PM05 Aquatic Vertebrate/Invertebrate Toxicology
Exhibit Hall
8:00 AM - Monday, 10 November 2003
(PM087) Assessment of Chronic Hazard to Rainbow Trout (Oncorhynchus mykiss) from Dietary Exposure to Di-isoheptyl Phthalate (DIHP).
Davi, R1, Febbo, E1, Letinski, D1, Blattenberger, R1, Peterson, D1, Parkerton, T1, Blas-Machado, U1, 2, 1 ExxonMobil Biomedical Sciences, Inc., Annandale, NJ, USA2 Oklahoma State University
ABSTRACT- Past aquatic toxicology studies have shown that di-alkyl phthalates with alkyl chain lengths of greater than six carbons do not pose a chronic toxicity hazard to aquatic organisms when exposed to these substances via the water. These findings are consistent with the low water solubility and bioconcentration potential of these substances. However, the diet provides another potential and likely route of chronic exposure that warrants consideration. Recent research has investigated the potential chronic effects on fish that may be caused by elevated dietary exposure to C8 to C10 dialkyl phthalates. The objective of the present study was to extend the available effects database to a C7 phthalate [di-isoheptyl phthalate (DIHP)] by determining if prolonged dietary exposure to this compound could produce chronic effects in rainbow trout. A single dietary concentration of 1000 ug/g was investigated to determine if effects could be detected under high, continuous dietary exposure in comparison with a control group fed uncontaminated diet. Exposure was initiated immediately after yolk-sac resorption (approximately 4 weeks of age) and continued for 10 months. Chronic endpoints investigated during the study included survival, growth and sex ratio as determined by histological examination of the gonads. DIHP in the diet was confirmed analytically throughout the test and found to be in good agreement with the nominal level. No DIHP-related effects were observed. However, practical difficulties observed in the use of histological analyses for sex determination questioned the general utility of this test endpoint. Two hours after feeding, chemical analysis of exposed fish showed that both DIHP and the corresponding monoester (MIHP) were found in the GI tract at levels of 25% and 10% of the daily dose, respectively, but not detected in fish muscle. However, MIHP was detected at very low levels in the liver confirming internal exposure of this metabolite arising from dietary exposure to DIHP. In a subsequent depuration study, MIHP was completely eliminated from the liver of exposed fish in 2 days. The lack of chronic effects observed in this study is consistent with other recent dietary toxicity studies with fish on C8-C10 phthalates. Study results also highlight the critical role that biotransformation serves in limiting the dietary bioaccumulation potential of this compound class.
Key words: biotransformation, phthalates, bioaccumulation, dietary