A-bomb survivors at Hiroshima and Nagasaki

PTI FEATURE
VOL NO XXIV (32)-2008 August 09, 2008
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INTERNATIONAL
PF-125/2008
A-bomb survivors at Hiroshima and Nagasaki
By Dr.K.S.Parthasarathy

As on March 31, 2007, 2,51,834 persons with an average age of 74.6 years, have received official “hibakusha” (known as A-bomb victims) health cards as atomic bomb survivors, but only 2200 of them have been certified as suffering from radiation-related diseases.
On 6th August 1945, exactly 63 years ago, an atom bomb destroyed Hiroshima. Three days later, Nagasaki faced a similar fate.
These cities then had an estimated population of 310,000 and 250,000 respectively. About 90,000- 140,000 in Hiroshima and 60,000- 80,000 people in Nagasaki died immediately or within two to four months after bombing, resulting from collapse of houses caused by the blast and from heat rays and fires and radiation exposure
As on March 31, 2007, 2,51,834 persons with an average age of 74.6 years, have received official “hibakusha” (known as A-bomb victims) health cards as atomic bomb survivors, but only 2200 of them have been certified as suffering from radiation-related diseases (The Asahi Shimbun, June 26, 2008). On June 24, a Nagasaki court ruled that 20 survivors deserve recognition as sufferers of radiation-caused illnesses, including those who do not meet the government’s new certification standards.
The sufferers to be certified according to the court were those with chronic hepatitis, cirrohosis of the liver, articular ailments and disorders resulting from embedded pieces of glass and other foreign objects; these people are entitled to receive 137,000 yen monthly in special medical benefits.
The Japanese Central government lost several cases, the latest was the 9th loss in the series. Government’s new standards issued this April, will certify people who were exposed to radiation within 3.5 km of ground zero and consequently developed any one of the designated diseases(cancer, leukemia, irradiation cataracts, hyperparathyroidism and radiation induced heart infarction) .
On July 19, this year, the Osaka District Court recognized four people as suffering from radiation illnesses caused by atomic bombings (The Yomiuri Shimbun, April 19, 2008). There were 11 claimants.
Several suits for recognition as atomic bomb sufferers are being pursued in different courts. The process is painfully slow.
Over an estimated 5000 atomic survivors living abroad did not receive any relief so far, though two court rulings in (Osaka and Nagasaki respectively) offered some hopes for them.
What is the current status of radiation health studies of A-bomb survivors in Japan?
Many believe in the myth that birth defects are more common among the children of the survivors of the atomic bombings at Hiroshima and Nagasaki. Physicians appointed by Atomic Bomb Casualty Commission (ABCC) did not see statistically demonstrable increase in major birth defects in 76,626 infants conceived and born in Hiroshima and Nagasaki over a period of six years starting from the late spring of 1948.
Pregnant women had special provisions for certain dietary staples. Because of this, the surveyors of new-borns could identify 90 per cent of the pregnancies that persisted for at least 20 weeks of gestation.
Physical examination of the new born and autopsies on as many stillborn infants revealed that neither the frequency of major birth defects nor the frequency of the most common birth defects differ significantly with radiation exposure of parents. The researchers examined some 21,788 infants shortly after birth and re-examined them eight to ten months later. The study covered 65,431 registered pregnancy terminations and appropriate control populations.
"The absence of a statistically significant effect of ionizing radiation on the frequency of major birth defects should not be construed as evidence that mutations were not induced by parental exposure to atomic radiation", Radiation Effects Research Foundation (RERF), the successor of ABCC cautioned.
The researchers saw mutations in every animal and plant species studied. The magnitude of a difference between two or more groups that can be detected statistically depends upon the number of observations made and on the natural frequency of the event under scrutiny as well as the difference between the groups resulting from exposure. The RERF study had the statistical power to detect a doubling of the rate of major congenital malformations, if such defects had occurred.
Long term study of the survivors of the atom bombing of Hiroshima and Nagasaki showed that high radiation exposures caused excess cancer in the exposed individuals. In 2007, scientists estimated that about 850 out of 17,448 solid cancers recorded during 1958 through 1998 may be due to radiation exposure. Radiation is thus shown to be a weak carcinogen.
Studies on 1600 children who were irradiated while they were in their mother's womb during the atomic bomb explosions in the two cities revealed that 30 of them suffered clinically severe mental retardation. Between 0 and 7 weeks post conception mental development was not affected. Between 8 and 15 weeks the sensitivity for mental retardation was maximum.
This is possibly because neuronal proliferation and cell migration in the cortex is most active during this period. From 15 weeks to 25 weeks the incidence of mental retardation was clearly lower. Generally mental retardation depended on radiation dose. There was no detectable threshold dose below which the effect was zero. But a threshold of 100 milligray cannot be ruled out. (milligray is a unit of radiation dose; the skin dose in some medical x-ray examinations can be as high as 1 milligray).
RERF studies suggest that there may be a small radiation associated increase in the risk of death for diseases such as myocardial infarction, chronic liver disease, thyroid diseases and uterine myoma among A-bomb survivors. There is some evidence that radiation caused an increase in cancer deaths among survivors who got exposed in their mothers' wombs. The number of such deaths is still small.
International organisations use the RERF data derived from the study of A- bomb survivors to establish radiation protection guidelines for radiation workers and the general populations. Whether low level radiation exposure will cause harmful effects in humans has not been demonstrated conclusively. Irrefutable evidence on the harmful effects, if any, due to low levels of radiation exposure is unlikely to emerge in the near future. Evidently, it is prudent to reduce all radiation exposures to, as low a value as is reasonably achievable.

