MDARD Michigan Core Pesticide Applicator Practice Exam

How is acute toxicity typically expressed?

1. As a percentage of dead organisms

2. As LD50 and LC50 values

3. By the chemical's stability rating

4. In parts per million (PPM)

The correct answer is: As LD50 and LC50 values

Acute toxicity is primarily expressed using LD50 and LC50 values, which are standardized measures that provide important information about the toxicity of a substance. LD50, or "lethal dose for 50%," indicates the dose of a chemical that kills 50% of a test population, typically measured in milligrams of substance per kilogram of body weight (mg/kg). LC50, or "lethal concentration for 50%," refers to the concentration of a substance in air or water that causes 50% mortality or a specified effect in test organisms. These values are critical for assessing the immediate harmful effects of pesticides and other toxic substances on living organisms, providing a quantifiable metric that can be used for comparisons across different chemicals and formulations. In contrast, while expressing toxicity as a percentage of dead organisms, a chemical's stability rating, or parts per million (PPM) may contribute to understanding a substance's overall profile, they do not specifically convey acute toxicity in the same standardized and quantifiable manner as LD50 and LC50. Thus, the use of LD50 and LC50 values is the most reliable way to express acute toxicity in a scientifically accepted format.