Tissue Residue Toxicity—Evaluations, Case Studies and Applications Session at the SETAC North America 31st Annual Meeting
James Meador (NOAA Fisheries) and Nelson Beyer (USGS)
Our session was focused on the tissue residue approach for assessing toxicity and managing chemical contamination, which is a methodology that complements other tools available to environmental risk assessors. We solicited presentations that highlighted selected contaminants as case studies that utilized tissue residues for toxicity assessments. The session was open to presentations covering a wide range of taxa, including birds, mammals, fish, and invertebrates.
The assessment of toxic effects based on tissue concentrations over the past 30 years has been gaining substantial interest and research effort. The tissue-residue effects approach (TRA) for characterizing toxic responses based on bioaccumulated contaminants is being used to reduce the observed variability for toxicity metrics across species and environmental conditions. Recently, it has evolved into a more expansive consideration of tissue residues as the dose metric for defining dose-response relationships, evaluating mixtures and pulse exposures, developing protective guidelines, enhancing predictive toxicity based on mode of action, forensic analysis, and conducting risk assessments. This approach has already been utilized for Superfund site assessments, Endangered Species Act consultations, and Natural Resource Damage Assessments.
As expected, the presentations covered a variety of topics related to tissue residue toxicity. Most of the talks were given by authors of chapters for a book on the subject that is currently in press (see link below). Nelson Beyer started the session by introducing the topic, explaining how the role of tissue concentrations in biota is becoming increasingly useful in risk assessment. After that, Harry Ohlendorf explained the kinetics of selenium in avian eggs, how the concentrations in the egg are related to the diet, and how seasonal movements of birds are related to potential poisoning from selenium. One of the more informative presentations was given by Bryan Brooks, who took on the daunting task of trying to help the audience make sense of the potential toxicological importance of the many poorly studied pharmaceuticals ingredients in aquatic systems, suggesting that lessons learned from the study of compounds active at the hypothalamic-pituitary-gonadal axis (endocrine disruptors/modulators) may reduce uncertainties. We had three presentations on chlorinated hydrocarbons. Matt Zwienik reviewed studies on the toxicity of polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) to mink, explaining how the use of toxic equivalency factors could help but that there were still difficulties in establishing reliable thresholds in tissues. Linda Martello reviewed the same group of chemicals in aquatic organisms, organized by different families of fish, and then interpreted the ecological importance of the residues with species sensitivity graphs. Andrea Fog described her work for the U.S. Environmental Protection Agency relating tissue residues of DDT in birds to effects, concluding that relying on egg residues reduced uncertainty in assessments and was preferable to estimating the dose based on exposure. Later in the session, Jim Meador demonstrated how environmental assessments for organotins can be improved with the use of tissue residues. In one example he showed that tissue concentrations for several organotins in a wide range of aquatic organisms and small mammals were essentially the same for lethality, despite vast differences among species in terms of exposure-based toxicity metrics. Amanda Harwood wrapped up the session by explaining the difficulties in using tissue residues of pesticides in tissues of aquatic animals, especially those that are rapidly metabolized once absorbed.
Authors’ contact information: firstname.lastname@example.org, email@example.com
Book: Environmental Contaminants in Biota: Interpreting Tissue Concentrations, Second Edition. W. Nelson Beyer and J.P. Meador (eds). Taylor and Francis. Available February 2011.
Journal: Several review articles on tissue residue toxicity resulting from a Pellston workshop on this topic will appear in the January 2011 issue of the SETAC journal Integrated Environmental Assessment and Management.
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