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TA8 Assessing Toxicity: Critical Body Residue Approach
(240) Variability in Organic Chemical Critical Body Residues.
Barron, M1, 1 P.E.A.K. Research, Longmont, CO, USA
ABSTRACT- Critical Body Residues (CBRs) are tissue concentrations of contaminants in aquatic organisms associated with adverse effects. This investigation evaluated the variability in CBRs for six organic chemical classes and mode of action categories: narcotics (polar, non-polar), excitatory agents, acetylcholinesterase inhibitors, reactives/irritants, central nervous system seizure agents, and aryl hydrocarbon receptor agonists. Existing databases on the association between tissue residues and toxicity in aquatic invertebrates and fish were evaluated to determine the range and coefficient of variation in CBRs as mmol/kg tissue. CBRs were extremely variable within each chemical class and mode of action category, with coefficients of variation greater than 10,000. Chemical classes with receptor mediated toxicity exhibited the greatest variability with an over 100,000 fold range in CBR values. High CBR variability was attributed to life stage and species differences in intrinsic sensitivity (e.g., receptor presence-affinity), exposure duration, bioaccumulation and biotransformation, and concomitant baseline and specific mechanisms of toxicity. Despite the potential utility of the CBR approach, broad application across chemical classes is not recommended because of high variability and the necessity of accurate chemical characterization and mode of action assignments for contaminant residues. In the absence of site-specific and life-stage specific CBRs, a conservative application of literature-based CBRs in ecological risk assessment is recommended.
Key words: fish, CBR, organic chemical, critical body residues
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