title: Toxic equivalence factors, problems and limitations.
abstract: It is a particular problem to set tolerance levels for mixtures containing chemicals classified as carcinogens. In the case of chlorinated dioxin and furan congeners, 'toxicity equivalence factors' (TEFs) were introduced. This concept has problems in itself and cannot be readily transferred to other mixtures, such as those of monocyclic nitroarenes in wastes of trinitrotoluene (TNT)-based explosives. The difficulties in finding suitable endpoints to compare the components are discussed (methaemoglobin formation; quantitative structure-activity relationships; mutagenicity; carcinogenicity). An alternative approach for the development tolerance levels in this instance is based on results obtained by measuring haemoglobin adducts as biomarkers of the most prevalent mixture components in humans.
authors.affiliation: Department of Toxicology, University of Würzburg, Germany.
authors.forename: H G
authors.initials: HG
authors.lastname: Neumann
mesh_terms: D000818:Animals; D001572:Benzofurans / Q000633:toxicity; D015415:Biomarkers; D002273:Carcinogens / Q000032:analysis / Q000633:toxicity*; D018736:DNA Adducts; D004249:DNA Damage / Q000187:drug effects / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000633:toxicity*; D006801:Humans; D011078:Polychlorinated Biphenyls / Q000032:analysis / Q000633:toxicity; D000072317:Polychlorinated Dibenzodioxins / Q000633:toxicity; D014303:Trinitrotoluene / Q000737:chemistry / Q000378:metabolism; D014481:United States; D014484:United States Environmental Protection Agency
chemical_list: D001572:Benzofurans; D015415:Biomarkers; D002273:Carcinogens; D018736:DNA Adducts; D004785:Environmental Pollutants; D000072317:Polychlorinated Dibenzodioxins; D014303:Trinitrotoluene; D011078:Polychlorinated Biphenyls