Question

Chronicity factor is given by the ratio of

• A. Acute LD50/Chronic LD50
• B. Acute LD 50/Chronic LD1
• C. Chronic LD50/Acute LD50
• D. Acute LD25/Chronic LD 75

Hint:

Remember that "Chronicity Factor" measures the relative safety of a compound over time. It is always calculated by dividing the acute value by the chronic value: $\text{CF} = \frac{\text{Acute } LD_{50}}{\text{Chronic } LD_{50}}$.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
The chronicity factor is a toxicological metric used to evaluate the cumulative toxicity of a chemical compound over time.
Key Formula or Approach:
The chronicity factor (CF) is mathematically defined as: \[ \text{Chronicity Factor} = \frac{\text{Acute } LD_{50}}{\text{Chronic } LD_{50}} \] Where: - $\text{Acute } LD_{50}$ is the single dose required to kill $50\%$ of a test population.
- $\text{Chronic } LD_{50}$ is the daily dose administered over a specified period (typically 90 days) required to kill $50\%$ of the population.

Step 2: Detailed Explanation:
Let us analyze the significance of this ratio:
- A chronicity factor close to 1 indicates that the compound does not accumulate in the body and does not cause cumulative damage (little difference between acute and chronic lethal doses).
- A chronicity factor greater than 2.0 indicates a cumulative toxic effect, meaning the compound is slowly eliminated, accumulates in tissues, or causes progressive, irreversible organ damage.
- Thus, the ratio of Acute $LD_{50}$ to Chronic $LD_{50}$ is the standard formula for the chronicity factor.

Step 3: Final Answer:
The ratio is Acute $LD_{50}$ Chronic $LD_{50}$, which corresponds to Option (A).