The toxicokinetics of hydrophobic contaminants in the invertebrate Mysis relicta.

Toxicokinetic studies were conducted using the invertebrate, Mysis relicta, and the hydrophobic contaminants, benzo(a)pyrene (BaP) and 2,2$\sp\prime$,4,4$\sp\prime$,5,5$\sp\prime$-hexachlorobiphenyl (HCB), on approximately a monthly basis. The uptake and depuration clearance constants from a water source for both BaP and HCB were observed to be similar, and showed marked seasonal changes from April to November. While the seasonality was initially presumed to be related to respiration rate changes of the animal, experimental work indicted that the uptake clearance constants for these chemicals are only weakly related to the respiration rate. Further, these chemicals do not appear to have a toxic effect at the concentrations employed as measured by respiration rate. A notable difference in the disposition of BaP and HCB is in the accumulation patterns when M. relicta is exposed both to contaminated food and water. While the accumulation of HCB appears to be additive with respect to food consumption, BaP accumulation is reduced by the consumption of contaminated food. It is hypothesized that BaP elimination (in either a parent or metabolite form) is enhanced by food consumption and subsequent fecal elimination. Perhaps this occurs via incorporation into the peritrophic membrane. Additionally, elimination rate constants appear to be proportional to the feeding rate suggesting that transport across the membrane in the animal is not a rate limiting step for elimination. Based on the analyses of the kinetics data, the fraction of contaminant input from food comprised less than 50%, suggesting that contaminant obtained from water is more important than that obtained from food for this animal. A kinetics based model was constructed using the toxicokinetic parameters with modifications for season and feeding. The model suggests that seasonality in concentrations of BaP and HCB in M. relicta vary by factors of 2-5 through the course of the year. Because of the paucity of analytical data for BaP and HCB in M. relicta, the annual average model concentrations for HCB were verified with PCB data. This comparison suggests that as a first approximation, a kinetics model can explain the observed concentrations in the animal.Ph.D.Environmental scienceHealth and Environmental SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/128257/2/8907032.pd