Update on the genetic effects of ionizing radiation

Article Abstract:

Last year, a published report in the medical literature indicated that the children of fathers exposed to low levels of irradiation may have an increased likelihood of leukemia and lymphoma. The public embraced these findings, as it seems to do with all indications of insidious hazards. However, further analyses have not confirmed this apparent effect of radiation. The largest group of people exposed to large amounts of radiation live in Japan. The survivors of the atomic bomb blast at Hiroshima have provided a unique opportunity for evaluating the long-term effects of radiation exposure. It is hoped that no similar research opportunities will become available in the future. Therefore, every effort has been made to ensure that the analysis of the Hiroshima victims and their offspring is as complete as possible. A group of 31,150 people has been assembled consisting of children of Hiroshima survivors born between 1946 and 1985. These individuals were matched by sex and age to people living in other cities whose parents received no radiation exposure. The two groups have been compared for the incidence of stillbirth, death among live-born children, physical development, some specific chromosome abnormalities, and major congenital defects. Also compared were biochemical data on 30 important proteins that might have been affected by mutation. No major differences have been identified which distinguish the group whose parents were exposed to radiation from those whose parents received no exposure. These results cast serious doubt on the studies that have indicated some threat to the children of workers exposed to low levels of radiation. These studies have involved considerably fewer people exposed to considerably lower levels of radiation than the survivors of Hiroshima. There are two possibilities that may explain the apparent increase in leukemia and lymphoma among the children of workers exposed to radiation. One possibility is that the effect is due to some cause other than the radiation exposure. The other is that the results are incorrect. (Consumer Summary produced by Reliance Medical Information, Inc.)

Demographic aspects, Ionizing radiation, Radiation (Physics), DNA damage, Radioactivity, editorial

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Cellular radiation dosimetry and its implications for estimation of radiation risks: illustrative results with technetium 99m-labeled microspheres and macroaggregates

Article Abstract:

The determination of what physical measure of absorbed low-level radiation is best correlated with cellular change, including mutation or cell death, is a controversial issue. The method devised by the Medical Internal Radiation Dose (MIRD) Committee typically assumes that all cells in an irradiated organ receive the same amount of radioactivity, an assumption that may not be valid. The sensitivity of different cell types within the same region may differ considerably, and, in addition, some radioactive agents concentrate preferentially around certain cell types. Radiolabeled (radioactive) technetium 99m, commonly used in imaging studies of the liver and spleen, appears to be absorbed much more by some cells (macrophages, a type of blood cell) than would be calculated according to a model that assumes homogeneous distribution. Absorbed doses in lung cells are calculated for two agents used to perfuse (fill the blood vessels) the lung, technetium 99m-labeled microspheres (average diameter, 25 microns) and technetium 99m-labeled macroaggregates (average diameter, 40 microns). Dosages were calculated for emitted electrons and photons (two kinds of subatomic particles). The probable path and location of the particles through and in the lung were taken into account by the model. The method is explained in detail. Results showed that this approach leads to calculated dosages of approximately one-fourth the value obtained using the MIRD method for most (92 percent) of the cells in the lung; it also leads to dosages between three and 7,500 times higher for the remaining cells. Although the implications for risk that may be derived from these findings cannot be evaluated, these results should lend impetus to attempts to develop dosimetric (radiation dose calculation) methods that include the heterogeneity of human tissue in their calculations. (Consumer Summary produced by Reliance Medical Information, Inc.)

Research, Analysis, Evaluation, Measurement, Radiotherapy, Dosage and administration, Radiology, Medical, Radiology, Radiation-sensitizing agents, Radiation sensitizing agents, Radiation tolerance

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Medical perspective on nuclear power

Article Abstract:

This report, issued by the American Medical Association (AMA) Council on Scientific Affairs, addresses the issues of whether nuclear power in the US is safe, whether a substantial risk exists for a nuclear disaster due to nuclear power plant operation, and what the role of the physician should be regarding nuclear power. Nuclear power plants produce energy by inducing fission; heavy atoms are split into lighter atoms producing enormous quantities of energy. Because of the increasing demand for energy, nuclear power must be considered a vital source. However, generating nuclear energy creates potential risks from storage of nuclear fuel, radioactive waste, exposure of nuclear power plant workers to radiation, and the possible release of radioactive material into the environment by a malfunctioning reactor, as happened at Three Mile Island and Chernobyl. The long-term effects of radiation include cancer, thyroid disease, cataracts and genetic defects. Despite its risks, the Council considers nuclear power to be an important source of energy for the future and considers the generating of nuclear energy in the US to be acceptably safe. Nuclear reactors are now being designed and constructed with adequate safeguards for preventing the release of radioactive material. Workers' exposure to radiation has diminished and is now extremely low. Congress has established guidelines for the disposal of nuclear waste and is continuing to address the problems of nuclear waste disposal. However, the risk of nuclear radiation exposure exists and physicians should become familiar with the methods for treating both the physical and psychological symptoms that may follow exposure to radiation. Physicians should also contribute to the public's understanding of the benefits and risks of nuclear power.

Care and treatment, Planning, Occupational health and safety, Occupational safety and health, Energy policy, American Medical Association, Radiation injuries, American Medical Association. Council on Scientific Affairs

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