Abstract—With microsomes prepared from a single human liver, 4, 4′-diaminodiphenyl sulphone (DDS), 4-acetyl-4-aminodiphenyl sulphone (MADDS), 4-acetyl-4-aminodiphenyl thioether (MADDT) and 4, 4′-diacetyldiphenyl thioether (DADDT) caused significantly greater methaemoglobin formation compared with control. In-vitro in the rat, the pattern of toxicity was slightly different: DADDT was not haemotoxic, whilst 3, 4′-diaminodiphenyl ...