Which statement about LC50 is incorrect?

• A. It is a measure of the dose that kills 50% of test organisms
• B. A lower LC50 indicates greater toxicity
• C. It is used to describe acute toxicity
• D. It measures the time to death in 50% of subjects

Answer: (D)

LC50 is the concentration of a chemical in the exposure medium that kills 50% of the test organisms within a defined period. It describes acute toxicity by linking a concentration to a mortality outcome after a set exposure time, so a smaller LC50 means higher toxicity because less chemical is needed to reach 50% mortality. It does not measure how long it takes for death to occur; that would be described by a time-to-death metric such as LT50. So the statement about measuring time to death is the one that’s not correct. Remember, LC50 focuses on concentration, whereas LD50 concerns dose per organism.