Saturday, August 27, 2011

Debating Dose

In a previous post I described the ICRP model, as explained by Chris Busby. Busby stated that the model essentially extrapolated the human effects from radiation by looking at how water absorbed radiation. (see http://majiasblog.blogspot.com/2011/08/short-history-of-risk-assessments-for.html )

Now I am going to describe how Busby differentiates the recently developed European model (ECRR) on evaluating radiation risk from the ICRP model. The following is excerpted from this link
http://euradcom.org/publications/iodinedosecalc15042011.pdf

(Excerpted) Dose, dose rate and contamination
Dose, or absorbed equivalent dose is given in Sieverts. It is this quantity that is used to predict radiation risk. It is a lump of radiation that has been delivered to your body.

Although for some radionuclide internal exposures, absorbed dose is a meaningless concept, because it is an average to all tissue rather than the energy delivered to the DNA, we can use weighting factors to convert the absorbed dose into the energy delivered to the DNA.

This is what the ECRR has done. A microSievert (mSv) is one millionth of a Sievert...
The ICRP cancer risk coefficient is about 0.05 per Sievert and that of the ECRR is 0.1 per Sievert. http://euradcom.org/publications/iodinedosecalc15042011.pdf
 MAJIA HERE: So, what the ECRR model has done is to weight the radiation dose so that it incorporates the biological impact on DNA rather than simply looking at the summative effect of the absorption of the radiation into tissues (at least, that is my understanding)

The ECRR's 2010 Recommendations can be found here

It is interesting to note that in the first link I've provided (http://euradcom.org/publications/iodinedosecalc15042011.pdf) Busby notes that even the ECRR's model fails to adequately predict the impact of radiation on children because they are so much more biologically vulnerable than adults.

Thus, Busby writes:

"The dose coefficient is perhaps as much as 5 times greater for children. Infant leukemia increased after Chernobyl at levels where the ICRP foetal doses from Caesium-137 were about 50microSieverts and the ECRR coefficients for Cs-137 would not have predicted these increases"
Majia Here: Ok now we understand the criticism of the ICRP model and have another model for studying the health risks of radiation but even that model understates children's risks (and the younger the child the greater the risk as a general rule).

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