Toxicological and Chemical Characterization of Organic Pollutants with Potential to Adversely Affect Fish
Abstract: Several investigations have described adverse effects in fish inhabiting polluted areas, though the causative, or aetiologic compounds have not been substantiated. Since environmental pollutants exist as complex mixtures, reliable risk estimations are difficult to obtain. Chemical analyses of known toxicants are not sufficient since unknown toxic compounds will not be identified. Diagnostic tools – biomarkers – will provide information on the potential toxicity, but only limited information on the aetiologic compounds. A promising strategy for pinpointing the major toxicants in environmental samples is to fractionate samples in several steps, guided by the toxicity of the isolated fractions. This enables a more precise identification of aetiologic compounds than the analysis of a non-fractionated sample.The present thesis describes the toxicological and chemical characterization of organic pollutants in the polychlorinated biphenyl (PCB) polluted bay Örserumsviken on Sweden’s Baltic coast. Compounds in organic extracts of abiotic matrices collected in the bay were separated by degree of aromaticity prior to exposing early life-stages of rainbow trout (Oncorhynchus mykiss). The fraction containing PCBs and other dicyclic aromatic compounds (DACs) was less potentially toxic than the fraction containing polycyclic aromatic compounds (PACs). An estimated 1-5% of the total ethoxyresorufin O-deethylase (EROD) induction could be explained by PCBs, and less than 4% by the most commonly monitored PACs. Though the aetiologic compounds were not identified, a significant part of the EROD induction was isolated in a PAC-subfraction containing compounds with more than five rings and the major part of teratogenicity was isolated in a fraction containing three- and four-ringed PACs. As markers for the unidentified potent compounds in the DAC- and PAC-fractions, PCBs and polycyclic aromatic hydrocarbons (PAHs) were analyzed in feral fish eggs from the bay. Adult northern pike (Esox lucius) had elevated levels of hepatic DNA adducts, which correlated with PAH concentrations in their eggs. ?PCB concentration in pike eggs was equal to the injected concentration in the highest dose of the DAC-fraction, which caused a 50-fold EROD induction in rainbow trout larvae. This demonstrates that the compounds present in the abiotic matrices posed a threat to all life-stages of fish in this area.The findings in this thesis clearly reveal the limits of our knowledge regarding compounds responsible for potential toxicity in field situations. We need to place greater emphasis on the toxicological and chemical implications of our continuous release of PACs and to work for much more restrictive regulations.
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