Bioaccumulation and metabolism of phthalate esters by oysters, brown shrimp, and sheepshead minnows

The bioaccumulation and metabolic fate of three phthalate esters, dimethylphthalate (DMP), dibutylphthalate (DBP) and di(2-ethylhexyl)phthalate (DEHP), were studied in three species. The species used, the oyster Crassostrea virginica, the brown shrimp Penaeus aztecus, and the sheepshead minnow Cyprinodon variegatus, were chosen for this study as previous studies indicated that these organisms possessed different capacities for detoxifying xenobiotics. The effects of concentration as well as ester chain length and species were studied. Bioaccumulation did not vary significantly among the three species, possibly due to high levels of individual variation. A trend to higher accumulation in oysters was noted. Bioaccumulation was significantly affected by chain length, with DBP accumulating to a greater extent than DMP or DEHP, and by the concentration of phthalate. Biodegradative indices, on the other hand, were not significantly affected by the ester used or by concentration, but did vary significantly with species. Oysters were less efficient in the biodegradation of the esters than fish or shrimp. The major metabolites found were the monoesters, phthalic acid, and a group of unidentified polar metabolites, probably conjugates. These latter metabolites did not appear in oysters, but were present in significant amounts in fish and shrimp.