Bleiverbindungen, organische
MAK-Begründung
Andrea Hartwig1 (Vorsitz der Ständigen Senatskommission zur Prüfung gesundheitsschädlicher Arbeitsstoffe, Deutsche Forschungsgemeinschaft)MAK Commission2
1 Institut für Angewandte Biowissenschaften, Abteilung Lebensmittelchemie und Toxikologie, Karlsruher Institut für Technologie (KIT), Adenauerring 20a, Geb. 50.41, 76131 Karlsruhe, Deutschland
2 Ständige Senatskommission zur Prüfung gesundheitsschädlicher Arbeitsstoffe, Deutsche Forschungsgemeinschaft, Kennedyallee 40, 53175 Bonn, Deutschland
Abstract
The German Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission) summarized and re-evaluated the data for organic lead compounds [e.g. 78-00-2, 75-74-1, 17393-68-9] to derive an occupational exposure limit value (maximum concentration at the workplace, MAK value) considering all toxicological end points. Relevant studies were identified from a literature search. The analyses of urine and faeces after exposure to tetraethyllead or tetramethyllead showed metabolism to inorganic lead. The significantly higher lipophilicity of tetraethyllead and tetramethyllead results in a higher uptake into the brain compared to lead ions and suggests a better uptake in neurons. This might explain the stronger neurotoxic effects observed after exposure to organic lead compounds. Reliable data to derive a MAK value for tetraethyllead, tetramethyllead and other organic lead compounds are not available. As metabolism leads to the formation of inorganic lead, at least the MAK value for inorganic lead must be met and therefore this value is adopted and the MAK value of tetraethyllead and tetramethyllead is lowered to 0.004 mg/m3, as lead. This MAK value also applies to other organic lead compounds. In analogy to the classifications made for inorganic lead compounds, the substances have been assigned to Carcinogen Category 4 and Germ Cell Mutagenicity Category 3 A. As it has been demonstrated unequivocally that lead induces damage to the human embryo and foetus and that these effects are to be expected even if the MAK and biological tolerance (BAT) values are not exceeded, lead has been assigned to Pregnancy Risk Group A. In analogy to inorganic lead, organic lead compounds have likewise been assigned to Pregnancy Risk Group A. According to skin absorption models, percutaneous absorption is expected to contribute significantly to systemic toxicity. Therefore, organic lead compounds have been designated with “H”. There are no data for respiratory or skin sensitization.
