The T-value in the score for hazard refers to acute toxicity. Underlying data for P, B, T and risk are from Fass.
Fass environmental information for Levaxin (levothyroxine) (downloaded 2019-03-11).
Persistence: "Test results from "closed bottle test" (guideline 301 D) shows that the biological degradation is 0% in 28 days. Levothyroxine is potentially persistent."
Bioaccumulation: Log Pow = 2.4. "Since log Pow < 4, the substance has low potential for bioaccumulation."
Toxicity: There are data for 3 trophic levels, most sensitive crustacean (Daphnia magna), OECD 202, EC50 497 mg/L.
PEC/PNEC is based on sales data in Sweden in year 2017. PEC/PNEC = 0.00000431 which gives the risk insignificant.
Pharmaceutial residues in the aquatic environment
In the report Pharmaceutial residues in the Stockholm aquatic environment, levothyroxine was excluded on the grounds that it is "natural".
Author: Health and Medical Care Administration, Region Stockholm