Persistent organic pollutants (POPs) in sediments and biota in coastal environments of India

Persistent organic pollutants (POPs) are semivolatile organic compounds of special concern because of their toxicity, persistence, long-range transport and bioaccumulation potential. They are present in the marine environment, notably in coastal areas affected by municipal sewage, agricultural and aquaculture effluents, industry and shipping traffic. The 7,555 km-length coastal region of India is the most vulnerable zone facing frequent geohazards, e.g. tsunami and flooding. It is contaminated from direct discharge of wastes from the densely populated coastal areas, runoff of fertilizers, dumping by vessels, oil spills, deforestation and ill-planned river basin developments. This chapter summarizes the knowlegde on residues of 5 classes of persistent organic pollutants (POPs) such as dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexane and its isomers (HCHs), polycyclic aromatic hydrocarbon and its congeners (PAHs), polychorinated biphenyl and its congeners (PCBs) and polybrominated diphenyl ether and its congeners (PBDEs) in the sediments and in selective biota: bivalve mollusks, fishes and marine mammals. Their potential ecotoxicological impacts on biota have also been assessed based on the sediment quality guidelines (SQG) specified by USEPA (The incidence and severity of sediment contamination in surface waters of the United States, vol 1, National sediment quality survey. EPA 823-R-97-006, Washington, DC, 1997a: Environmental protection agency, National Sediment Quality Survey, App D, Washington DC, 1997b) and by Canadian Council of Ministers of the Environment (CCME, Canadian quality guidelines for the protection of aquatic life-summary tables. Available from. http://www.ccme.ca/assets/pdf/sed summary-table.pdf, 2002). Contribution of DDT and its metabolites, DDT, DDD and DDE residues, varied in different Indian coastal regions predominated by pp′-DDT and pp′-DDD. The measured concentrations of HCHs were lower than DDTs in sediments. HCH and DDT residues in fish from coastal regions of India were lower than those in temperate countries indicating a lower accumulation in tropical fish, which might be ascribed to rapid volatilization of this insecticide in the tropical environment. Distribution of congener profiles of PCBs, PAHs and PBDEs reflects moderate to very low concentrations closely in conformity to other Asian coastal environment. Predominance of highly chlorinated PCB congeners was evident in comparison to lightly chlorinated PCBs, which are less persistent, have lower log_ko w and are more volatile than the former. The prevalence of 4-6 aromatic ring PAHs and cross plots of specific isomer ratios such as phenanthrene/anthracene, fluoranthene/pyrene and methylphenanthrene/phenanthrene suggest the predominance of wood and coal combustion sources, where the atmospheric deposition and surface runoff are the the major transport pathways. In case of PBDEs the nature of lesser-brominated congeners may be due to the extensive use of penta-BDE technical mixture or as a result of environmental debromination of higher brominated BDEs. The east coast of India, on an average, is found to be much more contaminated than the western counterpart which might be attributed to residues with their behavior, fate and bioaccumulation in the different trophic levels should be planned. An alarming situation has already emerged due to the presence of pesticide residues in the human breast milk as well as in the blubber of the endangered gangetic dolphin (Platanista gangetica) inhabiting both riverine and estuarine regions of the Ganga River. Hence authors suggest that a regular monitoring, assessment and reporting machineries should be implemented in accordance with appropriate environmental policies, laws and regulations to guarantee health of environment and human.