The Toxicity Equivalency Factor Scheme Applied To Municipal Incinerator Pcdd/Pcdf Emissions When Specific Congener Information Is Lacking

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Abstract
The 2,3,7,8-TCDD Toxicity EQuivalents (TEQ) approach provides a useful method for estimating the environmental risk of polychlorodibenzodioxin and polychlorodibenzofuran complex mixtures, thus making it possible to express their toxicological significance with only one number. Generally the conversion of the concentration units into those of TEQ requires an isomer-specific analysis and the appropriate Toxicity Equivalency Factors (TEF). In this paper we propose a "theoretical" model for estimating TEQ values of PCDD + PCDF mixtures which, starting from the experimental value of the PCDD + PCDF concentration (μg Nm-3) and the theoretical value of PCDD and PCDF fingerprints in the emissions from municipal incinerators, to make an estimate of the global toxicity in terms of ng TEQ Nm-3. The TEQ values estimated for a number of samples are in good agreement with those calculated from the isomer and congener experimental data. Given the investment and running costs plus the time and the analytical complexity in determining the congeners and single isomer concentrations, it seems that the proposed "theoretical" model is a reasonable tool for estimating the exposure hazard related to a complex mixture of PCDD/PCDFs emitted from municipal solid waste (MSW) incinerators. Another objective of this paper is to explore the consistency between scientific knowledge and the authority regulatory guidelines. This work shows that the Italian national emission standard (4 μg Nm-3) for the total PCDD + PCDF concentration is higher than the international target of 0.1 ng TEQ Nm-3. We suggest a value of 1 μg Nm-3 for TCDD + TCDF concentration if Italian regulators want to add a further constraint.