Toxicity Risks Associated With the Beta‐Blocker Metoprolol in Marine and Freshwater Organisms: A Review.

This article focuses on the environmental presence, sources, and toxicity of metoprolol, a second-generation β1-adrenergic receptor blocker used to treat cardiovascular diseases, in aquatic ecosystems. Metoprolol has been detected globally in surface waters and sewage treatment plant effluents at concentrations ranging from 0.66 to 8042 ng/L, with bioaccumulation observed in various aquatic species including invertebrates and fish. Toxicological studies report effects primarily on cardiac function and oxidative stress in about 20 aquatic species, though these effects generally occur at concentrations higher than those typically found in the environment. The review highlights knowledge gaps regarding metoprolol’s impacts on immune function, reproduction, and long-term effects, and recommends further research on low-concentration exposures, noncardiac endpoints, adverse outcome pathways for cardiac dysfunction, and trophic transfer, especially to apex predators and humans via seafood consumption.