Fwd: [ RadSafe ] Questions about radon Method by Raabe and Wrenn

Fri Apr 24 03:43:55 CDT 2009

Andy

I have used extensively the method developed by Raabe and Wrenn for  estimating the concentration decay products of radon in air. The elegant method consists of  tracking the decay of the total alpha activity on filter paper samples. I have used Glass Fibre filters of  10 cm diameter togetehr with a staplex sampler. Some of my observations have been presented at the Third International Conference on Natural Radiation at Houston Texas in 1972.

It was a pleasant surprise to read the details on radon dosimetry  WLM concept etc, areas I left thinking about over the past two decades

Regards
Parthasarathy

________________________________
From: "Andycgeo at aol.com" <Andycgeo at aol.com>
To: sid at swcp.com; radsafe at radlab.nl
Sent: Friday, 24 April, 2009 0:05:07
Subject: 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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