Xylidin, Isomere (2,3-Xylidin, 2,5-Xylidin, 3,4-Xylidin, 3,5-Xylidin)
MAK-Begründung, Nachtrag
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) re-evaluated 2,3-xylidine [87-59-2], 2,5-xylidine [95-78-3], 3,4-xylidine [95-64-7] and 3,5-xylidine [108-69-0] to assess whether the isomers can be assigned to the new Pregnancy Group B (suspected). This group has been recently introduced for substances suspected of causing prenatal toxicity. Data for prenatal developmental toxicity are not available for any of the xylidine isomers. All four xylidine isomers are indirect methaemoglobin (MetHb) formers. Compared to rodents, humans are far more sensitive to MetHb formation. As with CO-Hb, increased levels of MetHb can lead to impaired oxygen supply to the foetus. Due to their genotoxicity, no MAK value can be derived for the xylidine isomers. Therefore, the assignment to a risk-based pregnancy group is not applicable. As the NOAEC for developmental toxicity by MetHb in humans is not known and the foetus is much more sensitive to MetHb formation than the adult, there is a possibility of endangering the unborn child due to hypoxia. Thus, the xylidine isomers are suspected of causing prenatal toxicity and are assigned to Pregnancy Group B (suspected).
