354 



The extremely high levels in the brains of adult seals which were found merit 

 further attention in this respect. 



"(p) Methylmercury is shown to affect the detoxification systems of cells. The 

 possibility must, therefore, be considered of methylmercury acting synerglstically 

 with other foreign substances and, by changing their metabolism, render them 

 harmful or increase their toxicity." 



2. Cadmium. — Cadmium reaches the marine environment from a variety of 

 industrial processes, including the manufacture of storage batteries, plastics and 

 petroleum products. Like mercury, cadmium compounds tend to accumulate in 

 marine life, and to be ingested by humans consuming fish and shellfish. Only 

 a fraction of the cadmium taken into the body is actually absorbed, but ingested 

 cadmium appears to accumulate in the kidneys and the liver and is not eflRciently 

 excreted. While the effects of cadmium accumulation in humans are not fully 

 known, there is evidence that exposure even to low-levels may be as.sociated with 

 hypertension, cardiovascular disease, and perhaps to cancer. 



Cadmium is apparently a serious hazard to marine life. Cadmium chloride is 

 rated by the GESAMP experts as a bio-accumulate substance which is highly 

 toxic to living organisms, and ingestion may be lethal to fish at concentrations of 

 fractions of parts per million. 



3. Lead. — Lead compounds may become biologically concentrated at all levels 

 of the aquatic food chain when deposited in a marine area in significant 

 amounts. The presence of such concentrations in marine waters may cause death 

 to fish by suffocation through the formation of mucus over the body and gills, 

 and may cause blood cell damage. 



Lead can be a serious health hazard to humans when absorbed in suflScient 

 quantities over an extended period. Chronic lead poisoning tends to produce gas- 

 trointestinal and urinary tract disorders, anemia and stippled blood cells, head- 

 aches, and may even result in coma and death. However, it has apparently not 

 yet been established that ingestion of lead-contaminated fish is a significant 

 cause of lead poisoning in humans. For further details the reader is referred 

 to the monography "Hazards of Lead In The Environment, with particular refer- 

 ence to the Aquatic Environment" by Victor Lambon and Benjamin Lim, Federal 

 Water Quality Administration, U.S. Department of the Interior, August 1970. 



4. Arsenic. — Arsenic is a well-known cumulative toxin used in many industrial 

 processes. Arsenic compounds tend to be persistent in the aquatic environment, 

 to accumulate in sediments, and to concentrate in aquatic organisms. Relatively 

 small concentrations may produce toxic or lethal effects on various fish, benthic 

 organisms and food chain organisms when exposed over even short periods. In 

 humans, toxic effects may be caused either from ingestion or skin-absorption, 

 resulting in concentrations in the liver, kidney and spleen ; elimination through 

 urinary excretion is generally slow and incomplete. Cancer, liver damage and 

 heart ailments may be produced. 



5. Zinc. — Zinc occurs in the marine environment as a result of industrial ef- 

 fluents and the dumping of dredge spoils and other materials. Zinc is an essen- 

 tial nutrient for most life forms and where it does not exist in suflicient quan- 

 tities, there is cause for concern. However, the element can have toxic effects 

 in suflBcient concentrations. Six grams of zinc chloride and 45 grams of zinc sul- 

 fate have been reported to be fatal to humans, and sub-lethal concentrations 

 may interfere with iron metabolism. Fish may exhibit toxic reactions and gill 

 damage when significant zinc concentrations are present. Zinc .seems al.so to con- 

 centrate in shellfish, but the evidence of harmful effects on such organisms is 

 not conclusive. Furthermore, it is unclear as to whether any significant human 

 health hazard may be produced by food chain concentration in the marine 

 environment. 



6. Beryllium. — Beryllium is u.sed in electroplating processes and as a catalyst 

 in the manufacture of organic chemicals. Beryllium does not appear to be a 

 severe toxin when ingested, although it may cause pulmonary problem.s if in- 

 haled directly. Only a small proportion of that ingested is absorlied. and that 

 is rapidly excreted. There is a'so no evidence that beryllium is bioaccumulative 

 in the acquatic environment. However, beryllium apjiears to be toxic to terrestial 

 plant.s, and it is possible that it would have similar toxic effects on aquatic 

 plants. 



7. Chromium. — Chromium is also found in industrial wastes. Chromium ap- 

 pears to concentrate in plaktonic life and aquatic plants, and may substantially 

 decrease the rate of photo.synthesis in concentrations of as little as 1 milligram 

 per liter. On the other hand, salt-water fish appear to be able to tolerate sub- 



