This summary information comes from Fass.
Persistence. The potential for persistence of timolol cannot be excluded, due to lack of data.
Bioaccumulation. Timolol has low potential for bioaccumulation.
Toxicity. No data.
Risk. Risk of environmental impact of timolol cannot be excluded, due to the lack of environmental toxicity data.
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 2021-01-19).
Persistence: No data.
Bioaccumulation: log Kow = 1.8 (method unknown).
Toxicity: No data.
PEC is based on sales data in Sweden in year 2019. PEC = 0.0014 μg/L. "Calculation of a risk ratio is not possible, due to the lack of environmental toxicity data. Therefore, the following phrase is used: Risk of environmental impact of Timolol cannot be excluded, since no ecotoxicity data are available. However, according to the European Medicines Agency guideline on environmental risk assessment of medicinal products (EMA/CHMP/SWP/44447/00 corr2), the use of Timolol is unlikely to represent a risk for the environment, given that its predicted environmental concentration (PEC) is below the action limit 0.01 μg/L."
Author: Health and Medical Care Administration, Region Stockholm