[ RadSafe ] Research shows CT and nuclear imaging tests during pregnancy do not boost the risk of childhood cancer
Otto G. Raabe
ograabe at ucdavis.edu
Mon Oct 4 17:05:39 CDT 2010
At 12:51 PM 10/2/2010, Scott, Bobby wrote:
>Research shows CT and nuclear imaging tests during pregnancy do not
>boost the risk of childhood cancer
>
>http://www.ices.on.ca/webpage.cfm?site_id=1&org_id=117&morg_id=0&gsec_id
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As you surely already know, beginning in 1956 Alice Stewart and her
followers have demonstrated a strong statistical association between
pre-natal X-rays and childhood cancer in the Oxford Survey of
Childhood Cancer OSCC . These data and positions received
considerable prestige with the review of the data by Doll and
Wakeford (The British Journal of Radiology, Vol 70, Issue 830 130-139,1997)
Risk of childhood cancer from fetal irradiation
R Doll and R Wakeford
Imperial Cancer Research Fund Cancer Studies Unit, Radcliffe
Infirmary, Oxford, UK.
The association between the low dose of ionizing radiation received
by the fetus in utero from diagnostic radiography, particularly in
the last trimester of pregnancy, and the subsequent risk of cancer in
childhood provides direct evidence against the existence of a
threshold dose below which no excess risk arises, and has led to
changes in medical practice. Initially reported in 1956, a consistent
association has been found in many case-control studies in different
countries. The excess relative risk obtained from combining the
results of these studies has high statistical significance and
suggests that, in the past, a radiographic examination of the abdomen
of a pregnant woman produced a proportional increase in risk of about
40%. A corresponding causal relationship is not universally accepted
and this interpretation has been challenged on four grounds. On
review, the evidence against bias and confounding as alternative
explanations for the association is strong. Scrutiny of the
objections to causality suggests that they are not, or may not be,
valid. A causal explanation is supported by evidence indicating an
appropriate dose-response relationship and by animal experiments. It
is concluded that radiation doses of the order of 10 mGy received by
the fetus in utero produce a consequent increase in the risk of
childhood cancer. The excess absolute risk coefficient at this level
of exposure is approximately 6% per gray, although the exact value of
this risk coefficient remains uncertain.
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Prof. Otto G. Raabe, Ph.D., CHP
Center for Health & the Environment
University of California
One Shields Avenue
Davis, CA 95616
E-Mail: ograabe at ucdavis.edu
Phone: (530) 752-7754 FAX: (530) 758-6140
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