How does an LC50 test determine whether or not water is polluted?

An LC50 test determines the lethal concentration of a substance that causes death in 50% of a test population, typically aquatic organisms such as fish or invertebrates. By exposing these organisms to varying concentrations of water samples, researchers can assess the toxicity of the water. If the LC50 value is low, it indicates high toxicity and potential pollution, while a higher LC50 suggests lower toxicity and better water quality. Thus, the test helps evaluate the impact of pollutants on aquatic life and overall water health.