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Counting
Chernobyl's Cancer Cost
LISBON, Portugal, October 23, 2001 (ENS) - Chernobyl has
made medical history, accounting for the largest group of human cancers
associated with a known cause on a known date, ECCO 11, the European Cancer
Conference heard in Lisbon today.
Nearly 2,000 cases of thyroid cancer have
been linked to the world's worst nuclear accident which occurred in Ukraine on
April 26, 1986, and the number is still rising, according to some of the
world's most prestigious cancer researchers.
Professor Dillwyn Williams, of The
Strangeways Research Laboratory, Cambridge University, told the meeting,
"Four years after the accident, an excess of thyroid cancers was noted
among children who had been exposed to fall-out from the disaster. That
increase has continued and new cases are still being seen in those who were
children at the time of the accident."
One of the thousands of rescue workers who helped in the immediate
aftermath of the accident. (Photos
courtesy Chernobyl Charity Online)
Dr. Elaine Ron, of the U.S. National
Cancer Institute, in Bethesda, Maryland, explained, "Following external
radiation exposure, the elevated risk of thyroid cancer appears to continue
throughout life, but there is some indication that the risk may be highest 15
to 19 years after exposure."
External radiation is the only well
established cause of cancer of the thyroid gland. People under 20 are at a
increased risk of thyroid cancer after exposure to isotopes of iodine.
Professor Williams said, "Exposure to
isotopes of iodine gives the thyroid over a 1,000 times the average dose to the
rest of the body. The particular sensitivity of children to thyoid cancer after
radiation exposure can be linked to a combination of a higher thyroid dose and
the biology of thyroid growth which falls to a very low level in adult life.
Few of the patients with thyroid cancer have died, but help is still
needed."
The United Nations marked the 15th
anniversary of the disaster with an appeal for aid for the victims of
radiation. According to one report, five million people in the former Soviet
Union were exposed to radiation or other health hazards by the Chernobyl
catastrophe.
On April 25, 1986, the reactor crew at
Chernobyl-4 disabled automatic shutdown mechanisms before an attempted test of
the unit the next day. The test was intended to determine how long turbines
would spin and supply power following a loss of main electrical power supply.
Chernobyl's 4th reactor after the explosion and fire.
During the test, as flow of coolant water
to the reactor was reduced, power output increased. When the operator moved to
shut down the reactor from an unstable condition arising from previous errors,
a power surge took place.
The nuclear fuel elements ruptured, and
the resulting explosive force of steam lifted off the cover plate of the
reactor, releasing radioactivity into the atmosphere. A second explosion threw
out fragments of burning fuel and graphite from the reactpr core and allowed
air to rush in, causing the graphite moderator to burst into flames.
The graphite burned for nine days, causing
the main release of radioactivity into the environment.
Although only 31 people died in the
immediate aftermath of the accident, hundreds of thousands were reported to
have abandoned entire cities and settlements within the 30 kilometre (20 mile)
zone of extreme contamination.
Dr. Williams said, "The effects of
Chernobyl differed very greatly from those after the atomic bomb explosions. In
Japan, the exposure was very largely to whole body radiation from gamma rays
and neutrons. After Chernobyl the exposure was to isotopes in fall-out, and
apart from the inert gas xenon, the largest components were radioactive
isotopes of iodine."
Post Chernobyl cancer risks are not
restricted to the thyroid gland, the meeting was told. Victor Chizhikov, of the
Cancer Research Center, Kashirskoye, Moscow, reported that a study of former 43
Chernobyl clean-up workers had shown them to be at a significantly increased
risk of lung cancer. All of the 36 smokers and seven non-smokers in the study
group had evidence of inhaled radioactive dust in their lungs. They were
compared to a control group of 21 smokers and 23 non-smokers who had never been
exposed to radiation.
ECCO, the European Cancer Conference, is
one of the world's major multidisciplinary cancer conferences, providing a
platform for interaction and exchange between experimental and clinical
oncologists and cancer nurses.
The conference is organized every two
years by the Federation of European Cancer Societies for and on behalf of its
six member societies.
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