Re: Occupational exposure to radon update

[Christoph_Hofmeyr/CNS1@cns.co.za]

RADSAFERS and Bill Field,  Allow me to belatedly add a rock to the tailings
pile and propose an expansion of the 12th category.  Uranium and Radium are
well distributed in the ground and not confined to particular geological
formations.    Agricultural workers who till the land, particularly when
ploughing, obviously change (enhance) the emanation conditions for Radon
from the top layer of soil by changing the general porosity as well as the
concentration gradient by bringing higher concentrations  to the surface -
until a new equilibrium has developed.   The quantification of this effect
in terms of air Radon concentration could be a very interesting field of
study in the fields of Iowa (no pun intended) - millions of acres.   A few
inches below ground the Radon concentration is at least 3 orders of
magnitude higher than in the air above, explaining why small changes in the
transport conditions for Radon gas in the top layers or disturbance of the
concentration profiles could result in significant changes in emanation.
Care would have to be exercised to separate the surface disturbance effect
from other sources of fluctuation, e.g. barometric pressure.  The exposure
impact of temporarily enhanced Radon escape would depend on the dynamics of
the process, which would have to be investigated.  It seems logical that
persons in the proximity would be mainly affected, but that there should
also be a more general elevation of open air Radon concentrations in the
case of extensive operations.   The average life of Rn-222 is 5.5 days; the
daughter equilibrium factor (~ 0.8)  is established in about 2 hours.   I
think the effect should be considered seriously and investigated, although
in lighter vein, it remains doubtful whether the weekend gardener, pulling
weeds and turning the soil,  needs to be classified as a radworker....
Personal musings.
Chris Hofmeyr. chofmeyr@cns.co.za.   CNS, PO Box 7106, Centurion 0046,
South Africa. Fax +27 12 6635513.


Bill Field wrote:


Re: Occupational exposure to radon update




RADSAFERS

The following is a list of occupations that have the potential to result in
radon exposures exceeding those concentrations commonly encountered in
homes
near the work site.  This list has been compiled to date with the help of
radsafers.  Thanks to all that have emailed me.  I enjoyed some of the
discussions that accompanied the suggestions and the personal insight some
of
the radsafers shared.  If you can think of an occupation I have not
included,
please email me at mailto:bill-field@uiowa.edu.

1.  Mining -- including hard rock, uranium, vanadium, phosphate and coal.

2. Workers remediating radioactive sites including uranium mill sites and
mill
tailings.

3.  Radon mitigation contractors and testers

4.  Guides and care keepers of natural caves

5.  Employees of radon spas or health mines

6.  Phosphate fertilizer plant workers

7.  Oil refinery workers

8.  Utility tunnel workers

9.  Power plant workers including geothermal and coal

10.  Water plant operators (waterborne source)

11. Fish hatchery attendants (waterborne source)

12.  Incidental exposure in almost any occupation from local geological
sources

I would be interested in hearing whether or not other radsafers agree that
these are indeed occupations that expose workers to higher radon
concentrations than they may find in their home near their place of
employment.  Also, please email me directly if you can think of an
occupation
not on the list.

Thanks again,

Bill Field
bill-field@uiowa.edu




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