What does LC50 signify in terms of pesticide safety?

The term LC50 stands for "Lethal Concentration 50%" and signifies the concentration of a substance, such as a pesticide, that is lethal to 50% of a test population exposed to it. This measure is critical in determining the toxicity of a pesticide and helps establish safety guidelines for its use. Knowing the LC50 helps professionals gauge the potential risks of a pesticide to non-target organisms, including humans, wildlife, and beneficial insects, and assists in making informed decisions about safe application practices.

In contrast, the other choices do not accurately depict the definition of LC50. The option referring to "lethal concentration for all test subjects" would imply a 100% mortality rate, which is not the correct definition, as LC50 specifically refers to a 50% mortality rate. The option about the "lowest concentration for effective pest control" does not align with the toxicity focus of LC50, and the choice regarding "legal concentration limit in water" pertains to regulatory standards rather than toxicity measurements.