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Estetrol (E4) is a unique native estrogen produced by the human fetus during pregnancy. E4 formulated as the monohydrate is a new active substance that received a positive opinion from the Committee for Medicinal Products for Human Use (CHMP) for use in a combined oral contraceptive. E4 is projected to enter the aquatic environment through effluents discharged by sewage treatment plants. The environmental fate of E4 was investigated using a battery of studies designed to describe its physical/chemical characteristics and potential for persistence and bioaccumulation in the environment. The mean measured octanol/water partition coefficient (log KOW) of E4 was determined to be 1.65. In a ready biodegradability study, the mean biodegradation was 3% after 28 days incubation. E4 is not significantly sorbed to soils and sewage treatment solids with Freundlich isotherm adsorption coefficients Kf between 88 and 147 in soils and 35 and 36 in sludges, respectively. In a 100-d aerobic–aquatic biodegradation study into two systems, E4 biodegradation rates in water were 0.182/d and 0.057/d (half-life 3.81 and 12.08 d, respectively) and in sediment were 0.103/d and 0.169/d (half-life 6.71 and 4.09 d, respectively). The results presented illustrate the transient nature of E4 in the aquatic environment and indicate that bioaccumulation of E4 would not be expected.
Dr. Erick Nfon, Senior Regulatory Scientist, will present this research during the SETAC Europe 32nd Annual Meeting, May 15-19, 2022, in Denmark.
