Which term best describes the concentration of a chemical in the air that is lethal to 50% of test animals?

The term that best describes the concentration of a chemical in the air that is lethal to 50% of test animals is LC50. This designation is used in toxicology to indicate the concentration of a hazardous substance in air that causes death in 50% of a defined animal population after a specified exposure duration. It is a critical measurement in assessing the acute toxicity of substances, as it helps determine the potential risk to living organisms when exposed to airborne chemicals.

Understanding this concept is essential, especially in structural pest control, as applicators need to be aware of the toxic effects that pesticides can have when they volatilize into the air. In contrast, LD50 refers to the lethal dose required to kill 50% of a population when the substance is administered, typically through ingestion or injection, rather than inhalation. EC50 relates to the concentration of a substance that causes an effect in 50% of the test subjects but does not specifically refer to lethality. ID50 is not commonly used in toxicology and generally refers to infective doses in the context of pathogens rather than chemical exposure.