The problem with the current ICRP system of radiation protection, particularly for regulators, is that it fails to differentiate between the application of justification and optimisation to people in the circumstances of medical care or as part of a workforce, compared with their application to members of the general public in an environmental setting; plus the fact that it also fails to address the issue of potential impacts on the rest of the environment in any meaningful way. But if these deficiencies are to be addressed, it will be essential to consider how protection of both people and the living environment can be achieved within a broad philosophical framework, using complementary approaches, based on the same underlying scientific knowledge. This paper briefly examines some of these issues, and offers some suggestions for developing a common, or even a combined, approach. It draws upon recent suggestions made by the ICRP itself with regard to radiological protection, plus current activities-on several fronts-to provide an explicit basis for environmental protection.

Plate 1, Text-figs. 1-5)The accumulation from sea water of 6B Zn, M Mn, 59 Fe and 68 Co by the mussel, Mytilus edulis, has been studied in relation to the stable element levels of these isotopes both in the sea water and in individual tissues. For all four radionuclides the greatest accumulation occurred in the stomach and digestive gland samples and further localization of ^Zn and 69 Fe was demonstrated by autoradiography. As the animals were starved during the accumulation period the loss of stable elements by individual tissues was also followed. Again the most notable effect occurred in the digestive gland tissues with the exception of a large loss of iron by the foot. Autoradiography showed that after two weeks accumulation 69 Fe occurs in large clusters in the foot, notable in the byssus gland area. These clusters disappear after a further two week period and may thus be secreted into new byssus threads.The accumulation of nyclides was examined using a single exponential model and values obtained for flux rates, biological half times and asymptotic values were compared with the stable element concentration factors. An analysis of parameters of exchange of nuclides in individual tissues with the water was further examined using the Kendall coefficient of concordance which demonstrated that the highest exchange occurs in the order of stomach and digestive gland > gill > foot > mantle > gonad > adductor. The application of the Friedman test of two-way analysis of variance indicated that this order obtains for all four nuclides studied, despite the fact that in the aquaria used zinc and cobalt were largely soluble; that manganese was partly in the particulate form with the radionuclide used; and that iron was largely particulate in both stable and active forms. There is an indication that as well as accumulating nuclides via particulate matter in suspension the mucus itself is capable of sequestering them, even though they are in the soluble form, and may even preferentially accumulate soluble forms. The actual role of water in the accumulation of the nuclides studied appears to be relatively minor compared with that of food accumulation as estimated by difference from the calculated stable element values.

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Radiological protection has always been based on protection of man. Protection of the environment is often assumed to be implicit in the application of radiological protection generally, but this assumption is increasingly being challenged. It is therefore time to consider the feasibility of developing a complementary system for protecting the environment itself from ionising radiation, which would be both explicit and applicable to a wide range of situations. This paper outlines a possible approach using reference dose models and different types of dose effects.

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