Figure 3. The depth profile of TCDD-EQ at each site as determined by the P450RGS assay.

ERDC TN-DOER-C19

December 2000

Figure 3. The depth profile of TCDD-EQ at each site as determined by the P450RGS assay. Each bar

represents an average from three extracts from each of the five cores (15 samples per depth

per site). Note that at several stations the contamination varies with depth; such information

could not be obtained from chemical analysis alone due to prohibitively high costs

the detail obtained with this cell-based assay would have been prohibitively expensive using

GC-MS, costing at least $558,000 (155 samples with triplicate extractions, $1,200 per analysis)

compared with the $31,000 spent on the cell-based assay ($200 per sample, includes analysis of trip-

licate extractions).

Cell-based assays such as P450RGS can also be used to determine the bioavailability of contami-

nants, by analyzing both the media (e.g., water, soil, sediment) and organism (e.g., fish, worm, or

clam) of interest. Several currently proposed projects plan on using the cell-based assay to monitor

the efficacy of remediation techniques for polycyclic aromatic hydrocarbons (PAHs),

polychlorinated biphenyls (PCBs), and dioxins by exposing organisms to the soil or sediment be-

fore, during, and after remediation, then extracting them and analyzing the extracts with the

cell-based assay.

Development of New Cell-Based Assays. Cell-based techniques similar to that of the

P450RGS assay can also be developed for other contaminant classes. The metal-responsive

metallothionein gene is characterized well enough that a cell-based assay can be developed in a man-

ner similar to the P450RGS system (Iyengar, Muller, and Maclean 1996). Another class of