You are here:
CHIRAL POLLUTANTS: OCCURRENCE AND SIGNIFICANCE
To determine the environmental occurrences, fate, and effects of the enantiomers of selected chiral pesticides and other chiral pollutants.
This task involves process research to determine the environmental occurrence and fate of enantiomers of selected chiral pesticides, PCBs and other chiral pollutants with an emphasis on currently-used modern pesticides expected to have short to intermediate environmental half-lives. Enantiomeric selectivity manifests itself during biologically-mediated environmental processes (e.g., enzyme catalyzed transformations, transport across membranes), but not during abiotic processes. One enantiomer thus reacts more slowly than the other during microbial degradation and thereby comes to predominate in water/sediment systems, in plant and animal tissues, and in food residues. In addition, enantiomers have different biological effects: one is more toxic than the other, and, for chiral endocrine disrupters, exhibits differential disruption activity. The approach to this research involves 5 steps: 1) development of analytical techniques to separate enantiomers; 2) analysis of water, sediment, soil, biota and human exposure samples expected to contain chiral pollutants to determine the occurrences and enantiomeric ratios; 3) measurement of enantiomer degradation in selected environmental matrices to determine selectivity and rates of enantiomer degradation; 4) preparative separation/collection of the enantiomers of important pesticides and other pollutants for effects studies; and 5) measurement of the effects of the separate enantiomers of pesticides using various toxicity endpoints; testing will be done by other EPA laboratories and extramurally.