Several classical cases of pollutant management have evolved. The first involved 

 the release to the oceans of ruthenium-106. which is accumulated by the algae 

 Porphyra. A small population in south Wales uses the seaweed as a food in the 

 preparation of a pudding called laverbread. Although the pathway is now essentially 

 dormant because the consumers no longer receive their algae from the Windscale 

 area, monitoring is nevertheless still performed (Hunt, 1979). Figure I illustrates the 

 results of monitoring activities for this radionuclide. 



The laverbread story illustrates effectively the "critical pathways" approach 

 formulated in the United Kingdom. The guiding principle involves the identification 

 of the pathways by which a radioactive substance introduced to the environment can 

 return to the population. 1 n general, for the radioactive isotopes of a given element, 

 only one or two pathways are of importance. Of further importance is the identifica- 

 tion of the critical group within a given population that receives the highest dosage of 

 the radionuclide. United Kingdom policy explicitly attempts to control the release of 

 radioactive nuclides to the environment on the basis of protecting the most highly 

 exposed individual (Preston and Mitchell, 1973). 



The population exposed to ruthenium-106 through laverbread consumption 

 numbered 26,000. The critical group consumed about 160 grams (5.6 ounces) of the 

 product per day; exposure estimates have been based upon studies of this very small 

 subpopulation. The Porphyra that accumulated ruthenium-106 from the nuclear 

 activities at Windscale comprised only a part of the seaweed used by the critical pop- 

 ulation, although there were times when only the Windscale Porphyra were utilized. 

 In estimating total exposures of the critical population, the model assumes that no 

 dilution of the Windsca'e Porphyra with seaweedscontaining no ruthenium-106 has 

 taken place. The monitoring program covered sites where the seaweed could poten- 

 tially be harvested at distances up to40 km (25 mi) from Windscale. At the beginning 

 of the monitoring program, the dilution of Windscale seaweed with that from other 

 areas could be estimated, since all of the Porphyra was shipped by rail. The shipping 

 records were available up until the late 1960s, after which the use of rail transport 

 declined. Subsequently, the monitoring of the laverbread itself became necessary. 



External exposure of the public to gamma-emitting radionuclides that became 

 associated with particulate phases and subsequently entered the beach areas was also 

 recognized. The nuclides of concern in the past have been zirconium-95 and 

 niobium-95 (Preston and Mitchell. 1973). The critical population for external expo- 

 sure was revealed to be one salmon fisherman, whose activities were confined to a 

 single beach at one estuary where the silt and the clay minerals containing the radio- 

 active substances accumulated. This individual spent some 300 hours per year in his 

 pursuit of the salmon. This rather unique case emphasizes the need for social as well 

 as scientific studies. 



Another example considers public radiation exposure from radiocesium, which 

 is highly concentrated in fish and shellfish. The highest exposure to members of the 

 critical population, based upon their consumption of these marine products, was 3 1 

 percent of the ICRP-recommended dose limit in 1977 (Hunt. 1979). 



The significant lesson from these British activities is that highly toxic materials can 

 be released to the marine environment and can potentially return to impact human 

 health. With appropriate models and confirmatory monitoring procedures, risk to 

 the most susceptible individuals can be minimized. Further, of great significance is 

 the public dissemination of all information and data regarding the radioactive 

 releases. Table I shows the important releases from Windscale. Here, discharge 

 limits for individual or collectives of radionuclides are given and the percentage of 

 the limit utilized in 1977. Such data are issued on an annual basis. 



MERCURY AND SOCIETAL REACTION TIMES 



In 1963, following the Minimata Bay epidemic and a similar outbreak in Niigata, 

 Japan, where chemical factories discharged spent mercury wastes into natural 



3 



