Acute toxicity refers to injury from a single exposure; which indicator is commonly used?

• A. LD50
• B. LC50
• C. Chronic toxicity
• D. Lethal

Answer: (B)

Acute toxicity is about harm from a single exposure, so the standard way to express this hazard is LC50—the lethal concentration that kills 50% of exposed organisms in a defined short period. This measure reflects how dangerous a substance is when the danger comes from the amount present in the environment (air or water) at once, rather than the total amount taken into the body over time. LD50, by contrast, represents the lethal dose per body weight and is more about oral or dermal exposure. Chronic toxicity involves effects from repeated or long-term exposure, not a one-time event, and a simple “lethal” label doesn’t quantify risk.