AUSTRALASIAN RADIATION PROTECTION SOCIETY

"THE MYTHS OF CHERNOBYL"

PRESS RELEASE
August 4,  2000

AUSTRALASIAN RADIATION PROTECTION SOCIETY

August 4,  2000       PRESS RELEASE

THE MYTHS OF CHERNOBYL

One of the most widespread myths of recent times is that the Chernobyl nuclear reactor accident in 1986 caused many thousands of extra cancer deaths in neighbouring regions, and that public health has been severely affected by exposure to radiation.

According to the latest report of the United Nation Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) neither of these beliefs is true. UNSCEAR recently approved its UNSCEAR 2000 report and a review of its contents was presented at the International Radiation Protection Association Congress in Hiroshima in May. The report is expected to be published shortly.

Apart from the early fatalities in rescue workers who responded to the accident, the main health effect is an increased risk of non-fatal thyroid cancer in children. About 1800 cases of thyroid cancer have been diagnosed in those who were children at the time of the accident. This increased risk is linked to exposure to iodine-131, a radionuclide with a half-life of 8 days, which was a major component of the fission products released from the reactor. However, UNSCEAR reports no evidence of any other health effects attributable to radiation exposures. In particular, there has been no evidence of increases in cancer incidence or mortality. The risk of leukaemia, one of the main concerns due to its short latency period (5-10 years after radiation exposure in adults), is also not elevated in the exposed groups, including the recovery workers who received some of the highest exposures.

The accident on April 26 1986 in reactor 4 of the Chernobyl nuclear power plant caused the deaths of 30 power plant employees and firemen within a few days or weeks (including 28 deaths that were due to acute radiation exposure). Later on, during 1986-87, about 240 000 recovery workers were called on to take part in clean-up activities at the plant and within the 30-km exclusion zone established around the reactor. The remediation activities continued until 1990 and ultimately involved about 600 000 people.

In addition, about 116 000 people were evacuated from areas surrounding the reactor in 1986, because of large-scale radioactive releases of radioactive materials into the atmosphere. After 1986, about 220 000 people were relocated in what are now the three independent republics of the former Soviet Union: Belarus, the Russian Federation, and Ukraine. Wide areas of the three republics were contaminated and trace levels of released radionuclides were measurable in all countries of the Northern Hemisphere. The radiation exposures arising from the accident were due initially to iodine-131 and short-lived radionuclides, and subsequently to radiocaesiums from both external radiation and the consumption of foods.

The highest radiation doses arising from the accident were received by approximately 600 emergency workers and plant operators who were on the plant site during the night of the accident. Acute radiation sickness was experienced by 134 of these workers. The recovery operation workers, subsequently called upon to decontaminate the reactor site and roads, and to build the sarcophagus and a town for reactor personnel, received generally much lower doses. The average recorded doses decreased from about 170 millisievert (mSv) for those employed in 1986, to 130 mSv in 1987, and much lower values in subsequent years. (A lifetime dose from natural background radiation is typically 100 to 200 mSv, but is significantly greater in some parts of the world.)

Within a few weeks of the accident more than 100 000 persons were evacuated from the most contaminated areas of Ukraine and Belarus. While the thyroid doses, largely from ingestion of iodine-131, were significant, particularly in infants, doses to organs other than the thyroid were much smaller with effective doses (excluding the thyroid) of about 40 mSv in Belarus and 30 mSv in Ukraine. The thyroid cancer cases which arose were, regrettably, largely avoidable. No significant measures were taken at the time to reduce exposures by distributing stable iodine or by restricting the consumption of milk and fresh leafy vegetables in the vicinity of Chernobyl. If such countermeasures had been instituted, as in Poland, it is likely that the incidence of thyroid cancer would have been much reduced.

Many of the persons evacuated from the more contaminated areas after 1986 would, if they had remained, have received doses of not more than about 2 mSv per year, and in many cases the relocation of these people was unnecessary on radiological grounds. These relocations served mainly to heighten anxiety, and concerns and misconceptions about the dangers of radiation. Natural background radiation dose rates are normally in the range 2-10 mSv/y. The International Commission on Radiological Protection has issued new guidance on dose levels at which intervention should be considered and has proposed 10 mSv/y as a generic reference level below which intervention is not likely to be justifiable.

Apart from the radiation-associated thyroid cancers among those exposed in childhood, the only group that received doses high enough to possibly incur statistically detectable risks is the recovery operation workers. Among the emergency response workers there is a particular group of about 100 individuals who survived relatively high doses of radiation in the immediate, acute, phase of the accident and are currently experiencing health impairments as a consequence of their original injuries. Studies of this group will probably contribute to scientific knowledge on late effects of ionising radiation.

The UNSCEAR report notes that, of papers available to date regarding the estimation of health effects resulting from the Chernobyl accident, many suffer from methodological weaknesses such as inadequate diagnoses and classification of diseases, selection of inadequate control groups, or inadequate estimation of radiation doses. It concludes that, apart from the substantial increase in thyroid cancer after childhood exposure -

• there is no evidence, 14 years after the Chernobyl accident, of any other major public health impact caused by exposure to ionising radiation;
• no other increases in overall cancer incidence or mortality have been observed that could be associated with radiation exposure,
• there was no increase in the incidence of birth defects as a result of the accident.

The risk of leukaemia, one of the most sensitive indicators of radiation exposure, has not been found to be elevated even in the recovery operation workers or in children. In spite of claims of cancers, genetic effects and many other disorders, including statements by health and other officials in the countries concerned, there is no scientific proof of an increase in malignant or non-malignant disorders, somatic or mental, that is related to ionising radiation (except for thyroid cancers in children). The additional annual doses to residents in the contaminated zones are generally well within the normal range of variation of natural background radiation doses.

It must be concluded that reports of health effects caused by radiation have been greatly exaggerated. A particular example is that of the groups of children from around Chernobyl who visited other countries after the accident or who were filmed in hospitals following chemotherapy. These were widely reported to have been suffering sickness due to radiation. Many of the children appeared to be in poor health. However, with the possible exception of any thyroid cancer cases among them there is no evidence that their illnesses were caused by radioactive emissions from the damaged reactor.

NOTE FOR EDITORS

The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) was established in 1955 to advise the General Assembly of the United Nations on the sources and biological effects of ionising radiation. Its main objective is to assess radiation exposures and the possible consequences for human health. The Committees publications form the scientific basis on which international and national agencies develop appropriate radiation protection standards for workers, patients and the general public.

Dr A C McEwan
President
Australasian Radiation Protection Society