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RADIATION STANDARDS, INCLUDING FALLOUT
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Now, the current estimates are believed to be much better. The
earlier figure includes an enormous uncertainty.
;
Representative Hosmer. I have just one other question:
Do you think that any of these figures are meaningful unless a
factor is included for average leakage, miscalibration, and other defects in medical and dental radiation equipment?
Dr. Tartor. Those factors are worked into these numbers.
Representative Hosmer. Have you any idea what they amount to?
Dr. Tayzor. No, I am sorry, I don’t offhand. Exposure due to
leakage, inadequate shielding, and so on, with modern equipment is
a smail percentage of the direct beam dose to the patient; this I am
sureof.
Representative Hosmer. I am not so certain of it from whattestimony we have hadand also from the proportion of modern equipment
in use as against older equipment that is still in use.
Dr. Taytor. Modern equipment, as I think of it, became prevalent
in this country on a wide scale in roughly 1940. Equipment prior to
that was the open-tube type. It was relatively hazardous, and is now
hardly to be found. Shielded tube equipment camein the late 1930’s,
and it is almost universal at the present time. Even that equipment
has been improved upon gradually over the past two decades.
Representative Hosmer. Here is a survey of the New York City
Office of Radiation Control, as of January 31, 1962. (See app. 2,
Pb 612.) A fluoroscope survey showed that 71 percent of the shutters
o not adequately limit the X-ray beam. Radiographic units, 69 percent did not have the X-ray beam limited to the area of clinical interest. This was particularly true in connection with chest X-rays.
X-ray machines reinspected, they reinspected 740 and they found 64
percent of those had been brought up to standard. So I think unless
your figure for these leakages and so forth, is fairly high, the total
Figure you have given us is hard to evaluate as being very meaningful.
r. Taytor. Those leakage figures would normally come into the
results. I might say that the standards against which they are making
these comparisons are extremely high. If you allowthe field to
overlap the fluorescent screen or if you use too large a field you are not
multiplying your problem by factors of 5 or 10; you are multiplying
them by 10 or 15 percent. These are not the principal sources of
radiation exposure. The principal sourcesare the direct beam.
Representative Price.
Would you proceed with your statement?
Dr. Taytor. The third category is industrial and atomic energy
sources.
Here, except for waste products, the principal recipients of exposure
are radiation workers which represent only a fraction of a percent of
the population. In spite of their being allowed technically, to receive
exposures higher than the general public, their average is extremely
low. In comparison with many other industrial hazards the atomic
enerey and radiation industry generally must be regardedasrelatively
safe.
The balancing of risk and benefit in the industrial use of radiation
is almost impossible to evaluate, but because the risk seems to be so
small the balance is probably favorable. At present the contribution
of industrial radiation to the average per capita dose is probably less
than 0.4 percent of the total (0.5 milliremsper year).
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