Re: radon limits

["Otto G. Raabe" <ograabe@UCDAVIS.EDU>]

> At 10:59 AM 10/29/02 +0100, Jan Skowronek wrote: 
>
> I have a G. Akerblom's report to SSI "Radon Legislation and National Guidelines" (SSI Reprt 99:18, Juli 1999, ISSN 0282-4434) where he wrote (page 4): 
>
> "... In 1941, the US Advisory Committee on X-Ray and Radium Protecction set 10-8 microCi/cm3 (370 Bq/m3 EER) as the value of maximum permissible concentration (MPC) for ocupational exposure (40 hr/week) to 222Rn, including its daughter products (National Bureau of Standards, 1941: Safe Handling of Radioactive Luminous Compounds. Handbook H27. Superintendent of Documents, Washington, D.C.)." 
This value is lower than the MPC introduced by ICRP in 1953 (3700 Bq/m3). I wrote these informations in my paper but  the revisors questioned it. I have only G. Akerblom's paper and I can not verify it.
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October 30, 2002
Davis, CA

I have obtained a copy of NBS Handbook H27 and read it through. I must disagree with Akerblom's report on one point: no mention or consideration is given radon daughter products in this report. There are two references to the maximum recommended air concentration of radon gas, both in the context of ventilation in a work room where radium is being handled such as for luminous dial painting. The key citation is on page 9. "IIIe. VENTILATION.- General forced ventilation shall be provided for all workrooms and dark rooms so that the radon content of the air does not exceed 10**(-11) curie per liter in any place at any time." [370 Bq/m3]

Under such ventilation conditions there is little opportunity for radon daughter in-growth so that the probable state of equilibrium may be far from unity. In any case, the writers of H27 do not mention decay products. I believe that the importance of the decay products did not become apparent until many years after 1941. NBS Handbook H27 seems to address radon as if the decay products were unimportant, but the recommended level is much lower than the l WL standard of the 1950's. This report also considers radium intake and gamma ray exposures. Gamma exposures of 0.1 Roentgen per day were allowed (page 14, paragraph IVd.). It may be that the lower radon level was given as compensation for the other radiation exposures that were assumed to occur when working with radium. The 0.1 R per day could mean 0.5 R per week or about 0.2 Sv/year.

If you have a FAX number, I can FAX you the whole report. It is really quite short.

Otto




**********************************************
Prof. Otto G. Raabe, Ph.D., CHP
Center for Health & the Environment
(Street Address: Bldg. 3792, Old Davis Road) 
University of California, Davis, CA 95616
E-Mail: ograabe@ucdavis.edu
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