---PTI FEATURE

Cataract and A-bomb survivors

Friday, August 8, 2008, Chandigarh, India

K.S. Parthasarathy

On August 6, 1945, exactly 63 years ago, an atom bomb destroyed Hiroshima. Three days later, Nagasaki faced similar devastation. The Radiation Effects Research Foundation (RERF) at Hiroshima carries out several studies on the health status of A-bomb survivors. One such study is the effect of ionising radiation on the eye lens of the survivors.




The 63rd anniversary of the atomic bombing at Hiroshima was on August 6; that of Nagasaki is on August 9



Until now, the radiation protection specialists assumed that only high doses of radiation of two Gy cause cataracts, but new data from the A-bomb survivors suggest that the dose threshold for both minor opacities and vision limiting cataracts may be below one Gy (RERF Update Vol 19, Issue 1 2008). Gray (Gy) is a unit of radiation dose; it is equal to an energy absorption of one Joule per kilogramme.

“That important finding is causing major risk assessment groups to consider re-evaluating their guidelines for permissible occupational and medical exposures to the eye”, RERF scientists claimed.

Lens of the eye is like lens of a camera. Radiation causes partial opacity (cloudiness) of the eye lens. Symptoms of cataract usually appear after a latency period of several months (two to three years on average) following radiation exposure. Senile cataract which is common in old age advances with age; radiation cataract seldom does. Radiation cataract infrequently causes visual impairment.

Radiation cataract possibly has a “threshold”, a certain dose value below which no effect is observed.

How does radiation cataract develop? There is a transparent layer of epithelial cells on the interior frontal side of the capsule that covers the lens. This layer maintains the function of the lens by slowly growing toward the centre, achieved through cell division at the periphery (called the equator) of the lens (RERF Update, 2008). Because radiation is especially harmful to dividing cells, exposed cells at the equator are most prone to damage. The damaged cells move toward the rear of the lens before converging on the centre. Such cells prevent light from travelling straight forward, causing opacity.

Study of radiation-induced cataracts in A-bomb survivors started at the Atomic Bomb Casualty Commission (ABCC), the predecessor of the Radiation Effects Research Foundation. During 1963-64, scientists found a statistically significant radiation dose response for certain type of cataracts. Later study in 1978-80 gave similar results. Some analyses gave conflicting results.

Neriishi and coworkers concluded that there is radiation dose response for cataracts indicating a threshold below one Gy ( RERF Update, 2008).

The authors found similar evidence in other studies. A study of children exposed during the accident at the Chernobyl nuclear power station reported a subsequent excess of cataracts. A Swedish followup study of infants treated with radium indicated excess cataracts at a dose of one Gy to the eye. A NASA study of the health of 295 astronauts predicted that relatively low doses of space radiation might predispose the crew to an increased incidence and early appearance of cataracts (RERF update, 19, 1, 2008). A recent study of Chernobyl clean-up workers reported similar results.

RERF scientists thus quoted the International Commission on Radiological Protection: (ICRP,2007): “…the lens of the eye may be more radiosensitive than previously considered. In particular, among the atomic bomb survivors,…. and a group of children treated for skin hemangiomas….., there is evidence of excesses of ….. cataract at doses somewhat lower than expected. Whether ICRP may now lower the dose limits to the eye for radiation workers and members of the public or not is not clear.

The RERF researchers found out that stored lens images of A-bomb survivors have great potential in cataract research, for re-evaluation and followup of the cases and for standardisation of analyses in training new researchers.

RERF is starting a project to collect and store lens tissues removed from A-bomb survivors for future use. Such tissues may provide information on molecular biological changes in the formation of cataracts.

Cataract studies on children of A-bomb survivors conducted during 2002-2006 are being analysed to verify whether there are trans-generational effects of radiation on the eye lens. RERF started a glaucoma prevalence study in 2006; it will conclude by September 2008; the results may be published later.

Dr K.S.Parthasarathy is former Secretary, Atomic Energy Regulatory Board