Application of site-specific calibration data using the CALUX by XDS bioassay for dioxin-like chemicals in soil and...

The Chemically Activated Luciferase Gene Expression (CALUX) by Xenobiotic Detection Systems (XDS) bioassay was evaluated for the determination of the presence of dioxin and dioxin-like compounds in soil and sediment in two studies conducted under the U.S. Environmental Protection Agency's Superfund Innovative Technology Evaluation Monitoring and Measurement Technologies Program. In the first study, the results were compared with those generated by established laboratory methods (EPA Method 1613B) using high-resolution mass spectrometry (HRMS). The study results demonstrated that the technology could be used to screen for dioxin concentrations above and below threshold values (e.g., less than or greater than 1 or 50 picograms of toxicity equivalents per gram [pg TEQ/g]); however, the results were not linearly correlated to the HRMS results. A second study was initiated to evaluate performance on a site-specific basis. During the second study, the data from the XDS technology were evaluated in four ways: (1) uncalibrated to HRMS, (2) calibrated using an overall statistical model, (3) calibrated using statistical models generated on a site-specific basis, and (4) calibrated using site-specific calibration factors. The results showed that TEQ data produced by the XDS technology were more precise than the data reported during the first study. The second study also demonstrated that site-specific statistical models were better tools for understanding the relationship between the XDS and HRMS data than a single overall model generated from data from multiple sites. Ultimately, site-specific calibration was shown to be the best approach because it was a simple and accurate way of correcting the XDS data and improving comparability with HRMS.