[ RadSafe ] When Radiation Isn’t the Real Risk

[KARAM, PHILIP]

I suppose if you really want to get into the weeds then you'd also have to consider someone's age, health history, and genetic susceptibility to radiation. But then you could make the same comments about, say, drunk driving (people have different tolerances to alcohol), speed limits (based on the capabilities of your car plus reaction time plus driving skills), or smoking (some people are genetically more sensitive to smoke). But if we have regulatory limits tailored to each person according to their individual circumstances it will be nearly impossible to have any sort of effective regulation. At some point we have to treat everyone the same in the regulatory realm - or at least to divide the population into just a few manageable categories (e.g. rad workers and non-rad workers).

With regards to regulation, to some extent I suspect that, even if there is found to be a threshold, we will likely not see much change in regulatory limits. 

First, no politician will want to campaign as the person who made it possible for the public to be exposed to more radiation - and any agency head who tries to raise the limits will likely find him/herself looking for work. In addition, consider this. Say we find absolute proof that there is a threshold at 100 mSv (10 rem). Divide that number by, say, 70 and we get an annual exposure limit of about 1.4 mSv/yr for the general public. Add a safety factor (or figure a longer lifespan) and we come up with pretty much the same limit we have today. Finding evidence of a threshold would be scientifically exciting - but I'm guessing it would have virtually no impact on annual exposure limits.

Andy


-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of jjshonka at shonka.com
Sent: Wednesday, September 23, 2015 10:04 AM
To: The International Radiation Protection (Health Physics) Mailing List
Subject: Re: [ RadSafe ] When Radiation Isn’t the Real Risk

Is there any published article that discusses how regulations might change if LNT is no longer the law of the land?  I can see problems with implementation of rules.  With multiple agencies (EPA and NRC in the US), will regulations even have the same basis across all agencies?  




With LNT, the “slope of the curve” or risk per Sievert is same for all levels of exposure.  This makes regulating an activity that irradiates people very simple, in that the contribution from other exposures need not be considered to apply a risk or cost per exposure.  With a variable risk per Sievert (or non-LNT, with an emphasis on non-linear), would one have to consider all exposures to know where on the risk curve you are?  


If an environmental restoration project occurs in a high background area, does the cleanup criteria “differ” from another project in a low background area because the risk per exposure differs?  And by “differ”, limits could be higher or lower for either project, depending on the final “agreed upon” shape of the dose response curve.  If I have a worker with significant exposure from medical issues, or is a frequent flyer with high exposure from his travel, must I consider that as well as his occupational exposure to control his risk?  What if the worker lives in a house with high radon concentration (C. Waltrus at Limerick NPP is a famous example).  Clearly their risk per rem would differ under a non-LNT assumption from other workers.  Do the effluent limits for a reactor change in areas with higher background, such as the Reading Prong area of Pennsylvania as compared to Florida?   




Without the simplicity of the LNT assumption, many issues arise.  Radiation carcinogenesis already has a time (and dose rate) dependency.  Does the risk to a newly hired worker depend on past exposures (occupational and non-occupational) in previous years?  Must I consider past exposures and the time and dose rate of the various past exposures in limiting the exposure of a new employee?  Will my limits for a specific employee change over the years with past exposure history? 


I know some would argue that the limits will be so high because of hormesis that no controls would be needed.  However, I recall that UNSCEAR reports some flyers like couriers have 100 mSv per year from galactic cosmic radiation alone (and there are other sources that occur in flying), and many medical procedures, including radiation therapy have exposures that exceed 100 mSv.  Some high background areas have external gamma background approaching 50 mSv as well.




I do not think the regulatory agencies will no longer be needed.  I wonder how regulations will change.

 



Joseph J. Shonka, Ph.D.
Shonka Research Associates, Inc.
119 Ridgemore Circle


Toccoa, GA 30577
770-509-7606
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