Superfund Innovative Technology Evaluation (SITE)
Note: EPA no longer updates this information, but it may be useful as a reference or resource.
|Technologies for Monitoring
& Measurement of Dioxin and Dioxin-like Compounds in Soil and Sediment
(Xenobiotic Detection Systems, Inc. CALUX by XDS)
A demonstration of technologies for determining the presence of dioxin and dioxin-like compounds in soil and sediment was conducted under the U.S. Environmental Protection Agency’s (EPA’s) Superfund Innovative Technology Evaluation Program in Saginaw, Michigan, at Green Point Environmental Learning Center from April 26 to May 5, 2004. This innovative technology verification report describes the objectives and the results of that demonstration, and serves to verify the performance and cost of the Xenobiotic Detection Systems, Inc., CALUX® by XDS. Four other technologies were evaluated as part of this demonstration, and separate reports have been prepared for each technology. The objectives of the demonstration included evaluating the technology’s accuracy, precision, sensitivity, sample throughput, tendency for matrix effects, and cost. The test also included an assessment of how well the technology’s results compared to those generated by established laboratory methods using high-resolution mass spectrometry (HRMS). The demonstration objectives were accomplished by evaluating the results generated by the technology from 209 soil, sediment, and extract samples. The test samples included performance evaluation (PE) samples (i.e., contaminant concentrations were certified or the samples were spiked with known contaminants) and environmental samples collected from 10 different sampling locations.
The Xenobiotic Detection Systems, Inc., CALUX® by XDS is an aryl hydrocarbon-receptor bioassay that individually reports the total toxicity equivalents (TEQ) of dioxins/furans and polychlorinated biphenyls (PCBs) in the sample. As part of the performance evaluation, the technology results were compared to TEQ results generated by a reference laboratory, AXYS Analytical Services, using EPA Methods 1613B and 1668A. When comparing the CALUX® by XDS results with HRMS TEQ results from the certified samples and the reference methods, the reader should keep in mind the limitations of the TEQ approach, noting that it is possible that Ah-receptor binding compounds that are being measured during the CALUX® by XDS analysis are not all accounted for in the reference laboratory TEQ result and that the World Health Organization toxicity equivalency factors used to generate the reference laboratory TEQs may differ from the assay Ah-receptor binding affinity for certain analytes. Therefore, the technology should not be viewed as producing an equivalent measurement value to HRMS TEQ values for all samples. Since the technology measures an actual biological response, it is possible that the technology may give a better representation of the true toxicity from a risk assessment standpoint.
The CALUX® by XDS generally reported data higher than the certified PE and reference laboratory values for TEQD/F and total TEQ, but were generally lower than the certified PE and reference laboratory values for TEQPCB. The technology’s estimated method detection limit was similar to what was reported by the developer (0.53 to 0.63 pg/g TEQD/F). No statistically significant matrix effects were observed by matrix type (soil vs. sediment vs. extract) or polynuclear aromatic hydrocarbon concentration. Twenty-one percent of the CALUX® by XDS results from replicate sample sets that were analyzed in the laboratory and in the field showed a significant statistical difference, and only total TEQ value showed a statistically significant effect due to sample type (performance evaluation vs. environmental vs. extract). The technology had a fairly high rate of false positive and false negative results around 1 picogram/gram (pg/g) TEQPCB (15% and 23%, respectively), but it had significantly fewer false positives and false negatives for total TEQ (4% and 1%, respectively) and TEQD/F (6% and 0%, respectively). When comparing XDS’s results to the reference laboratory for samples above and below 50 pg/g TEQ, all of the false positive and false negative rates for all TEQ types were less than 10%. These data suggest that the XDS technology could be an effective tool to screen for samples above or below 1 pg/g TEQ for TEQD/F and total TEQ, and that it could be effective for all three types of TEQ values to determine results above or below 50 pg/g TEQ, particularly considering that both the cost ($89,564 vs. $398,029) and the time (six weeks vs. eight months) to analyze the 209 demonstration samples were significantly less than that of the reference laboratory.