Median toxic dose

Median toxic dose (also known as TD50) is a measure of the toxicity of a substance, specifically, the dose at which half of the test organisms will show adverse effects. It is used in toxicology to assess the relative safety or danger of a substance.

Definition

The median toxic dose is defined as the dose of a substance that is toxic to 50% of a population of test organisms. This is typically determined through laboratory testing, where a group of organisms is exposed to various doses of the substance and the effects are observed. The TD50 is the dose at which half of the organisms show adverse effects.

Calculation

The TD50 is calculated using statistical methods. The doses are plotted on a graph, with the percentage of organisms showing adverse effects on the y-axis and the dose on the x-axis. The TD50 is the dose at which the line crosses the 50% mark on the y-axis.

Use in Toxicology

In toxicology, the TD50 is used to compare the toxicity of different substances. A lower TD50 indicates a more toxic substance, as a smaller dose is needed to cause adverse effects in half of the test organisms. The TD50 is one of several measures used to assess toxicity, along with the lethal dose 50 (LD50), which is the dose at which half of the organisms die.

Limitations

While the TD50 is a useful measure of toxicity, it has limitations. It does not provide information on the severity of the toxic effects, only the dose at which they occur. It also does not account for differences in susceptibility among individuals in the population. Furthermore, it is based on laboratory testing, which may not accurately reflect real-world exposure scenarios.

See also

• Lethal dose 50
• Toxicology
• Dose-response relationship

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