- 68 - SUMMARY The atomic era has added new radioisotopes to our environment. For the radioisotopes in the sea, the effect upon man as a health hazard is potentially greater than the effect upon the fish and shellfish that take up the radioisotopes. Radioisotopes emit lonizing radiations that are biologically destructive. The primary site of damage is the cell, but the exact manner in which the cell is affected is not known. The relationship of radiation dose to biological effect is well known for large doses but not for small doese of the size that now occur in the ocean. whic A maximum permissible dose -- a dose for ere or genetic injury -- has been established and is used to calculate the maximum permissible concentration of radio- isotopes in air and water (food). Because the range in MPC values for various radioisotopes may be as great as one million, an evaluation of the hazard requires that the radioisotopes in the sample be known as well as the amount of radioactivity.