Features Methotrexate Azathioprine Chemical structure Physical property [8] pKa: 4.7, log Kow: -1.8, solubility: 3×103 mg/L log Kow: 0.1, solubility: insoluble in water Environmental occurrence [36, 56] hospital effluent: 1 µg/L, river water: < 6.2 ng/L hospital effluent: 15 ng/L Ecotoxicology [58] EC50 > 10 mg/L in various assays --- Treatment strategy [21, 24, 32, 59, 60] KMnO4, NaOCl, O3, electrolysis NaOCl, Fenton reagent

Table 5: Summary of antimetabolites (folate acid analogues and purines).