humans from radiological damage by developing "dose-response relationships for radiation effects which are the basis for risk estimation" yet, simultaneously, you say that "exposure limits are set [in order] to limit exposure occurrences to an acceptable frequency and thus to prevent unacceptable levels of risk." Who defines "acceptable?" What does this term mean?
Consider the recently released BEIR VII report which sets the "acceptable" level of cancer incidence at 1 person in 100 (over an assumed 70-year lifespan) that can be attributed to man-made sources of radiation; this is within the context of a known risk of 1 in 100 cancer incidence from background radiation -- exclusive of radon exposure.
Most non-radioactive pollutants are allowed by current USA standards to present an acceptable risk of disease incidence of no more than 1 person in 1000. Some pollutants are allowed to present an acceptable risk of disease incidence of no more than 1 person in 1,000,000 (one million).
Why is radioactivity allowed to cause a risk 10 times greater than that allowed for other pollutants?
Who is allowed to define the acceptable level of risk and who shall bear this risk? Please be clear that the people who assume the risk in no way do so voluntarily. Exposure to industrial sources of radiation is the epitome of involuntary risk. The people who must bear this risk are not being properly represented in the decision-making processes to set the acceptable level.
We understand that ICRP is not setting standards, but rather providing guidelines. But you must understand that what you recommend often becomes standard and you have a responsibility to include or allow for all information. We feel you have left out relevant information in the protection recommendations.
In your report, you admit some scientific shortcomings in the risk dosimetric protection quantities. You state that the protection standards should not be used for retrospective analysis of disease induction. But if the protection standards are inappropriate for disease analysis, why are they appropriate for initial population protection? Doesn't this mean you are leaving some people unprotected?
For instance you do not fully account for gender, nor age, nor individual radiosensitivity; you say that information about the damage to the circulatory system is "too scant to consider," and you make no effort to account for the bystander effect nor for genomic instability, claiming that the data are not fully formed.
We understand that the science is complex and answers are not always available. But to continue on as if these effects were non-existent is irresponsible. You must account for "the least of us" in your formulas. The standard formula should consider the most sensitive sub-population and set the overall standard for them. This is the only humane way to handle a situation where we are being involuntarily exposed. Averages doom a certain number of people to disease.
Finally, it is short-sighted to limit the consideration of genetic effects of radiation exposure only to the first two generations. Continued exposure to low-dose radiation during subsequent generations may very well increase the number of mutations which causes human radiation sensitivity to increase. This unrecognized vicious circle invalidates all of your current assumptions.
The fact remains that many studies, including studies on mutation heritability and genomic instability, do not account for protracted radiation exposure over many generations. Because of this limited view, long-term involuntary exposure to low dose, low-LET radiation could result in much greater risk and damage than your models currently enable you to imagine.
We would ask you to please take note of this recent study:
Mutagenesis. 2005 Jul 12
Gamma irradiation of Type B spermatogonia leads to heritable genomic instability in four generations of mice.
Baulch JE, Raabe OG.
Center for Health and the Environment, University of California, Davis, California, CA 95616, USA.
In the abstract it concludes "These results indicate that irradiated spermatogonia develop a capacity to transmit a type of heritable genomic instability to four generations of offspring."
While the researchers use of a dose of 1 Gy to the spermatogonia looks high, this dose is within the realm of possibility when dealing with internal radiation damage to single cells from incorporated radionuclides and not imparted or averaged to the entire body.
In summary, we applaud the many important advances the ICRP has taken with this current report, but you must also take responsibility for your shortcomings and address them immediately. Protect for the most sensitive until the science is better understood. This is not only possible but necessary. Not doing so could create mistakes which can not be undone.
Thank you for consideration of these comments.
Nuclear Information & Resource Service