RE: Radon in the News -Reply

[Laurie Taylor <laurie-taylor@uiowa.edu>]

In answer to your question regarding uranium miners and smoking.....

The health effects due to radon progeny are derived mainly from studies of lung cancer in underground miners in the U.S., Canada, Sweden and Czechoslovakia.  Studies of the human health effects of radon have several limitations.  The main limitations of which concern weak estimations of exposure and the complicating role of smoking in the causation of the lung cancers observed in miners.  Only the U.S. uranium miner study contains relatively complete smoking histories.  In that study 3/4 of the miners were smokers.  Of the 383 cases of lung cancer observed in the U.S. study, 356 (93%) occurred in smokers and 25 occurred in non-smokers (the smoking histories of two cases were unknown).  Also, as far as I am aware, there are no studies of high radon areas in the U.S. which have demonstrated a statistically significant association between radon exposure and lung cancer.  It is still an unsettled question (whether the press and the EPA like to admit it or not) as to whether or not radon causes lung cancer in humans in the absence of smoking.  Another possible confounding factor raises interesting questions about the etiology of lung cancer in underground miners.  A study by Scram, et. al. (1993) reported mutagenic mycotoxins from the throat swabs of Czechoslovakian miners.  They hypothesize that the inhalation of dust contaminated with the molds of Aspergillus and Penicillium may be another risk factor responsible for the continued high cancer rate of the miner population.

Also, when Rn-222 decays, the resulting RnD rapidly diffuse and most become attached to airborne particles or surfaces.  Attached RnD deposit throughout the respiratory tract as a function of the particle size and distribution of the carrier aerosol.  Unattached RnD are assumed to be significantly more hazardous than aerosol-attached Rnd.  The type of breathing (nose and/or mouth) influences the site of deposition of unattached RnD also.  A large fraction of unattached RnD deposits in the nose with nasal breathing.  However, oral breathing causes unattached RnD to deposit on the bronchial epithelium where the lung cancer target cells seem to be located.

The fraction of RnD attached to airborne particles is highly dependent on particle concentration.  Deposition of RnD on surfaces is rapid for clean indoor air.   However, as indoor paraticle concentration increases (e.g., from cigarette smoking), the fraction of RnD attached to airborne particles increases and the concentration of airborne RnD increases (this is interesting in the light of exposure due to second-hand cigarette smoke).

Remeber that tobacco and tobacco smoke are a significant source of RnD daughter product exposure to the smoker!  I refer you to NCRP Report No. 95 (1987) concerning tobacco products.  The RnD's which seem to cause the detrimental effects are Pb-210 and Po-210.  The presence of these daughters appear to result from the deposition of airborne radon decay products on the leaves of the tobasso plant during its growth.  This report indicated that the maximum average dose-equivalent rate due to smoking 30 cigarettes per day to small areas of the bronchial epithelium at segmental bifucations of each of the approx. 50-55 millium adult smokers in the U.S. would be 800 to 1000 rad/year.  Applying a quality factor of 20 , this would yield an annual dose equivalent of about 16 rem.  This report goes on to attempt to convert this to an effective dose equivalent of 1,300 mrem per year.  

My, my!  One might wonder if the EPA or any one else engaged in radon/lung cancer studies has ever bothered to figure out just how many of the radon detectors the EPA sent out were set to homes of smokers and just how skewed radon estimates for the U.S. might really be???  Could it be possible that our current lung cancer dilema might really be due to smoking and the breathing of primary and secondary tobacco smoke?  Remeber lung cancer was not a common disease before smoking caught on as an enjoyable vice.  

These thoughts are purely those of my active imagination and do not necessarily represent those of my employer!!

At 02:21 PM 9/16/98 -0500, you wrote:
>Didn't a lot of the miners smoke also?
>
>Mark C. Hammond
>Health Physicist
>Arkansas Department of Health
>Division of Radiation Control
>and Emergency Management
>4815 West Markham, Slot #30
>Little Rock, Arkansas 72205
>(800) 482-5400 ext. 2865 or
>(501) 661-2865
>
>-----Original Message-----
>From:	Michael S Ford [SMTP:MFORD@pantex.com]
>Sent:	Wednesday, September 16, 1998 12:25 PM
>To:	Multiple recipients of list
>Subject:	Radon in the News -Reply
>
>Since I'm feeling *particularly* dense today, would someone from
>radon community please explain to me how radon has been
>singled out as the only causative agent for lung cancer deaths in U
>miners when:
>
>1.  At the time of the studies (beginning circa 1875 to 1960's), U
>miners did not (and still don't for the most part) wear respirators.
>
>2.  If they did not wear respirators, the were then exposed to U dust,
>other types of ore dust, exhaust fumes with known carcinogens and
>other sundry harmful agents.
>
>I asked this of folks in the US Mine Safety and Health
>Administration following their recent Federal Register release on
>radon exposure records and got no response whatsoever to my
>query.  Hmmmm....
>
>Thanks for getting me spun up, Andy!  ;-)
>v/r
>Michael
>*************************
>Michael S. Ford, CHP
>Texas Radiation Advisory Board
>Address:
>Radiation Safety Department
>Battelle Pantex
>Amarillo, TX
>806.477.5727 phone
>806.477.4198 fax
>mford@pantex.com
>*************************
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