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RE: Medical radiation workers see reduction in cancer risk
Isn't 1 Gy equal to 100 rads. 30 Gy would be ... Deadly!
--
Sent from my PalmOne Treo
-----Original Message-----
From: Stabin, Michael
Date: 9/22/04 8:18 am
To: John Jacobus, radsafe, know_nukes@yahoogroups.com
Subj: RE: Medical radiation workers see reduction in cancer risk
I have to agree that a level of 30 Gy per year should not be recommended
for radiation workers.
Mike
Michael G. Stabin, PhD, CHP
Assistant Professor of Radiology and Radiological Sciences
Department of Radiology and Radiological Sciences
Vanderbilt University
1161 21st Avenue South
Nashville, TN 37232-2675
Phone (615) 343-0068
Fax (615) 322-3764
Pager (615) 835-5153
e-mail michael.g.stabin@vanderbilt.edu
internet www.doseinfo-radar.com
-----Original Message-----
From: owner-radsafe@list.vanderbilt.edu
[mailto:owner-radsafe@list.vanderbilt.edu] On Behalf Of John Jacobus
Sent: Wednesday, September 22, 2004 7:35 AM
To: radsafe; know_nukes@yahoogroups.com
Subject: Medical radiation workers see reduction in cancer risk
I saw this through another list server and thought it
would be of interest.
-----------------------
Medical radiation workers see reduction in cancer risk
9/21/04
By: Shalmali Pal
Thanks to stringent radiation protection policies, the
cancer risk for modern imaging professionals has been significantly
reduced. Unfortunately, the same cannot be said for their predecessors,
who showed markedly higher rates of disease, according to a
meta-analysis in the journal Radiology. Shinji Yoshinaga, Ph.D., and
colleagues from Japan and the U.S. reviewed previously published
epidemiologic data on cancer risks in more than 270,000 international
radiologists and technologists.
While close attention should be paid to the risk posed
to patients from localized, high radiation doses, the detrimental
effects of worker exposure to low doses over the whole body should not
be neglected, said Yoshinaga, who is from the National Cancer Institute
(NCI) in Bethesda, MD, and the National Institute for Radiological
Sciences in Chiba, Japan. Yoshinaga's co-authors are also from the NCI.
The authors compiled data from eight studies conducted
in the U.S., the U.K., Denmark, China, Japan, and
Canada between 1920 and 1998.
"These cohorts represent a valuable source of
information obtained from a large number of people who
worked over several decades during which modern
radiology and radiologic protection evolved," they
wrote (Radiology, September 16, 2004).
The authors parsed the earlier studies for the
standardized mortality ratio (SMR), or the ratio of
the number of deaths, and the standardized incidence
ratio (SIR), which is the ratio of the number of
incident cases. The specific disease processes they
examined included leukemia, melanoma, and breast
cancer.
Their two main findings were as follows: Increased
mortality due to leukemia was found among radiology professionals who
worked before 1950, when recommended radiation doses started at a high
of 30 Gy per year, before dropping to 0.3 Sv per year, and then down to
0.1 Sv per year.
The SMR/SIR was 1.75-2.29 for leukemia found in U.S. radiologists,
Japanese technologists, and male Chinese x-ray workers. From 1920-1939,
the SMR was 1.38 for all cancers in U.S. radiologists versus other
physician specialties.
For women workers employed between 1940 and 1949, the
relative risk for breast cancer was elevated (2.17),
especially if they'd been exposed to radiation for one
to four years. The authors noted a particular trend
among pre-1950 Canadian radiation workers: Melanoma
was limited to dental workers, who may have held
bitewing film in patients' mouths during x-ray,
resulting in high exposure to their hands.
Second, lower exposure levels were recorded after
1957, when the International Commission on
Radiological Protection (ICRP) reduced the suggested
dose limit to 0.05 Sv per year. In 1990, the
commission revamped that policy to an occupational
dose limit of an average of 0.02 Sv per year, over
five years, and not to exceed an annual dose of 0.05
Sv in a single year.
After 1950, the SMR for all types of cancer was less
than 1. In addition to better dose parameters, a trend
known as the "healthy-worker effect" may have
contributed to the reduction as these professionals
tend to lead healthier lifestyles and have better
access to medical care, the authors stated.
"We found no clear evidence of cancer risk in any of
the latest subcohorts of radiologists or
technologists," the group concluded. "While safe
radiation practices currently are an assumed part of
medical radiation work ... it is important to continue follow-up."
Future research should include data on individual
doses to radiation workers, which would allow for a
direct comparison of risk between high-dose and
low-dose settings. In addition, the authors cautioned
that workers from 1960-1982 have yet to enter the time
period when background cancer risk is increased.
Radiation protection practices will require updates
based on exposure levels of new radiologic procedures.
By Shalmali Pal
AuntMinnie.com staff writer
September 21, 2004
=====
+++++++++++++++++++
"A devotee of Truth may not do anything in deference to convention. He
must always hold himself open to correction, and whenever he discovers
himself to be wrong he must confess it at all costs and atone for it."
Monhandas K. Gandhi, in "Autobiography"
-- John
John Jacobus, MS
Certified Health Physicist
e-mail: crispy_bird@yahoo.com
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