Dietary uptake kinetics of 2,2',5,5'-tetrachlorobiphenyl in rainbow trout.

The disposition of [UL-(14)C]2,2',5,5'-tetrachlorobiphenyl (TCB) in rainbow trout (Oncorhynchus mykiss) was studied in acute dietary exposures using TCB-contaminated fathead minnows (Pimephales promelas). Trout were sampled at several postfeeding time points and TCB-derived radioactivity was measured in gut contents and selected tissues. Gastric evacuation was exponential with time and was 95% complete within 36 h of feeding. The ratio of activity in upper intestinal tissue to that in blood declined between 6 and 48 h, as did the lumenal contents/tissue ratio. Stomach content lipid declined between 0 and 24 h, while the lipid content of chyme remained relatively constant. These observations are consistent with liquid phase emptying of lipid and TCB to the upper intestine followed by rapid coassimilation. Tissue/blood activity ratios for the stomach, lower intestine, muscle, liver, and kidney were constant and probably represented near equilibrium conditions. The fat/blood activity ratio increased through 96 h, indicating that TCB was redistributing to fat. The lower intestinal tissue/feces activity ratio increased between 6 and 24 h and then declined rapidly. Fecal lipid content also increased between 6 and 24 h, but the amount of this increase was insufficient to explain observed changes in the distribution of TCB-derived activity. A small amount of 3-hydroxy TCB was detected in feces. Generally, however, metabolism had little or no impact on the uptake, distribution or elimination of TCB. Measured assimilation efficiencies exceeded 90% and are the highest ever reported in fish feeding studies with TCB.

Data quality objectives in environmental research planning.

This paper presents highlights of a Data Quality Objectives course relating the Environmental Protection Agency's (EPA) seven step research planning process to research efforts at the U.S. EPA National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, in Duluth, Minnesota. Introductory materials were derived from "Guidance for the Data Quality Objectives Process, EPA QA/G-4." Case studies illustrate decisions that were made during the systematic planning process and subsequent experimentation. This paper demonstrates how the Data Quality Objectives Process clearly links research goals and objectives with the final product. Application of the process to environmental research ensures that environmental research data are of known, credible, defensible and usable quality.