Table 1 . Principal Discharge of Liquid Radioactive Waste from Windscale, 

 1977 (Hunt, 1979) 



waters, methyl mercury chloride was identified as the active toxin. During the same 

 period in Sweden some disastrous impacts upon fish and wildlife through their 

 consumption of organic mercurial pesticides, often used as seed coatings, alerted 

 some scientists to study the environmental chemistry of mercury. From such investi- 

 gations, it was established that uncontaminated fish had a mercury burden primarily 

 in the form of methyl mercury. 



The first group to evaluate systematically the risks in the consumption offish 

 containing mercury was appointed in 1968 by the Swedish National Institute of 

 Public Health in conjunction with the Swedish Board of Health and the Swedish 

 National Veterinary Board. The group assessed the toxicological evidence from the 

 Japanese epidemics and the fish-eating habits of both the Japanese and Scandi- 

 navian populations. Some Swedish individuals who consumed large quantities of 

 fish and who had no symptoms of Minimata Bay disease had mercury concentra- 

 tions in their hair and blood similar to those of the Japanese who had shown neuro- 

 logical symptoms of the disease. The results emphasized the varying sensitivities of 

 individuals to methyl mercury poisoning and the different eating patterns of popula- 

 tions from different countries. The average daily consumptions of fish per day in 

 Japan and Sweden are 84 and 56 grams (3 and 2 ounces) day, respectively, while in 

 the United States the value is I 7 grams (0.6 ounces) day. The evaluation by the 

 Swedish Group (Anonymous, 1973) indicated that 10 percent of the Swedish popula- 

 tion might carry the maximum tolerable level in their bodies through the consump- 

 tion of fish containing 0.5 ppm of mercury (wet weight). This amount has not yet 

 produced Minimata Bay disease. A safety factor often is built into the calculations. 

 The limit of 0.5 ppm of mercury in fish, or modifications of it, has been adopted not 

 only by Sweden but by many other northern European countries and by the United 

 States. 



The important lesson from the mercury tragedy is that scientists can reach an 

 understanding of a critical pollution problem in the coastal zone and can propose 

 remedial action in decades. It took a bit over two decades for the Japanese govern- 

 ment to halt the discharge of mercury into the coastal zone and for other countries to 

 define acceptable mercury levels in seafoods. The levels of mercury in fish from the 

 Baltic Sea were markedly reduced when the Swedish government, acting upon the 

 advice of its scientists, banned the discharge of mercury wastes from chemical plants. 



DDT AND THE INTEGRITY OF ECOSYSTEMS 



Whereas the protection of human health has been the goal of regulating the inputs 

 of radioactive substances and mercury to the marine environment, another criterion 

 for curbing discharges developed alter DDT and other chlorinated hydrocarbon 

 biocides were broadcast about the surface of the earth beginning in 1946. This 

 criterion was the maintenance of the integrity of ecosystems. Several scientists 

 recognized the potential deleterious impacts of DDT on nontarget organisms very 



