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Chemical Safety Information - Glossary
Highly Toxic
The term Highly Toxic is to some extent imprecise, and exactly how it is defined varies from one regulatory or standards body to another. A typical (and widely-used) definition follows:
Highly toxic - A chemical falling within any of the following categories:
(a) A chemical with a median lethal dose (LD50) of 50 milligrams or less per kilogram of bodyweight when administered orally to albino rats weighing between 200 and 300 grams each.
(b) A chemical with a median lethal dose (LD50) of 200 milligrams or less per kilogram of body weight when administered by continuous contact for 24 hours (or less if death occurs within 24 hours) with the bare skin of albino rabbits weighing between 2 and 3 kilograms each.
(c) A chemical that has a median lethal concentration (LD50) in air of 200 parts per million by volume or less of gas or vapor, or 2 milligrams per liter or less of mist, fume or dust, when administered by continuous inhalation for 1 hour (or less if death occurs within 1 hour) to albino rats weighing between 200 and 300 grams each.
