The T-value in the score for hazard refers to chronic toxicity. Underlying data for P, B, T and risk comes from Fass.se, see below.
Measurements of etonogestrel in the environment are lacking.Etonogestrel is the active metabolite of desogestrel.
Etonogestrel has approximately the same ability to bind to the androgen receptor in fish such as levonorgestrel. A substance's ability to activate the androgen receptor in fish is believed to contribute to increased risk of environmental impact. Etonogestrel also binds to SHBG (Sex Hormone Binding Globulin). Binding to SHBG is believed to contribute to increased bioconcentration (and thus potency) in fish. Based on this, it can be assumed that there is a risk associated with the use of etonogestrel/desogestrel and that these substances appear additive with other androgenic gestagens in the environment.
Fass environmental information for Nexplanon (etonogestrel) (downloaded 2018-07-02).
Persistence: "Sediment Transformation (OECD 308) (Ref. XII): DT50 in water: 10-11 days; DT50 in sediment: 35-70 days; DT50 in total system: 9.2-50 days."
Bioaccumulation: "Log Kow = 3.5. Bioaccumulation (OECD 305): Flow through study with Bluegill sunfish (Lepomis macrochirus) Lipid normalized kinetic BCF = 128."
Chronic toxicity: There is NOEC for 3 trophic levels, lowest NOEC 183 days for fish (Oryzias latipes) 2.7 nanog/L.
PEC/PNEC is based on sales data in Sweden in year 2015. PEC/PNEC = 3.1 which gives the risk moderate.
Author: Health and Medical Care Administration, Region Stockholm