Fwd: [ RadSafe ] Questions about radon

Andycgeo at aol.com Andycgeo at aol.com
Thu Apr 23 13:52:04 CDT 2009 

  
____________________________________
 From: Andycgeo at aol.com
To: sid at swcp.com, radsafe at radlab.nl
Sent: 4/23/2009  2:44:40 P.M. Eastern Daylight Time
Subj: Fwd: [ RadSafe ] Questions about  radon



Dr. Raabe's explanation of the Radon and Radon Decay  Product radiation 
dose 
to the lung is the best so far.
After all, Otto  Raabe is one of the first radon rangers that dealt  with 
the issue  back in the mid 1960's at the university of  Rochester.  
Everyone  
dealing with Radon issues should download his  clear explanation on  the 
WLM 
and radiation dose to the respiratory tract.

Andy George,  
a contemporary Radon Ranger of Otto Raabe. 


____________________________________
From: ograabe at ucdavis.edu
To:  sjd at swcp.com, radsafe at radlab.nl
Sent:  4/23/2009 1:38:50 P.M. Eastern  Daylight Time
Subj: Re: [ RadSafe ]  Questions about  radon


At 05:34 PM 4/22/2009, Steven Dapra wrote:
>Is   anything true in this quote?
>
>           "The "action level" recommended by the Environmental 
> Protection   Agency for radon in the air is 4 picocuries/liter of 
> air. It is   difficult to convert air concentrations to actual 
> exposures in  rems  or sieverts, but estimates are in the range of 4 
> to 14 rem  per year  at that concentration. That makes it greater 
> that all  the other  routine environmental exposures   combined."
***************************************
April 23,   2009

Airborne radon-222 gas with its decay products, which are   
constituents of the uranium-238 decay series, is the most  significant  
source of natural background radiation exposure yielding  an annual  
dose by inhalation of about 2.4 rem to the target  bronchial 
epithelium  of the average American (BEIR V, 1990). Since  the tissue 
weighting factor  for the bronchial epithelium is 0.08  (the whole lung 
is 0.12) this  translates to an effective dose of  about 200 mrem per 
year. This is about  2/3 of the annual dose from  naturally occurring 
ionizing radiation  sources. "That makes it  greater that all the other 
routine environmental  exposures  combined."

Following inhalation of radon and its decay  products  most of the 
absorbed ionizing radiation dose is deposited in the   tracheobronchial 
region of the lungs by radon's short-lived   alpha-radiation emitting 
daughters, that are solid metals rather  than  gases. Less than about 
5% of the absorbed dose to the target  tissue is  from radon gas. The 
dose delivered depends on the  so-called working level  (WL) of 
daughter rather than on the radon  concentration and the exposure  is 
commonly described in working  level months (WLM).The daughters  
deposit in the lung airways during  inhalation attached to naturally  
present airborne particles or as  small molecular clusters (so-called  
unattached daughters). The  amount of dose delivered by the decay  
products depend on the  so-called unattached fraction and the size  
distribution of the  airborne dust particles. Hence, the dose 
delivered  for a given  concentration of radon gas varies widely 
depending on the  local  airborne particle and daughter equilibrium 
situations. They ar   different in homes from that in uranium mines.

The WL unit is  defined  as any combination of the short-lived radon 
progeny in one  liter of air  that will result in the emission of 
130,000 MeV of  alpha particle energy.  Air having a radon-222 
concentration of 3.7  kBq/m3 (100 pCi/liter) with  the progeny in 
secular equilibrium would  represent 1 WL. The exposure  associated 
with a typical work month in  a uranium mine 170 h at 1 WL is  called 
an exposure of 1 working  level month, WLM. Dosimetric models  indicate 
that the nominal dose  to the bronchial epithelium associated with  
inhalation of radon  decay product aerosols by a uranium miner is 
about  6 mGy/WLM.  Assuming an alpha radiation quality factor of 20, 
this yields  an  absorbed dose of about 120 mSv/WLM or 12 rem/WLM. With 
a cancer   weighting factor of 0.08 for the bronchial epithelium, the 
effective  dose  for cancer induction is about 10 mSv/WLM or 1 rem/WLM.

At 4  pCi/liter  radon per liter in home room air, 12 hours per day  
residence in the home  for one year and assuming a uranium mine  
atmosphere (which room air is  not), the calculated annual exposure  
would be 12 hours time 365 days per  year = 4380 hours or 4380/170 =  
26 working months at 4/100 WL =  1  WLM. This suggests an  epithelial 
tissue absorbed of 12 rem. The  statement:  ["The  action level 
recommended by the Environmental  Protection Agency for  radon in the 
air is 4 picocuries/liter of air. It is  difficult to  convert air 
concentrations to actual exposures in rems or  sieverts,  but estimates 
are in the range of 4 to 14 rem per year at that   concentration."] is 
reasonable given the occupancy, aerosol,  daughter  equilibrium 
uncertainties. Of course, the effective dose  for lung cancer  is 8% of 
these values, or in the range from about  0.3 to 1 rem.

In  contrast, he annual average absorbed dose to the  lungs' bronchial  
epithelium from Po-210 for a typical cigarette  smoker is estimated to  
be about 16 rem, about 7 times the U.S.  annual average dose of 2.4 
rem  from natural radon-220 and its decay  products (NCRP-95,   1987d).



**********************************************
Prof.   Otto G. Raabe, Ph.D., CHP
Center for Health & the   Environment
University of California
One Shields Avenue
Davis,  CA  95616
E-Mail: ograabe at ucdavis.edu
Phone: (530)  752-7754   FAX:  (530)  758-6140
***********************************************    
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