higher, more likely to be causing biologi- 

 cal effects, and more spatially variable 

 in urban, as opposed to njral, coastal 

 areas. The same assumptions have led 

 to sites being closer together in estuar- 

 ies and bays than along open coasts. 



Contaminants Measured 



The NS&T Program monitors concen- 

 trations of trace metals and organic 

 compounds in sediment and in tissues. 

 Except for most chlorinated organic 

 compounds — DDT and PCB, for ex- 

 ample, whose existence is due to hu- 

 man activity — some concentration of 

 chemicals in sediments and organisms 

 is natural and would be present even in 

 the absence of human activity. Only 

 sediments and tissues that contain 

 chemical concentrations in excess of 

 natural levels are considered to be 

 "contaminated." 



The exact line demarcating natural 

 concentrations from contamination is 

 not easily drawn because it depends on 

 many local and regional conditions. This 

 report highlights NS&T sites where 

 concentrations are highest and, while 

 cases exist where high concentrations 

 might be natural, for the most part, they 

 are due to discharges to coastal waters 

 from human activities. 



Data on concentrations of the seven 

 trace metals and four groups of organic 

 compounds listed in Table 1 are used in 

 this report to describe the status and 

 trends of contamination in the coastal 

 and estuarine areas of the U.S. Con- 

 centrations of all of these chemicals can 

 serve as indicators of human activity. 

 While the metals all have different uses, 

 they can be categorized as chemicals 

 whose discharge to the environment 



has been enhanced through industriali- 

 zation. 



The groups of organic compounds can- 

 not be categorized so generally. Two of 

 those groups, total DDT (tDDT) and 

 chlordane (tCdane), are chlorinated 

 pesticides. Use of DDT in the United 

 States was banned in 1970. The use of 

 chlordane on crops and ornamental 

 plants was first restricted in 1974. Its 

 major use as a termiticide came under 

 severe restriction in 1988. 



Polychlorinated biphenyls (tPCB) are a 

 mixture of compounds based on the 

 biphenyl molecule chlorinated to vari- 

 ous extents. It was first used in 1 929 for 

 a number of industrial purposes. Its high 

 heat capacity and low dielectric con- 

 stant were exploited for its major use in 

 electrical transformers and capacitors. 

 Its use in the United States began to be 

 phased out in 1971 and it has been 

 banned in new devices since 1976. 



All of these banned compounds — 

 tDDT, tCdane, and tPCB — continue to 

 be used in other countries and still exist 

 in the environment. In the United States, 

 chlordane is still in the ground as a ter- 

 miticide, PCB-containing devices are 

 still in use, and DDT, while no longer 

 used, remains in the environment be- 

 cause (like chlordane and PCB) of its 

 resistance to degradation. The pesti- 

 cide DDT is metabolized to DDE and 

 DDD in the environment, but the tDDT 

 group of compounds resists further 

 degradation. 



Polycyclic aromatic hydrocarbons 

 (.PAHs) are like metals in the sense that 

 they are not synthetic but occur natu- 

 rally. They are found in fossil fuels such 

 as coal and oil. Their existence, though. 



