Re[2]: Rn, Epidemiology + thoron

[Yarmoshenko IV <ivylist@ECKO.URAN.RU>]

Bill,

Some clarifications on thoron.

Half  life  of  Pb-212  (thoron  daughter)  is about 10 h consequently

thoron  progeny  is  equally  distributed within the room. Due to high

variability   of   thoron   equilibrium  factor  indoor,  thoron  gas

concentration  measurement  does not surrogate thoron progeny exposure

assessment (as in the radon case). Unfortunately I'm not familiar with

any  integral  passive technique of thoron progeny measurements and as

far  as  I understand the retrospective measurements of thoron progeny

is  impossible (am I right?). We used the grab sampling techniques for

surveys  in  Ural  region  of  Russia, by which results thoron progeny

contributes  from  5  to  30  %  to  total  average Rn+Tn exposures by

settlements.



Regards,

Ilia



Ilia Yarmoshenko

Radiation Laboratory

Institute of Industrial Ecology

Ekaterinburg

Russia





RWF> Regarding thoron, because of its short half life, the distance it travels is

RWF> much less.  But, if you are sleeping right next to a source, you can get a

RWF> significant exposure.  The glass based detector we used in Iowa has

RWF> specificity for thoron so we do plan to look at that down the road as we

RWF> clear some other hurdles.  We do have those measurements already performed.

RWF> One interesting note is that outdoor thoron exposure may be greater than we

RWF> thought.





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