Life-cycle exposure of fathead minnows to environmentally relevant concentrations of the β-blocker drug propranolol.

Propranolol is a human pharmaceutical β-blocker that has been detected in municipal wastewater effluents at ng/L to low μg/L. To assess the potential of this compound to affect fish, fathead minnow (Pimephales promelas) were exposed for a life cycle in a flow-through system to nominal propranolol concentrations of 0.87 ng/L, 8.7 ng/L, 87 ng/L, 870 ng/L, and 8700 ng/L. Measured propranolol concentrations were below detection for the 2 lowest exposure concentrations, and were 76 ng/L, 580 ng/L, and 7800 ng/L for the 3 highest exposure concentrations. During the 162-d to 165-d exposure, no significant changes in weights or lengths were seen in fathead minnows, although the highest concentration of propranolol did cause a 15% decrease in survival of larval and juvenile stage fish compared with controls. At maturity, there were no significant changes in condition factor, liver-somatic index, or secondary sex characteristics in propranolol-exposed male or female fish. Female gonadosomatic index was significantly decreased in fish exposed to the highest concentrations of propranolol, probably because of increased egg-laying. Fathead minnows from all propranolol exposures produced more eggs than control fish, with fish exposed to 7800 ng/L propranolol producing 70% more eggs per female (p = 0.060), and having significantly increased clutch size (p = 0.008). Egg quality, % fertilization, % hatching, and % deformities in F1 fry were unaffected by propranolol exposure of fish. Propranolol exposure caused no effects in fathead minnows, except at the highest exposure concentration (7800 ng/L), where there were slight decreases in survival of juvenile minnows, and indications of increased reproduction. The present study is important because it is the first to assess the potential for effects in fish exposed to propranolol for a life cycle. Environ Toxicol Chem 2017;36:1644-1651. © 2016 SETAC.