heavy shipping traffic in this region of the world. Moreover, 

 there is extensive offshore oil production in the South China 

 Sea and a high occurrence ot tar balls would also be expected. 

 The greater frequency of occurrence of plastic pellets compared 

 to tar balls is noteworthy. The longevity of plastics in the 

 marine environment likely contributes to the increase of this 

 material in the oceans. 



The distribution of plastics in the Pacific Ocean was 

 largely a function of the major currents. All stations sampled 

 that contained plastics were along a l()°N latitude convergence 

 lying between the North Equatorial Current and the North 

 Equatorial Countercurrent (Fig. 1 ). The most likely source of 

 the plastics recovered at this convergence would either be from 

 ships or as industrial waste from plastic-producing Pacific Rim 

 countries. 



All plastic sample extracts were analyzed for the organic 

 compounds listed in Table 3. None of the samples contained 

 quantifiable concentrations of organochlorine pesticides, PCB's, 

 aliphatic hydrocarbons, or polycyclic aromatic hydrocarbons 

 included in the analyses. The absence of detectable levels of 

 these contaminants suggests that the plastics that were collected 

 at sea did not adsorb any of these compounds, either because 

 the plastic surface did not facilitate this or because the 

 contaminants were not present in sufficient concentrations. 



In the field experiment conducted in Chesapeake Bay's 

 Baltimore Harbor, plastic polyethylene pellets left floating in 

 the water for 24 h were extracted and analyzed using the same 



TABLE 3 



Organic compounds included in the analysis of extractions of 

 plastics 



Chlorinated 

 Pesticides 

 ami PCB's 



Aliphatic 

 Hydrocarbons 



Polycyclic 



Aromatic 

 Hvdrocarbons 



Heptachlorepoxide 

 Oxychlordane 

 Trans - chlordane 

 Cis - chlordane 

 Trans - nonachlor 

 Cis - nonachlor 

 Dieldrin 

 I .mil i ii 

 p.p" - DDT 

 p.p" • DDD 



p.p" 1)1)1 



PBC(1254) 



n - dodecane 

 n - tridecane 

 n - tetradecane 

 n - pentadecane 

 Nonycyclohexane 

 n - hexadecane 

 n - heptadecane 

 n_- octadecane 

 n - nonadecane 

 n - eicosane 



Tetrameth) I- 

 pentadecane 



Naphthalene 



Fluorene 



Phenanthrene 



Anthracene 



Fliioranthrene 



Pj rene 



1.2. -ben/anthracene 



Chrysene 



Benzo(b)fluoranthene 



9,10- 



diphenylanthrocene 



Benzo(e)pyrene 



Benzo(a)pyrene 

 1.2.5.6- dibenz 

 anthracene 

 Benzo(g,h,i)perylene 

 Pen lene 



The lower limit of quantification was 0.05 ug/g for aliphatic 

 hydrocarbons, 0.4 ug/g lor polycyclic hydrocarbons, mis ug/g for 

 chlorinated pesticides, and 0.25 ug/g foi l'( !B's based on a 0.2 g 



sample. 



methods as those collected at sea. A sample of the microlayer 

 was taken the same time these plastics were placed in the water 

 and was analyzed for the same contaminants as the plastic 

 extracts. Two aromatic compounds, pyrene and fluoranthene, 

 were detected in the microlayer sample: however, only 

 fluoranthene was present in the extract of the polyethylene 

 pellets. 



These data indicate that polyethylene pellets have the 

 potential to adsorb at least one organic compound, fluoranthene. 

 from ambient seawater. The specific mechanism of adsorption 

 could be either a binding of the organic compound to the plastic 

 surface directly or to a film of water surrounding the plastic 

 pellet. It is possible that other contaminants, especially those 

 occurring in high concentrations in the microlayer, could also 

 be adsorbed to floating plastic debris. Therefore, a potential for 

 the transfer of certain organic pollutants from plastics to 

 organisms that ingest them does exist. Plastics may serve as a 

 vehicle for pollutant transport that may enhance exposure of 

 organisms; however, if plastics also concentrate contaminants 

 from the water this would result in an even greater hazard to 

 marine organisms. 



The other aspect of chemical-induced toxicosis resulting 

 from plastic ingestion is that of the potential release of chemicals 

 from the plastic to the organism. In the second experiment, 

 none of the extracts of the acidic digestive solutions, or the 

 hexane extraction of plastic pellets contained quantifiable 

 concentrations of any of the hydrocarbon contaminants. These 

 data suggest that even when exposed to mild heat, acids, and 

 hexane, polyethylene pellets did not release appreciable 

 quantities of chemicals. However, plastics subjected to real 

 avian digestive systems would also be exposed to digestive 

 enzymes and tor possibly much longer periods of time. Ryan 

 ( 1988b) found that domestic chickens fed polyethv lene pellets 

 retained 98.3% ofthemoveran 18-day period. Moreover, there 

 are many types of plastics and additives to plastics that could 

 potentially be released during digestive processes in marine 

 vertebrates. 



Results of this study show that raw material plastic pellets 

 are becoming increasingly more common in areas of the Pacific 

 Ocean far removed from industrial sources. Although tar balls 

 were once considered more common and widely distributed 

 than marine plastics, their occurrence in the present stud) was 

 less than that of plastics even in areas where oil development 

 and tanker traffic is hea\ \ . Plastic pellets do have the potential 

 to adsorb certain organic contaminants from seawater: however, 

 the types of compounds that can be adsorbed and possibly 

 concentrated is not well understood. Polyethylene pellets 

 subjected lo conditions simulating the avian digestive system 

 did not release detectable levels of chemicals However, other 

 types of plastics, and those that contain additives, were not 

 tested. 



Clearly, fish, seabirds, and other marine organisms will 

 continue to be exposed to plastics at increasing rates. Regulations 

 prohibiting ocean dumping of plastics have already been 

 enacted: however, recycling, waste management, degradable 

 plastics, and other alternatives must continue to he developed 

 and implemented to abate the global problem of plastics in the 

 oceans of the world. 



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