The amount of an ingested or injected substance that results in the death of 50 percent of the test population is:

The amount of an ingested or injected substance that results in the death of 50 percent of the test population is:

• A. LC50
• B. LD50
• C. DC50
• D. IS50

Answer: (B)

LD50 is the lethal dose for 50% of a test population. When a substance is ingested or injected, the dose is expressed as mass per body weight (usually mg per kg). This metric shows how potent a chemical is via that exposure route: a smaller LD50 means higher toxicity because a smaller amount is needed to kill half the group. In practice, LD50 values come from controlled animal studies and help compare hazards between substances. The other ideas refer to different exposure scenarios. LC50 describes the lethal concentration in air for inhalation, not ingestion or injection. DC50 and IS50 aren’t standard terms for this context (the related ID50 idea applies to infectious doses, not chemical toxicity via ingestion).

LD50 is the lethal dose for 50% of a test population. When a substance is ingested or injected, the dose is expressed as mass per body weight (usually mg per kg). This metric shows how potent a chemical is via that exposure route: a smaller LD50 means higher toxicity because a smaller amount is needed to kill half the group. In practice, LD50 values come from controlled animal studies and help compare hazards between substances.

The other ideas refer to different exposure scenarios. LC50 describes the lethal concentration in air for inhalation, not ingestion or injection. DC50 and IS50 aren’t standard terms for this context (the related ID50 idea applies to infectious doses, not chemical toxicity via ingestion).