Re: Fwd: Fed Express worker received 1.5 rem from Ir-192source, etc.

["Jim Hardeman" <Jim_Hardeman@MAIL.DNR.STATE.GA.US>]

Colleagues —



I forwarded Eric's message to a good friend of mine here in Atlanta, who just happens to have been the Director of Radiation Medicine at ORAU several years back. His reply is below.



Jim Hardeman

Jim_Hardeman@mail.dnr.state.ga.us 



>>> Fun Fong MD FACEP <ffong@emory.edu> 5/4/2002 0:48:36 >>>

> Subject:

>

> Fed Express worker received 1.5 rem from Ir-192 source

> From:

>

> goldinem@SONGS.SCE.COM 

> Date:

>

> Fri, 3 May 2002 15:07:51 -0700

> To:

>

> radsafe@list.vanderbilt.edu 

>

>

>Can anyone out there (someone from REACTS?) tell us how clinicians can

>accurately measure exposure to 1.5 rem based on blood tests (lymphocyte

>chromosome aberrations?)  If the worker is about 25 years old, his/her

>lifetime dose has to be close to or above 7 or 8 rem anyway.  I thought

>that "natural exposure" would contribute to enough chromosome aberrations

>that dose estimating is difficult below 5 or 10 rem.

>

>--A FEDERAL EXPRESS WORKER RECEIVED 15 MSV (1.5 REM) FROM AN Ir-192 package

>during transit of the iridium package at Roissy Charles de Gaulle airport

>near Paris in early January, results of medical examinations have

>indicated.

>Authorities had concluded in March that the package had begun to leak only

>at the end of its trip, in the U.S., a conclusion the new French finding

>appears to contradict. Officials of French nuclear safety authority DGSNR

>said today they had informed colleagues in Sweden, where the package

>originated at Studsvik AB, and the U.S., its final destination, of the

>findings of the blood tests on two FedEx workers, one of whom was found to

>be contaminated. At the time of the accident, which was rated at Level 3 on

>the International Nuclear Event Scale, U.S. authorities said the driver of

>a

>delivery truck on the final leg of the package's trip to a New Orleans

>suburb had received a dose estimated at 3.4 milliSievert.

>

>Eric M. Goldin, CHP

><goldinem@songs.sce.com>

>

It is very difficult to measure exposures under 10-15 rem.  The old gold 

standard technique of lymphocyte cytogenetics has great difficulty in 

measuring exposures under 5 - 10 rem because 1) it has been a manual 

technique and 2) one would have to sample about 10,000 lymphocytes to 

get statistical significant numbers for exposure below 10 rem.  It would 

be a very labor intensive proposition to try to measure doses under 10 

rem on a regular basis at this time.  There is also a time factor for 

lymphocyte cytogenetics.  The half-life of a usual lymphocyte population 

is been roughly described to me to be approximately 10,000 days.  So 

with time after exposure, obtaining statistical significance becomes 

more and more difficult.  



Other automated techiques for biodosimetry, such as micronuclei 

analysis, hold theoretical promise that they may be able to read lower 

doses, but have not been clearly established as a clearly superior 

technique to lymphocyte cytogenetics.  Other techniques that hold 

promise are premature chromosom condensation assay (PCC) and 

radiation-responsive DNA mutations and gene-expression targets that can 

be analyzed with polymerase-chain-reaction (PCR) assays (a technique 

only now being explored).  AFRRI would have a handle on the latest 

developments and would probably by the best candidate to consult for 

low-dose exposure.  They are probably willing to give their new 

techniques a reality-check.  



Baseline exposure for someone might indeed be 7 - 8 rem, but one will 

also remember that many medical procedures also generate significantl 

exposures.  A CT of the head (that I order ALL the time) is 0.75 - 1 rad 

to the head.  A bone scan is usually 5 rads.  A CT of the abdomen and 

pelvis is anywhere from 2 - 5 rads ( and the radiologists usually want 

scans with and without contrast)!.  The medical radiation exposure 

history must be known as well in any biodosimetry estimation.



The simplest technique for determining a prompt radiation exposure of 15 

rads or more is with a sperm count, an easy to obtain test.  One sperm 

count should be taken ASAP after exposure and then 6 weeks after 

exposure.  If one remembers deterministic threshold literature, one 

exposed to 15 rads or more might expect oligospermia for up to 2 years 

afterwards.  If the initial sperm count is not collected, a low sperm 

count will not confirm exposure, but one cannot rule out a possible 

exposure.  It must be remembered that there is an increasing incidence 

of low sperm count within the American population (what is happening to 

us guys?) and the initial baseline sperm count is important as a good 

control.  A normal sperm count would, however, effectively rule out 

exposure to more than 15 rad up to 2 years after exposure.  It must be 

remembered that the sperm count  may be "voluntarily alterable" to some 

degree and have some uncertainty, based on, shall we say, "demand of 

usage."  Enough said.



Hope this helps.  Perhaps someone else has additional comments?



Fun Fong, MD FACEP

Former Director of Radiation Medicine 90-93, Oak Ridge Associated 

Universities 



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