Re: Cs137 in soil and cancer risk

[Jean-Michel Mure <Jean-Michel.Mure@andra.fr>]

Here's what I worked out from you activity C=0.017 pCi/g

C=0.629 Bq/kg
Dose conversion factor for a contaminated soil assuming Ba137m and Cs137 are
in secular equilibirum (which is reasonably acceptable regarding Ba137m
half-life (T=4.86E-6 y))
= 1.09 E-6 Sv/y per Bq/kg (AECL, 1989) *
or = 1.14E-6 Sv/y per Bq/kg (ORNL, 1993) 

Hence EDE=6.86E-7 Sv/y (with *)

Taking a risk per Sv of about 5E-2 letal cancer/Sv (ICRP 60), you get a risk
of 3.43E-8 cancer/y which is not far from what you found. Maybe should you
give the numbers you used.

But anyway the cancer risk is quite low at this level of soil activity
compared to an average natural dose/y of around 2.5 mSv which yields a risk
of 1.25E-4 letal cancer/y (4 orders of magnitude greater).

By the way, could you indicate me the procedure to follow to join the
riskanal mailing list.

Best regards
JM
At 09:40 07/01/1997 -0600, you wrote:
>
>The following was posted to the riskanal discussion list.  Someone
>in this forum may be better able to answer his question.
>
>Mike Baker ... baker@groves.neep.wisc.edu
>
>----------------------------------------------------------------------
>Originator: riskanal@listserv.pnl.gov
>----------------------------------------------------------------------
>
>Date: Mon, 06 Jan 1997 16:45:10 -0800
>From: DJeffrey@EMCONINC.COM (Jeffrey, David)
>Subject: Chernobyl radionuclide risk reality chec
>
>
>Here's a little quiz for you rad risk buffs out there.  I recently got my 
>hands on some
>slides used in a presentation at, I believe, the recent SETAC meeting in 
>Washington.  In flipping through the slides, which were given to attendees 
>as a handout, I found an interesting figure showing concentrations of 
>cesium-137 in soil as a function of distance and location with respect to 
>the exploded reactor site.  This figure shows surface concentrations on the 
>order of hundreds to even thousands of "kBq/m2".
>
>I was curious about just how bad/high these levels were, so I did a little 
>unit conversion math and found a PRG-like value of 0.017 pCi/g to protect 
>against external radiation from cesium-137 in soil for a target cancer risk 
>of 1E-07.
>
>The thing that bothers me about my computation is that, if my math is right, 
>and if these surface levels of cesium-137 are right, these levels of 
>cesium-137 are completely "off the chart" riskwise. Can some more 
>knowledgable rad risk person out there check my numbers.  I have assumed a 1 
>cm mixing depth, in order to be able to relate a surface concentration with 
>a 'per mass' soil concentration.
>
>Incidentally, this data is for cesium-137 measured on 1/1/95, so even though 
>the this isotope has a fairly short half-life (30 years), at these levels, 
>if they're right, that's not much consolation. And if the data and my 
>computations are correct....remind me to stay the heck away from the Ukraine 
>and Belarussia, at least for the next several hundred cesium-137 halflifes!
>
>Oh, one more thing....I DO NOT apologize in advance for any steenking 
>cross-postings, so there. We all have 'delete' buttons.
>------------------------------
>
>
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Jean-Michel MURE
ANDRA
DESS/SBSE
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