A toxic equivalency factor scale for polychlorinated dibenzofurans

Area of Science:

• Environmental Chemistry
• Toxicology
• Biochemistry

Background:

• Polychlorinated dibenzofurans (PCDFs) are persistent organic pollutants with significant toxicological concerns.
• Assessing the toxic equivalency factors (TEFs) of PCDFs is crucial for risk assessment.
• The ethoxyresorufin O-deethylase (EROD) induction assay is a sensitive biomarker for dioxin-like compound toxicity.

Purpose of the Study:

• To evaluate the EROD induction potency of 20 polychlorinated dibenzofurans (PCDFs) using a H4IIE rat hepatoma cell bioassay.
• To establish a quantitative structure-activity relationship (QSAR) for predicting the toxic equivalency factors (TEFs) of PCDFs.
• To identify potent PCDF congeners as EROD inducers.

Main Methods:

• Utilized the H4IIE rat hepatoma cell bioassay to measure EROD induction.
• Calibrated the bioassay response against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) to calculate TEFs.
• Employed multivariate chemical characterization and 37 physicochemical descriptors to build a QSAR model using partial least-squares (PLS).

Main Results:

• EROD induction potency varied across PCDFs by nearly seven orders of magnitude (ED50 values from 25 to 100,000,000 pg/mg).
• A robust QSAR model was developed and validated, demonstrating sound predictive power for TEF values.
• The QSAR model predicted that a substantial number of PCDF congeners exhibit potent EROD induction activity.

Conclusions:

• The H4IIE cell bioassay effectively quantifies EROD induction by PCDFs.
• QSAR modeling provides a valuable tool for predicting the toxicity of PCDF congeners.
• Numerous PCDF congeners possess significant potential to induce EROD, highlighting their environmental and health risks.