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 questionned
it. I have only G. Akerblom's paper and I can not verify it.
Jan Skowronek
Central Mining Institute
Plac Gwarkow 1
40-166 Katowice, Poland
e-mail: brxjs@boruta.gig.katowice.pl or brxjs@o2.pl