Tissue-Related Polychlorinated Biphenyls Accumulation in Mediterranean Cetaceans: Assessment of Toxicological Status

Polychlorinated biphenyls (PCBs) have been synthesized for use as technical mixtures in a multitude of industrial applications such as impregnating wood, paper and fabric, and as engine oil additives, capacitor fluids, transformer coolants, paint and sealant plasticizers. These compounds are lipophilic in nature and biomagnify through food chains, so bioaccumulation in the lipid fraction of tissues of long living species that occupy a top trophic position might be of special concern. Cetaceans, in particular, being typical end-points in the marine food chain, and possessing a limited capacity to metabolize these toxic contaminants (Tanabe et al., 1988; Tanabe, 2002), have a high accumulation potential and, as a consequence, are most vulnerable to the long-term toxic effects of such chemicals. Cetacean populations living in the Mediterranean basin are especially exposed to this type of pollution because of the semi-enclosed nature of this sea, surrounded by highly industrialized countries. The morbillivirus infection of Mediterranean dolphins during the last decades has been linked to the presence of elevated PCB concentrations in the corpses of dead animals (Kannan et al., 1993; Aguilar and Borrell, 1994). Known organochlorine-mediated toxic effects in marine mammals include immune system depression and thereby increase in susceptibly to microbial and parasitic infections, as well as reproductive impairment, alteration of growth and skeletal deformities (Addison, 1989; Helle et al., 1990; Zakharov et al., 1997). In this context, the need for a continuous monitoring of organochlorine load in these species is obvious. Such an observation is reinforced by the proposal that, globally, PCB concentrations in marine biota will continue increasing in forthcoming decades since only a small fraction of the total amount released has reached the oceans (Tanabe, 1988; Reijnders, 1996). Reijnders (1996) estimated that only about 1% of the PCB produced had reached the ocean in the mid-1990s, and Tateya et al. (1988) suggested that levels of PCBs in marine mammals would peak between 2000 and 2030. Taking into account all these facts, this study presents the results from analyses of PCBs and their distribution in liver, kidney, lung, and tissue muscle of 12 specimens of Mediterranean bottlenose dolphins (Tursiops truncatus). Furthermore, toxic equivalent concentrations (TEQs) based on available toxic equivalent factors (Van den Berg et al., 1998) of a number of congeners are calculated and their relative contribution to the total toxic burden in the analyzed tissues is presented.