Figure 2. Correlation of P450RGS and EROD assays on 10 SA/SG-cleaned NYDMMP sediment extracts

Technical Note DOER-C8

July 1999

(Means of six replicates SD)

of P450RGS TEQs with GC/MS TEQs to 0.148 for the comparison of EROD TEQs with GC/MS.

The P450RGS assay produced an approximately 10-fold higher response to the crude extracts than

did the EROD assay, indicating a greater sensitivity to PAHs.

The distribution of contributions of the chlorinated and of the PAH contaminants to TEQs in the

cell-based assays is shown in Table 1. In the crude NYDMMP sediment extracts, the PCDD/PCDF

contributed about one-fourth of the total TEQs with PAHs making up nearly all of the rest. However,

in the cleaned extracts, PCDD/PCDF accounted for approximately 97 percent of the total TEQs,

assuming that all PAHs were removed with the SA/SG cleanup. Because the PAH content was

high, the presence of unknown AhR-active compounds in the crude extracts would not likely affect

the calculated GC/MS TEQs significantly. In contrast, the presence of unknown dioxin-like

compounds in the cleaned extracts could drastically underestimate the GC/MS TEQs. Such

compounds are known to exist and may contribute significantly to toxicity in some environmental

media. For example, polybrominated analogs of PCDD/PCDF have similar enzyme induction

potencies (Mason et al. 1987), and these have been identified in environmental samples (Sellstrom

et al. 1993). The presence of AhR-active compounds in the extracts that were not accounted for in

the chemical analysis may partly explain the poor correlations of TEQs by either assay with TEQs

from sediment chemistry.