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View Actual EPA Method 4435 (PDF File)
EPA Method 4435:METHOD FOR TOXIC EQUIVALENTS (TEQS) DETERMINATIONS FOR DIOXIN-LIKE CHEMICAL ACTIVITY WITH THE CALUX? BIOASSAY
Summary:Method 4435 is a bio-analytical screening procedure for dioxin-like compounds in soils/sediments. This method is based on the ability of dioxin and related chemicals to activate the Ah receptor (AhR), a chemical-responsive DNA binding protein that is responsible for producing the toxic and biological effects of these chemicals. Measurement of the level of activation of AhR-dependent gene expression by a chemical or chemical extract provides a measure by which to estimate the relative potency and toxic potential of these chemicals and/or extracts with resulting values expressed as Toxic Equivalents (TEQs).
Scope:This method is a relatively rapid screening method capable of estimating the Toxic Equivalents (TEQs) concentration for dioxin-like chemicals in a sample. The sample is extracted in an organic solvent and fractionated through the sample processing procedure (See Sec. 11). An extract that contains the halogenated dioxins/furans is separated from an extract containing the halogenated biphenyls. These extracts are applied to monolayers of H1L6.1c3 cells and the amount of luciferase induction is measured after 20 to 24 hours. A standard dilution series of 2,3,7,8-TCDD is included on each plate of cells. Estimation of dioxin/2,3,7,8-TCDD-like TEQ activity present in the sample extract is performed by extrapolation to the 2,3,7,8-TCDD standard curve by least squares estimates with the 4 parameter Hill Equation.