Re: Radon and Respiratory protection

[GELSG@AOL.COM]

This has been a problem for me for over 15 years.  I believe Mr. Beckel has 

touched on a valid point, one I discussed by email with Dr. Cohen a number of 

years ago.



I do not disagree with the points that Dr. Cohen has made about reducing dust 

particulates causing an increase in the unattached fraction of radon 

daughters.  I think it is also important to restate the fact that filtration will have 

no effect on the radon concentration.  But the largest contributer to lung 

dose is from the daughter products attached to particulates which deposit in the 

lungs and decay prior to biological removal.  Po-218 and Po-214 in 

particular.



So far, I hope we are all in agreement.  I believe that, in the real world, a 

HEPA filter will do a LOT of good in reducing the actual dose to people.  I'm 

talking about a place like my home where there are doors opening and closing, 

windows that leak, people cooking, and grandchildren chasing the cat.  The 

studies on unattached fraction were done in a laboratory where scientists could 

control things like humidity and particulate concentrations.  That was a 

necessity since particulate concentration was a key parameter for measurement.  In 

that controlled, lab atmosphere, it is easy to see how one could reach the 

conclusion that "reducing particle concentration necessarily caused an increase 

in unattached fraction" of radon daughters.



As long as there is no significant depletion in the number of particles in 

the home due to the operation of a HEPA filtration unit, I think there would be 

a large reduction in lung dose from radon (attached) daughters with very 

little increase in the unattached fraction.  In other words, you would need a 

particle source to replenish those carrying radon daughters that are trapped on the 

HEPA filter.  If you don't have grandchildren chasing your cat, light a 

couple of candles or run a humidifier in the winter and open a window in the 

summer.  Frankly, I wonder whether any home would have a significant increase in 

unattached fraction similar to that found in a laboratory experimental chamber.



I think Dade Moeller suggested a similar radon dose reduction strategy quite 

a few years ago, and the only argument I recall against such a strategy was 

the fear of increasing the unattached fraction of radon daughters.  I don't 

think that is a serious concern in the average home.  Are any of you aware of any 

studies of unattached fraction in places other than an experimental chamber?



G. L. Gels



In a message dated 9/3/03 12:26:22 PM Eastern Daylight Time, blc+@PITT.EDU 

writes:





> On Wed, 3 Sep 2003, Jay Beckel wrote:

> 

> > Do HEPA cartridges provide ANY protection at all in a radon atmosphere?  

> Are

> > there any studies out there that would back up any theories of radon

> > attachment to particles and therefore being caught up in the HEPA?

> 

>     --This is a complicated question. The danger from radon comes from

> radon progeny which normally attach to fine dust particles. Thus, removing

> dust from the air inhaled reduces inhalation of these, reducing the

> "working level". But removing the dust from the air causes an increased

> fraction of the progeny to remain unattached to dust particles, and

> unattached radon progeny are more likely to attach to the bronchial

> surfaces which makes them more dangerous. These two effects approximately

> compensate, so little is gained by filtering dust out of the room air.

> Filtering dust out of air as it is inhaled would be quite useful in

> reducing exposure, but this is not convenient in most cases.

>     There is no need for HEPA filters, which are to remove over 99% of

> the dust. Removing 80% or 90% would do nearly as much good.

>