ATTACHMENT 4

   
                       FOR OFFICIAL USE ONLY

The Files                                    July 17, 1951

William F. Bale

MEASUREMENTS OF AIR-BORNE RADIOACTIVITY IN A COLORADO PLATEAU
URANIUM MINE

Plans to visit and take measurements at one other mine, at least,
in this area, were abandoned because of automobile trouble and a
request for Mr. Holaday to attend a meeting at Los Alamos.

Conclusions based upon data collected:  The fact that radon
degradation products were found in amounts equivalent to
equilibrium with a substantial fraction of the radon present
gives confirming evidence to the hypothesis that the hazard
associated with radon is largely from the air-borne degradation
products rather than from radon itself.

This conclusion, in turn, suggests that a realistic and useful
monitoring procedure in mines may consist of the collection and
radioactive measurement of atmospheric dust samples.  Such dust
sampling might supplement or replace radon concentration
determinations.

Before making definite recommendations on the above point, it
would seem desirable to extend measurements of the type made at
Freedom No. 2 mine to other representative radon-producing mines
of the Colorado plateau area.  In a step in this direction I
propose to return the retention apparatus to Mr. Holaday on loan
for his use after some indicated modification of the apparatus
has been completed.

As a result of preliminary survey carried out by Mr. Holaday and
his associates of the U.S.P.H.S., it seems apparent that not only
are high radon concentrations common in uranium mines in
operation today, but that radon in considerable amounts has
probably been present in Colorado plateau mines for many years,
including mines not producing uranium or radon.  Theoretical
considerations indicate that polonium concentrations in the mines
may be closely correlated with integrated radon and radon
degradation product exposure in such individuals.  It seems
worthwhile to conduct an experimental study along these lines to
find out whether in fact determinations of lifetime integrated
exposures can be made by such means.

Such miners represent the only substantial group of human
individuals with long standing lung exposure to substantial doses
of radiation.  Is such, their potential worth in settling
permissible values of lung exposure to radiation may be
comparable to that of the intentional or unintentional human
recipients of radium in setting permissible limits for the
radioactivity burden of bone.

I believe Mr. Holaday and his associates of the U.S.P.H.S. are to
be commended for their inauguration of a conservative and useful
exploration of radiation hazards among uranium miners of the
Colorado plateau.  They seem to


                       FOR OFFICIAL USE ONLY

The Files                -3-                 July 17, 1951

William F. Bale

MEASUREMENTS OF AIR-BORNE RADIOACTIVITY IN A COLORADO PLATEAU
URANIUM MINE

have conducted their work so far without unduly alarming miners
as to hidden hazards that may exist, or in any way impeding
mining operations.  They appreciate, I am sure, the assistance
given them by members of the Health and Safety Division,
"illegible," particularly in instrumentation for measuring the
integrated exposure of miners to radon under actual working
conditions.  They deserve the future assistance of competent AEC
personnel in formulating adequate safety measures for miners as
far as exposure to radiation and other toxic materials is
concerned and in gaining their acceptance as a part of routine
mining practices.

Attachment:  Table 1

WFB:MC