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Last updated: July 23, 2017

What Does Poison Mean?

A poison is any synthetic substance that interferes with biological processes in living organisms. Poisonous substances may be encountered in industrial processes and agriculture. Their toxicity is measured according to their LD50, a measurement that is expressed in milligrams per kilogram of body mass. At LD50 dosage, 50 percent of lab animals would have suffered fatalities as a result of exposure to the toxic substance.

Safeopedia Explains Poison

Internationally, poisons are classified into one of three classes based on their LD50. Class 1 poisons are further divided into extremely hazardous (Class 1a) or highly hazardous (Class 1b) categories. Class 2 poisons are considered to be moderately hazardous and Class 3 poisons are defined as slightly hazardous. The European Union recognizes further poison classes including:

  • Class 4: corrosive
  • Class 5: irritant
  • Class 6: sensitizing
  • Class 7: carcinogenic
  • Class 8: mutagenic

According to international poison safety laws, all poisonous substances must be labelled as such and the label must include pictograms indicating the safety precautions and personal protective equipment required for safe use.


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