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 Dermovat (clobetasol propionate) (downloaded 2019-01-17)
Persistence: "< 5% primary (removal of parent) degradation in 14 days (OECD 302). [---] Clobetasol propionate is not readily degradable or inherently biodegradable. The phrase “Clobetasol propionate is potentially persistent” is thus chosen."
Bioaccumulation: Log Pow = 3.49. "Since log Dow < 4 at pH 7, the substance has low potential for bioaccumulation."
Toxicity: There are data for 3 trophic levels, most sensitive fish (Oncorhyncus mykiss) EC50 for fish = 750 microg/L.
PEC/PNEC is based on sales data in Sweden in year 2016. PEC/PNEC = 0.00129 which gives the risk insignificant.
Author: Department of Strategic Careers, Stockholm County Council.