Lethal Dose 50% (LD50)

Grace Taylor
8 min read
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Study Guide Overview
This study guide covers LD50 and LC50, including their definitions, calculation, and application in risk assessment. It explains how to interpret these values, compare toxicity across substances, and understand the limitations of the data. The guide also discusses other toxicity measures like NOAEL, ED50, and the history and methods of LD50/LC50 testing, including ethical concerns. Finally, it provides practice questions and exam tips for the AP Environmental Science exam.
#AP Environmental Science: Toxicity & LD50 - Your Ultimate Guide 🧪
Hey future AP Environmental Scientists! Let's break down the concept of LD50 and related toxicity measures. This guide is designed to be your go-to resource for acing the exam, especially the night before! We'll make sure everything clicks, and you feel super confident. Let's dive in!
#Understanding Lethal Dose (LD50) and Lethal Concentration (LC50)
#What are LD50 and LC50?
- LD50 (Lethal Dose 50): The amount of a substance (usually in mg/kg of body weight) that kills 50% of a test population of animals. Think of it as the dose that's lethal to half the group. It's like a toxicity benchmark.
- LC50 (Lethal Concentration 50): Similar to LD50, but it measures the concentration of a substance (in air or water) that kills 50% of a test population. It's used for substances in the environment (air, water) rather than direct doses.
LD50 and LC50 are acute toxicity measures, meaning they look at immediate effects, not long-term ones. They are also a measure of relative toxicity, not absolute safety.
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Quick Memory Aid: LD vs LC
Think of LD as Dose (direct amount given), and LC as Concentration (amount in the environment).
#Examples of LD50 Values
Substance | Route | LD50 (mg/kg in rats) | Notes |
---|---|---|---|
Nicotine | Oral | ~50 | Very toxic |
Caffeine | Oral | ~190 | Moderately toxic |
Aspirin | Oral | ~200 | Moderately toxic |
Ethanol (Alcohol) | Oral | ~7,000 | Relatively low toxicity |
Table Salt | Oral | ~3,000 | Relatively low toxicity |
*Note: These values are for ...

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