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 Hybrizyme Corporation AhRC PCR™ Kit. 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 Hybrizyme Corporation AhRC PCR™ Kit is a technology that reports the concentration of aryl hydrocarbon (Ah) receptor binding compounds in a sample, and the units are reported as Ah Receptor Binding Units (AhRBU). At the time of the demonstration, this particular test was intended for use as a screening tool to rank samples from those inducing the greatest Ah receptor (AhR) activity to those inducing the least AhR activity rather than to provide highly accurate toxicity equivalents (TEQ). The developer’s goal is a highly portable screening technology that can help to determine areas of greatest concern for cleanup at a site and can help to minimize the number of more expensive analyses needed for specific analytes. It has been suggested that correlation between the Hybrizyme AhRBU results and HRMS TEQ results could be established by first characterizing a site and calibrating the Hybrizyme results to HRMS results. This approach was not evaluated during this demonstration. 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. Therefore, the technology’s results were compared to the HRMS D/F and PCB data as well as polynuclear aromatic hydrocarbon (PAH) data in terms of ranking sample concentrations from low to high, rather than in a quantitative fashion of AhRBU vs TEQ. PAH concentrations were included in the comparison because Hybrizyme’s kit responds to these compounds. The suite of PAHs that were quantified in the samples using gas chromatograph/mass spectrometry. The PAHs were a selected target list for this demonstration and likely do not include all of the PAHs that are responsive to this kit. The HRMS reference D/F and PCB data were generated by AXYS Analytical Services, using EPA Methods 1613B and 1668A.
Sample concentrations that were ranked by Hybrizyme from low to high were compared to the PE certified concentration and reference laboratory data, including contributions from PAHs where PAH data were available. The Hybrizyme ranking agreed with the certified values for higher concentration samples, but was inconsistent for lower concentration samples. The Hybrizyme technology’s concentration ranking was consistent with the reference laboratory ranking for the environmental samples 70 to 90% of the time. The technology’s calculated estimated method detection limit was 71 AhRBU. A significant effect was not observed for the reproducibility of Hybrizyme results by matrix type (soil, sediment, extract) or by PAH concentration, but a significant effect was observed for sample type (PE vs. environmental vs. extract) with the PE samples having a significantly higher mean RSD value (44%) compared to the environmental (19%) and the extract (14%) samples. The data generated and evaluated during this demonstration showed that the Hybrizyme technology could be used as an effective tool to rank sample concentrations from low to high AhR activity within a particular environmental site, particularly considering that the cost ($35,023 vs. $398,029) and the time (< two weeks vs. eight months) to analyze the 209 demonstration samples was significantly less than that of the reference laboratory.