Dose-Response
A poison is any agent capable of producing a deleterious effect. Paracelsus (1493-1541) pointed out how almost any substace is a poison if given at a high enough dose:
"What is there that is not poison? All things are poison and nithing is wihtout poison. Soley the dose determines that a thing is not a poison."
Usually the toxicity of chemicals is assessed as the dose that causes death in 50% of experimental animals (LD50), giving a means for comparison of toxicity amoung chemicals, for example:
| Agent | LD50 mg/kg |
| Ethyl alcohol | 10,000 |
| Morphine sulfate | 900 |
| Nicotine | 1 |
| Tetrodotoxin | 0.10 |
| Dioxin (TCDD) | 0.001 |
| Botulism toxin | 0.00001 |
Incomplete...
Some nonnutritional substances that are considered toxic may impart beneficial or stimulatory effects at low doses, even when they produce adverse effects at higher doses. This concept is known as hormesis and has been shown for radiation effects and responses to chemicals. The dose-response curve for such a toxicant will have a U shape near the threshold.
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