352 



the proposed convention will contribute to the development of a greater under- 

 standing in this area by encouraging nations to exchange their exi)eriences and 

 to carry out their dumping operations in a careful, analytic manner while the 

 necessary research progresses. 



Some work, of course, has already been done by international groups of experts 

 to explore the effects of ocean pollution. Attachment III contains a hazard profile 

 of some 200 substances prepared by a panel of experts of the Joint Group of Ex- 

 perts on the Scientific Aspects of Marine Pollution (GESAMP), rating the effects 

 of each substance in five important aspects : bioaccumulation, damage to living 

 resources, hazards to human health, through oral intake and through skin con- 

 tact and inhalation, and reduction of amenities. The Environmental Protection 

 Agency has pointed out that the hazard profiles developed by GESAMP were 

 originally developed to deal with the problem of chemical tank machines from 

 bulk chemical ships and marine casualties. Consequently the feasibility of their 

 direct application to ocean dumping is not clear, i.e. single incident evaluations 

 being used for repeated discharge situations. However, the annex should provide 

 the reader with useful background information. Attachment IV contains an 

 analysis of the environment effects of over 25 substances or groups of substances 

 prepared as part of the working documents for the UN Stockholm Conference. 



With the various caveats, outlined above the following is a more detailed de- 

 scription of the apparent effects of some of the most hazardous substances that 

 have been a cause of some concern. 



a. Metal and metal compounds 



1. Mercury. — Metallic mercury has long been thought to be an environmentally 

 inert substance which would settle to the bottom of water bodies and cause few 

 harmful effects. It is now apparent, however, that mercury introduced into the 

 environment can easily be transformed into highly toxic forms which may ac- 

 cumulate in sediments and organisms in dangerous concentrations. 



Metallic mercury can be transformed by bacterial action into methylmercury, 

 a highly toxic compound which persists in the marine environment, is a.ssimilated 

 by aquatic plants and ingested by various forms of marine animals, and tends to 

 be retained for long ijeriods within organisms. As a result, methylmercury can 

 be readily inge.sted by humans eating contaminated fish and shellfish, and most 

 of the methylmercury so ingested may be absorlied and concentrated in vital 

 organs. In particular, methylmercury appears to concentrate in the brain, liver, 

 kidneys and red blood cells, and remains in the system for a substantial time be- 

 fore it is naturally eliminated. It is also readily transmitted into the fetus of an 

 exposed mother. 



Bodily disorders which may be traceable to methylmercury jwi.soning include 

 sensory disorders, genetic damage through disturbances in the mechanisms of 

 cell division and chromosome breakage, and birth defects and brain damage in 

 prenatally exposed children. While these effects in humans are not yet fully 

 validated, it is clear that methylmercury has a serious potential for damage to 

 human health. Smilar health hazards may be presented by ingestion, inhalation 

 or absorption through the skin of significant amounts of other organic mercury 

 compounds, and inorganic mercury salts or vapors. 



Methylmercury and other mercury salts may also cause similar toxic effects 

 in domestic animals, fish and planktonic life and may interfere with reproduction 

 and photosynthesis. Mercury concentrations are particularly hazardous at higher 

 levels in the food chain, such as predatory birds. 



One of the best known and most tragic cases of mercury poi.soning in recent 

 years took place in .Japan. Between 1953 and 1J>60. Ill persons were reported to 

 have been killed or to have suffered serious neurological damage near Minamata, 

 Japan, as a result of eating fish and shellfish caught in areas contaminated by 

 mercury. Among these were 19 congenitally defective babies whose mothers had 

 eaten the fish and shellfish. Subsequently, at Niigata 26 more cases of mercury 

 poisoning were noted. The fish eaten by th«> affected Japanese contained from 5 

 to 20 parts per million of methylmercury. 



It should be noted that the Environmental Directorate of the Organization for 

 Economic Cooperation and Development has performe<l an exhaustive study of 

 the existing knowledge on the overall biological impact of mercury through its 

 Sector Group on I'nintended Occurrence of Chemicals in the Environment. The 

 conclusions of that report are as follows : 



"Present knowledge of the biological impact of mercury at micro and macro 

 level as described in this report, leads to the following conclusions : 



