Which measures two acute toxicity indicators used in pesticide testing?

• A. LD50 and LC50
• B. NOAEL and LOAEL
• C. EC50 and IC50
• D. TD50 and ED50

Answer: (A)

Acute toxicity results are about the immediate danger after a short-term exposure. The two measures used to quantify that danger are LD50 and LC50. LD50, or lethal dose for 50% of the test subjects, is expressed as the amount of chemical per unit of body weight (for example, mg of substance per kg) given by a particular route (such as oral or dermal). It tells you how much needs to be absorbed to kill half the animals in the test. LC50, or lethal concentration for 50%, is expressed as a concentration in the air (mg per liter or mg per cubic meter) for inhalation exposure, indicating the concentration required to kill half the animals in a given time frame. Together these metrics give a direct sense of a pesticide’s acute hazard: lower values mean higher acute toxicity.

Other options don’t measure acute lethality in the same way. NOAEL and LOAEL focus on observed effects at different dose levels over longer exposures, not immediate lethality. EC50 and IC50 describe concentrations that produce half-maximal effects or inhibition in in vitro assays, not whole-animal acute lethality. TD50 and ED50 relate to toxic or effective doses for particular outcomes in other contexts and aren’t the standard acute-toxicity indicators used in pesticide testing.