Superfund Innovative Technology Evaluation (SITE)
Note: EPA no longer updates this information, but it may be useful as a reference or resource.
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 Wako Pure Chemical Industries, Ltd. Dioxin ELISA Kit Wako (for environmental). 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 Wako Pure Chemical Industries, Ltd. Dioxin ELISA Kit Wako (for environmental) is an immunoassay technology that reports total dioxin/furan concentration in a sample. The sample units are in pg/g 2,3,7,8- tetrachlorodibenzo-p-dioxin (TCDD) equivalents (EQ). While the kit is most reactive to 2,3,7,8-TCDD, it is responsive to all dioxin/furans at some level. As part of the PE, the technology results were compared to toxicity equivalent (TEQ) results generated by a reference laboratory, AXYS Analytical Services, using EPA Method 1613B, which involves the use of HRMS. It should be noted that the results generated by this technology may not directly correlate to HRMS TEQD/F in all cases because it is known that the congener responses and cross-reactivity of the kit are not identical to the toxicity equivalency factors that are used to convert congener HRMS concentration values to TEQD/F. The effect of cross-reactivities may contribute to this technology’s reporting results that are biased high or low compared to HRMS TEQD/F results. Therefore, this technology should not be viewed as producing an equivalent measurement value to HRMS TEQD/F, but as a screening value to approximate HRMS TEQD/F concentration. It has been suggested that correlation between the Wako and HRMS TEQ could be improved by first characterizing a site and calibrating the Wako results to HRMS results. Subsequent analysis using the Wako kit for samples obtained from this site may then show better correlation with the HRMS TEQ result. This approach was not evaluated during this demonstration.
A summary of the performance of the Dioxin ELISA Kit Wako (for environmental) is as follows: The Wako results were biased both positively and negatively relative to the certified and reference laboratory results. No statistically significant matrix effects were observed by sample type (PE vs. environmental vs. extract), matrix type (soil vs. sediment vs. extract), or polynuclear aromatic hydrocarbon concentration. Wako completed all 209 sample analyses in the field within a nine-day period. The technology’s estimated method detection limit (83 to 201 pg/g 2,3,7,8-TCDD EQ) was significantly higher than was reported by the developer (20 pg/g 2,3,7,8-TCDD EQ), but PE samples with TEQ concentrations in the precisely appropriate range for evaluation of this technology’s detection limit were not available, so these calculated values should be considered a rough estimate. The kit had a false positive rate of 10% and a false negative rate of 13% around 20 pg/g TEQ. The kit had the same false positive rate around 50 pg/g (10%), but less false negatives (8%). These data suggest that the Wako kit could be an effective screening tool for determining sample results above and below 20 pg/g TEQ, and even more effective as a screen for samples above and below 50 pg/g TEQ, particularly considering that the cost to analyze the 209 demonstration samples was significantly less than that of the reference laboratory ($150,294 vs. $213,580). All samples were analyzed on-site in 9 days (in comparison to the reference laboratory, which took 8 months to report all results).