MA5 Novel Methods for Bioaccumulation Assessment
203 Oregon Ballroom
8:00 AM - 12:00 PM, Monday
() Assessing bioconcentration using a pragmatic dietary bioaccumulation test.
Parkerton, T1, Letinksi, D1, Febbo, E1, Blattenberger, R1, Dzamba, C1, Connelly, M1, 1 ExxonMobil Biomedical Sciences Inc., Annandale, NJ, USA
ABSTRACT- Worldwide regulatory initiatives require reliable estimates of bioconcentration as a critical endpoint for decision-making in chemical management. However, the traditional test used to determine the bioconcentration factor (BCF) is not ideally suited to poorly water soluble substances that are often the focus of concern. Practical disadvantages of this test include: difficulty in maintaining aqueous concentrations of often volatile and degradable test substances; required sensitivity in quantifying test substance concentrations in water and tissue above detection limits; uncertainty regarding the bioavailability of test substance in water; intensive animal use; and cost. To overcome these limitations, a dietary bioaccumulation test has been developed. The method involves spiking the test substance into a commercial diet. The spiked diet is then fed daily at a fixed ration to juvenile rainbow trout for a period of one to two weeks. The fish are then transferred to a clean tank and fed uncontaminated diet. During this depuration period, fish are periodically sampled, weighed and analyzed for parent test substance. Based on these experimental data, the growth-corrected half-life, dietary assimilation efficiency and biomagnification factor (BMF) are determined. The BMF represents the lipid-normalized ratio of chemical in fish to diet at steady-state and provides a diagnostic measure of biomagnification potential. To allow test results to be compared to BCF triggers specified in regulatory schemes, the experimentally derived half-life is coupled with a predicted estimate of the uptake clearance to calculate the BCF. The uptake clearance is estimated from the weight of the fish and the Log Kow of the test substance. BCFs derived via dietary tests for a variety of nonionic organic chemicals were found to correlate well with BCFs derived via aqueous exposure and correctly differentiate test substances with high bioconcentration potential. Insights obtained from application of the dietary test to various hydrocarbon classes and petrochemicals will be dicussed highlighting the role of biotransformation processes in both the tissues and gut of fish.
Key words: biomagnification, bioconcentration, biotransformation, hydrocarbons