Re: radon (fwd)

[FRAMEP@ORAU.GOV]

On May 24 Diane Tkach forwarded the following:

>I have had a question from one of our physical plant employees.
>There is a building in which a "radon recovery system" was
>installed, which runs 24 hours a day.  The basis for the
>installation was "readings 1% above the acceptable levels".
>Obviously he is wondering if this is really neccessary.
>(Instant disclaimer, I haven't asked whether the 1% was
>measured before or after the system was installed, but I
>assume that the system reduces the level below the limit).
>Could anyone give me information on the precision of
>determining acceptable levels?  Is 1% really noticeable or
>did we buy into some distributor's ad campaign?  Any other
>feel for the overall risk of radon these days?  My sense is
>that smokers are at real risk, but what about children?
>dogs? (We have a lot of variety among our students.)

 Is 1% really noticeable?  No. I'm not sure what the EPA + (I
 generally make the sign of the cross at the mention
 of EPA  - just kidding guys, I don't mean it) uses now, but in the
 old days they required an accuracy of only 25% to pass their
 measurement proficiency program. Currently, the precision of
 two duplicate measurements  at or above 4pCi/l is within the
 EPA acceptable "in control" level if they are within 14% of
 each other.

 Is a "radon recovery (reduction?) system" really necessary?
 No. Is it a good idea?   I think so if the measurement of 4
 pCi/l was in an occupied area and the cost judged
 reasonable.  Mitigation is voluntary and levels below 4pCi/l
 still carry risk (if us HPs don't think levels near the DAC
 carry risk, how can we collect a paycheck and face ourselves
 in the mirror each morning?) Its no different than
 installing a shield for gamma rays.


 Overall risk? EPA +, NCRP, ICRP, BEIR IV, all put the lifetime risk
 of dying of lung cancer at 2% or so  from an
 lifetime exposure of 1 working level month (WLM) per year.
 This is roughly what you would get if you were continuously
 exposed to 4pCi/l. This 2% is for a mixed population: old
 and young, men and women, smokers and non-smokers. Most folk
 agree that the risk from radon is greater to smokers. EPA
 estimates the risk from 4pCi/l to non-smokers and smokers at
 roughly 0.2 and 3% respectively. I think BEIR IV had a
 similar ratio.

 Children? The ICRP folk assume that exposures to those under 20
 carry three times the risk of exposures to those over 20.
 This is based on the effects of gamma rays on
 the survivors of Hiroshima and Nagasaki. You don't have
 children working in uranium mines  so the effects of radon
 on them is mostly guesswork. Children can be assumed to
 receive higher doses however (NCRP 78).

 Dogs? Yes, they too are presumably at risk. Studies on dogs(mostly
 beagles) indicate damage to the lungs and life shortening.
 The dogs receiving exposures of 13,000 WLM (ouch)  had life
 expectencies of ca. 5 years compared to unexposed dogs with
 15 year expectancies.

 In humans there is no good evidence for effects from radon exposures
 under 50 WLM or so coming out of the miner studies. Why is
 it reasonable to assume a risk at low levels? : at 4pCi/l
 you will exceed 50 WLM in your lifetime; chronic exposures
 to alpha appear to do more damage than acute exposures; it
 is the prudent thing to do. After all, I don't think that
 a statistically significant risk from gamma has been identified
 below 20 rads but I'd still be upset if workers were
 routinely getting 1 rad/year.

                         Paul Frame  framep@orau.gov
                         Oak Ridge Assoc. Univ.