GSTM1 and methemoglobinemia: The higher level of 4-ABP-Hb adduct formation is not attributed to the superior reactivity of HONH-4-ABP with HbO2 since HNOH-AαC induces more methemoglobinemia in erythrocytes in vitro and forms higher levels of the Hb-sulfinamide than does HONH-4-ABP [226].