may later affect many benthic species by exposing 

 them to radiation. Also, any radioactivity leached 

 from the sediments back to the water again be- 

 comes available for uptake by the biota. Even be- 

 fore the radioactivity is leached from the sediment, 

 it may become available to the biota due to a 

 variation in the strength of the bonds between the 

 different radionuclides and the sediment particles. 

 Loosely bound radionuclides can be "stripped" 

 from particles of sediment and utilized by bottom- 

 feeding organisms. 



Plants and animals, to be of any significance in 

 the cycling of radionuclides in the aquatic environ- 

 ment, must accumulate the radionuclide, retain it, 

 be eaten by another organism, and be digestible. 

 However, even if an organism accumulates and 

 retains a radionuclide and is not eaten before it 

 dies, the radionuclide will enter the "biological 

 cycle" through organisms that decompose the dead 

 organic material into its elemental components. 

 Plants and animals that become radioactive in this 

 biological cycle can pose a health hazard when 

 eaten by man. 



Aquatic life may receive radiation from radio- 

 nuclides present in the water and substrate and 

 also from radionuclides that may accumulate 

 within their tissues. Humans can acquire radionu- 

 clides via many pathways, but among the most 

 important are drinking water or edible fish and 

 shellfish that have concentrated nuclides from the 

 water. In order to prevent unacceptable doses of 

 radiation from reaching humans, fish, and other 

 important organisms, the concentrations of radio- 

 nuclides in water, both fresh and marine, must be 

 restricted. 



The effects of radiation on organisms have been 

 the subject of intense investigation for many years. 

 Careful consideration of pertinent portions of the 

 vast amount of available information by such or- 

 ganizations as the International Commission on 

 Radiological Protection (ICRP), the National 

 Committee on Radiation Protection and Measure- 

 ments (NCRP), and the Federal Radiation Coun- 

 cil (FRC) has resulted in recommendations on the 

 maximum doses of radiation that people may be 

 allowed to receive under various circumstances 

 (U.S. Department of Commerce, 1963). The rec- 

 ommended levels for the general public are sub- 

 stantially more conservative than those for persons 

 who work with radiation sources or radionuclides, 

 but in both cases the recommended levels assume 

 that the exposure will be sustained essentially 

 throughout the life or period of employment of the 

 person. 



The ICRP and NCRP have calculated the quan- 

 tities of individual radionuclides that a person can 



ingest each day without accumulating levels in 

 various body organs that deliver radiation doses 

 in excess of the recommended limits. These quanti- 

 ties contained in the volume of water ingested 

 daily (2.2 liters) are referred to as "maximum per- 

 missible concentrations (MPC) in water." The 

 FRC, recognizing that people may jngest radio- 

 nuclides from foods and other sources as well as 

 from drinking water, has provided guidance on 

 the basis of transient rates of intake from all 

 sources, but only for a few nuclides (radium-226, 

 iodine-131, strontium-90, and strontium-89). 



The PHS Drinking Water Standards (US- 

 DHEW, 1962) are responsive to the recom- 

 mendations of the FRC, ICRP, and NCRP, and 

 provide appropriate protection against unaccept- 

 able radiation dose levels to people where drinking 

 water is the only significant source of exposure 

 above natural background. Where fish or other 

 fresh or marine products that have accumulated 

 radioactive materials are used as food" by humaiis, 

 the concentrations of the nuclides in the water 

 must be further restricted to provide assurance 

 that the total intake of radionuclides from all 

 sources will not exceed the recommended levels. 



The radiation dose received by fish and other 

 aquatic forms will be greater than that received by 

 people who drink the water or eat the fish. Even 

 so, this does not place the fish in risk of suffering 

 radiation damage. The radiation protection guides 

 for people have been established with prudence, 

 for continued exposure over a normal life span, 

 and with appropriate risk (safety) factors. Virtu- 

 ally all of the available evidence shows that the 

 concentrations of radionuclides in fish and shell- 

 fish that would limit their use as food are substan- 

 tially below the concentrations that would injure 

 the organisms from radiation. Therefore, at this 

 time there appears to be no need for establishing 

 separate criteria for radioactive materials in water 

 beyond those needed to limit the intake to humans. 



Recommendation: (1) No radioactive materials 

 should be present in receiving waters as a consequence 

 of the failure of an installation to exercise practical and 

 economical controls to minimize releases. This recom- 

 mendation is responsive to the recommendations of the 

 FRC that: "There can be no single permissible or ac- 

 ceptable level of exposure without regard to the reason 

 for permitting the exposure. It should be general prac- 

 tice to reduce exposure to radiation, and positive effort 

 should be carried out to fulfill the sense of these recom- 

 mendations. It is basic that exposure to radiation should 

 result from a real determination of its necessity." 



(2) No radionuclide or mixture of radionuclides 

 should be present at concentrations greater than those 

 specified in the PHS Drinking Water standards 

 (USDHEW, 1962). This recommendation assures that 

 people will receive no more than acceptable amounts 



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