Radioactivity in the Marine Environment (1971) / Chapter Skim
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RADIATION EFFECTS
RADIATION EFFECTS
Pages 223-239
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From page 223... ...
. TABLE 5 Calculated and Measured Radiation Dose Rates from Contaminated Media to Fish Eggs under Experimental Conditions" Fish Concentration Factor Nuclide Water Concentration (pCi/liter)
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From page 224... ...
Nuclear power and desalination plants imply not only some release of radioactive materials to the sea but also release of heat and highly saline water. As the metabolism of poikilotherms is dependent on temperature, it is easy to understand the greater radiosensitivity observed following elevation of the temperature during or after radiation exposure.
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From page 225... ...
reports that exposure of young blue crabs, Callinectes sapidus, to 60Co at 3.2 rads/hr resulted in significantly more rapid growth than that of crabs irradiated at 7.3 and 29.0 rads/hr or of control crabs. Since molting is associated with growth, the percentage increase in width of molted carapaces was monitored; it was found to be related to the radiation dose rate.
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He investigated the effects of gamma radiation on the intrinsic rate of natural increase, r. The dose rates used ranged from 25 to 75 R/hr, and the cultures were exposed for about 19 hr/day.
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The estimated gamma dose to the Bikini Drosophila population was 3,000-8,000 R, but the absorbed dose is not known. The conclusion was reached that the genetic load of detrimental and lethal factors of the irradiated Drosophila populations had been increased but was returning to a normal range.
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Irish Sea Apart from the Pacific Proving Grounds, the Irish Sea coastal area adjacent to the Windscale reprocessing plant of the United Kingdom Atomic Energy Authority probably represents the most important area known with respect to the degree of contamination in the marine environment (Mauchline and Templeton, 1964)
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also studied the fecundity of a natural population of fish, Gambusia affinis affinis, that had been exposed to chronic irradiation in White Oak Creek for many generations, compared with a control population. The calculated dose rate from the bottom sediments was 10.9 rads/ day.
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Field studies on the effects of radiation indicate that our best technologies and methods cannot demonstrate effects on marine ecosystems, at prevailing dose rates, that are clearly and uniquely attributable to ionizing radiation.
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1965. Radiation doses from some types of marine biota under present-day conditions, p.
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1962. The effects of continuous gamma radiation on the intrinsic rate of natural increase ofDaphnia pulex.
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847-859. In Disposal of radioactive wastes into seas, oceans, and surface waters.
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These relationships involve how, where, what kinds, and in what amounts radioactive materials are introduced into the seas, and the ways and extent to which the seas and their resources are used by man. It is the purpose of this chapter to identify the relationships that are now recognized as important in assessing human radiation exposure, to discuss ways in which the presence of radioactive materials can be translated into estimates of radiation dose to people, to provide perspectives on the magnitude of exposure from marine sources in relation to acceptable dose limits, and to summarize the status of radioactive contamination in the seas after the first quarter century of use of atomic energy.
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Radiation exposure of man as a result of the introduction of artificial radioactive contaminants into the marine environment may occur by one or more of several pathways, and only careful evaluation can determine the most important or critical pathways in particular situations. The following pathways are the ones that normally merit consideration, however.
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ACCEPTABLE DOSE The Concept Exposure of man to ionizing radiation entails a risk of deleterious biological effects, and if man wishes to benefit from the use of atomic energy, some risk will be involved. Radiation doses must therefore be limited to a level at which the risks involved are acceptable to the individual and to society as a whole; such doses may be termed "acceptable doses." Recommendations with respect to acceptable doses are made from time to time by the International Commission on Radiological Protection (ICRP)
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For radioactive materials deposited in the body, dose rates are related to a permissible body (or organ) burden for specific radionuclides, and these in turn are related to a permissible continuous daily intake sufficient to establish and maintain that body burden.
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METHODS OF EVALUATION In order to put a particular level of radioactive contamination in the marine environment in proper perspective, estimates must be made of the radiation dose to man that may result. It is now rather standard practice to make such estimates prior to the planned introduction of radioactive materials into the sea, not only to determine whether the proposed operation is in fact feasible (safe)
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From page 239... ...
Much of the public's wariness of radioactive contamination of the environment is justified because the true risks to man have not been published in either a timely or an easily understood manner. Dose Prediction Predictions of the radiation dose that may be received by people as a result of radioactive contamination of the marine environment ordinarily begin with a comprehensive review of the uses that man makes of the sea in the region of interest and with the selection of a few postulated pathways by which internal and external exposures of greatest magnitude appear most likely to occur.
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