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 abbreviation stands for "Lethal Concentration 50%," which is a widely recognized measure used in toxicology to indicate the concentration of a substance in the air or in an aquatic environment that would cause the death of 50% of a specific test population.

LC50 values are crucial in assessing the potential harm of chemicals and allow researchers and regulatory authorities to evaluate the risks posed by exposure to various substances. It provides a standardized way to compare the toxicity of different chemicals under controlled conditions, helping in the determination of safety regulations and guidelines for handling and exposure.

In contrast, LD50 refers to the dose of a substance that is lethal to 50% of test subjects, typically measured through ingestion or injection rather than inhalation. EC50 pertains to the concentration causing an effect in 50% of the test subjects, which is important for assessing sub-lethal effects rather than lethal outcomes. ID50 is not commonly used in this context, making it less relevant for discussing lethal concentrations of air-borne chemicals.