2. Regardless of cost, the entire population must not receive more than 1 rem per person over 30 years When this kind of material is discharged into the sea, one must be sure that the isotopes do not become trapped or concentrated in the sea bed. Unlike the other isotopes in the discharge, it has been found that plutonium – 239 does in fact become bound in sediment.
Most of the isotope becomes bound near the point of discharge as shown in as a result of this finding, it may be necessary to reduce the amount of radioactive plutonium in the discharge. It is possible to monitor the amount of radioactive isotopes in the sea by making use of biological monitoring organisms which live attached to the sea bed for long periods in the same area. In Finland, the authorities are studying mussels (Mytilus) in order to obtain an early warning of any environmental danger from their nuclear power programme. It is worth noting whether or not the background radiation (in the sea) is significantly affected by nuclear waste discharge. The normal level is about 350 m rads per year.
In the Irish sea near the Wind’ scale reprocessing plant, the background is about 600 m rads per day. This sea area is one of the few places where records of fish landings are available and where the water has higher than normal levels of radioactivity. So far no effects of the radiation have been found. The sensitivity of animals towards radiation varies inversely but the dose required to cause mortality is above 100 rads (1 Gy). Below this level, genetic changes can be expected. These have been detected at doses around 10 rads.
Note, however, that this is far above the levels produced by pollution so far. There is very little reliable evidence to allow definite predictions to be made regarding the possibility that man-made radiation could affect the mutation rate to any significant extent. However, there are good reasons for saying that the environmental background should be kept as low as possible. Mutations are occurring all the times at a natural rate which is partly due to radiation and partly due to other factors such as chance and chemical processes which are unrelated to radiation. If we do anything to increase the mutation rate, it is probable that we shall increase the number of undesirable mutations faster than those which are desirable.
In general, if organisms have a high rate of reproductivity and normally experience a high selective pressure from the environment, they will be less likely to suffer from an increase in the mutation rate. This is because the undesirable mutations are ruthlessly eliminated during the struggle for survival. In populations like the human race, selection is less vigorous and undesirable mutations will tend to persist and be accumulated.