Underlying data for P, B, T and risk are from Fass.
Below is information about timolol from Scientific discussion for Ganfort (bimatoprost, timolol) EMA 2006.
"The PECsurfacewater values from the Phase I exposure assessment of bimatoprost and timolol were calculated to 8.4 x 10-6 and 1.4 x 10-5 μg/L, which is significantly less than the action limit of 0.01 μg/L described in the draft guideline “Guideline on the Environmental Risk Assessment of Medicinal products for Human use”. Ganfort is unlikely to pose a risk to the environment."
Fass environmental information for timolol from Azarga (brinzolamide, timolol) (downloaded 2018-10-30).
Persistence: No data.
Bioaccumulation: log Kow = 1.8 (method unknown).
Toxicity: No data.
"Calculation of a risk ratio is not possible, due to the lack of environmental toxicity data."
Author: Department of Strategic Careers, Stockholm County Council.