Re: S-35 Radioactive Contamination

[mwilliam@mailbox.uq.oz.au (Michael Williamson)]

The dose to the basal skin layer from a particular amount of S35
contamination  shouldnt be too hard to calculate: most authorities seem to
agree on a value of about 0.35 microSv/hr per Bq cm-2 to the 7 mgm cm-1
layer (Iv'e quoted these in semi-SI units as these are the ones I use: the
units in published papers are usually horrible. i.e. Sv/year etc).  . The
paper published by Richard Faw in Health Physics V63(4) p 443-448 1992 is
the most up to date reference.

For decontamination I would try applying a saturated potassium permanganate
solution, allowing it to dry and de-coloring with 10% sodium metabislphite
soln.  I know of a lab that recently had success with this method on a
similar S35 methionine skin contamination.  I am afraid I dont know whether
absorption or desquamation is responsible for the overnight decrease.  I
would suspect desquamation though, because this compound binds very tightly
to the fatty acids in the skin and would probably stay put at the
contamination site (I could be wrong, biochemists may know better).

A 24 hr urine sample is a good idea, but watch out for chemiluminescence
(CL) effects - they can produce rather alarming (and misleading) count
rates.  Samples should be repeatedly counted for a number of hours to allow
the CL effect to decay.

I would be interested to hear how the accident occurred.  The one I was
involved with happened when a lab worker tried to peel back the metal seal
on a stock solution vial by hand after failing to get it open with forceps.



Michael Williamson                              ph +61 7 365 4504
Radiation Protection Adviser                    fax +61 7 365 1577
Occupational Health and Safety Unit
University of Queensland
Brisbane 4072
Australia